Xlib - C Language X Interface

X Consortium Standard

James Gettys

   Digital Equipment Corporation
   Cambridge Research Laboratory

Robert W. Scheifler

   Massachusetts Institute of Technology
   Laboratory for Computer Science

Chuck Adams

   Tektronix, Inc.

Vania Joloboff

   Open Software Foundation

Hideki Hiura

   Sun Microsystems, Inc.

Bill McMahon

   Hewlett-Packard Company

Ron Newman

   Massachusetts Institute of Technology

Al Tabayoyon

   Tektronix, Inc.

Glenn Widener

   Tektronix, Inc.

Shigeru Yamada

   Fujitsu OSSI

   X Version 11, Release 7.7

   Copyright © 1985, 1986, 1987, 1988, 1989, 1991, 1994, 1996,
   2002 The Open Group

   Permission is hereby granted, free of charge, to any person
   obtaining a copy of this software and associated documentation
   files (the "Software"), to deal in the Software without
   restriction, including without limitation the rights to use,
   copy, modify, merge, publish, distribute, sublicense, and/or
   sell copies of the Software, and to permit persons to whom the
   Software is furnished to do so, subject to the following
   conditions:

   The above copyright notice and this permission notice shall be
   included in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   NONINFRINGEMENT. IN NO EVENT SHALL THE OPEN GROUP BE LIABLE FOR
   ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
   CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   THE SOFTWARE.

   Except as contained in this notice, the name of The Open Group
   shall not be used in advertising or otherwise to promote the
   sale, use or other dealings in this Software without prior
   written authorization from The Open Group.

   Copyright © 1985, 1986, 1987, 1988, 1989, 1991 Digital
   Equipment Corporation

   Permission to use, copy, modify and distribute this
   documentation for any purpose and without fee is hereby
   granted, provided that the above copyright notice appears in
   all copies and that both that copyright notice and this
   permission notice appear in supporting documentation, and that
   the names of Digital and Tetronix not be used in in advertising
   or publicity pertaining to distribution of the software without
   specific, written prior permission. Digital and Tetronix make
   no representations about the suitability of the software
   described herein for any purpose. It is provided "as is"
   without express or implied warranty.

   TekHVC is a trademark of Tektronix, Inc.
     __________________________________________________________

   Table of Contents

   Acknowledgments
   1. Introduction to Xlib

        Overview of the X Window System
        Errors
        Standard Header Files
        Generic Values and Types
        Naming and Argument Conventions within Xlib
        Programming Considerations
        Character Sets and Encodings
        Formatting Conventions

   2. Display Functions

        Opening the Display
        Obtaining Information about the Display, Image Formats, or
                Screens

              Display Macros
              Image Format Functions and Macros
              Screen Information Macros

        Generating a NoOperation Protocol Request
        Freeing Client-Created Data
        Closing the Display
        Using X Server Connection Close Operations
        Using Xlib with Threads
        Using Internal Connections

   3. Window Functions

        Visual Types
        Window Attributes

              Background Attribute
              Border Attribute
              Gravity Attributes
              Backing Store Attribute
              Save Under Flag
              Backing Planes and Backing Pixel Attributes
              Event Mask and Do Not Propagate Mask Attributes
              Override Redirect Flag
              Colormap Attribute
              Cursor Attribute

        Creating Windows
        Destroying Windows
        Mapping Windows
        Unmapping Windows
        Configuring Windows
        Changing Window Stacking Order
        Changing Window Attributes

   4. Window Information Functions

        Obtaining Window Information
        Translating Screen Coordinates
        Properties and Atoms
        Obtaining and Changing Window Properties
        Selections

   5. Pixmap and Cursor Functions

        Creating and Freeing Pixmaps
        Creating, Recoloring, and Freeing Cursors

   6. Color Management Functions

        Color Structures
        Color Strings

              RGB Device String Specification
              RGB Intensity String Specification
              Device-Independent String Specifications

        Color Conversion Contexts and Gamut Mapping
        Creating, Copying, and Destroying Colormaps
        Mapping Color Names to Values
        Allocating and Freeing Color Cells
        Modifying and Querying Colormap Cells
        Color Conversion Context Functions

              Getting and Setting the Color Conversion Context of
                      a Colormap

              Obtaining the Default Color Conversion Context
              Color Conversion Context Macros
              Modifying Attributes of a Color Conversion Context
              Creating and Freeing a Color Conversion Context

        Converting between Color Spaces
        Callback Functions

              Prototype Gamut Compression Procedure
              Supplied Gamut Compression Procedures
              Prototype White Point Adjustment Procedure
              Supplied White Point Adjustment Procedures

        Gamut Querying Functions

              Red, Green, and Blue Queries
              CIELab Queries
              CIELuv Queries
              TekHVC Queries

        Color Management Extensions

              Color Spaces
              Adding Device-Independent Color Spaces
              Querying Color Space Format and Prefix
              Creating Additional Color Spaces
              Parse String Callback
              Color Specification Conversion Callback
              Function Sets
              Adding Function Sets
              Creating Additional Function Sets

   7. Graphics Context Functions

        Manipulating Graphics Context/State
        Using Graphics Context Convenience Routines

              Setting the Foreground, Background, Function, or
                      Plane Mask

              Setting the Line Attributes and Dashes
              Setting the Fill Style and Fill Rule
              Setting the Fill Tile and Stipple
              Setting the Current Font
              Setting the Clip Region
              Setting the Arc Mode, Subwindow Mode, and Graphics
                      Exposure

   8. Graphics Functions

        Clearing Areas
        Copying Areas
        Drawing Points, Lines, Rectangles, and Arcs

              Drawing Single and Multiple Points
              Drawing Single and Multiple Lines
              Drawing Single and Multiple Rectangles
              Drawing Single and Multiple Arcs

        Filling Areas

              Filling Single and Multiple Rectangles
              Filling a Single Polygon
              Filling Single and Multiple Arcs

        Font Metrics

              Loading and Freeing Fonts
              Obtaining and Freeing Font Names and Information
              Computing Character String Sizes
              Computing Logical Extents
              Querying Character String Sizes

        Drawing Text

              Drawing Complex Text
              Drawing Text Characters
              Drawing Image Text Characters

        Transferring Images between Client and Server

   9. Window and Session Manager Functions

        Changing the Parent of a Window
        Controlling the Lifetime of a Window
        Managing Installed Colormaps
        Setting and Retrieving the Font Search Path
        Grabbing the Server
        Killing Clients
        Controlling the Screen Saver
        Controlling Host Access

              Adding, Getting, or Removing Hosts
              Changing, Enabling, or Disabling Access Control

   10. Events

        Event Types
        Event Structures
        Event Masks
        Event Processing Overview
        Keyboard and Pointer Events

              Pointer Button Events
              Keyboard and Pointer Events

        Window Entry/Exit Events

              Normal Entry/Exit Events
              Grab and Ungrab Entry/Exit Events

        Input Focus Events

              Normal Focus Events and Focus Events While Grabbed
              Focus Events Generated by Grabs

        Key Map State Notification Events
        Exposure Events

              Expose Events
              GraphicsExpose and NoExpose Events

        Window State Change Events

              CirculateNotify Events
              ConfigureNotify Events
              CreateNotify Events
              DestroyNotify Events
              GravityNotify Events
              MapNotify Events
              MappingNotify Events
              ReparentNotify Events
              UnmapNotify Events
              VisibilityNotify Events

        Structure Control Events

              CirculateRequest Events
              ConfigureRequest Events
              MapRequest Events
              ResizeRequest Events

        Colormap State Change Events
        Client Communication Events

              ClientMessage Events
              PropertyNotify Events
              SelectionClear Events
              SelectionRequest Events
              SelectionNotify Events

   11. Event Handling Functions

        Selecting Events
        Handling the Output Buffer
        Event Queue Management
        Manipulating the Event Queue

              Returning the Next Event
              Selecting Events Using a Predicate Procedure
              Selecting Events Using a Window or Event Mask

        Putting an Event Back into the Queue
        Sending Events to Other Applications
        Getting Pointer Motion History
        Handling Protocol Errors

              Enabling or Disabling Synchronization
              Using the Default Error Handlers

   12. Input Device Functions

        Pointer Grabbing
        Keyboard Grabbing
        Resuming Event Processing
        Moving the Pointer
        Controlling Input Focus
        Manipulating the Keyboard and Pointer Settings
        Manipulating the Keyboard Encoding

   13. Locales and Internationalized Text Functions

        X Locale Management
        Locale and Modifier Dependencies
        Variable Argument Lists
        Output Methods

              Output Method Overview
              Output Method Functions
              X Output Method Values
              Output Context Functions
              Output Context Values
              Creating and Freeing a Font Set
              Obtaining Font Set Metrics
              Drawing Text Using Font Sets

        Input Methods

              Input Method Overview
              Input Method Management
              Input Method Functions
              Input Method Values
              Input Context Functions
              Input Context Values
              Input Method Callback Semantics
              Event Filtering
              Getting Keyboard Input
              Input Method Conventions

        String Constants

   14. Inter-Client Communication Functions

        Client to Window Manager Communication

              Manipulating Top-Level Windows
              Converting String Lists
              Setting and Reading Text Properties
              Setting and Reading the WM_NAME Property
              Setting and Reading the WM_ICON_NAME Property
              Setting and Reading the WM_HINTS Property
              Setting and Reading the WM_NORMAL_HINTS Property
              Setting and Reading the WM_CLASS Property
              Setting and Reading the WM_TRANSIENT_FOR Property
              Setting and Reading the WM_PROTOCOLS Property
              Setting and Reading the WM_COLORMAP_WINDOWS Property
              Setting and Reading the WM_ICON_SIZE Property
              Using Window Manager Convenience Functions

        Client to Session Manager Communication

              Setting and Reading the WM_COMMAND Property
              Setting and Reading the WM_CLIENT_MACHINE Property

        Standard Colormaps

              Standard Colormap Properties and Atoms
              Setting and Obtaining Standard Colormaps

   15. Resource Manager Functions

        Resource File Syntax
        Resource Manager Matching Rules
        Quarks
        Creating and Storing Databases
        Merging Resource Databases
        Looking Up Resources
        Storing into a Resource Database
        Enumerating Database Entries
        Parsing Command Line Options

   16. Application Utility Functions

        Using Keyboard Utility Functions

              KeySym Classification Macros

        Using Latin-1 Keyboard Event Functions
        Allocating Permanent Storage
        Parsing the Window Geometry
        Manipulating Regions

              Creating, Copying, or Destroying Regions
              Moving or Shrinking Regions
              Computing with Regions
              Determining if Regions Are Empty or Equal
              Locating a Point or a Rectangle in a Region

        Using Cut Buffers
        Determining the Appropriate Visual Type
        Manipulating Images
        Manipulating Bitmaps
        Using the Context Manager

   A. Xlib Functions and Protocol Requests
   B. X Font Cursors
   C. Extensions

        Basic Protocol Support Routines
        Hooking into Xlib

              Hooks into the Library
              Hooks onto Xlib Data Structures

        GC Caching
        Graphics Batching
        Writing Extension Stubs

              Requests, Replies, and Xproto.h
              Request Format
              Starting to Write a Stub Procedure
              Locking Data Structures
              Sending the Protocol Request and Arguments
              Variable Length Arguments
              Replies
              Synchronous Calling
              Allocating and Deallocating Memory
              Portability Considerations
              Deriving the Correct Extension Opcode

   D. Compatibility Functions

        X Version 11 Compatibility Functions

              Setting Standard Properties
              Setting and Getting Window Sizing Hints
              Getting and Setting an XStandardColormap Structure
              Parsing Window Geometry
              Getting the X Environment Defaults

        X Version 10 Compatibility Functions

              Drawing and Filling Polygons and Curves
              Associating User Data with a Value

   Glossary
   Index

   List of Tables

   A.1. Protocol requests made by each Xlib function
   A.2. Xlib functions which use each Protocol Request

Acknowledgments

   The design and implementation of the first 10 versions of X
   were primarily the work of three individuals: Robert Scheifler
   of the MIT Laboratory for Computer Science and Jim Gettys of
   Digital Equipment Corporation and Ron Newman of MIT, both at
   MIT Project Athena. X version 11, however, is the result of the
   efforts of dozens of individuals at almost as many locations
   and organizations. At the risk of offending some of the players
   by exclusion, we would like to acknowledge some of the people
   who deserve special credit and recognition for their work on
   Xlib. Our apologies to anyone inadvertently overlooked.

Release 1

   Our thanks does to Ron Newman (MIT Project Athena), who
   contributed substantially to the design and implementation of
   the Version 11 Xlib interface.

   Our thanks also goes to Ralph Swick (Project Athena and
   Digital) who kept it all together for us during the early
   releases. He handled literally thousands of requests from
   people everywhere and saved the sanity of at least one of us.
   His calm good cheer was a foundation on which we could build.

   Our thanks also goes to Todd Brunhoff (Tektronix) who was
   ``loaned'' to Project Athena at exactly the right moment to
   provide very capable and much-needed assistance during the
   alpha and beta releases. He was responsible for the successful
   integration of sources from multiple sites; we would not have
   had a release without him.

   Our thanks also goes to Al Mento and Al Wojtas of Digital's
   ULTRIX Documentation Group. With good humor and cheer, they
   took a rough draft and made it an infinitely better and more
   useful document. The work they have done will help many
   everywhere. We also would like to thank Hal Murray (Digital
   SRC) and Peter George (Digital VMS) who contributed much by
   proofreading the early drafts of this document.

   Our thanks also goes to Jeff Dike (Digital UEG), Tom Benson,
   Jackie Granfield, and Vince Orgovan (Digital VMS) who helped
   with the library utilities implementation; to Hania Gajewska
   (Digital UEG-WSL) who, along with Ellis Cohen (CMU and
   Siemens), was instrumental in the semantic design of the window
   manager properties; and to Dave Rosenthal (Sun Microsystems)
   who also contributed to the protocol and provided the sample
   generic color frame buffer device-dependent code.

   The alpha and beta test participants deserve special
   recognition and thanks as well. It is significant that the bug
   reports (and many fixes) during alpha and beta test came almost
   exclusively from just a few of the alpha testers, mostly
   hardware vendors working on product implementations of X. The
   continued public contribution of vendors and universities is
   certainly to the benefit of the entire X community.

   Our special thanks must go to Sam Fuller, Vice-President of
   Corporate Research at Digital, who has remained committed to
   the widest public availability of X and who made it possible to
   greatly supplement MIT's resources with the Digital staff in
   order to make version 11 a reality. Many of the people
   mentioned here are part of the Western Software Laboratory
   (Digital UEG-WSL) of the ULTRIX Engineering group and work for
   Smokey Wallace, who has been vital to the project's success.
   Others not mentioned here worked on the toolkit and are
   acknowledged in the X Toolkit documentation.

   Of course, we must particularly thank Paul Asente, formerly of
   Stanford University and now of Digital UEG-WSL, who wrote W,
   the predecessor to X, and Brian Reid, formerly of Stanford
   University and now of Digital WRL, who had much to do with W's
   design.

   Finally, our thanks goes to MIT, Digital Equipment Corporation,
   and IBM for providing the environment where it could happen.

Release 4

   Our thanks go to Jim Fulton (MIT X Consortium) for designing
   and specifying the new Xlib functions for Inter-Client
   Communication Conventions (ICCCM) support.

   We also thank Al Mento of Digital for his continued effort in
   maintaining this document and Jim Fulton and Donna Converse
   (MIT X Consortium) for their much-appreciated efforts in
   reviewing the changes.

Release 5

   The principal authors of the Input Method facilities are Vania
   Joloboff (Open Software Foundation) and Bill McMahon
   (Hewlett-Packard). The principal author of the rest of the
   internationalization facilities is Glenn Widener (Tektronix).
   Our thanks to them for keeping their sense of humor through a
   long and sometimes difficult design process. Although the words
   and much of the design are due to them, many others have
   contributed substantially to the design and implementation. Tom
   McFarland (HP) and Frank Rojas (IBM) deserve particular
   recognition for their contributions. Other contributors were:
   Tim Anderson (Motorola), Alka Badshah (OSF), Gabe Beged-Dov
   (HP), Chih-Chung Ko (III), Vera Cheng (III), Michael Collins
   (Digital), Walt Daniels (IBM), Noritoshi Demizu (OMRON),
   Keisuke Fukui (Fujitsu), Hitoshoi Fukumoto (Nihon Sun), Tim
   Greenwood (Digital), John Harvey (IBM), Hideki Hiura (Sun),
   Fred Horman (AT&T), Norikazu Kaiya (Fujitsu), Yuji Kamata
   (IBM), Yutaka Kataoka (Waseda University), Ranee Khubchandani
   (Sun), Akira Kon (NEC), Hiroshi Kuribayashi (OMRON), Teruhiko
   Kurosaka (Sun), Seiji Kuwari (OMRON), Sandra Martin (OSF),
   Narita Masahiko (Fujitsu), Masato Morisaki (NTT), Nelson Ng
   (Sun), Takashi Nishimura (NTT America), Makato Nishino (IBM),
   Akira Ohsone (Nihon Sun), Chris Peterson (MIT), Sam Shteingart
   (AT&T), Manish Sheth (AT&T), Muneiyoshi Suzuki (NTT), Cori
   Mehring (Digital), Shoji Sugiyama (IBM), and Eiji Tosa (IBM).

   We are deeply indebted to Tatsuya Kato (NTT), Hiroshi
   Kuribayashi (OMRON), Seiji Kuwari (OMRON), Muneiyoshi Suzuki
   (NTT), and Li Yuhong (OMRON) for producing one of the first
   complete sample implementation of the internationalization
   facilities, and Hiromu Inukai (Nihon Sun), Takashi Fujiwara
   (Fujitsu), Hideki Hiura (Sun), Yasuhiro Kawai (Oki
   Technosystems Laboratory), Kazunori Nishihara (Fuji Xerox),
   Masaki Takeuchi (Sony), Katsuhisa Yano (Toshiba), Makoto
   Wakamatsu (Sony Corporation) for producing the another complete
   sample implementation of the internationalization facilities.

   The principal authors (design and implementation) of the Xcms
   color management facilities are Al Tabayoyon (Tektronix) and
   Chuck Adams (Tektronix). Joann Taylor (Tektronix), Bob Toole
   (Tektronix), and Keith Packard (MIT X Consortium) also
   contributed significantly to the design. Others who contributed
   are: Harold Boll (Kodak), Ken Bronstein (HP), Nancy Cam (SGI),
   Donna Converse (MIT X Consortium), Elias Israel (ISC), Deron
   Johnson (Sun), Jim King (Adobe), Ricardo Motta (HP), Chuck Peek
   (IBM), Wil Plouffe (IBM), Dave Sternlicht (MIT X Consortium),
   Kumar Talluri (AT&T), and Richard Verberg (IBM).

   We also once again thank Al Mento of Digital for his work in
   formatting and reformatting text for this manual, and for
   producing man pages. Thanks also to Clive Feather (IXI) for
   proof-reading and finding a number of small errors.

Release 6

   Stephen Gildea (X Consortium) authored the threads support.
   Ovais Ashraf (Sun) and Greg Olsen (Sun) contributed
   substantially by testing the facilities and reporting bugs in a
   timely fashion.

   The principal authors of the internationalization facilities,
   including Input and Output Methods, are Hideki Hiura (SunSoft)
   and Shigeru Yamada (Fujitsu OSSI). Although the words and much
   of the design are due to them, many others have contributed
   substantially to the design and implementation. They are:
   Takashi Fujiwara (Fujitsu), Yoshio Horiuchi (IBM), Makoto Inada
   (Digital), Hiromu Inukai (Nihon SunSoft), Song JaeKyung
   (KAIST), Franky Ling (Digital), Tom McFarland (HP), Hiroyuki
   Miyamoto (Digital), Masahiko Narita (Fujitsu), Frank Rojas
   (IBM), Hidetoshi Tajima (HP), Masaki Takeuchi (Sony), Makoto
   Wakamatsu (Sony), Masaki Wakao (IBM), Katsuhisa Yano(Toshiba)
   and Jinsoo Yoon (KAIST).

   The principal producers of the sample implementation of the
   internationalization facilities are: Jeffrey Bloomfield
   (Fujitsu OSSI), Takashi Fujiwara (Fujitsu), Hideki Hiura
   (SunSoft), Yoshio Horiuchi (IBM), Makoto Inada (Digital),
   Hiromu Inukai (Nihon SunSoft), Song JaeKyung (KAIST), Riki
   Kawaguchi (Fujitsu), Franky Ling (Digital), Hiroyuki Miyamoto
   (Digital), Hidetoshi Tajima (HP), Toshimitsu Terazono
   (Fujitsu), Makoto Wakamatsu (Sony), Masaki Wakao (IBM), Shigeru
   Yamada (Fujitsu OSSI) and Katsuhisa Yano (Toshiba).

   The coordinators of the integration, testing, and release of
   this implementation of the internationalization facilities are
   Nobuyuki Tanaka (Sony) and Makoto Wakamatsu (Sony).

   Others who have contributed to the architectural design or
   testing of the sample implementation of the
   internationalization facilities are: Hector Chan (Digital),
   Michael Kung (IBM), Joseph Kwok (Digital), Hiroyuki Machida
   (Sony), Nelson Ng (SunSoft), Frank Rojas (IBM), Yoshiyuki
   Segawa (Fujitsu OSSI), Makiko Shimamura (Fujitsu), Shoji
   Sugiyama (IBM), Lining Sun (SGI), Masaki Takeuchi (Sony),
   Jinsoo Yoon (KAIST) and Akiyasu Zen (HP).

   Jim Gettys
   Cambridge Research Laboratory
   Digital Equipment Corporation
   Robert W. Scheifler
   Laboratory for Computer Science
   Massachusetts Institute of Technology

Release 7

   This document is made available to you in modern formats such
   as HTML and PDF thanks to the efforts of Matt Dew, who
   converted the original troff sources to DocBook/XML and edited
   them into shape; along with Gaetan Nadon and Alan Coopersmith,
   who set up the formatting machinery in the libX11 builds and
   performed further editing of the DocBook markup.

Chapter 1. Introduction to Xlib

   Table of Contents

   Overview of the X Window System
   Errors
   Standard Header Files
   Generic Values and Types
   Naming and Argument Conventions within Xlib
   Programming Considerations
   Character Sets and Encodings
   Formatting Conventions

   The X Window System is a network-transparent window system that
   was designed at MIT. X display servers run on computers with
   either monochrome or color bitmap display hardware. The server
   distributes user input to and accepts output requests from
   various client programs located either on the same machine or
   elsewhere in the network. Xlib is a C subroutine library that
   application programs (clients) use to interface with the window
   system by means of a stream connection. Although a client
   usually runs on the same machine as the X server it is talking
   to, this need not be the case.

   Xlib - C Language X Interface is a reference guide to the
   low-level C language interface to the X Window System protocol.
   It is neither a tutorial nor a user's guide to programming the
   X Window System. Rather, it provides a detailed description of
   each function in the library as well as a discussion of the
   related background information. Xlib - C Language X Interface
   assumes a basic understanding of a graphics window system and
   of the C programming language. Other higher-level abstractions
   (for example, those provided by the toolkits for X) are built
   on top of the Xlib library. For further information about these
   higher-level libraries, see the appropriate toolkit
   documentation. The X Window System Protocol provides the
   definitive word on the behavior of X. Although additional
   information appears here, the protocol document is the ruling
   document.

   To provide an introduction to X programming, this chapter
   discusses:
     * Overview of the X Window System
     * Errors
     * Standard header files
     * Generic values and types
     * Naming and argument conventions within Xlib
     * Programming considerations
     * Character sets and encodings
     * Formatting conventions

Overview of the X Window System

   Some of the terms used in this book are unique to X, and other
   terms that are common to other window systems have different
   meanings in X. You may find it helpful to refer to the
   glossary, which is located at the end of the book.

   The X Window System supports one or more screens containing
   overlapping windows or subwindows. A screen is a physical
   monitor and hardware that can be color, grayscale, or
   monochrome. There can be multiple screens for each display or
   workstation. A single X server can provide display services for
   any number of screens. A set of screens for a single user with
   one keyboard and one pointer (usually a mouse) is called a
   display.

   All the windows in an X server are arranged in strict
   hierarchies. At the top of each hierarchy is a root window,
   which covers each of the display screens. Each root window is
   partially or completely covered by child windows. All windows,
   except for root windows, have parents. There is usually at
   least one window for each application program. Child windows
   may in turn have their own children. In this way, an
   application program can create an arbitrarily deep tree on each
   screen. X provides graphics, text, and raster operations for
   windows.

   A child window can be larger than its parent. That is, part or
   all of the child window can extend beyond the boundaries of the
   parent, but all output to a window is clipped by its parent. If
   several children of a window have overlapping locations, one of
   the children is considered to be on top of or raised over the
   others, thus obscuring them. Output to areas covered by other
   windows is suppressed by the window system unless the window
   has backing store. If a window is obscured by a second window,
   the second window obscures only those ancestors of the second
   window that are also ancestors of the first window.

   A window has a border zero or more pixels in width, which can
   be any pattern (pixmap) or solid color you like. A window
   usually but not always has a background pattern, which will be
   repainted by the window system when uncovered. Child windows
   obscure their parents, and graphic operations in the parent
   window usually are clipped by the children.

   Each window and pixmap has its own coordinate system. The
   coordinate system has the X axis horizontal and the Y axis
   vertical with the origin [0, 0] at the upper-left corner.
   Coordinates are integral, in terms of pixels, and coincide with
   pixel centers. For a window, the origin is inside the border at
   the inside, upper-left corner.

   X does not guarantee to preserve the contents of windows. When
   part or all of a window is hidden and then brought back onto
   the screen, its contents may be lost. The server then sends the
   client program an Expose event to notify it that part or all of
   the window needs to be repainted. Programs must be prepared to
   regenerate the contents of windows on demand.

   X also provides off-screen storage of graphics objects, called
   pixmaps. Single plane (depth 1) pixmaps are sometimes referred
   to as bitmaps. Pixmaps can be used in most graphics functions
   interchangeably with windows and are used in various graphics
   operations to define patterns or tiles. Windows and pixmaps
   together are referred to as drawables.

   Most of the functions in Xlib just add requests to an output
   buffer. These requests later execute asynchronously on the X
   server. Functions that return values of information stored in
   the server do not return (that is, they block) until an
   explicit reply is received or an error occurs. You can provide
   an error handler, which will be called when the error is
   reported.

   If a client does not want a request to execute asynchronously,
   it can follow the request with a call to XSync, which blocks
   until all previously buffered asynchronous events have been
   sent and acted on. As an important side effect, the output
   buffer in Xlib is always flushed by a call to any function that
   returns a value from the server or waits for input.

   Many Xlib functions will return an integer resource ID, which
   allows you to refer to objects stored on the X server. These
   can be of type Window, Font, Pixmap, Colormap, Cursor, and
   GContext, as defined in the file <X11/X.h>. These resources are
   created by requests and are destroyed (or freed) by requests or
   when connections are closed. Most of these resources are
   potentially shareable between applications, and in fact,
   windows are manipulated explicitly by window manager programs.
   Fonts and cursors are shared automatically across multiple
   screens. Fonts are loaded and unloaded as needed and are shared
   by multiple clients. Fonts are often cached in the server. Xlib
   provides no support for sharing graphics contexts between
   applications.

   Client programs are informed of events. Events may either be
   side effects of a request (for example, restacking windows
   generates Expose events) or completely asynchronous (for
   example, from the keyboard). A client program asks to be
   informed of events. Because other applications can send events
   to your application, programs must be prepared to handle (or
   ignore) events of all types.

   Input events (for example, a key pressed or the pointer moved)
   arrive asynchronously from the server and are queued until they
   are requested by an explicit call (for example, XNextEvent or
   XWindowEvent). In addition, some library functions (for
   example, XRaiseWindow) generate Expose and ConfigureRequest
   events. These events also arrive asynchronously, but the client
   may wish to explicitly wait for them by calling XSync after
   calling a function that can cause the server to generate
   events.

Errors

   Some functions return Status, an integer error indication. If
   the function fails, it returns a zero. If the function returns
   a status of zero, it has not updated the return arguments.
   Because C does not provide multiple return values, many
   functions must return their results by writing into
   client-passed storage. By default, errors are handled either by
   a standard library function or by one that you provide.
   Functions that return pointers to strings return NULL pointers
   if the string does not exist.

   The X server reports protocol errors at the time that it
   detects them. If more than one error could be generated for a
   given request, the server can report any of them.

   Because Xlib usually does not transmit requests to the server
   immediately (that is, it buffers them), errors can be reported
   much later than they actually occur. For debugging purposes,
   however, Xlib provides a mechanism for forcing synchronous
   behavior (see section 11.8.1). When synchronization is enabled,
   errors are reported as they are generated.

   When Xlib detects an error, it calls an error handler, which
   your program can provide. If you do not provide an error
   handler, the error is printed, and your program terminates.

Standard Header Files

   The following include files are part of the Xlib standard:

   <X11/Xlib.h>

   This is the main header file for Xlib. The majority of all Xlib
   symbols are declared by including this file. This file also
   contains the preprocessor symbol XlibSpecificationRelease. This
   symbol is defined to have the 6 in this release of the
   standard. (Release 5 of Xlib was the first release to have this
   symbol.)

   <X11/X.h>

   This file declares types and constants for the X protocol that
   are to be used by applications. It is included automatically
   from <X11/Xlib.h> so application code should never need to
   reference this file directly.

   <X11/Xcms.h>

   This file contains symbols for much of the color management
   facilities described in chapter 6. All functions, types, and
   symbols with the prefix "Xcms", plus the Color Conversion
   Contexts macros, are declared in this file. <X11/Xlib.h> must
   be included before including this file.

   <X11/Xutil.h>

   This file declares various functions, types, and symbols used
   for inter-client communication and application utility
   functions, which are described in chapters 14 and 16.
   <X11/Xlib.h> must be included before including this file.

   <X11/Xresource.h>

   This file declares all functions, types, and symbols for the
   resource manager facilities, which are described in chapter 15.
   <X11/Xlib.h> must be included before including this file.

   <X11/Xatom.h>

   This file declares all predefined atoms, which are symbols with
   the prefix "XA_".

   <X11/cursorfont.h>

   This file declares the cursor symbols for the standard cursor
   font, which are listed in Appendix B. All cursor symbols have
   the prefix "XC_".

   <X11/keysymdef.h>

   This file declares all standard KeySym values, which are
   symbols with the prefix "XK_". The KeySyms are arranged in
   groups, and a preprocessor symbol controls inclusion of each
   group. The preprocessor symbol must be defined prior to
   inclusion of the file to obtain the associated values. The
   preprocessor symbols are XK_MISCELLANY, XK_XKB_KEYS, XK_3270,
   XK_LATIN1, XK_LATIN2, XK_LATIN3, XK_LATIN4, XK_KATAKANA,
   XK_ARABIC, XK_CYRILLIC, XK_GREEK, XK_TECHNICAL, XK_SPECIAL,
   XK_PUBLISHING, XK_APL, XK_HEBREW, XK_THAI, and XK_KOREAN.

   <X11/keysym.h>

   This file defines the preprocessor symbols XK_MISCELLANY,
   XK_XKB_KEYS, XK_LATIN1, XK_LATIN2, XK_LATIN3, XK_LATIN4, and
   XK_GREEK and then includes <X11/keysymdef.h>.

   <X11/Xlibint.h>

   This file declares all the functions, types, and symbols used
   for extensions, which are described in Appendix C. This file
   automatically includes <X11/Xlib.h>.

   <X11/Xproto.h>

   This file declares types and symbols for the basic X protocol,
   for use in implementing extensions. It is included
   automatically from <X11/Xlibint.h>, so application and
   extension code should never need to reference this file
   directly.

   <X11/Xprotostr.h>

   This file declares types and symbols for the basic X protocol,
   for use in implementing extensions. It is included
   automatically from <X11/Xproto.h>, so application and extension
   code should never need to reference this file directly.

   <X11/X10.h>

   This file declares all the functions, types, and symbols used
   for the X10 compatibility functions, which are described in
   Appendix D.

Generic Values and Types

   The following symbols are defined by Xlib and used throughout
   the manual:
     * Xlib defines the type Bool and the Boolean values True and
       False.
     * None is the universal null resource ID or atom.
     * The type XID is used for generic resource IDs.
     * The type XPointer is defined to be char * and is used as a
       generic opaque pointer to data.

Naming and Argument Conventions within Xlib

   Xlib follows a number of conventions for the naming and syntax
   of the functions. Given that you remember what information the
   function requires, these conventions are intended to make the
   syntax of the functions more predictable.

   The major naming conventions are:
     * To differentiate the X symbols from the other symbols, the
       library uses mixed case for external symbols. It leaves
       lowercase for variables and all uppercase for user macros,
       as per existing convention.
     * All Xlib functions begin with a capital X.
     * The beginnings of all function names and symbols are
       capitalized.
     * All user-visible data structures begin with a capital X.
       More generally, anything that a user might dereference
       begins with a capital X.
     * Macros and other symbols do not begin with a capital X. To
       distinguish them from all user symbols, each word in the
       macro is capitalized.
     * All elements of or variables in a data structure are in
       lowercase. Compound words, where needed, are constructed
       with underscores (_).
     * The display argument, where used, is always first in the
       argument list.
     * All resource objects, where used, occur at the beginning of
       the argument list immediately after the display argument.
     * When a graphics context is present together with another
       type of resource (most commonly, a drawable), the graphics
       context occurs in the argument list after the other
       resource. Drawables outrank all other resources.
     * Source arguments always precede the destination arguments
       in the argument list.
     * The x argument always precedes the y argument in the
       argument list.
     * The width argument always precedes the height argument in
       the argument list.
     * Where the x, y, width, and height arguments are used
       together, the x and y arguments always precede the width
       and height arguments.
     * Where a mask is accompanied with a structure, the mask
       always precedes the pointer to the structure in the
       argument list.

Programming Considerations

   The major programming considerations are:
     * Coordinates and sizes in X are actually 16-bit quantities.
       This decision was made to minimize the bandwidth required
       for a given level of performance. Coordinates usually are
       declared as an int in the interface. Values larger than 16
       bits are truncated silently. Sizes (width and height) are
       declared as unsigned quantities.
     * Keyboards are the greatest variable between different
       manufacturers' workstations. If you want your program to be
       portable, you should be particularly conservative here.
     * Many display systems have limited amounts of off-screen
       memory. If you can, you should minimize use of pixmaps and
       backing store.
     * The user should have control of their screen real estate.
       Therefore, you should write your applications to react to
       window management rather than presume control of the entire
       screen. What you do inside of your top-level window,
       however, is up to your application. For further
       information, see chapter 14 and the Inter-Client
       Communication Conventions Manual.

Character Sets and Encodings

   Some of the Xlib functions make reference to specific character
   sets and character encodings. The following are the most
   common:

   X Portable Character Set

   A basic set of 97 characters, which are assumed to exist in all
   locales supported by Xlib. This set contains the following
   characters:

   a..z A..Z 0..9 !"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~ <space>, <tab>
   , and <newline>

   This set is the left/lower half of the graphic character set of
   ISO8859-1 plus space, tab, and newline. It is also the set of
   graphic characters in 7-bit ASCII plus the same three control
   characters. The actual encoding of these characters on the host
   is system dependent.

   Host Portable Character Encoding

   The encoding of the X Portable Character Set on the host. The
   encoding itself is not defined by this standard, but the
   encoding must be the same in all locales supported by Xlib on
   the host. If a string is said to be in the Host Portable
   Character Encoding, then it only contains characters from the X
   Portable Character Set, in the host encoding.

   Latin-1

   The coded character set defined by the ISO8859-1 standard.

   Latin Portable Character Encoding

   The encoding of the X Portable Character Set using the Latin-1
   codepoints plus ASCII control characters. If a string is said
   to be in the Latin Portable Character Encoding, then it only
   contains characters from the X Portable Character Set, not all
   of Latin-1.

   STRING Encoding

   Latin-1, plus tab and newline.

   POSIX Portable Filename Character Set

   The set of 65 characters, which can be used in naming files on
   a POSIX-compliant host, that are correctly processed in all
   locales. The set is:

   a..z A..Z 0..9 ._-

Formatting Conventions

   Xlib - C Language X Interface uses the following conventions:
     * Global symbols are printed in this special font. These can
       be either function names, symbols defined in include files,
       or structure names. When declared and defined, function
       arguments are printed in italics. In the explanatory text
       that follows, they usually are printed in regular type.
     * Each function is introduced by a general discussion that
       distinguishes it from other functions. The function
       declaration itself follows, and each argument is
       specifically explained. Although ANSI C function prototype
       syntax is not used, Xlib header files normally declare
       functions using function prototypes in ANSI C environments.
       General discussion of the function, if any is required,
       follows the arguments. Where applicable, the last paragraph
       of the explanation lists the possible Xlib error codes that
       the function can generate. For a complete discussion of the
       Xlib error codes, see section 11.8.2.
     * To eliminate any ambiguity between those arguments that you
       pass and those that a function returns to you, the
       explanations for all arguments that you pass start with the
       word specifies or, in the case of multiple arguments, the
       word specify. The explanations for all arguments that are
       returned to you start with the word returns or, in the case
       of multiple arguments, the word return. The explanations
       for all arguments that you can pass and are returned start
       with the words specifies and returns.
     * Any pointer to a structure that is used to return a value
       is designated as such by the _return suffix as part of its
       name. All other pointers passed to these functions are used
       for reading only. A few arguments use pointers to
       structures that are used for both input and output and are
       indicated by using the _in_out suffix.

Chapter 2. Display Functions

   Table of Contents

   Opening the Display
   Obtaining Information about the Display, Image Formats, or
          Screens

        Display Macros
        Image Format Functions and Macros
        Screen Information Macros

   Generating a NoOperation Protocol Request
   Freeing Client-Created Data
   Closing the Display
   Using X Server Connection Close Operations
   Using Xlib with Threads
   Using Internal Connections

   Before your program can use a display, you must establish a
   connection to the X server. Once you have established a
   connection, you then can use the Xlib macros and functions
   discussed in this chapter to return information about the
   display. This chapter discusses how to:
     * Open (connect to) the display
     * Obtain information about the display, image formats, or
       screens
     * Generate a NoOperation protocol request
     * Free client-created data
     * Close (disconnect from) a display
     * Use X Server connection close operations
     * Use Xlib with threads
     * Use internal connections

Opening the Display

   To open a connection to the X server that controls a display,
   use XOpenDisplay.

   Display *XOpenDisplay(char *display_name);

   display_name

   Specifies the hardware display name, which determines the
   display and communications domain to be used. On a
   POSIX-conformant system, if the display_name is NULL, it
   defaults to the value of the DISPLAY environment variable.

   The encoding and interpretation of the display name are
   implementation-dependent. Strings in the Host Portable
   Character Encoding are supported; support for other characters
   is implementation-dependent. On POSIX-conformant systems, the
   display name or DISPLAY environment variable can be a string in
   the format:


        protocol/hostname:number.screen_number

   protocol

   Specifies a protocol family or an alias for a protocol family.
   Supported protocol families are implementation dependent. The
   protocol entry is optional. If protocol is not specified, the /
   separating protocol and hostname must also not be specified.

   hostname

   Specifies the name of the host machine on which the display is
   physically attached. You follow the hostname with either a
   single colon (:) or a double colon (::).

   number

   Specifies the number of the display server on that host
   machine. You may optionally follow this display number with a
   period (.). A single CPU can have more than one display.
   Multiple displays are usually numbered starting with zero.

   screen_number

   Specifies the screen to be used on that server. Multiple
   screens can be controlled by a single X server. The
   screen_number sets an internal variable that can be accessed by
   using the DefaultScreen macro or the XDefaultScreen function if
   you are using languages other than C (see section 2.2.1).

   For example, the following would specify screen 1 of display 0
   on the machine named ``dual-headed'':

dual-headed:0.1

   The XOpenDisplay function returns a Display structure that
   serves as the connection to the X server and that contains all
   the information about that X server. XOpenDisplay connects your
   application to the X server through TCP or DECnet
   communications protocols, or through some local inter-process
   communication protocol. If the protocol is specified as "tcp",
   "inet", or "inet6", or if no protocol is specified and the
   hostname is a host machine name and a single colon (:)
   separates the hostname and display number, XOpenDisplay
   connects using TCP streams. (If the protocol is specified as
   "inet", TCP over IPv4 is used. If the protocol is specified as
   "inet6", TCP over IPv6 is used. Otherwise, the implementation
   determines which IP version is used.) If the hostname and
   protocol are both not specified, Xlib uses whatever it believes
   is the fastest transport. If the hostname is a host machine
   name and a double colon (::) separates the hostname and display
   number, XOpenDisplay connects using DECnet. A single X server
   can support any or all of these transport mechanisms
   simultaneously. A particular Xlib implementation can support
   many more of these transport mechanisms.

   If successful, XOpenDisplay returns a pointer to a Display
   structure, which is defined in <X11/Xlib.h>. If XOpenDisplay
   does not succeed, it returns NULL. After a successful call to
   XOpenDisplay, all of the screens in the display can be used by
   the client. The screen number specified in the display_name
   argument is returned by the DefaultScreen macro (or the
   XDefaultScreen function). You can access elements of the
   Display and Screen structures only by using the information
   macros or functions. For information about using macros and
   functions to obtain information from the Display structure, see
   section 2.2.1.

   X servers may implement various types of access control
   mechanisms (see section 9.8).

Obtaining Information about the Display, Image Formats, or Screens

   The Xlib library provides a number of useful macros and
   corresponding functions that return data from the Display
   structure. The macros are used for C programming, and their
   corresponding function equivalents are for other language
   bindings. This section discusses the:
     * Display macros
     * Image format functions and macros
     * Screen information macros

   All other members of the Display structure (that is, those for
   which no macros are defined) are private to Xlib and must not
   be used. Applications must never directly modify or inspect
   these private members of the Display structure. The
   XDisplayWidth, XDisplayHeight, XDisplayCells, XDisplayPlanes,
   XDisplayWidthMM, and XDisplayHeightMM functions in the next
   sections are misnamed. These functions really should be named
   Screenwhatever and XScreenwhatever, not Displaywhatever or
   XDisplaywhatever. Our apologies for the resulting confusion.

Display Macros

   Applications should not directly modify any part of the Display
   and Screen structures. The members should be considered
   read-only, although they may change as the result of other
   operations on the display.

   The following lists the C language macros, their corresponding
   function equivalents that are for other language bindings, and
   what data both can return.
AllPlanes

   unsigned long XAllPlanes(void);

   Both return a value with all bits set to 1 suitable for use in
   a plane argument to a procedure.

   Both BlackPixel and WhitePixel can be used in implementing a
   monochrome application. These pixel values are for permanently
   allocated entries in the default colormap. The actual RGB (red,
   green, and blue) values are settable on some screens and, in
   any case, may not actually be black or white. The names are
   intended to convey the expected relative intensity of the
   colors.

   BlackPixel(display, screen_number);

   unsigned long XBlackPixel(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the black pixel value for the specified screen.

   WhitePixel(display, screen_number);

   unsigned long XWhitePixel(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the white pixel value for the specified screen.

   ConnectionNumber(display);

   int XConnectionNumber(Display *display);

   display

   Specifies the connection to the X server.

   Both return a connection number for the specified display. On a
   POSIX-conformant system, this is the file descriptor of the
   connection.

   DefaultColormap(display, screen_number);

   Colormap XDefaultColormap(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the default colormap ID for allocation on the
   specified screen. Most routine allocations of color should be
   made out of this colormap.

   DefaultDepth(display, screen_number);

   int XDefaultDepth(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the depth (number of planes) of the default root
   window for the specified screen. Other depths may also be
   supported on this screen (see XMatchVisualInfo).

   To determine the number of depths that are available on a given
   screen, use XListDepths.

   int *XListDepths(Display *display, int screen_number, int
   *count_return);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   count_return

   Returns the number of depths.

   The XListDepths function returns the array of depths that are
   available on the specified screen. If the specified
   screen_number is valid and sufficient memory for the array can
   be allocated, XListDepths sets count_return to the number of
   available depths. Otherwise, it does not set count_return and
   returns NULL. To release the memory allocated for the array of
   depths, use XFree.

   DefaultGC(display, screen_number);

   GC XDefaultGC(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the default graphics context for the root window of
   the specified screen. This GC is created for the convenience of
   simple applications and contains the default GC components with
   the foreground and background pixel values initialized to the
   black and white pixels for the screen, respectively. You can
   modify its contents freely because it is not used in any Xlib
   function. This GC should never be freed.

   DefaultRootWindow(display);

   Window XDefaultRootWindow(Display *display);

   display

   Specifies the connection to the X server.

   Both return the root window for the default screen.

   DefaultScreenOfDisplay(display);

   Screen *XDefaultScreenOfDisplay(Display *display);

   display

   Specifies the connection to the X server.

   Both return a pointer to the default screen.

   ScreenOfDisplay(display, screen_number);

   Screen *XScreenOfDisplay(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return a pointer to the indicated screen.

   DefaultScreen(display);

   int XDefaultScreen(Display *display);

   display

   Specifies the connection to the X server.

   Both return the default screen number referenced by the
   XOpenDisplay function. This macro or function should be used to
   retrieve the screen number in applications that will use only a
   single screen.

   DefaultVisual(display, screen_number);

   Visual *XDefaultVisual(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the default visual type for the specified screen.
   For further information about visual types, see section 3.1.

   DisplayCells(display, screen_number);

   int XDisplayCells(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the number of entries in the default colormap.

   DisplayPlanes(display, screen_number);

   int XDisplayPlanes(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the depth of the root window of the specified
   screen. For an explanation of depth, see the glossary.

   DisplayString(display);

   char *XDisplayString(Display *display);

   display

   Specifies the connection to the X server.

   Both return the string that was passed to XOpenDisplay when the
   current display was opened. On POSIX-conformant systems, if the
   passed string was NULL, these return the value of the DISPLAY
   environment variable when the current display was opened. These
   are useful to applications that invoke the fork system call and
   want to open a new connection to the same display from the
   child process as well as for printing error messages.

   long XExtendedMaxRequestSize(Display *display);

   display

   Specifies the connection to the X server.

   The XExtendedMaxRequestSize function returns zero if the
   specified display does not support an extended-length protocol
   encoding; otherwise, it returns the maximum request size (in
   4-byte units) supported by the server using the extended-length
   encoding. The Xlib functions XDrawLines, XDrawArcs,
   XFillPolygon, XChangeProperty, XSetClipRectangles, and
   XSetRegion will use the extended-length encoding as necessary,
   if supported by the server. Use of the extended-length encoding
   in other Xlib functions (for example, XDrawPoints,
   XDrawRectangles, XDrawSegments, XFillArcs, XFillRectangles,
   XPutImage) is permitted but not required; an Xlib
   implementation may choose to split the data across multiple
   smaller requests instead.

   long XMaxRequestSize(Display *display);

   display

   Specifies the connection to the X server.

   The XMaxRequestSize function returns the maximum request size
   (in 4-byte units) supported by the server without using an
   extended-length protocol encoding. Single protocol requests to
   the server can be no larger than this size unless an
   extended-length protocol encoding is supported by the server.
   The protocol guarantees the size to be no smaller than 4096
   units (16384 bytes). Xlib automatically breaks data up into
   multiple protocol requests as necessary for the following
   functions: XDrawPoints, XDrawRectangles, XDrawSegments,
   XFillArcs, XFillRectangles, and XPutImage.

   LastKnownRequestProcessed(display);

   unsigned long XLastKnownRequestProcessed(Display *display);

   display

   Specifies the connection to the X server.

   Both extract the full serial number of the last request known
   by Xlib to have been processed by the X server. Xlib
   automatically sets this number when replies, events, and errors
   are received.

   NextRequest(display);

   unsigned long XNextRequest(Display *display);

   display

   Specifies the connection to the X server.

   Both extract the full serial number that is to be used for the
   next request. Serial numbers are maintained separately for each
   display connection.

   ProtocolVersion(display);

   int XProtocolVersion(Display *display);

   display

   Specifies the connection to the X server.

   Both return the major version number (11) of the X protocol
   associated with the connected display.

   ProtocolRevision(display);

   int XProtocolRevision(Display *display);

   display

   Specifies the connection to the X server.

   Both return the minor protocol revision number of the X server.

   QLength(display);

   int XQLength(Display *display);

   display

   Specifies the connection to the X server.

   Both return the length of the event queue for the connected
   display. Note that there may be more events that have not been
   read into the queue yet (see XEventsQueued).

   RootWindow(display, screen_number);

   Window XRootWindow(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the root window. These are useful with functions
   that need a drawable of a particular screen and for creating
   top-level windows.

   ScreenCount(display);

   int XScreenCount(Display *display);

   display

   Specifies the connection to the X server.

   Both return the number of available screens.

   ServerVendor(display);

   char *XServerVendor(Display *display);

   display

   Specifies the connection to the X server.

   Both return a pointer to a null-terminated string that provides
   some identification of the owner of the X server
   implementation. If the data returned by the server is in the
   Latin Portable Character Encoding, then the string is in the
   Host Portable Character Encoding. Otherwise, the contents of
   the string are implementation-dependent.

   VendorRelease(display);

   int XVendorRelease(Display *display);

   display

   Specifies the connection to the X server.

   Both return a number related to a vendor's release of the X
   server.

Image Format Functions and Macros

   Applications are required to present data to the X server in a
   format that the server demands. To help simplify applications,
   most of the work required to convert the data is provided by
   Xlib (see sections 8.7 and 16.8).

   The XPixmapFormatValues structure provides an interface to the
   pixmap format information that is returned at the time of a
   connection setup. It contains:
typedef struct {
        int depth;
        int bits_per_pixel;
        int scanline_pad;
} XPixmapFormatValues;

   To obtain the pixmap format information for a given display,
   use XListPixmapFormats.

   XPixmapFormatValues *XListPixmapFormats(Display *display, int
   *count_return);

   display

   Specifies the connection to the X server.

   count_return

   Returns the number of pixmap formats that are supported by the
   display.

   The XListPixmapFormats function returns an array of
   XPixmapFormatValues structures that describe the types of Z
   format images supported by the specified display. If
   insufficient memory is available, XListPixmapFormats returns
   NULL. To free the allocated storage for the XPixmapFormatValues
   structures, use XFree.

   The following lists the C language macros, their corresponding
   function equivalents that are for other language bindings, and
   what data they both return for the specified server and screen.
   These are often used by toolkits as well as by simple
   applications.

   ImageByteOrder(display);

   int XImageByteOrder(Display *display);

   display

   Specifies the connection to the X server.

   Both specify the required byte order for images for each
   scanline unit in XY format (bitmap) or for each pixel value in
   Z format. The macro or function can return either LSBFirst or
   MSBFirst.

   XBitmapUnit(display);

   int XBitmapUnit(Display *display);

   display

   Specifies the connection to the X server.

   Both return the size of a bitmap's scanline unit in bits. The
   scanline is calculated in multiples of this value.

   BitmapBitOrder(display);

   int XBitmapBitOrder(Display *display);

   display

   Specifies the connection to the X server.

   Within each bitmap unit, the left-most bit in the bitmap as
   displayed on the screen is either the least significant or most
   significant bit in the unit. This macro or function can return
   LSBFirst or MSBFirst.

   BitmapPad(display);

   int XBitmapPad(Display *display);

   display

   Specifies the connection to the X server.

   Each scanline must be padded to a multiple of bits returned by
   this macro or function.

   DisplayHeight(display, screen_number);

   int XDisplayHeight(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return an integer that describes the height of the screen
   in pixels.

   DisplayHeightMM(display, screen_number);

   int XDisplayHeightMM(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the height of the specified screen in millimeters.

   DisplayWidth(display, screen_number);

   int XDisplayWidth(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the width of the screen in pixels.

   DisplayWidthMM(display, screen_number);

   int XDisplayWidthMM(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   Both return the width of the specified screen in millimeters.

Screen Information Macros

   The following lists the C language macros, their corresponding
   function equivalents that are for other language bindings, and
   what data they both can return. These macros or functions all
   take a pointer to the appropriate screen structure.

   BlackPixelOfScreen(screen);

   unsigned long XBlackPixelOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the black pixel value of the specified screen.

   XWhitePixelOfScreen(screen);

   unsigned long XWhitePixelOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the white pixel value of the specified screen.

   CellsOfScreen(screen);

   int XCellsOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the number of colormap cells in the default
   colormap of the specified screen.

   DefaultColormapOfScreen(screen);

   Colormap XDefaultColormapOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the default colormap of the specified screen.

   DefaultDepthOfScreen(screen);

   int XDefaultDepthOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the depth of the root window.

   DefaultGCOfScreen(screen);

   GC XDefaultGCOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return a default graphics context (GC) of the specified
   screen, which has the same depth as the root window of the
   screen. The GC must never be freed.

   XDefaultVisualOfScreen(screen);

   Visual *XDefaultVisualOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the default visual of the specified screen. For
   information on visual types, see section 3.1.

   DoesBackingStore(screen);

   int XDoesBackingStore(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return a value indicating whether the screen supports
   backing stores. The value returned can be one of WhenMapped,
   NotUseful, or Always (see section 3.2.4).

   DoesSaveUnders(screen);

   Bool XDoesSaveUnders(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return a Boolean value indicating whether the screen
   supports save unders. If True, the screen supports save unders.
   If False, the screen does not support save unders (see section
   3.2.5).

   DisplayOfScreen(screen);

   Display *XDisplayOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the display of the specified screen.

   ScreenNumberOfScreen(screen);

   long XScreenNumberOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   The XScreenNumberOfScreen function returns the screen index
   number of the specified screen.

   EventMaskOfScreen(screen);

   long XEventMaskOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the event mask of the root window for the specified
   screen at connection setup time.

   WidthOfScreen(screen);

   int XWidthOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the width of the specified screen in pixels.

   HeightOfScreen(screen);

   int XHeightOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the height of the specified screen in pixels.

   WidthMMOfScreen(screen);

   int XWidthMMOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the width of the specified screen in millimeters.

   HeightMMOfScreen(screen);

   int XHeightMMOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the height of the specified screen in millimeters.

   MaxCmapsOfScreen(screen);

   int XMaxCmapsOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the maximum number of installed colormaps supported
   by the specified screen (see section 9.3).

   MinCmapsOfScreen(screen);

   int XMinCmapsOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the minimum number of installed colormaps supported
   by the specified screen (see section 9.3).

   PlanesOfScreen(screen);

   int XPlanesOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the depth of the root window.

   RootWindowOfScreen(screen);

   Window XRootWindowOfScreen(Screen *screen);

   screen

   Specifies the appropriate Screen structure.

   Both return the root window of the specified screen.

Generating a NoOperation Protocol Request

   To execute a NoOperation protocol request, use XNoOp.

   XNoOp(Display *display);

   display

   Specifies the connection to the X server.

   The XNoOp function sends a NoOperation protocol request to the
   X server, thereby exercising the connection.

Freeing Client-Created Data

   To free in-memory data that was created by an Xlib function,
   use XFree.

   XFree(void *data);

   data

   Specifies the data that is to be freed.

   The XFree function is a general-purpose Xlib routine that frees
   the specified data. You must use it to free any objects that
   were allocated by Xlib, unless an alternate function is
   explicitly specified for the object. A NULL pointer cannot be
   passed to this function.

Closing the Display

   To close a display or disconnect from the X server, use
   XCloseDisplay.

   XCloseDisplay(Display *display);

   display

   Specifies the connection to the X server.

   The XCloseDisplay function closes the connection to the X
   server for the display specified in the Display structure and
   destroys all windows, resource IDs (Window, Font, Pixmap,
   Colormap, Cursor, and GContext), or other resources that the
   client has created on this display, unless the close-down mode
   of the client has been changed (see XSetCloseDownMode).
   Therefore, these windows, resource IDs, and other resources
   should never be referenced again or an error will be generated.
   Before exiting, you should call XCloseDisplay explicitly so
   that any pending errors are reported as XCloseDisplay performs
   a final XSync operation.

   XCloseDisplay can generate a BadGC error.

   Xlib provides a function to permit the resources owned by a
   client to survive after the client's connection is closed. To
   change a client's close-down mode, use XSetCloseDownMode.

   XSetCloseDownMode(Display *display, int close_mode);

   display

   Specifies the connection to the X server.

   close_mode

   Specifies the client close-down mode. You can pass DestroyAll,
   RetainPermanent, or RetainTemporary.

   The XSetCloseDownMode function defines what will happen to the
   client's resources at connection close. A connection starts in
   DestroyAll mode. For information on what happens to the
   client's resources when the close_mode argument is
   RetainPermanent or RetainTemporary, see section 2.6.

   XSetCloseDownMode can generate a BadValue error.

Using X Server Connection Close Operations

   When the X server's connection to a client is closed either by
   an explicit call to XCloseDisplay or by a process that exits,
   the X server performs the following automatic operations:
     * It disowns all selections owned by the client (see
       XSetSelectionOwner).
     * It performs an XUngrabPointer and XUngrabKeyboard if the
       client has actively grabbed the pointer or the keyboard.
     * It performs an XUngrabServer if the client has grabbed the
       server.
     * It releases all passive grabs made by the client.
     * It marks all resources (including colormap entries)
       allocated by the client either as permanent or temporary,
       depending on whether the close-down mode is RetainPermanent
       or RetainTemporary. However, this does not prevent other
       client applications from explicitly destroying the
       resources (see XSetCloseDownMode).

   When the close-down mode is DestroyAll, the X server destroys
   all of a client's resources as follows:
     * It examines each window in the client's save-set to
       determine if it is an inferior (subwindow) of a window
       created by the client. (The save-set is a list of other
       clients' windows that are referred to as save-set windows.)
       If so, the X server reparents the save-set window to the
       closest ancestor so that the save-set window is not an
       inferior of a window created by the client. The reparenting
       leaves unchanged the absolute coordinates (with respect to
       the root window) of the upper-left outer corner of the
       save-set window.
     * It performs a MapWindow request on the save-set window if
       the save-set window is unmapped. The X server does this
       even if the save-set window was not an inferior of a window
       created by the client.
     * It destroys all windows created by the client.
     * It performs the appropriate free request on each nonwindow
       resource created by the client in the server (for example,
       Font, Pixmap, Cursor, Colormap, and GContext).
     * It frees all colors and colormap entries allocated by a
       client application.

   Additional processing occurs when the last connection to the X
   server closes. An X server goes through a cycle of having no
   connections and having some connections. When the last
   connection to the X server closes as a result of a connection
   closing with the close_mode of DestroyAll, the X server does
   the following:
     * It resets its state as if it had just been started. The X
       server begins by destroying all lingering resources from
       clients that have terminated in RetainPermanent or
       RetainTemporary mode.
     * It deletes all but the predefined atom identifiers.
     * It deletes all properties on all root windows (see section
       4.3).
     * It resets all device maps and attributes (for example, key
       click, bell volume, and acceleration) as well as the access
       control list.
     * It restores the standard root tiles and cursors.
     * It restores the default font path.
     * It restores the input focus to state PointerRoot.

   However, the X server does not reset if you close a connection
   with a close-down mode set to RetainPermanent or
   RetainTemporary.

Using Xlib with Threads

   On systems that have threads, support may be provided to permit
   multiple threads to use Xlib concurrently.

   To initialize support for concurrent threads, use XInitThreads.

   Status XInitThreads(void);

   The XInitThreads function initializes Xlib support for
   concurrent threads. This function must be the first Xlib
   function a multi-threaded program calls, and it must complete
   before any other Xlib call is made. This function returns a
   nonzero status if initialization was successful; otherwise, it
   returns zero. On systems that do not support threads, this
   function always returns zero.

   It is only necessary to call this function if multiple threads
   might use Xlib concurrently. If all calls to Xlib functions are
   protected by some other access mechanism (for example, a mutual
   exclusion lock in a toolkit or through explicit client
   programming), Xlib thread initialization is not required. It is
   recommended that single-threaded programs not call this
   function.

   To lock a display across several Xlib calls, use XLockDisplay.

   XLockDisplay(Display *display);

   display

   Specifies the connection to the X server.

   The XLockDisplay function locks out all other threads from
   using the specified display. Other threads attempting to use
   the display will block until the display is unlocked by this
   thread. Nested calls to XLockDisplay work correctly; the
   display will not actually be unlocked until XUnlockDisplay has
   been called the same number of times as XLockDisplay. This
   function has no effect unless Xlib was successfully initialized
   for threads using XInitThreads.

   To unlock a display, use XUnlockDisplay.

   XUnlockDisplay(Display *display);

   display

   Specifies the connection to the X server.

   The XUnlockDisplay function allows other threads to use the
   specified display again. Any threads that have blocked on the
   display are allowed to continue. Nested locking works
   correctly; if XLockDisplay has been called multiple times by a
   thread, then XUnlockDisplay must be called an equal number of
   times before the display is actually unlocked. This function
   has no effect unless Xlib was successfully initialized for
   threads using XInitThreads.

Using Internal Connections

   In addition to the connection to the X server, an Xlib
   implementation may require connections to other kinds of
   servers (for example, to input method servers as described in
   chapter 13). Toolkits and clients that use multiple displays,
   or that use displays in combination with other inputs, need to
   obtain these additional connections to correctly block until
   input is available and need to process that input when it is
   available. Simple clients that use a single display and block
   for input in an Xlib event function do not need to use these
   facilities.

   To track internal connections for a display, use
   XAddConnectionWatch.

   typedef void (*XConnectionWatchProc)(Display *display, XPointer
   client_data, int fd, Bool opening, XPointer *watch_data);

   Status XAddConnectionWatch(Display *display,
   XConnectionWatchProc procedure, XPointer client_data);

   display

   Specifies the connection to the X server.

   procedure

   Specifies the procedure to be called.

   client_data

   Specifies the additional client data.

   The XAddConnectionWatch function registers a procedure to be
   called each time Xlib opens or closes an internal connection
   for the specified display. The procedure is passed the display,
   the specified client_data, the file descriptor for the
   connection, a Boolean indicating whether the connection is
   being opened or closed, and a pointer to a location for private
   watch data. If opening is True, the procedure can store a
   pointer to private data in the location pointed to by
   watch_data; when the procedure is later called for this same
   connection and opening is False, the location pointed to by
   watch_data will hold this same private data pointer.

   This function can be called at any time after a display is
   opened. If internal connections already exist, the registered
   procedure will immediately be called for each of them, before
   XAddConnectionWatch returns. XAddConnectionWatch returns a
   nonzero status if the procedure is successfully registered;
   otherwise, it returns zero.

   The registered procedure should not call any Xlib functions. If
   the procedure directly or indirectly causes the state of
   internal connections or watch procedures to change, the result
   is not defined. If Xlib has been initialized for threads, the
   procedure is called with the display locked and the result of a
   call by the procedure to any Xlib function that locks the
   display is not defined unless the executing thread has
   externally locked the display using XLockDisplay.

   To stop tracking internal connections for a display, use
   XRemoveConnectionWatch.

   Status XRemoveConnectionWatch(Display *display,
   XConnectionWatchProc procedure, XPointer client_data);

   display

   Specifies the connection to the X server.

   procedure

   Specifies the procedure to be called.

   client_data

   Specifies the additional client data.

   The XRemoveConnectionWatch function removes a previously
   registered connection watch procedure. The client_data must
   match the client_data used when the procedure was initially
   registered.

   To process input on an internal connection, use
   XProcessInternalConnection.

   void XProcessInternalConnection(Display *display, int fd);

   display

   Specifies the connection to the X server.

   fd

   Specifies the file descriptor.

   The XProcessInternalConnection function processes input
   available on an internal connection. This function should be
   called for an internal connection only after an operating
   system facility (for example, select or poll) has indicated
   that input is available; otherwise, the effect is not defined.

   To obtain all of the current internal connections for a
   display, use XInternalConnectionNumbers.

   Status XInternalConnectionNumbers(Display *display, int ** fd,
   int * count_return);

   display

   Specifies the connection to the X server.

   fd_return

   Returns the file descriptors.

   count_return

   Returns the number of file descriptors.

   The XInternalConnectionNumbers function returns a list of the
   file descriptors for all internal connections currently open
   for the specified display. When the allocated list is no longer
   needed, free it by using XFree. This functions returns a
   nonzero status if the list is successfully allocated;
   otherwise, it returns zero.

Chapter 3. Window Functions

   Table of Contents

   Visual Types
   Window Attributes

        Background Attribute
        Border Attribute
        Gravity Attributes
        Backing Store Attribute
        Save Under Flag
        Backing Planes and Backing Pixel Attributes
        Event Mask and Do Not Propagate Mask Attributes
        Override Redirect Flag
        Colormap Attribute
        Cursor Attribute

   Creating Windows
   Destroying Windows
   Mapping Windows
   Unmapping Windows
   Configuring Windows
   Changing Window Stacking Order
   Changing Window Attributes

Visual Types

   On some display hardware, it may be possible to deal with color
   resources in more than one way. For example, you may be able to
   deal with a screen of either 12-bit depth with arbitrary
   mapping of pixel to color (pseudo-color) or 24-bit depth with 8
   bits of the pixel dedicated to each of red, green, and blue.
   These different ways of dealing with the visual aspects of the
   screen are called visuals. For each screen of the display,
   there may be a list of valid visual types supported at
   different depths of the screen. Because default windows and
   visual types are defined for each screen, most simple
   applications need not deal with this complexity. Xlib provides
   macros and functions that return the default root window, the
   default depth of the default root window, and the default
   visual type (see sections 2.2.1 and 16.7).

   Xlib uses an opaque Visual structure that contains information
   about the possible color mapping. The visual utility functions
   (see section 16.7) use an XVisualInfo structure to return this
   information to an application. The members of this structure
   pertinent to this discussion are class, red_mask, green_mask,
   blue_mask, bits_per_rgb, and colormap_size. The class member
   specifies one of the possible visual classes of the screen and
   can be StaticGray, StaticColor, TrueColor, GrayScale,
   PseudoColor, or DirectColor.

   The following concepts may serve to make the explanation of
   visual types clearer. The screen can be color or grayscale, can
   have a colormap that is writable or read-only, and can also
   have a colormap whose indices are decomposed into separate RGB
   pieces, provided one is not on a grayscale screen. This leads
   to the following diagram:
                      Color        Gray-Scale
                   R/O    R/W      R/O   R/W
----------------------------------------------
 Undecomposed    Static  Pseudo   Static  Gray
   Colormap      Color   Color    Gray    Scale

 Decomposed       True   Direct
   Colormap       Color  Color
----------------------------------------------

   Conceptually, as each pixel is read out of video memory for
   display on the screen, it goes through a look-up stage by
   indexing into a colormap. Colormaps can be manipulated
   arbitrarily on some hardware, in limited ways on other
   hardware, and not at all on other hardware. The visual types
   affect the colormap and the RGB values in the following ways:

     * For PseudoColor, a pixel value indexes a colormap to
       produce independent RGB values, and the RGB values can be
       changed dynamically.
     * GrayScale is treated the same way as PseudoColor except
       that the primary that drives the screen is undefined. Thus,
       the client should always store the same value for red,
       green, and blue in the colormaps.
     * For DirectColor, a pixel value is decomposed into separate
       RGB subfields, and each subfield separately indexes the
       colormap for the corresponding value. The RGB values can be
       changed dynamically.
     * TrueColor is treated the same way as DirectColor except
       that the colormap has predefined, read-only RGB values.
       These RGB values are server dependent but provide linear or
       near-linear ramps in each primary.
     * StaticColor is treated the same way as PseudoColor except
       that the colormap has predefined, read-only,
       server-dependent RGB values.
     * StaticGray is treated the same way as StaticColor except
       that the RGB values are equal for any single pixel value,
       thus resulting in shades of gray. StaticGray with a
       two-entry colormap can be thought of as monochrome.

   The red_mask, green_mask, and blue_mask members are only
   defined for DirectColor and TrueColor. Each has one contiguous
   set of bits with no intersections. The bits_per_rgb member
   specifies the log base 2 of the number of distinct color values
   (individually) of red, green, and blue. Actual RGB values are
   unsigned 16-bit numbers. The colormap_size member defines the
   number of available colormap entries in a newly created
   colormap. For DirectColor and TrueColor, this is the size of an
   individual pixel subfield.

   To obtain the visual ID from a Visual, use XVisualIDFromVisual.

   VisualID XVisualIDFromVisual(Visual *visual);

   visual

   Specifies the visual type.

   The XVisualIDFromVisual function returns the visual ID for the
   specified visual type.

Window Attributes

   All InputOutput windows have a border width of zero or more
   pixels, an optional background, an event suppression mask
   (which suppresses propagation of events from children), and a
   property list (see section 4.3). The window border and
   background can be a solid color or a pattern, called a tile.
   All windows except the root have a parent and are clipped by
   their parent. If a window is stacked on top of another window,
   it obscures that other window for the purpose of input. If a
   window has a background (almost all do), it obscures the other
   window for purposes of output. Attempts to output to the
   obscured area do nothing, and no input events (for example,
   pointer motion) are generated for the obscured area.

   Windows also have associated property lists (see section 4.3).

   Both InputOutput and InputOnly windows have the following
   common attributes, which are the only attributes of an
   InputOnly window:
     * win-gravity
     * event-mask
     * do-not-propagate-mask
     * override-redirect
     * cursor

   If you specify any other attributes for an InputOnly window, a
   BadMatch error results.

   InputOnly windows are used for controlling input events in
   situations where InputOutput windows are unnecessary. InputOnly
   windows are invisible; can only be used to control such things
   as cursors, input event generation, and grabbing; and cannot be
   used in any graphics requests. Note that InputOnly windows
   cannot have InputOutput windows as inferiors.

   Windows have borders of a programmable width and pattern as
   well as a background pattern or tile. Pixel values can be used
   for solid colors. The background and border pixmaps can be
   destroyed immediately after creating the window if no further
   explicit references to them are to be made. The pattern can
   either be relative to the parent or absolute. If
   ParentRelative, the parent's background is used.

   When windows are first created, they are not visible (not
   mapped) on the screen. Any output to a window that is not
   visible on the screen and that does not have backing store will
   be discarded. An application may wish to create a window long
   before it is mapped to the screen. When a window is eventually
   mapped to the screen (using XMapWindow), the X server generates
   an Expose event for the window if backing store has not been
   maintained.

   A window manager can override your choice of size, border
   width, and position for a top-level window. Your program must
   be prepared to use the actual size and position of the top
   window. It is not acceptable for a client application to resize
   itself unless in direct response to a human command to do so.
   Instead, either your program should use the space given to it,
   or if the space is too small for any useful work, your program
   might ask the user to resize the window. The border of your
   top-level window is considered fair game for window managers.

   To set an attribute of a window, set the appropriate member of
   the XSetWindowAttributes structure and OR in the corresponding
   value bitmask in your subsequent calls to XCreateWindow and
   XChangeWindowAttributes, or use one of the other convenience
   functions that set the appropriate attribute. The symbols for
   the value mask bits and the XSetWindowAttributes structure are:

   /* Window attribute value mask bits */
/* Window attribute value mask bits */
#define    CWBackPixmap                    (1L<<0)
#define    CWBackPixel                     (1L<<1)
#define    CWBorderPixmap                  (1L<<2)
#define    CWBorderPixel                   (1L<<3)
#define    CWBitGravity                    (1L<<4)
#define    CWWinGravity                    (1L<<5)
#define    CWBackingStore                  (1L<<6)
#define    CWBackingPlanes                 (1L<<7)
#define    CWBackingPixel                  (1L<<8)
#define    CWOverrideRedirect              (1L<<9)
#define    CWSaveUnder                     (1L<<10)
#define    CWEventMask                     (1L<<11)
#define    CWDontPropagate                 (1L<<12)
#define    CWColormap                      (1L<<13)
#define    CWCursor                        (1L<<14)



/* Values */

typedef struct {
     Pixmap background_pixmap;     /* background, None, or ParentRelativ
e */
     unsigned long background_pixel;     /* background pixel */
     Pixmap border_pixmap;          /* border of the window or CopyFromP
arent */
     unsigned long border_pixel;     /* border pixel value */
     int bit_gravity;     /* one of bit gravity values */
     int win_gravity;     /* one of the window gravity values */
     int backing_store;     /* NotUseful, WhenMapped, Always */
     unsigned long backing_planes;     /* planes to be preserved if poss
ible */
     unsigned long backing_pixel;     /* value to use in restoring plane
s */
     Bool save_under;     /* should bits under be saved? (popups) */
     long event_mask;     /* set of events that should be saved */
     long do_not_propagate_mask;     /* set of events that should not pr
opagate */
     Bool override_redirect;     /* boolean value for override_redirect
*/
     Colormap colormap;     /* color map to be associated with window */
     Cursor cursor;          /* cursor to be displayed (or None) */
} XSetWindowAttributes;

   The following lists the defaults for each window attribute and
   indicates whether the attribute is applicable to InputOutput
   and InputOnly windows:
   Attribute             Default          InputOutput InputOnly
   background-pixmap     None             Yes         No
   background-pixel      Undefined        Yes         No
   border-pixmap         CopyFromParent   Yes         No
   border-pixel          Undefined        Yes         No
   bit-gravity           ForgetGravity    Yes         No
   win-gravity           NorthWestGravity Yes         Yes
   backing-store         NotUseful        Yes         No
   backing-planes        All ones         Yes         No
   backing-pixel         zero             Yes         No
   save-under            False            Yes         No
   event-mask            empty set        Yes         Yes
   do-not-propagate-mask empty set        Yes         Yes
   override-redirect     False            Yes         Yes
   colormap              CopyFromParent   Yes         No
   cursor                None             Yes         Yes

Background Attribute

   Only InputOutput windows can have a background. You can set the
   background of an InputOutput window by using a pixel or a
   pixmap.

   The background-pixmap attribute of a window specifies the
   pixmap to be used for a window's background. This pixmap can be
   of any size, although some sizes may be faster than others. The
   background-pixel attribute of a window specifies a pixel value
   used to paint a window's background in a single color.

   You can set the background-pixmap to a pixmap, None (default),
   or ParentRelative. You can set the background-pixel of a window
   to any pixel value (no default). If you specify a
   background-pixel, it overrides either the default
   background-pixmap or any value you may have set in the
   background-pixmap. A pixmap of an undefined size that is filled
   with the background-pixel is used for the background. Range
   checking is not performed on the background pixel; it simply is
   truncated to the appropriate number of bits.

   If you set the background-pixmap, it overrides the default. The
   background-pixmap and the window must have the same depth, or a
   BadMatch error results. If you set background-pixmap to None,
   the window has no defined background. If you set the
   background-pixmap to ParentRelative:
     * The parent window's background-pixmap is used. The child
       window, however, must have the same depth as its parent, or
       a BadMatch error results.
     * If the parent window has a background-pixmap of None, the
       window also has a background-pixmap of None.
     * A copy of the parent window's background-pixmap is not
       made. The parent's background-pixmap is examined each time
       the child window's background-pixmap is required.
     * The background tile origin always aligns with the parent
       window's background tile origin. If the background-pixmap
       is not ParentRelative, the background tile origin is the
       child window's origin.

   Setting a new background, whether by setting background-pixmap
   or background-pixel, overrides any previous background. The
   background-pixmap can be freed immediately if no further
   explicit reference is made to it (the X server will keep a copy
   to use when needed). If you later draw into the pixmap used for
   the background, what happens is undefined because the X
   implementation is free to make a copy of the pixmap or to use
   the same pixmap.

   When no valid contents are available for regions of a window
   and either the regions are visible or the server is maintaining
   backing store, the server automatically tiles the regions with
   the window's background unless the window has a background of
   None. If the background is None, the previous screen contents
   from other windows of the same depth as the window are simply
   left in place as long as the contents come from the parent of
   the window or an inferior of the parent. Otherwise, the initial
   contents of the exposed regions are undefined. Expose events
   are then generated for the regions, even if the
   background-pixmap is None (see section 10.9).

Border Attribute

   Only InputOutput windows can have a border. You can set the
   border of an InputOutput window by using a pixel or a pixmap.

   The border-pixmap attribute of a window specifies the pixmap to
   be used for a window's border. The border-pixel attribute of a
   window specifies a pixmap of undefined size filled with that
   pixel be used for a window's border. Range checking is not
   performed on the background pixel; it simply is truncated to
   the appropriate number of bits. The border tile origin is
   always the same as the background tile origin.

   You can also set the border-pixmap to a pixmap of any size
   (some may be faster than others) or to CopyFromParent
   (default). You can set the border-pixel to any pixel value (no
   default).

   If you set a border-pixmap, it overrides the default. The
   border-pixmap and the window must have the same depth, or a
   BadMatch error results. If you set the border-pixmap to
   CopyFromParent, the parent window's border-pixmap is copied.
   Subsequent changes to the parent window's border attribute do
   not affect the child window. However, the child window must
   have the same depth as the parent window, or a BadMatch error
   results.

   The border-pixmap can be freed immediately if no further
   explicit reference is made to it. If you later draw into the
   pixmap used for the border, what happens is undefined because
   the X implementation is free either to make a copy of the
   pixmap or to use the same pixmap. If you specify a
   border-pixel, it overrides either the default border-pixmap or
   any value you may have set in the border-pixmap. All pixels in
   the window's border will be set to the border-pixel. Setting a
   new border, whether by setting border-pixel or by setting
   border-pixmap, overrides any previous border.

   Output to a window is always clipped to the inside of the
   window. Therefore, graphics operations never affect the window
   border.

Gravity Attributes

   The bit gravity of a window defines which region of the window
   should be retained when an InputOutput window is resized. The
   default value for the bit-gravity attribute is ForgetGravity.
   The window gravity of a window allows you to define how the
   InputOutput or InputOnly window should be repositioned if its
   parent is resized. The default value for the win-gravity
   attribute is NorthWestGravity.

   If the inside width or height of a window is not changed and if
   the window is moved or its border is changed, then the contents
   of the window are not lost but move with the window. Changing
   the inside width or height of the window causes its contents to
   be moved or lost (depending on the bit-gravity of the window)
   and causes children to be reconfigured (depending on their
   win-gravity). For a change of width and height, the (x, y)
   pairs are defined:

   Gravity Direction Coordinates
   NorthWestGravity  (0, 0)
   NorthGravity      (Width/2, 0)
   NorthEastGravity  (Width, 0)
   WestGravity       (0, Height/2)
   CenterGravity     (Width/2, Height/2)
   EastGravity       (Width, Height/2)
   SouthWestGravity  (0, Height)
   SouthGravity      (Width/2, Height)
   SouthEastGravity  (Width, Height)

   When a window with one of these bit-gravity values is resized,
   the corresponding pair defines the change in position of each
   pixel in the window. When a window with one of these
   win-gravities has its parent window resized, the corresponding
   pair defines the change in position of the window within the
   parent. When a window is so repositioned, a GravityNotify event
   is generated (see section 10.10.5).

   A bit-gravity of StaticGravity indicates that the contents or
   origin should not move relative to the origin of the root
   window. If the change in size of the window is coupled with a
   change in position (x, y), then for bit-gravity the change in
   position of each pixel is (-x, -y), and for win-gravity the
   change in position of a child when its parent is so resized is
   (-x, -y). Note that StaticGravity still only takes effect when
   the width or height of the window is changed, not when the
   window is moved.

   A bit-gravity of ForgetGravity indicates that the window's
   contents are always discarded after a size change, even if a
   backing store or save under has been requested. The window is
   tiled with its background and zero or more Expose events are
   generated. If no background is defined, the existing screen
   contents are not altered. Some X servers may also ignore the
   specified bit-gravity and always generate Expose events.

   The contents and borders of inferiors are not affected by their
   parent's bit-gravity. A server is permitted to ignore the
   specified bit-gravity and use Forget instead.

   A win-gravity of UnmapGravity is like NorthWestGravity (the
   window is not moved), except the child is also unmapped when
   the parent is resized, and an UnmapNotify event is generated.

Backing Store Attribute

   Some implementations of the X server may choose to maintain the
   contents of InputOutput windows. If the X server maintains the
   contents of a window, the off-screen saved pixels are known as
   backing store. The backing store advises the X server on what
   to do with the contents of a window. The backing-store
   attribute can be set to NotUseful (default), WhenMapped, or
   Always.

   A backing-store attribute of NotUseful advises the X server
   that maintaining contents is unnecessary, although some X
   implementations may still choose to maintain contents and,
   therefore, not generate Expose events. A backing-store
   attribute of WhenMapped advises the X server that maintaining
   contents of obscured regions when the window is mapped would be
   beneficial. In this case, the server may generate an Expose
   event when the window is created. A backing-store attribute of
   Always advises the X server that maintaining contents even when
   the window is unmapped would be beneficial. Even if the window
   is larger than its parent, this is a request to the X server to
   maintain complete contents, not just the region within the
   parent window boundaries. While the X server maintains the
   window's contents, Expose events normally are not generated,
   but the X server may stop maintaining contents at any time.

   When the contents of obscured regions of a window are being
   maintained, regions obscured by noninferior windows are
   included in the destination of graphics requests (and source,
   when the window is the source). However, regions obscured by
   inferior windows are not included.

Save Under Flag

   Some server implementations may preserve contents of
   InputOutput windows under other InputOutput windows. This is
   not the same as preserving the contents of a window for you.
   You may get better visual appeal if transient windows (for
   example, pop-up menus) request that the system preserve the
   screen contents under them, so the temporarily obscured
   applications do not have to repaint.

   You can set the save-under flag to True or False (default). If
   save-under is True, the X server is advised that, when this
   window is mapped, saving the contents of windows it obscures
   would be beneficial.

Backing Planes and Backing Pixel Attributes

   You can set backing planes to indicate (with bits set to 1)
   which bit planes of an InputOutput window hold dynamic data
   that must be preserved in backing store and during save unders.
   The default value for the backing-planes attribute is all bits
   set to 1. You can set backing pixel to specify what bits to use
   in planes not covered by backing planes. The default value for
   the backing-pixel attribute is all bits set to 0. The X server
   is free to save only the specified bit planes in the backing
   store or the save under and is free to regenerate the remaining
   planes with the specified pixel value. Any extraneous bits in
   these values (that is, those bits beyond the specified depth of
   the window) may be simply ignored. If you request backing store
   or save unders, you should use these members to minimize the
   amount of off-screen memory required to store your window.

Event Mask and Do Not Propagate Mask Attributes

   The event mask defines which events the client is interested in
   for this InputOutput or InputOnly window (or, for some event
   types, inferiors of this window). The event mask is the bitwise
   inclusive OR of zero or more of the valid event mask bits. You
   can specify that no maskable events are reported by setting
   NoEventMask (default).

   The do-not-propagate-mask attribute defines which events should
   not be propagated to ancestor windows when no client has the
   event type selected in this InputOutput or InputOnly window.
   The do-not-propagate-mask is the bitwise inclusive OR of zero
   or more of the following masks: KeyPress, KeyRelease,
   ButtonPress, ButtonRelease, PointerMotion, Button1Motion,
   Button2Motion, Button3Motion, Button4Motion, Button5Motion, and
   ButtonMotion. You can specify that all events are propagated by
   setting NoEventMask (default).

Override Redirect Flag

   To control window placement or to add decoration, a window
   manager often needs to intercept (redirect) any map or
   configure request. Pop-up windows, however, often need to be
   mapped without a window manager getting in the way. To control
   whether an InputOutput or InputOnly window is to ignore these
   structure control facilities, use the override-redirect flag.

   The override-redirect flag specifies whether map and configure
   requests on this window should override a
   SubstructureRedirectMask on the parent. You can set the
   override-redirect flag to True or False (default). Window
   managers use this information to avoid tampering with pop-up
   windows (see also chapter 14).

Colormap Attribute

   The colormap attribute specifies which colormap best reflects
   the true colors of the InputOutput window. The colormap must
   have the same visual type as the window, or a BadMatch error
   results. X servers capable of supporting multiple hardware
   colormaps can use this information, and window managers can use
   it for calls to XInstallColormap. You can set the colormap
   attribute to a colormap or to CopyFromParent (default).

   If you set the colormap to CopyFromParent, the parent window's
   colormap is copied and used by its child. However, the child
   window must have the same visual type as the parent, or a
   BadMatch error results. The parent window must not have a
   colormap of None, or a BadMatch error results. The colormap is
   copied by sharing the colormap object between the child and
   parent, not by making a complete copy of the colormap contents.
   Subsequent changes to the parent window's colormap attribute do
   not affect the child window.

Cursor Attribute

   The cursor attribute specifies which cursor is to be used when
   the pointer is in the InputOutput or InputOnly window. You can
   set the cursor to a cursor or None (default).

   If you set the cursor to None, the parent's cursor is used when
   the pointer is in the InputOutput or InputOnly window, and any
   change in the parent's cursor will cause an immediate change in
   the displayed cursor. By calling XFreeCursor, the cursor can be
   freed immediately as long as no further explicit reference to
   it is made.

Creating Windows

   Xlib provides basic ways for creating windows, and toolkits
   often supply higher-level functions specifically for creating
   and placing top-level windows, which are discussed in the
   appropriate toolkit documentation. If you do not use a toolkit,
   however, you must provide some standard information or hints
   for the window manager by using the Xlib inter-client
   communication functions (see chapter 14).

   If you use Xlib to create your own top-level windows (direct
   children of the root window), you must observe the following
   rules so that all applications interact reasonably across the
   different styles of window management:
     * You must never fight with the window manager for the size
       or placement of your top-level window.
     * You must be able to deal with whatever size window you get,
       even if this means that your application just prints a
       message like ``Please make me bigger'' in its window.
     * You should only attempt to resize or move top-level windows
       in direct response to a user request. If a request to
       change the size of a top-level window fails, you must be
       prepared to live with what you get. You are free to resize
       or move the children of top-level windows as necessary.
       (Toolkits often have facilities for automatic relayout.)
     * If you do not use a toolkit that automatically sets
       standard window properties, you should set these properties
       for top-level windows before mapping them.

   For further information, see chapter 14 and the Inter-Client
   Communication Conventions Manual.

   XCreateWindow is the more general function that allows you to
   set specific window attributes when you create a window.
   XCreateSimpleWindow creates a window that inherits its
   attributes from its parent window.

   The X server acts as if InputOnly windows do not exist for the
   purposes of graphics requests, exposure processing, and
   VisibilityNotify events. An InputOnly window cannot be used as
   a drawable (that is, as a source or destination for graphics
   requests). InputOnly and InputOutput windows act identically in
   other respects (properties, grabs, input control, and so on).
   Extension packages can define other classes of windows.

   To create an unmapped window and set its window attributes, use
   XCreateWindow.

   Window XCreateWindow(Display *display, Window parent, int x,
   int y, unsigned int width, unsigned int height, unsigned int
   border_width, int depth, unsigned int class, Visual *visual,
   unsigned long valuemask, XSetWindowAttributes *attributes);

   display

   Specifies the connection to the X server.

   parent

   Specifies the parent window.

   x

   y

   Specify the x and y coordinates, which are the top-left outside
   corner of the created window's borders and are relative to the
   inside of the parent window's borders.

   width

   height

   Specify the width and height, which are the created window's
   inside dimensions and do not include the created window's
   borders. The dimensions must be nonzero, or a BadValue error
   results.

   border_width

   Specifies the width of the created window's border in pixels.

   depth

   Specifies the window's depth. A depth of CopyFromParent means
   the depth is taken from the parent.

   class

   Specifies the created window's class. You can pass InputOutput,
   InputOnly, or CopyFromParent. A class of CopyFromParent means
   the class is taken from the parent.

   visual

   Specifies the visual type. A visual of CopyFromParent means the
   visual type is taken from the parent.

   valuemask

   Specifies which window attributes are defined in the attributes
   argument. This mask is the bitwise inclusive OR of the valid
   attribute mask bits. If valuemask is zero, the attributes are
   ignored and are not referenced.

   attributes

   Specifies the structure from which the values (as specified by
   the value mask) are to be taken. The value mask should have the
   appropriate bits set to indicate which attributes have been set
   in the structure.

   The XCreateWindow function creates an unmapped subwindow for a
   specified parent window, returns the window ID of the created
   window, and causes the X server to generate a CreateNotify
   event. The created window is placed on top in the stacking
   order with respect to siblings.

   The coordinate system has the X axis horizontal and the Y axis
   vertical with the origin [0, 0] at the upper-left corner.
   Coordinates are integral, in terms of pixels, and coincide with
   pixel centers. Each window and pixmap has its own coordinate
   system. For a window, the origin is inside the border at the
   inside, upper-left corner.

   The border_width for an InputOnly window must be zero, or a
   BadMatch error results. For class InputOutput, the visual type
   and depth must be a combination supported for the screen, or a
   BadMatch error results. The depth need not be the same as the
   parent, but the parent must not be a window of class InputOnly,
   or a BadMatch error results. For an InputOnly window, the depth
   must be zero, and the visual must be one supported by the
   screen. If either condition is not met, a BadMatch error
   results. The parent window, however, may have any depth and
   class. If you specify any invalid window attribute for a
   window, a BadMatch error results.

   The created window is not yet displayed (mapped) on the user's
   display. To display the window, call XMapWindow. The new window
   initially uses the same cursor as its parent. A new cursor can
   be defined for the new window by calling XDefineCursor. The
   window will not be visible on the screen unless it and all of
   its ancestors are mapped and it is not obscured by any of its
   ancestors.

   XCreateWindow can generate BadAlloc, BadColor, BadCursor,
   BadMatch, BadPixmap, BadValue, and BadWindow errors.

   To create an unmapped InputOutput subwindow of a given parent
   window, use XCreateSimpleWindow.

   Window XCreateSimpleWindow(Display *display, Window parent, int
   x, int y, unsigned int width, unsigned int height, unsigned int
   border_width, unsigned long border, unsigned long background);

   display

   Specifies the connection to the X server.

   parent

   Specifies the parent window.

   x

   y

   Specify the x and y coordinates, which are the top-left outside
   corner of the new window's borders and are relative to the
   inside of the parent window's borders.

   width

   height

   Specify the width and height, which are the created window's
   inside dimensions and do not include the created window's
   borders. The dimensions must be nonzero, or a BadValue error
   results.

   border_width

   Specifies the width of the created window's border in pixels.

   border

   Specifies the border pixel value of the window.

   background

   Specifies the background pixel value of the window.

   The XCreateSimpleWindow function creates an unmapped
   InputOutput subwindow for a specified parent window, returns
   the window ID of the created window, and causes the X server to
   generate a CreateNotify event. The created window is placed on
   top in the stacking order with respect to siblings. Any part of
   the window that extends outside its parent window is clipped.
   The border_width for an InputOnly window must be zero, or a
   BadMatch error results. XCreateSimpleWindow inherits its depth,
   class, and visual from its parent. All other window attributes,
   except background and border, have their default values.

   XCreateSimpleWindow can generate BadAlloc, BadMatch, BadValue,
   and BadWindow errors.

Destroying Windows

   Xlib provides functions that you can use to destroy a window or
   destroy all subwindows of a window.

   To destroy a window and all of its subwindows, use
   XDestroyWindow.

   XDestroyWindow(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XDestroyWindow function destroys the specified window as
   well as all of its subwindows and causes the X server to
   generate a DestroyNotify event for each window. The window
   should never be referenced again. If the window specified by
   the w argument is mapped, it is unmapped automatically. The
   ordering of the DestroyNotify events is such that for any given
   window being destroyed, DestroyNotify is generated on any
   inferiors of the window before being generated on the window
   itself. The ordering among siblings and across subhierarchies
   is not otherwise constrained. If the window you specified is a
   root window, no windows are destroyed. Destroying a mapped
   window will generate Expose events on other windows that were
   obscured by the window being destroyed.

   XDestroyWindow can generate a BadWindow error.

   To destroy all subwindows of a specified window, use
   XDestroySubwindows.

   XDestroySubwindows(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XDestroySubwindows function destroys all inferior windows
   of the specified window, in bottom-to-top stacking order. It
   causes the X server to generate a DestroyNotify event for each
   window. If any mapped subwindows were actually destroyed,
   XDestroySubwindows causes the X server to generate Expose
   events on the specified window. This is much more efficient
   than deleting many windows one at a time because much of the
   work need be performed only once for all of the windows, rather
   than for each window. The subwindows should never be referenced
   again.

   XDestroySubwindows can generate a BadWindow error.

Mapping Windows

   A window is considered mapped if an XMapWindow call has been
   made on it. It may not be visible on the screen for one of the
   following reasons:
     * It is obscured by another opaque window.
     * One of its ancestors is not mapped.
     * It is entirely clipped by an ancestor.

   Expose events are generated for the window when part or all of
   it becomes visible on the screen. A client receives the Expose
   events only if it has asked for them. Windows retain their
   position in the stacking order when they are unmapped.

   A window manager may want to control the placement of
   subwindows. If SubstructureRedirectMask has been selected by a
   window manager on a parent window (usually a root window), a
   map request initiated by other clients on a child window is not
   performed, and the window manager is sent a MapRequest event.
   However, if the override-redirect flag on the child had been
   set to True (usually only on pop-up menus), the map request is
   performed.

   A tiling window manager might decide to reposition and resize
   other clients' windows and then decide to map the window to its
   final location. A window manager that wants to provide
   decoration might reparent the child into a frame first. For
   further information, see sections 3.2.8 and 10.10. Only a
   single client at a time can select for
   SubstructureRedirectMask.

   Similarly, a single client can select for ResizeRedirectMask on
   a parent window. Then, any attempt to resize the window by
   another client is suppressed, and the client receives a
   ResizeRequest event.

   To map a given window, use XMapWindow.

   XMapWindow(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XMapWindow function maps the window and all of its
   subwindows that have had map requests. Mapping a window that
   has an unmapped ancestor does not display the window but marks
   it as eligible for display when the ancestor becomes mapped.
   Such a window is called unviewable. When all its ancestors are
   mapped, the window becomes viewable and will be visible on the
   screen if it is not obscured by another window. This function
   has no effect if the window is already mapped.

   If the override-redirect of the window is False and if some
   other client has selected SubstructureRedirectMask on the
   parent window, then the X server generates a MapRequest event,
   and the XMapWindow function does not map the window. Otherwise,
   the window is mapped, and the X server generates a MapNotify
   event.

   If the window becomes viewable and no earlier contents for it
   are remembered, the X server tiles the window with its
   background. If the window's background is undefined, the
   existing screen contents are not altered, and the X server
   generates zero or more Expose events. If backing-store was
   maintained while the window was unmapped, no Expose events are
   generated. If backing-store will now be maintained, a
   full-window exposure is always generated. Otherwise, only
   visible regions may be reported. Similar tiling and exposure
   take place for any newly viewable inferiors.

   If the window is an InputOutput window, XMapWindow generates
   Expose events on each InputOutput window that it causes to be
   displayed. If the client maps and paints the window and if the
   client begins processing events, the window is painted twice.
   To avoid this, first ask for Expose events and then map the
   window, so the client processes input events as usual. The
   event list will include Expose for each window that has
   appeared on the screen. The client's normal response to an
   Expose event should be to repaint the window. This method
   usually leads to simpler programs and to proper interaction
   with window managers.

   XMapWindow can generate a BadWindow error.

   To map and raise a window, use XMapRaised.

   XMapRaised(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XMapRaised function essentially is similar to XMapWindow in
   that it maps the window and all of its subwindows that have had
   map requests. However, it also raises the specified window to
   the top of the stack. For additional information, see
   XMapWindow.

   XMapRaised can generate multiple BadWindow errors.

   To map all subwindows for a specified window, use
   XMapSubwindows.

   XMapSubwindows(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XMapSubwindows function maps all subwindows for a specified
   window in top-to-bottom stacking order. The X server generates
   Expose events on each newly displayed window. This may be much
   more efficient than mapping many windows one at a time because
   the server needs to perform much of the work only once, for all
   of the windows, rather than for each window.

   XMapSubwindows can generate a BadWindow error.

Unmapping Windows

   Xlib provides functions that you can use to unmap a window or
   all subwindows.

   To unmap a window, use XUnmapWindow.

   XUnmapWindow(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XUnmapWindow function unmaps the specified window and
   causes the X server to generate an UnmapNotify event. If the
   specified window is already unmapped, XUnmapWindow has no
   effect. Normal exposure processing on formerly obscured windows
   is performed. Any child window will no longer be visible until
   another map call is made on the parent. In other words, the
   subwindows are still mapped but are not visible until the
   parent is mapped. Unmapping a window will generate Expose
   events on windows that were formerly obscured by it.

   XUnmapWindow can generate a BadWindow error.

   To unmap all subwindows for a specified window, use
   XUnmapSubwindows.

   XUnmapSubwindows(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XUnmapSubwindows function unmaps all subwindows for the
   specified window in bottom-to-top stacking order. It causes the
   X server to generate an UnmapNotify event on each subwindow and
   Expose events on formerly obscured windows. Using this function
   is much more efficient than unmapping multiple windows one at a
   time because the server needs to perform much of the work only
   once, for all of the windows, rather than for each window.

   XUnmapSubwindows can generate a BadWindow error.

Configuring Windows

   Xlib provides functions that you can use to move a window,
   resize a window, move and resize a window, or change a window's
   border width. To change one of these parameters, set the
   appropriate member of the XWindowChanges structure and OR in
   the corresponding value mask in subsequent calls to
   XConfigureWindow. The symbols for the value mask bits and the
   XWindowChanges structure are:

/* Configure window value mask bits */
#define      CWX              (1<<0)
#define      CWY              (1<<1)
#define      CWWidth          (1<<2)
#define      CWHeight         (1<<3)
#define      CWBorderWidth    (1<<4)
#define      CWSibling        (1<<5)
#define      CWStackMode      (1<<6)

/* Values */

typedef struct {
     int x, y;
     int width, height;
     int border_width;
     Window sibling;
     int stack_mode;
} XWindowChanges;

   The x and y members are used to set the window's x and y
   coordinates, which are relative to the parent's origin and
   indicate the position of the upper-left outer corner of the
   window. The width and height members are used to set the inside
   size of the window, not including the border, and must be
   nonzero, or a BadValue error results. Attempts to configure a
   root window have no effect.

   The border_width member is used to set the width of the border
   in pixels. Note that setting just the border width leaves the
   outer-left corner of the window in a fixed position but moves
   the absolute position of the window's origin. If you attempt to
   set the border-width attribute of an InputOnly window nonzero,
   a BadMatch error results.

   The sibling member is used to set the sibling window for
   stacking operations. The stack_mode member is used to set how
   the window is to be restacked and can be set to Above, Below,
   TopIf, BottomIf, or Opposite.

   If the override-redirect flag of the window is False and if
   some other client has selected SubstructureRedirectMask on the
   parent, the X server generates a ConfigureRequest event, and no
   further processing is performed. Otherwise, if some other
   client has selected ResizeRedirectMask on the window and the
   inside width or height of the window is being changed, a
   ResizeRequest event is generated, and the current inside width
   and height are used instead. Note that the override-redirect
   flag of the window has no effect on ResizeRedirectMask and that
   SubstructureRedirectMask on the parent has precedence over
   ResizeRedirectMask on the window.

   When the geometry of the window is changed as specified, the
   window is restacked among siblings, and a ConfigureNotify event
   is generated if the state of the window actually changes.
   GravityNotify events are generated after ConfigureNotify
   events. If the inside width or height of the window has
   actually changed, children of the window are affected as
   specified.

   If a window's size actually changes, the window's subwindows
   move according to their window gravity. Depending on the
   window's bit gravity, the contents of the window also may be
   moved (see section 3.2.3).

   If regions of the window were obscured but now are not,
   exposure processing is performed on these formerly obscured
   windows, including the window itself and its inferiors. As a
   result of increasing the width or height, exposure processing
   is also performed on any new regions of the window and any
   regions where window contents are lost.

   The restack check (specifically, the computation for BottomIf,
   TopIf, and Opposite) is performed with respect to the window's
   final size and position (as controlled by the other arguments
   of the request), not its initial position. If a sibling is
   specified without a stack_mode, a BadMatch error results.

   If a sibling and a stack_mode are specified, the window is
   restacked as follows:
   Above The window is placed just above the sibling.
   Below The window is placed just below the sibling.
   TopIf If the sibling occludes the window, the window is placed
   at the top of the stack.
   BottomIf If the window occludes the sibling, the window is
   placed at the bottom of the stack.
   Opposite If the sibling occludes the window, the window is
   placed at the top of the stack. If the window occludes the
   sibling, the window is placed at the bottom of the stack.

   If a stack_mode is specified but no sibling is specified, the
   window is restacked as follows:
   Above The window is placed at the top of the stack.
   Below The window is placed at the bottom of the stack.
   TopIf If any sibling occludes the window, the window is placed
   at the top of the stack.
   BottomIf If the window occludes any sibling, the window is
   placed at the bottom of the stack.
   Opposite If any sibling occludes the window, the window is
   placed at the top of the stack. If the window occludes any
   sibling, the window is placed at the bottom of the stack.

   Attempts to configure a root window have no effect.

   To configure a window's size, location, stacking, or border,
   use XConfigureWindow.

   XConfigureWindow(Display *display, Window w, unsigned int
   value_mask, XWindowChanges *values);

   display

   Specifies the connection to the X server.

   w

   Specifies the window to be reconfigured.

   value_mask

   Specifies which values are to be set using information in the
   values structure. This mask is the bitwise inclusive OR of the
   valid configure window values bits.

   values

   Specifies the XWindowChanges structure.

   The XConfigureWindow function uses the values specified in the
   XWindowChanges structure to reconfigure a window's size,
   position, border, and stacking order. Values not specified are
   taken from the existing geometry of the window.

   If a sibling is specified without a stack_mode or if the window
   is not actually a sibling, a BadMatch error results. Note that
   the computations for BottomIf, TopIf, and Opposite are
   performed with respect to the window's final geometry (as
   controlled by the other arguments passed to XConfigureWindow),
   not its initial geometry. Any backing store contents of the
   window, its inferiors, and other newly visible windows are
   either discarded or changed to reflect the current screen
   contents (depending on the implementation).

   XConfigureWindow can generate BadMatch, BadValue, and BadWindow
   errors.

   To move a window without changing its size, use XMoveWindow.

   XMoveWindow(Display *display, Window w, int x, int y);

   display

   Specifies the connection to the X server.

   w

   Specifies the window to be moved.

   x

   y

   Specify the x and y coordinates, which define the new location
   of the top-left pixel of the window's border or the window
   itself if it has no border.

   The XMoveWindow function moves the specified window to the
   specified x and y coordinates, but it does not change the
   window's size, raise the window, or change the mapping state of
   the window. Moving a mapped window may or may not lose the
   window's contents depending on if the window is obscured by
   nonchildren and if no backing store exists. If the contents of
   the window are lost, the X server generates Expose events.
   Moving a mapped window generates Expose events on any formerly
   obscured windows.

   If the override-redirect flag of the window is False and some
   other client has selected SubstructureRedirectMask on the
   parent, the X server generates a ConfigureRequest event, and no
   further processing is performed. Otherwise, the window is
   moved.

   XMoveWindow can generate a BadWindow error.

   To change a window's size without changing the upper-left
   coordinate, use XResizeWindow.

   XResizeWindow(Display *display, Window w, unsigned int width,
   unsigned int height);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   width

   height

   Specify the width and height, which are the interior dimensions
   of the window after the call completes.

   The XResizeWindow function changes the inside dimensions of the
   specified window, not including its borders. This function does
   not change the window's upper-left coordinate or the origin and
   does not restack the window. Changing the size of a mapped
   window may lose its contents and generate Expose events. If a
   mapped window is made smaller, changing its size generates
   Expose events on windows that the mapped window formerly
   obscured.

   If the override-redirect flag of the window is False and some
   other client has selected SubstructureRedirectMask on the
   parent, the X server generates a ConfigureRequest event, and no
   further processing is performed. If either width or height is
   zero, a BadValue error results.

   XResizeWindow can generate BadValue and BadWindow errors.

   To change the size and location of a window, use
   XMoveResizeWindow.

   XMoveResizeWindow(Display *display, Window w, int x, int y,
   unsigned int width, unsigned int height);

   display

   Specifies the connection to the X server.

   w

   Specifies the window to be reconfigured.

   x

   y

   Specify the x and y coordinates, which define the new position
   of the window relative to its parent.

   width

   height

   Specify the width and height, which define the interior size of
   the window.

   The XMoveResizeWindow function changes the size and location of
   the specified window without raising it. Moving and resizing a
   mapped window may generate an Expose event on the window.
   Depending on the new size and location parameters, moving and
   resizing a window may generate Expose events on windows that
   the window formerly obscured.

   If the override-redirect flag of the window is False and some
   other client has selected SubstructureRedirectMask on the
   parent, the X server generates a ConfigureRequest event, and no
   further processing is performed. Otherwise, the window size and
   location are changed.

   XMoveResizeWindow can generate BadValue and BadWindow errors.

   To change the border width of a given window, use
   XSetWindowBorderWidth.

   XSetWindowBorderWidth(Display *display, Window w, unsigned int
   width);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   width

   Specifies the width of the window border.

   The XSetWindowBorderWidth function sets the specified window's
   border width to the specified width.

   XSetWindowBorderWidth can generate a BadWindow error.

Changing Window Stacking Order

   Xlib provides functions that you can use to raise, lower,
   circulate, or restack windows.

   To raise a window so that no sibling window obscures it, use
   XRaiseWindow.

   XRaiseWindow(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XRaiseWindow function raises the specified window to the
   top of the stack so that no sibling window obscures it. If the
   windows are regarded as overlapping sheets of paper stacked on
   a desk, then raising a window is analogous to moving the sheet
   to the top of the stack but leaving its x and y location on the
   desk constant. Raising a mapped window may generate Expose
   events for the window and any mapped subwindows that were
   formerly obscured.

   If the override-redirect attribute of the window is False and
   some other client has selected SubstructureRedirectMask on the
   parent, the X server generates a ConfigureRequest event, and no
   processing is performed. Otherwise, the window is raised.

   XRaiseWindow can generate a BadWindow error.

   To lower a window so that it does not obscure any sibling
   windows, use XLowerWindow.

   XLowerWindow(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XLowerWindow function lowers the specified window to the
   bottom of the stack so that it does not obscure any sibling
   windows. If the windows are regarded as overlapping sheets of
   paper stacked on a desk, then lowering a window is analogous to
   moving the sheet to the bottom of the stack but leaving its x
   and y location on the desk constant. Lowering a mapped window
   will generate Expose events on any windows it formerly
   obscured.

   If the override-redirect attribute of the window is False and
   some other client has selected SubstructureRedirectMask on the
   parent, the X server generates a ConfigureRequest event, and no
   processing is performed. Otherwise, the window is lowered to
   the bottom of the stack.

   XLowerWindow can generate a BadWindow error.

   To circulate a subwindow up or down, use XCirculateSubwindows.

   XCirculateSubwindows(Display *display, Window w, int
   direction);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   direction

   Specifies the direction (up or down) that you want to circulate
   the window. You can pass RaiseLowest or LowerHighest.

   The XCirculateSubwindows function circulates children of the
   specified window in the specified direction. If you specify
   RaiseLowest, XCirculateSubwindows raises the lowest mapped
   child (if any) that is occluded by another child to the top of
   the stack. If you specify LowerHighest, XCirculateSubwindows
   lowers the highest mapped child (if any) that occludes another
   child to the bottom of the stack. Exposure processing is then
   performed on formerly obscured windows. If some other client
   has selected SubstructureRedirectMask on the window, the X
   server generates a CirculateRequest event, and no further
   processing is performed. If a child is actually restacked, the
   X server generates a CirculateNotify event.

   XCirculateSubwindows can generate BadValue and BadWindow
   errors.

   To raise the lowest mapped child of a window that is partially
   or completely occluded by another child, use
   XCirculateSubwindowsUp.

   XCirculateSubwindowsUp(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XCirculateSubwindowsUp function raises the lowest mapped
   child of the specified window that is partially or completely
   occluded by another child. Completely unobscured children are
   not affected. This is a convenience function equivalent to
   XCirculateSubwindows with RaiseLowest specified.

   XCirculateSubwindowsUp can generate a BadWindow error.

   To lower the highest mapped child of a window that partially or
   completely occludes another child, use
   XCirculateSubwindowsDown.

   XCirculateSubwindowsDown(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XCirculateSubwindowsDown function lowers the highest mapped
   child of the specified window that partially or completely
   occludes another child. Completely unobscured children are not
   affected. This is a convenience function equivalent to
   XCirculateSubwindows with LowerHighest specified.

   XCirculateSubwindowsDown can generate a BadWindow error.

   To restack a set of windows from top to bottom, use
   XRestackWindows.

   XRestackWindows(Display *display, Window windows[], int
   nwindows);

   display

   Specifies the connection to the X server.

   windows

   Specifies an array containing the windows to be restacked.

   nwindows

   Specifies the number of windows to be restacked.

   The XRestackWindows function restacks the windows in the order
   specified, from top to bottom. The stacking order of the first
   window in the windows array is unaffected, but the other
   windows in the array are stacked underneath the first window,
   in the order of the array. The stacking order of the other
   windows is not affected. For each window in the window array
   that is not a child of the specified window, a BadMatch error
   results.

   If the override-redirect attribute of a window is False and
   some other client has selected SubstructureRedirectMask on the
   parent, the X server generates ConfigureRequest events for each
   window whose override-redirect flag is not set, and no further
   processing is performed. Otherwise, the windows will be
   restacked in top-to-bottom order.

   XRestackWindows can generate a BadWindow error.

Changing Window Attributes

   Xlib provides functions that you can use to set window
   attributes. XChangeWindowAttributes is the more general
   function that allows you to set one or more window attributes
   provided by the XSetWindowAttributes structure. The other
   functions described in this section allow you to set one
   specific window attribute, such as a window's background.

   To change one or more attributes for a given window, use
   XChangeWindowAttributes.

   XChangeWindowAttributes(Display *display, Window w, unsigned
   long valuemask, XSetWindowAttributes *attributes);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   valuemask

   Specifies which window attributes are defined in the attributes
   argument. This mask is the bitwise inclusive OR of the valid
   attribute mask bits. If valuemask is zero, the attributes are
   ignored and are not referenced. The values and restrictions are
   the same as for XCreateWindow.

   attributes

   Specifies the structure from which the values (as specified by
   the value mask) are to be taken. The value mask should have the
   appropriate bits set to indicate which attributes have been set
   in the structure (see section 3.2).

   Depending on the valuemask, the XChangeWindowAttributes
   function uses the window attributes in the XSetWindowAttributes
   structure to change the specified window attributes. Changing
   the background does not cause the window contents to be
   changed. To repaint the window and its background, use
   XClearWindow. Setting the border or changing the background
   such that the border tile origin changes causes the border to
   be repainted. Changing the background of a root window to None
   or ParentRelative restores the default background pixmap.
   Changing the border of a root window to CopyFromParent restores
   the default border pixmap. Changing the win-gravity does not
   affect the current position of the window. Changing the
   backing-store of an obscured window to WhenMapped or Always, or
   changing the backing-planes, backing-pixel, or save-under of a
   mapped window may have no immediate effect. Changing the
   colormap of a window (that is, defining a new map, not changing
   the contents of the existing map) generates a ColormapNotify
   event. Changing the colormap of a visible window may have no
   immediate effect on the screen because the map may not be
   installed (see XInstallColormap). Changing the cursor of a root
   window to None restores the default cursor. Whenever possible,
   you are encouraged to share colormaps.

   Multiple clients can select input on the same window. Their
   event masks are maintained separately. When an event is
   generated, it is reported to all interested clients. However,
   only one client at a time can select for
   SubstructureRedirectMask, ResizeRedirectMask, and
   ButtonPressMask. If a client attempts to select any of these
   event masks and some other client has already selected one, a
   BadAccess error results. There is only one
   do-not-propagate-mask for a window, not one per client.

   XChangeWindowAttributes can generate BadAccess, BadColor,
   BadCursor, BadMatch, BadPixmap, BadValue, and BadWindow errors.

   To set the background of a window to a given pixel, use
   XSetWindowBackground.

   XSetWindowBackground(Display *display, Window w, unsigned long
   background_pixel);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   background_pixel

   Specifies the pixel that is to be used for the background.

   The XSetWindowBackground function sets the background of the
   window to the specified pixel value. Changing the background
   does not cause the window contents to be changed.
   XSetWindowBackground uses a pixmap of undefined size filled
   with the pixel value you passed. If you try to change the
   background of an InputOnly window, a BadMatch error results.

   XSetWindowBackground can generate BadMatch and BadWindow
   errors.

   To set the background of a window to a given pixmap, use
   XSetWindowBackgroundPixmap.

   XSetWindowBackgroundPixmap(Display *display, Window w, Pixmap
   background_pixmap);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   background_pixmap

   Specifies the background pixmap, ParentRelative, or None.

   The XSetWindowBackgroundPixmap function sets the background
   pixmap of the window to the specified pixmap. The background
   pixmap can immediately be freed if no further explicit
   references to it are to be made. If ParentRelative is
   specified, the background pixmap of the window's parent is
   used, or on the root window, the default background is
   restored. If you try to change the background of an InputOnly
   window, a BadMatch error results. If the background is set to
   None, the window has no defined background.

   XSetWindowBackgroundPixmap can generate BadMatch, BadPixmap,
   and BadWindow errors. XSetWindowBackground and
   XSetWindowBackgroundPixmap do not change the current contents
   of the window.

   To change and repaint a window's border to a given pixel, use
   XSetWindowBorder.

   XSetWindowBorder(Display *display, Window w, unsigned long
   border_pixel);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   border_pixel

   Specifies the entry in the colormap.

   The XSetWindowBorder function sets the border of the window to
   the pixel value you specify. If you attempt to perform this on
   an InputOnly window, a BadMatch error results.

   XSetWindowBorder can generate BadMatch and BadWindow errors.

   To change and repaint the border tile of a given window, use
   XSetWindowBorderPixmap.

   XSetWindowBorderPixmap(Display *display, Window w, Pixmap
   border_pixmap);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   border_pixmap

   Specifies the border pixmap or CopyFromParent.

   The XSetWindowBorderPixmap function sets the border pixmap of
   the window to the pixmap you specify. The border pixmap can be
   freed immediately if no further explicit references to it are
   to be made. If you specify CopyFromParent, a copy of the parent
   window's border pixmap is used. If you attempt to perform this
   on an InputOnly window, a BadMatch error results.

   XSetWindowBorderPixmap can generate BadMatch, BadPixmap, and
   BadWindow errors.

   To set the colormap of a given window, use XSetWindowColormap.

   XSetWindowColormap(Display *display, Window w, Colormap
   colormap);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   colormap

   Specifies the colormap.

   The XSetWindowColormap function sets the specified colormap of
   the specified window. The colormap must have the same visual
   type as the window, or a BadMatch error results.

   XSetWindowColormap can generate BadColor, BadMatch, and
   BadWindow errors.

   To define which cursor will be used in a window, use
   XDefineCursor.

   XDefineCursor(Display *display, Window w, Cursor cursor);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   cursor

   Specifies the cursor that is to be displayed or None.

   If a cursor is set, it will be used when the pointer is in the
   window. If the cursor is None, it is equivalent to
   XUndefineCursor.

   XDefineCursor can generate BadCursor and BadWindow errors.

   To undefine the cursor in a given window, use XUndefineCursor.

   XUndefineCursor(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XUndefineCursor function undoes the effect of a previous
   XDefineCursor for this window. When the pointer is in the
   window, the parent's cursor will now be used. On the root
   window, the default cursor is restored.

   XUndefineCursor can generate a BadWindow error.

Chapter 4. Window Information Functions

   Table of Contents

   Obtaining Window Information
   Translating Screen Coordinates
   Properties and Atoms
   Obtaining and Changing Window Properties
   Selections

   After you connect the display to the X server and create a
   window, you can use the Xlib window information functions to:
     * Obtain information about a window
     * Translate screen coordinates
     * Manipulate property lists
     * Obtain and change window properties
     * Manipulate selections

Obtaining Window Information

   Xlib provides functions that you can use to obtain information
   about the window tree, the window's current attributes, the
   window's current geometry, or the current pointer coordinates.
   Because they are most frequently used by window managers, these
   functions all return a status to indicate whether the window
   still exists.

   To obtain the parent, a list of children, and number of
   children for a given window, use XQueryTree.

   Status XQueryTree(Display *display, Window w, Window
   *root_return, Window *parent_return, Window **children_return,
   unsigned int *nchildren_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window whose list of children, root, parent, and
   number of children you want to obtain.

   root_return

   Returns the root window.

   parent_return

   Returns the parent window.

   children_return

   Returns the list of children.

   nchildren_return

   Returns the number of children.

   The XQueryTree function returns the root ID, the parent window
   ID, a pointer to the list of children windows (NULL when there
   are no children), and the number of children in the list for
   the specified window. The children are listed in current
   stacking order, from bottom-most (first) to top-most (last).
   XQueryTree returns zero if it fails and nonzero if it succeeds.
   To free a non-NULL children list when it is no longer needed,
   use XFree.

   XQueryTree can generate a BadWindow error.

   To obtain the current attributes of a given window, use
   XGetWindowAttributes.

   Status XGetWindowAttributes(Display *display, Window w,
   XWindowAttributes *window_attributes_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window whose current attributes you want to
   obtain.

   window_attributes_return

   Returns the specified window's attributes in the
   XWindowAttributes structure.

   The XGetWindowAttributes function returns the current
   attributes for the specified window to an XWindowAttributes
   structure.



typedef struct {
     int x, y;                     /* location of window */
     int width, height;            /* width and height of window */
     int border_width;             /* border width of window */
     int depth;                    /* depth of window */
     Visual *visual;               /* the associated visual structure */
     Window root;                  /* root of screen containing window *
/
     int class;                    /* InputOutput, InputOnly*/
     int bit_gravity;              /* one of the bit gravity values */
     int win_gravity;              /* one of the window gravity values *
/
     int backing_store;            /* NotUseful, WhenMapped, Always */
     unsigned long backing_planes; /* planes to be preserved if possible
 */
     unsigned long backing_pixel;  /* value to be used when restoring pl
anes */
     Bool save_under;              /* boolean, should bits under be save
d? */
     Colormap colormap;            /* color map to be associated with wi
ndow */
     Bool map_installed;           /* boolean, is color map currently in
stalled*/
     int map_state;                /* IsUnmapped, IsUnviewable, IsViewab
le */
     long all_event_masks;         /* set of events all people have inte
rest in*/
     long your_event_mask;         /* my event mask */
     long do_not_propagate_mask;   /* set of events that should not prop
agate */
     Bool override_redirect;       /* boolean value for override-redirec
t */
     Screen *screen;               /* back pointer to correct screen */
} XWindowAttributes;

   The x and y members are set to the upper-left outer corner
   relative to the parent window's origin. The width and height
   members are set to the inside size of the window, not including
   the border. The border_width member is set to the window's
   border width in pixels. The depth member is set to the depth of
   the window (that is, bits per pixel for the object). The visual
   member is a pointer to the screen's associated Visual
   structure. The root member is set to the root window of the
   screen containing the window. The class member is set to the
   window's class and can be either InputOutput or InputOnly.

   The bit_gravity member is set to the window's bit gravity and
   can be one of the following:
   ForgetGravity    EastGravity
   NorthWestGravity SouthWestGravity
   NorthGravity     SouthGravity
   NorthEastGravity SouthEastGravity
   WestGravity      StaticGravity

   The win_gravity member is set to the window's window gravity
   and can be one of the following:
   UnmapGravity     SouthWestGravity
   NorthWestGravity SouthGravity
   NorthGravity     SouthEastGravity
   NorthEastGravity StaticGravity
   WestGravity      CenterGravity
   EastGravity

   For additional information on gravity, see section 3.2.3.

   The backing_store member is set to indicate how the X server
   should maintain the contents of a window and can be WhenMapped,
   Always, or NotUseful. The backing_planes member is set to
   indicate (with bits set to 1) which bit planes of the window
   hold dynamic data that must be preserved in backing_stores and
   during save_unders. The backing_pixel member is set to indicate
   what values to use for planes not set in backing_planes.

   The save_under member is set to True or False. The colormap
   member is set to the colormap for the specified window and can
   be a colormap ID or None. The map_installed member is set to
   indicate whether the colormap is currently installed and can be
   True or False. The map_state member is set to indicate the
   state of the window and can be IsUnmapped, IsUnviewable, or
   IsViewable. IsUnviewable is used if the window is mapped but
   some ancestor is unmapped.

   The all_event_masks member is set to the bitwise inclusive OR
   of all event masks selected on the window by all clients. The
   your_event_mask member is set to the bitwise inclusive OR of
   all event masks selected by the querying client. The
   do_not_propagate_mask member is set to the bitwise inclusive OR
   of the set of events that should not propagate.

   The override_redirect member is set to indicate whether this
   window overrides structure control facilities and can be True
   or False. Window manager clients should ignore the window if
   this member is True.

   The screen member is set to a screen pointer that gives you a
   back pointer to the correct screen. This makes it easier to
   obtain the screen information without having to loop over the
   root window fields to see which field matches.

   XGetWindowAttributes can generate BadDrawable and BadWindow
   errors.

   To obtain the current geometry of a given drawable, use
   XGetGeometry.

   Status XGetGeometry(Display *display, Drawable d, Window
   *root_return, int *x_return, int *y_return, unsigned int
   *width_return, unsigned int *height_return, unsigned int
   *border_width_return, unsigned int *depth_return);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable, which can be a window or a pixmap.

   root_return

   Returns the root window.

   x_return

   y_return

   Return the x and y coordinates that define the location of the
   drawable. For a window, these coordinates specify the
   upper-left outer corner relative to its parent's origin. For
   pixmaps, these coordinates are always zero.

   width_return

   height_return

   Return the drawable's dimensions (width and height). For a
   window, these dimensions specify the inside size, not including
   the border.

   border_width_return

   Returns the border width in pixels. If the drawable is a
   pixmap, it returns zero.

   depth_return

   Returns the depth of the drawable (bits per pixel for the
   object).

   The XGetGeometry function returns the root window and the
   current geometry of the drawable. The geometry of the drawable
   includes the x and y coordinates, width and height, border
   width, and depth. These are described in the argument list. It
   is legal to pass to this function a window whose class is
   InputOnly.

   XGetGeometry can generate a BadDrawable error.

Translating Screen Coordinates

   Applications sometimes need to perform a coordinate
   transformation from the coordinate space of one window to
   another window or need to determine which window the pointing
   device is in. XTranslateCoordinates and XQueryPointer fulfill
   these needs (and avoid any race conditions) by asking the X
   server to perform these operations.

   To translate a coordinate in one window to the coordinate space
   of another window, use XTranslateCoordinates.

   Bool XTranslateCoordinates(Display *display, Window src_w,
   Window dest_w, int src_x, int src_y, int *dest_x_return, int
   *dest_y_return, Window *child_return);

   display

   Specifies the connection to the X server.

   src_w

   Specifies the source window.

   dest_w

   Specifies the destination window.

   src_x

   src_y

   Specify the x and y coordinates within the source window.

   dest_x_return

   dest_y_return

   Return the x and y coordinates within the destination window.

   child_return

   Returns the child if the coordinates are contained in a mapped
   child of the destination window.

   If XTranslateCoordinates returns True, it takes the src_x and
   src_y coordinates relative to the source window's origin and
   returns these coordinates to dest_x_return and dest_y_return
   relative to the destination window's origin. If
   XTranslateCoordinates returns False, src_w and dest_w are on
   different screens, and dest_x_return and dest_y_return are
   zero. If the coordinates are contained in a mapped child of
   dest_w, that child is returned to child_return. Otherwise,
   child_return is set to None.

   XTranslateCoordinates can generate a BadWindow error.

   To obtain the screen coordinates of the pointer or to determine
   the pointer coordinates relative to a specified window, use
   XQueryPointer.

   Bool XQueryPointer(Display *display, Window w, Window
   *root_return, Window *child_return, int *root_x_return, int
   *root_y_return, int *win_x_return, int *win_y_return, unsigned
   int *mask_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   root_return

   Returns the root window that the pointer is in.

   child_return

   Returns the child window that the pointer is located in, if
   any.

   root_x_return

   root_y_return

   Return the pointer coordinates relative to the root window's
   origin.

   win_x_return

   win_y_return

   Return the pointer coordinates relative to the specified
   window.

   mask_return

   Returns the current state of the modifier keys and pointer
   buttons.

   The XQueryPointer function returns the root window the pointer
   is logically on and the pointer coordinates relative to the
   root window's origin. If XQueryPointer returns False, the
   pointer is not on the same screen as the specified window, and
   XQueryPointer returns None to child_return and zero to
   win_x_return and win_y_return. If XQueryPointer returns True,
   the pointer coordinates returned to win_x_return and
   win_y_return are relative to the origin of the specified
   window. In this case, XQueryPointer returns the child that
   contains the pointer, if any, or else None to child_return.

   XQueryPointer returns the current logical state of the keyboard
   buttons and the modifier keys in mask_return. It sets
   mask_return to the bitwise inclusive OR of one or more of the
   button or modifier key bitmasks to match the current state of
   the mouse buttons and the modifier keys.

   Note that the logical state of a device (as seen through Xlib)
   may lag the physical state if device event processing is frozen
   (see section 12.1).

   XQueryPointer can generate a BadWindow error.

Properties and Atoms

   A property is a collection of named, typed data. The window
   system has a set of predefined properties (for example, the
   name of a window, size hints, and so on), and users can define
   any other arbitrary information and associate it with windows.
   Each property has a name, which is an ISO Latin-1 string. For
   each named property, a unique identifier (atom) is associated
   with it. A property also has a type, for example, string or
   integer. These types are also indicated using atoms, so
   arbitrary new types can be defined. Data of only one type may
   be associated with a single property name. Clients can store
   and retrieve properties associated with windows. For efficiency
   reasons, an atom is used rather than a character string.
   XInternAtom can be used to obtain the atom for property names.

   A property is also stored in one of several possible formats.
   The X server can store the information as 8-bit quantities,
   16-bit quantities, or 32-bit quantities. This permits the X
   server to present the data in the byte order that the client
   expects. If you define further properties of complex type, you
   must encode and decode them yourself. These functions must be
   carefully written if they are to be portable. For further
   information about how to write a library extension, see
   appendix C. The type of a property is defined by an atom, which
   allows for arbitrary extension in this type scheme.

   Certain property names are predefined in the server for
   commonly used functions. The atoms for these properties are
   defined in <X11/Xatom.h>. To avoid name clashes with user
   symbols, the #define name for each atom has the XA_ prefix. For
   an explanation of the functions that let you get and set much
   of the information stored in these predefined properties, see
   chapter 14.

   The core protocol imposes no semantics on these property names,
   but semantics are specified in other X Consortium standards,
   such as the Inter-Client Communication Conventions Manual and
   the X Logical Font Description Conventions.

   You can use properties to communicate other information between
   applications. The functions described in this section let you
   define new properties and get the unique atom IDs in your
   applications.

   Although any particular atom can have some client
   interpretation within each of the name spaces, atoms occur in
   five distinct name spaces within the protocol:
     * Selections
     * Property names
     * Property types
     * Font properties
     * Type of a ClientMessage event (none are built into the X
       server)

   The built-in selection property names are:
   PRIMARY SECONDARY

   The built-in property names are:
   CUT_BUFFER0     RESOURCE_MANAGER
   CUT_BUFFER1     WM_CLASS
   CUT_BUFFER2     WM_CLIENT_MACHINE
   CUT_BUFFER3     WM_COLORMAP_WINDOWS
   CUT_BUFFER4     WM_COMMAND
   CUT_BUFFER5     WM_HINTS
   CUT_BUFFER6     WM_ICON_NAME
   CUT_BUFFER7     WM_ICON_SIZE
   RGB_BEST_MAP    WM_NAME
   RGB_BLUE_MAP    WM_NORMAL_HINTS
   RGB_DEFAULT_MAP WM_PROTOCOLS
   RGB_GRAY_MAP    WM_STATE
   RGB_GREEN_MAP   WM_TRANSIENT_FOR
   RGB_RED_MAP     WM_ZOOM_HINTS

   The built-in property types are:
   ARC      PIXMAP
   ATOM     POINT
   BITMAP   RGB_COLOR_MAP
   CARDINAL RECTANGLE
   COLORMAP STRING
   CURSOR   VISUALID
   DRAWABLE WINDOW
   FONT     WM_HINTS
   INTEGER  WM_SIZE_HINTS

   The built-in font property names are:
   MIN_SPACE           STRIKEOUT_DESCENT
   NORM_SPACE          STRIKEOUT_ASCENT
   MAX_SPACE           ITALIC_ANGLE
   END_SPACE           X_HEIGHT
   SUPERSCRIPT_X       QUAD_WIDTH
   SUPERSCRIPT_Y       WEIGHT
   SUBSCRIPT_X         POINT_SIZE
   SUBSCRIPT_Y         RESOLUTION
   UNDERLINE_POSITION  COPYRIGHT
   UNDERLINE_THICKNESS NOTICE
   FONT_NAME           FAMILY_NAME
   FULL_NAME           CAP_HEIGHT

   For further information about font properties, see section 8.5.

   To return an atom for a given name, use XInternAtom.

   Atom XInternAtom(Display *display, char *atom_name, Bool
   only_if_exists);

   display

   Specifies the connection to the X server.

   atom_name

   Specifies the name associated with the atom you want returned.

   only_if_exists

   Specifies a Boolean value that indicates whether the atom must
   be created.

   The XInternAtom function returns the atom identifier associated
   with the specified atom_name string. If only_if_exists is
   False, the atom is created if it does not exist. Therefore,
   XInternAtom can return None. If the atom name is not in the
   Host Portable Character Encoding, the result is
   implementation-dependent. Uppercase and lowercase matter; the
   strings ``thing'', ``Thing'', and ``thinG'' all designate
   different atoms. The atom will remain defined even after the
   client's connection closes. It will become undefined only when
   the last connection to the X server closes.

   XInternAtom can generate BadAlloc and BadValue errors.

   To return atoms for an array of names, use XInternAtoms.

   Status XInternAtoms(Display *display, char **names, int count,
   Bool only_if_exists, Atom *atoms_return);

   display

   Specifies the connection to the X server.

   names

   Specifies the array of atom names.

   count

   Specifies the number of atom names in the array.

   only_if_exists

   Specifies a Boolean value that indicates whether the atom must
   be created.

   atoms_return

   Returns the atoms.

   The XInternAtoms function returns the atom identifiers
   associated with the specified names. The atoms are stored in
   the atoms_return array supplied by the caller. Calling this
   function is equivalent to calling XInternAtom for each of the
   names in turn with the specified value of only_if_exists, but
   this function minimizes the number of round-trip protocol
   exchanges between the client and the X server.

   This function returns a nonzero status if atoms are returned
   for all of the names; otherwise, it returns zero.

   XInternAtoms can generate BadAlloc and BadValue errors.

   To return a name for a given atom identifier, use XGetAtomName.

   char *XGetAtomName(Display *display, Atom atom);

   display

   Specifies the connection to the X server.

   atom

   Specifies the atom for the property name you want returned.

   The XGetAtomName function returns the name associated with the
   specified atom. If the data returned by the server is in the
   Latin Portable Character Encoding, then the returned string is
   in the Host Portable Character Encoding. Otherwise, the result
   is implementation-dependent. To free the resulting string, call
   XFree.

   XGetAtomName can generate a BadAtom error.

   To return the names for an array of atom identifiers, use
   XGetAtomNames.

   Status XGetAtomNames(Display *display, Atom *atoms, int count,
   char **names_return);

   display

   Specifies the connection to the X server.

   atoms

   Specifies the array of atoms.

   count

   Specifies the number of atoms in the array.

   names_return

   Returns the atom names.

   The XGetAtomNames function returns the names associated with
   the specified atoms. The names are stored in the names_return
   array supplied by the caller. Calling this function is
   equivalent to calling XGetAtomName for each of the atoms in
   turn, but this function minimizes the number of round-trip
   protocol exchanges between the client and the X server.

   This function returns a nonzero status if names are returned
   for all of the atoms; otherwise, it returns zero.

   XGetAtomNames can generate a BadAtom error.

Obtaining and Changing Window Properties

   You can attach a property list to every window. Each property
   has a name, a type, and a value (see section 4.3). The value is
   an array of 8-bit, 16-bit, or 32-bit quantities, whose
   interpretation is left to the clients. The type char is used to
   represent 8-bit quantities, the type short is used to represent
   16-bit quantities, and the type long is used to represent
   32-bit quantities.

   Xlib provides functions that you can use to obtain, change,
   update, or interchange window properties. In addition, Xlib
   provides other utility functions for inter-client communication
   (see chapter 14).

   To obtain the type, format, and value of a property of a given
   window, use XGetWindowProperty.

   int XGetWindowProperty(Display *display, Window w, Atom
   property, long long_offset, long long_length, Bool delete, Atom
   req_type, Atom *actual_type_return, int *actual_format_return,
   unsigned long *nitems_return, unsigned long
   *bytes_after_return, unsigned char **prop_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window whose property you want to obtain.

   property

   Specifies the property name.

   long_offset

   Specifies the offset in the specified property (in 32-bit
   quantities) where the data is to be retrieved.

   long_length

   Specifies the length in 32-bit multiples of the data to be
   retrieved.

   delete

   Specifies a Boolean value that determines whether the property
   is deleted.

   req_type

   Specifies the atom identifier associated with the property type
   or AnyPropertyType.

   actual_type_return

   Returns the atom identifier that defines the actual type of the
   property.

   actual_format_return

   Returns the actual format of the property.

   nitems_return

   Returns the actual number of 8-bit, 16-bit, or 32-bit items
   stored in the prop_return data.

   bytes_after_return

   Returns the number of bytes remaining to be read in the
   property if a partial read was performed.

   prop_return

   Returns the data in the specified format.

   The XGetWindowProperty function returns the actual type of the
   property; the actual format of the property; the number of
   8-bit, 16-bit, or 32-bit items transferred; the number of bytes
   remaining to be read in the property; and a pointer to the data
   actually returned. XGetWindowProperty sets the return arguments
   as follows:
     * If the specified property does not exist for the specified
       window, XGetWindowProperty returns None to
       actual_type_return and the value zero to
       actual_format_return and bytes_after_return. The
       nitems_return argument is empty. In this case, the delete
       argument is ignored.
     * If the specified property exists but its type does not
       match the specified type, XGetWindowProperty returns the
       actual property type to actual_type_return, the actual
       property format (never zero) to actual_format_return, and
       the property length in bytes (even if the
       actual_format_return is 16 or 32) to bytes_after_return. It
       also ignores the delete argument. The nitems_return
       argument is empty.
     * If the specified property exists and either you assign
       AnyPropertyType to the req_type argument or the specified
       type matches the actual property type, XGetWindowProperty
       returns the actual property type to actual_type_return and
       the actual property format (never zero) to
       actual_format_return. It also returns a value to
       bytes_after_return and nitems_return, by defining the
       following values:
     * N = actual length of the stored property in bytes (even if
       the format is 16 or 32) I = 4 * long_offset T = N - I L =
       MINIMUM(T, 4 * long_length) A = N - (I + L)
     * The returned value starts at byte index I in the property
       (indexing from zero), and its length in bytes is L. If the
       value for long_offset causes L to be negative, a BadValue
       error results. The value of bytes_after_return is A, giving
       the number of trailing unread bytes in the stored property.

   If the returned format is 8, the returned data is represented
   as a char array. If the returned format is 16, the returned
   data is represented as a short array and should be cast to that
   type to obtain the elements. If the returned format is 32, the
   returned data is represented as a long array and should be cast
   to that type to obtain the elements.

   XGetWindowProperty always allocates one extra byte in
   prop_return (even if the property is zero length) and sets it
   to zero so that simple properties consisting of characters do
   not have to be copied into yet another string before use.

   If delete is True and bytes_after_return is zero,
   XGetWindowProperty deletes the property from the window and
   generates a PropertyNotify event on the window.

   The function returns Success if it executes successfully. To
   free the resulting data, use XFree.

   XGetWindowProperty can generate BadAtom, BadValue, and
   BadWindow errors.

   To obtain a given window's property list, use XListProperties.

   Atom *XListProperties(Display *display, Window w, int
   *num_prop_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window whose property list you want to obtain.

   num_prop_return

   Returns the length of the properties array.

   The XListProperties function returns a pointer to an array of
   atom properties that are defined for the specified window or
   returns NULL if no properties were found. To free the memory
   allocated by this function, use XFree.

   XListProperties can generate a BadWindow error.

   To change a property of a given window, use XChangeProperty.

   XChangeProperty(Display *display, Window w, Atom property, Atom
   type, int format, int mode, unsignedchar *data, int nelements);

   display

   Specifies the connection to the X server.

   w

   Specifies the window whose property you want to change.

   property

   Specifies the property name.

   type

   Specifies the type of the property. The X server does not
   interpret the type but simply passes it back to an application
   that later calls XGetWindowProperty.

   format

   Specifies whether the data should be viewed as a list of 8-bit,
   16-bit, or 32-bit quantities. Possible values are 8, 16, and
   32. This information allows the X server to correctly perform
   byte-swap operations as necessary. If the format is 16-bit or
   32-bit, you must explicitly cast your data pointer to an
   (unsigned char *) in the call to XChangeProperty.

   mode

   Specifies the mode of the operation. You can pass
   PropModeReplace, PropModePrepend, or PropModeAppend.

   data

   Specifies the property data.

   nelements

   Specifies the number of elements of the specified data format.

   The XChangeProperty function alters the property for the
   specified window and causes the X server to generate a
   PropertyNotify event on that window. XChangeProperty performs
   the following:
     * If mode is PropModeReplace, XChangeProperty discards the
       previous property value and stores the new data.
     * If mode is PropModePrepend or PropModeAppend,
       XChangeProperty inserts the specified data before the
       beginning of the existing data or onto the end of the
       existing data, respectively. The type and format must match
       the existing property value, or a BadMatch error results.
       If the property is undefined, it is treated as defined with
       the correct type and format with zero-length data.

   If the specified format is 8, the property data must be a char
   array. If the specified format is 16, the property data must be
   a short array. If the specified format is 32, the property data
   must be a long array.

   The lifetime of a property is not tied to the storing client.
   Properties remain until explicitly deleted, until the window is
   destroyed, or until the server resets. For a discussion of what
   happens when the connection to the X server is closed, see
   section 2.6. The maximum size of a property is server dependent
   and can vary dynamically depending on the amount of memory the
   server has available. (If there is insufficient space, a
   BadAlloc error results.)

   XChangeProperty can generate BadAlloc, BadAtom, BadMatch,
   BadValue, and BadWindow errors.

   To rotate a window's property list, use
   XRotateWindowProperties.

   XRotateWindowProperties(Display *display, Window w, Atom
   properties[], int num_prop, int npositions);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   properties

   Specifies the array of properties that are to be rotated.

   num_prop

   Specifies the length of the properties array.

   npositions

   Specifies the rotation amount.

   The XRotateWindowProperties function allows you to rotate
   properties on a window and causes the X server to generate
   PropertyNotify events. If the property names in the properties
   array are viewed as being numbered starting from zero and if
   there are num_prop property names in the list, then the value
   associated with property name I becomes the value associated
   with property name (I + npositions) mod N for all I from zero
   to N - 1. The effect is to rotate the states by npositions
   places around the virtual ring of property names (right for
   positive npositions, left for negative npositions). If
   npositions mod N is nonzero, the X server generates a
   PropertyNotify event for each property in the order that they
   are listed in the array. If an atom occurs more than once in
   the list or no property with that name is defined for the
   window, a BadMatch error results. If a BadAtom or BadMatch
   error results, no properties are changed.

   XRotateWindowProperties can generate BadAtom, BadMatch, and
   BadWindow errors.

   To delete a property on a given window, use XDeleteProperty.

   XDeleteProperty(Display *display, Window w, Atom property);

   display

   Specifies the connection to the X server.

   w

   Specifies the window whose property you want to delete.

   property

   Specifies the property name.

   The XDeleteProperty function deletes the specified property
   only if the property was defined on the specified window and
   causes the X server to generate a PropertyNotify event on the
   window unless the property does not exist.

   XDeleteProperty can generate BadAtom and BadWindow errors.

Selections

   Selections are one method used by applications to exchange
   data. By using the property mechanism, applications can
   exchange data of arbitrary types and can negotiate the type of
   the data. A selection can be thought of as an indirect property
   with a dynamic type. That is, rather than having the property
   stored in the X server, the property is maintained by some
   client (the owner). A selection is global in nature (considered
   to belong to the user but be maintained by clients) rather than
   being private to a particular window subhierarchy or a
   particular set of clients.

   Xlib provides functions that you can use to set, get, or
   request conversion of selections. This allows applications to
   implement the notion of current selection, which requires that
   notification be sent to applications when they no longer own
   the selection. Applications that support selection often
   highlight the current selection and so must be informed when
   another application has acquired the selection so that they can
   unhighlight the selection.

   When a client asks for the contents of a selection, it
   specifies a selection target type. This target type can be used
   to control the transmitted representation of the contents. For
   example, if the selection is ``the last thing the user clicked
   on'' and that is currently an image, then the target type might
   specify whether the contents of the image should be sent in XY
   format or Z format.

   The target type can also be used to control the class of
   contents transmitted, for example, asking for the ``looks''
   (fonts, line spacing, indentation, and so forth) of a paragraph
   selection, not the text of the paragraph. The target type can
   also be used for other purposes. The protocol does not
   constrain the semantics.

   To set the selection owner, use XSetSelectionOwner.

   XSetSelectionOwner(Display *display, Atom selection, Window
   owner, Time time);

   display

   Specifies the connection to the X server.

   selection

   Specifies the selection atom.

   owner

   Specifies the owner of the specified selection atom. You can
   pass a window or None.

   time

   Specifies the time. You can pass either a timestamp or
   CurrentTime.

   The XSetSelectionOwner function changes the owner and
   last-change time for the specified selection and has no effect
   if the specified time is earlier than the current last-change
   time of the specified selection or is later than the current X
   server time. Otherwise, the last-change time is set to the
   specified time, with CurrentTime replaced by the current server
   time. If the owner window is specified as None, then the owner
   of the selection becomes None (that is, no owner). Otherwise,
   the owner of the selection becomes the client executing the
   request.

   If the new owner (whether a client or None) is not the same as
   the current owner of the selection and the current owner is not
   None, the current owner is sent a SelectionClear event. If the
   client that is the owner of a selection is later terminated
   (that is, its connection is closed) or if the owner window it
   has specified in the request is later destroyed, the owner of
   the selection automatically reverts to None, but the
   last-change time is not affected. The selection atom is
   uninterpreted by the X server. XGetSelectionOwner returns the
   owner window, which is reported in SelectionRequest and
   SelectionClear events. Selections are global to the X server.

   XSetSelectionOwner can generate BadAtom and BadWindow errors.

   To return the selection owner, use XGetSelectionOwner.

   Window XGetSelectionOwner(Display *display, Atom selection);

   display

   Specifies the connection to the X server.

   selection

   Specifies the selection atom whose owner you want returned.

   The XGetSelectionOwner function returns the window ID
   associated with the window that currently owns the specified
   selection. If no selection was specified, the function returns
   the constant None. If None is returned, there is no owner for
   the selection.

   XGetSelectionOwner can generate a BadAtom error.

   To request conversion of a selection, use XConvertSelection.

   XConvertSelection(Display *display, Atom selection, Atom
   target, Atom property, Window requestor, Time time);

   display

   Specifies the connection to the X server.

   selection

   Specifies the selection atom.

   target

   Specifies the target atom.

   property

   Specifies the property name. You also can pass None.

   requestor

   Specifies the requestor.

   time

   Specifies the time. You can pass either a timestamp or
   CurrentTime.

   XConvertSelection requests that the specified selection be
   converted to the specified target type:
     * If the specified selection has an owner, the X server sends
       a SelectionRequest event to that owner.
     * If no owner for the specified selection exists, the X
       server generates a SelectionNotify event to the requestor
       with property None.

   The arguments are passed on unchanged in either of the events.
   There are two predefined selection atoms: PRIMARY and
   SECONDARY.

   XConvertSelection can generate BadAtom and BadWindow errors.

Chapter 5. Pixmap and Cursor Functions

   Table of Contents

   Creating and Freeing Pixmaps
   Creating, Recoloring, and Freeing Cursors

Creating and Freeing Pixmaps

   Pixmaps can only be used on the screen on which they were
   created. Pixmaps are off-screen resources that are used for
   various operations, such as defining cursors as tiling patterns
   or as the source for certain raster operations. Most graphics
   requests can operate either on a window or on a pixmap. A
   bitmap is a single bit-plane pixmap.

   To create a pixmap of a given size, use XCreatePixmap.

   Pixmap XCreatePixmap(Display *display, Drawable d, unsigned int
   width, unsigned int height, unsigned int depth);

   display

   Specifies the connection to the X server.

   d

   Specifies which screen the pixmap is created on.

   width

   height

   Specify the width and height, which define the dimensions of
   the pixmap.

   depth

   Specifies the depth of the pixmap.

   The XCreatePixmap function creates a pixmap of the width,
   height, and depth you specified and returns a pixmap ID that
   identifies it. It is valid to pass an InputOnly window to the
   drawable argument. The width and height arguments must be
   nonzero, or a BadValue error results. The depth argument must
   be one of the depths supported by the screen of the specified
   drawable, or a BadValue error results.

   The server uses the specified drawable to determine on which
   screen to create the pixmap. The pixmap can be used only on
   this screen and only with other drawables of the same depth
   (see XCopyPlane for an exception to this rule). The initial
   contents of the pixmap are undefined.

   XCreatePixmap can generate BadAlloc, BadDrawable, and BadValue
   errors.

   To free all storage associated with a specified pixmap, use
   XFreePixmap.

   XFreePixmap(Display *display, Pixmap pixmap);

   display

   Specifies the connection to the X server.

   pixmap

   Specifies the pixmap.

   The XFreePixmap function first deletes the association between
   the pixmap ID and the pixmap. Then, the X server frees the
   pixmap storage when there are no references to it. The pixmap
   should never be referenced again.

   XFreePixmap can generate a BadPixmap error.

Creating, Recoloring, and Freeing Cursors

   Each window can have a different cursor defined for it.
   Whenever the pointer is in a visible window, it is set to the
   cursor defined for that window. If no cursor was defined for
   that window, the cursor is the one defined for the parent
   window.

   From X's perspective, a cursor consists of a cursor source,
   mask, colors, and a hotspot. The mask pixmap determines the
   shape of the cursor and must be a depth of one. The source
   pixmap must have a depth of one, and the colors determine the
   colors of the source. The hotspot defines the point on the
   cursor that is reported when a pointer event occurs. There may
   be limitations imposed by the hardware on cursors as to size
   and whether a mask is implemented. XQueryBestCursor can be used
   to find out what sizes are possible. There is a standard font
   for creating cursors, but Xlib provides functions that you can
   use to create cursors from an arbitrary font or from bitmaps.

   To create a cursor from the standard cursor font, use
   XCreateFontCursor.

   #include <X11/cursorfont.h>

   Cursor XCreateFontCursor(Display *display, unsigned int shape);

   display

   Specifies the connection to the X server.

   shape

   Specifies the shape of the cursor.

   X provides a set of standard cursor shapes in a special font
   named cursor. Applications are encouraged to use this interface
   for their cursors because the font can be customized for the
   individual display type. The shape argument specifies which
   glyph of the standard fonts to use.

   The hotspot comes from the information stored in the cursor
   font. The initial colors of a cursor are a black foreground and
   a white background (see XRecolorCursor). For further
   information about cursor shapes, see appendix B.

   XCreateFontCursor can generate BadAlloc and BadValue errors.

   To create a cursor from font glyphs, use XCreateGlyphCursor.

   Cursor XCreateGlyphCursor(Display *display, Font source_font,
   Font mask_font, unsigned int source_char, unsigned int
   mask_char, XColor *foreground_color, XColor *background_color);

   display

   Specifies the connection to the X server.

   source_font

   Specifies the font for the source glyph.

   mask_font

   Specifies the font for the mask glyph or None.

   source_char

   Specifies the character glyph for the source.

   mask_char

   Specifies the glyph character for the mask.

   foreground_color

   Specifies the RGB values for the foreground of the source.

   background_color

   Specifies the RGB values for the background of the source.

   The XCreateGlyphCursor function is similar to
   XCreatePixmapCursor except that the source and mask bitmaps are
   obtained from the specified font glyphs. The source_char must
   be a defined glyph in source_font, or a BadValue error results.
   If mask_font is given, mask_char must be a defined glyph in
   mask_font, or a BadValue error results. The mask_font and
   character are optional. The origins of the source_char and
   mask_char (if defined) glyphs are positioned coincidently and
   define the hotspot. The source_char and mask_char need not have
   the same bounding box metrics, and there is no restriction on
   the placement of the hotspot relative to the bounding boxes. If
   no mask_char is given, all pixels of the source are displayed.
   You can free the fonts immediately by calling XFreeFont if no
   further explicit references to them are to be made.

   For 2-byte matrix fonts, the 16-bit value should be formed with
   the byte1 member in the most significant byte and the byte2
   member in the least significant byte.

   XCreateGlyphCursor can generate BadAlloc, BadFont, and BadValue
   errors.

   To create a cursor from two bitmaps, use XCreatePixmapCursor.

   Cursor XCreatePixmapCursor(Display *display, Pixmap source,
   Pixmap mask, XColor *foreground_color, XColor
   *background_color, unsigned int x, unsigned int y);

   display

   Specifies the connection to the X server.

   source

   Specifies the shape of the source cursor.

   mask

   Specifies the cursor's source bits to be displayed or None.

   foreground_color

   Specifies the RGB values for the foreground of the source.

   background_color

   Specifies the RGB values for the background of the source.

   x

   y

   Specify the x and y coordinates, which indicate the hotspot
   relative to the source's origin.

   The XCreatePixmapCursor function creates a cursor and returns
   the cursor ID associated with it. The foreground and background
   RGB values must be specified using foreground_color and
   background_color, even if the X server only has a StaticGray or
   GrayScale screen. The foreground color is used for the pixels
   set to 1 in the source, and the background color is used for
   the pixels set to 0. Both source and mask, if specified, must
   have depth one (or a BadMatch error results) but can have any
   root. The mask argument defines the shape of the cursor. The
   pixels set to 1 in the mask define which source pixels are
   displayed, and the pixels set to 0 define which pixels are
   ignored. If no mask is given, all pixels of the source are
   displayed. The mask, if present, must be the same size as the
   pixmap defined by the source argument, or a BadMatch error
   results. The hotspot must be a point within the source, or a
   BadMatch error results.

   The components of the cursor can be transformed arbitrarily to
   meet display limitations. The pixmaps can be freed immediately
   if no further explicit references to them are to be made.
   Subsequent drawing in the source or mask pixmap has an
   undefined effect on the cursor. The X server might or might not
   make a copy of the pixmap.

   XCreatePixmapCursor can generate BadAlloc and BadPixmap errors.

   To determine useful cursor sizes, use XQueryBestCursor.

   Status XQueryBestCursor(Display *display, Drawable d, unsigned
   int width, unsigned int height, unsigned int *width_return,
   unsigned int *height_return);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable, which indicates the screen.

   width

   height

   Specify the width and height of the cursor that you want the
   size information for.

   width_return

   height_return

   Return the best width and height that is closest to the
   specified width and height.

   Some displays allow larger cursors than other displays. The
   XQueryBestCursor function provides a way to find out what size
   cursors are actually possible on the display. It returns the
   largest size that can be displayed. Applications should be
   prepared to use smaller cursors on displays that cannot support
   large ones.

   XQueryBestCursor can generate a BadDrawable error.

   To change the color of a given cursor, use XRecolorCursor.

   XRecolorCursor(Display *display, Cursor cursor, XColor
   *foreground_color, XColor *background_color);

   display

   Specifies the connection to the X server.

   cursor

   Specifies the cursor.

   foreground_color

   Specifies the RGB values for the foreground of the source.

   background_color

   Specifies the RGB values for the background of the source.

   The XRecolorCursor function changes the color of the specified
   cursor, and if the cursor is being displayed on a screen, the
   change is visible immediately. The pixel members of the XColor
   structures are ignored; only the RGB values are used.

   XRecolorCursor can generate a BadCursor error.

   To free (destroy) a given cursor, use XFreeCursor.

   XFreeCursor(Display *display, Cursor cursor);

   display

   Specifies the connection to the X server.

   cursor

   Specifies the cursor.

   The XFreeCursor function deletes the association between the
   cursor resource ID and the specified cursor. The cursor storage
   is freed when no other resource references it. The specified
   cursor ID should not be referred to again.

   XFreeCursor can generate a BadCursor error.

Chapter 6. Color Management Functions

   Table of Contents

   Color Structures
   Color Strings

        RGB Device String Specification
        RGB Intensity String Specification
        Device-Independent String Specifications

   Color Conversion Contexts and Gamut Mapping
   Creating, Copying, and Destroying Colormaps
   Mapping Color Names to Values
   Allocating and Freeing Color Cells
   Modifying and Querying Colormap Cells
   Color Conversion Context Functions

        Getting and Setting the Color Conversion Context of a
                Colormap

        Obtaining the Default Color Conversion Context
        Color Conversion Context Macros
        Modifying Attributes of a Color Conversion Context
        Creating and Freeing a Color Conversion Context

   Converting between Color Spaces
   Callback Functions

        Prototype Gamut Compression Procedure
        Supplied Gamut Compression Procedures
        Prototype White Point Adjustment Procedure
        Supplied White Point Adjustment Procedures

   Gamut Querying Functions

        Red, Green, and Blue Queries
        CIELab Queries
        CIELuv Queries
        TekHVC Queries

   Color Management Extensions

        Color Spaces
        Adding Device-Independent Color Spaces
        Querying Color Space Format and Prefix
        Creating Additional Color Spaces
        Parse String Callback
        Color Specification Conversion Callback
        Function Sets
        Adding Function Sets
        Creating Additional Function Sets

   Each X window always has an associated colormap that provides a
   level of indirection between pixel values and colors displayed
   on the screen. Xlib provides functions that you can use to
   manipulate a colormap. The X protocol defines colors using
   values in the RGB color space. The RGB color space is device
   dependent; rendering an RGB value on differing output devices
   typically results in different colors. Xlib also provides a
   means for clients to specify color using device-independent
   color spaces for consistent results across devices. Xlib
   supports device-independent color spaces derivable from the CIE
   XYZ color space. This includes the CIE XYZ, xyY, L*u*v*, and
   L*a*b* color spaces as well as the TekHVC color space.

   This chapter discusses how to:
     * Create, copy, and destroy a colormap
     * Specify colors by name or value
     * Allocate, modify, and free color cells
     * Read entries in a colormap
     * Convert between color spaces
     * Control aspects of color conversion
     * Query the color gamut of a screen
     * Add new color spaces

   All functions, types, and symbols in this chapter with the
   prefix ``Xcms'' are defined in <X11/Xcms.h>. The remaining
   functions and types are defined in <X11/Xlib.h>.

   Functions in this chapter manipulate the representation of
   color on the screen. For each possible value that a pixel can
   take in a window, there is a color cell in the colormap. For
   example, if a window is 4 bits deep, pixel values 0 through 15
   are defined. A colormap is a collection of color cells. A color
   cell consists of a triple of red, green, and blue (RGB) values.
   The hardware imposes limits on the number of significant bits
   in these values. As each pixel is read out of display memory,
   the pixel is looked up in a colormap. The RGB value of the cell
   determines what color is displayed on the screen. On a
   grayscale display with a black-and-white monitor, the values
   are combined to determine the brightness on the screen.

   Typically, an application allocates color cells or sets of
   color cells to obtain the desired colors. The client can
   allocate read-only cells. In which case, the pixel values for
   these colors can be shared among multiple applications, and the
   RGB value of the cell cannot be changed. If the client
   allocates read/write cells, they are exclusively owned by the
   client, and the color associated with the pixel value can be
   changed at will. Cells must be allocated (and, if read/write,
   initialized with an RGB value) by a client to obtain desired
   colors. The use of pixel value for an unallocated cell results
   in an undefined color.

   Because colormaps are associated with windows, X supports
   displays with multiple colormaps and, indeed, different types
   of colormaps. If there are insufficient colormap resources in
   the display, some windows will display in their true colors,
   and others will display with incorrect colors. A window manager
   usually controls which windows are displayed in their true
   colors if more than one colormap is required for the color
   resources the applications are using. At any time, there is a
   set of installed colormaps for a screen. Windows using one of
   the installed colormaps display with true colors, and windows
   using other colormaps generally display with incorrect colors.
   You can control the set of installed colormaps by using
   XInstallColormap and XUninstallColormap.

   Colormaps are local to a particular screen. Screens always have
   a default colormap, and programs typically allocate cells out
   of this colormap. Generally, you should not write applications
   that monopolize color resources. Although some hardware
   supports multiple colormaps installed at one time, many of the
   hardware displays built today support only a single installed
   colormap, so the primitives are written to encourage sharing of
   colormap entries between applications.

   The DefaultColormap macro returns the default colormap. The
   DefaultVisual macro returns the default visual type for the
   specified screen. Possible visual types are StaticGray,
   GrayScale, StaticColor, PseudoColor, TrueColor, or DirectColor
   (see section 3.1).

Color Structures

   Functions that operate only on RGB color space values use an
   XColor structure, which contains:



typedef struct {
        unsigned long pixel;    /* pixel value */
        unsigned short red, green, blue;        /* rgb values */
        char flags;     /* DoRed, DoGreen, DoBlue */
        char pad;
} XColor;

   The red, green, and blue values are always in the range 0 to
   65535 inclusive, independent of the number of bits actually
   used in the display hardware. The server scales these values
   down to the range used by the hardware. Black is represented by
   (0,0,0), and white is represented by (65535,65535,65535). In
   some functions, the flags member controls which of the red,
   green, and blue members is used and can be the inclusive OR of
   zero or more of DoRed, DoGreen, and DoBlue.

   Functions that operate on all color space values use an
   XcmsColor structure. This structure contains a union of
   substructures, each supporting color specification encoding for
   a particular color space. Like the XColor structure, the
   XcmsColor structure contains pixel and color specification
   information (the spec member in the XcmsColor structure).



typedef unsigned long XcmsColorFormat;                  /* Color Specifi
cation Format */

typedef struct {
        union {
                XcmsRGB RGB;
                XcmsRGBi RGBi;
                XcmsCIEXYZ CIEXYZ;
                XcmsCIEuvY CIEuvY;
                XcmsCIExyY CIExyY;
                XcmsCIELab CIELab;
                XcmsCIELuv CIELuv;
                XcmsTekHVC TekHVC;
                XcmsPad Pad;
        } spec;
        unsigned long pixel;
        XcmsColorFormat format;
} XcmsColor;                    /* Xcms Color Structure */

   Because the color specification can be encoded for the various
   color spaces, encoding for the spec member is identified by the
   format member, which is of type XcmsColorFormat. The following
   macros define standard formats.
#define          XcmsUndefinedFormat   0x00000000
#define          XcmsCIEXYZFormat      0x00000001  /* CIE XYZ */
#define          XcmsCIEuvYFormat      0x00000002  /* CIE u'v'Y */
#define          XcmsCIExyYFormat      0x00000003  /* CIE xyY */
#define          XcmsCIELabFormat      0x00000004  /* CIE L*a*b* */
#define          XcmsCIELuvFormat      0x00000005  /* CIE L*u*v* */
#define          XcmsTekHVCFormat      0x00000006  /* TekHVC */
#define          XcmsRGBFormat         0x80000000  /* RGB Device */
#define          XcmsRGBiFormat        0x80000001  /* RGB Intensity */

   Formats for device-independent color spaces are distinguishable
   from those for device-dependent spaces by the 32nd bit. If this
   bit is set, it indicates that the color specification is in a
   device-dependent form; otherwise, it is in a device-independent
   form. If the 31st bit is set, this indicates that the color
   space has been added to Xlib at run time (see section 6.12.4).
   The format value for a color space added at run time may be
   different each time the program is executed. If references to
   such a color space must be made outside the client (for
   example, storing a color specification in a file), then
   reference should be made by color space string prefix (see
   XcmsFormatOfPrefix and XcmsPrefixOfFormat).

   Data types that describe the color specification encoding for
   the various color spaces are defined as follows:



typedef double XcmsFloat;

typedef struct {
        unsigned short red;     /* 0x0000 to 0xffff */
        unsigned short green;   /* 0x0000 to 0xffff */
        unsigned short blue;    /* 0x0000 to 0xffff */
} XcmsRGB;              /* RGB Device */



typedef struct {
        XcmsFloat red;  /* 0.0 to 1.0 */
        XcmsFloat green;        /* 0.0 to 1.0 */
        XcmsFloat blue; /* 0.0 to 1.0 */
} XcmsRGBi;             /* RGB Intensity */



typedef struct {
        XcmsFloat X;
        XcmsFloat Y;    /* 0.0 to 1.0 */
        XcmsFloat Z;
} XcmsCIEXYZ;           /* CIE XYZ */



typedef struct {
        XcmsFloat u_prime;      /* 0.0 to ~0.6 */
        XcmsFloat v_prime;      /* 0.0 to ~0.6 */
        XcmsFloat Y;    /* 0.0 to 1.0 */
} XcmsCIEuvY;           /* CIE u'v'Y */



typedef struct {
        XcmsFloat x;    /* 0.0 to ~.75 */
        XcmsFloat y;    /* 0.0 to ~.85 */
        XcmsFloat Y;    /* 0.0 to 1.0 */
} XcmsCIExyY;           /* CIE xyY */



typedef struct {
        XcmsFloat L_star;       /* 0.0 to 100.0 */
        XcmsFloat a_star;
        XcmsFloat b_star;
} XcmsCIELab;           /* CIE L*a*b* */



typedef struct {
        XcmsFloat L_star;       /* 0.0 to 100.0 */
        XcmsFloat u_star;
        XcmsFloat v_star;
} XcmsCIELuv;           /* CIE L*u*v* */



typedef struct {
        XcmsFloat H;    /* 0.0 to 360.0 */
        XcmsFloat V;    /* 0.0 to 100.0 */
        XcmsFloat C;    /* 0.0 to 100.0 */
} XcmsTekHVC;           /* TekHVC */



typedef struct {
        XcmsFloat pad0;
        XcmsFloat pad1;
        XcmsFloat pad2;
        XcmsFloat pad3;
} XcmsPad;              /* four doubles */

   The device-dependent formats provided allow color specification
   in:
     * RGB Intensity (XcmsRGBi)
     * Red, green, and blue linear intensity values,
       floating-point values from 0.0 to 1.0, where 1.0 indicates
       full intensity, 0.5 half intensity, and so on.
     * RGB Device (XcmsRGB)
     * Red, green, and blue values appropriate for the specified
       output device. XcmsRGB values are of type unsigned short,
       scaled from 0 to 65535 inclusive, and are interchangeable
       with the red, green, and blue values in an XColor
       structure.

   It is important to note that RGB Intensity values are not gamma
   corrected values. In contrast, RGB Device values generated as a
   result of converting color specifications are always gamma
   corrected, and RGB Device values acquired as a result of
   querying a colormap or passed in by the client are assumed by
   Xlib to be gamma corrected. The term RGB value in this manual
   always refers to an RGB Device value.

Color Strings

   Xlib provides a mechanism for using string names for colors. A
   color string may either contain an abstract color name or a
   numerical color specification. Color strings are
   case-insensitive.

   Color strings are used in the following functions:
     * XAllocNamedColor
     * XcmsAllocNamedColor
     * XLookupColor
     * XcmsLookupColor
     * XParseColor
     * XStoreNamedColor

   Xlib supports the use of abstract color names, for example, red
   or blue. A value for this abstract name is obtained by
   searching one or more color name databases. Xlib first searches
   zero or more client-side databases; the number, location, and
   content of these databases is implementation-dependent and
   might depend on the current locale. If the name is not found,
   Xlib then looks for the color in the X server's database. If
   the color name is not in the Host Portable Character Encoding,
   the result is implementation-dependent.

   A numerical color specification consists of a color space name
   and a set of values in the following syntax:

<color_space_name>:<value>/.../<value>

   The following are examples of valid color strings.

"CIEXYZ:0.3227/0.28133/0.2493"
"RGBi:1.0/0.0/0.0"
"rgb:00/ff/00"
"CIELuv:50.0/0.0/0.0"

   The syntax and semantics of numerical specifications are given
   for each standard color space in the following sections.

RGB Device String Specification

   An RGB Device specification is identified by the prefix
   ``rgb:'' and conforms to the following syntax:

rgb:<red>/<green>/<blue>

    <red>, <green>, <blue> := h | hh | hhh | hhhh
    h := single hexadecimal digits (case insignificant)

   Note that h indicates the value scaled in 4 bits, hh the value
   scaled in 8 bits, hhh the value scaled in 12 bits, and hhhh the
   value scaled in 16 bits, respectively.

   Typical examples are the strings ``rgb:ea/75/52'' and
   ``rgb:ccc/320/320'', but mixed numbers of hexadecimal digit
   strings (``rgb:ff/a5/0'' and ``rgb:ccc/32/0'') are also
   allowed.

   For backward compatibility, an older syntax for RGB Device is
   supported, but its continued use is not encouraged. The syntax
   is an initial sharp sign character followed by a numeric
   specification, in one of the following formats:



#RGB    (4 bits each)
#RRGGBB (8 bits each)
#RRRGGGBBB      (12 bits each)
#RRRRGGGGBBBB   (16 bits each)

   The R, G, and B represent single hexadecimal digits. When fewer
   than 16 bits each are specified, they represent the most
   significant bits of the value (unlike the ``rgb:'' syntax, in
   which values are scaled). For example, the string ``#3a7'' is
   the same as ``#3000a0007000''.

RGB Intensity String Specification

   An RGB intensity specification is identified by the prefix
   ``rgbi:'' and conforms to the following syntax:

rgbi:<red>/<green>/<blue>

   Note that red, green, and blue are floating-point values
   between 0.0 and 1.0, inclusive. The input format for these
   values is an optional sign, a string of numbers possibly
   containing a decimal point, and an optional exponent field
   containing an E or e followed by a possibly signed integer
   string.

Device-Independent String Specifications

   The standard device-independent string specifications have the
   following syntax:

CIEXYZ:<X>/<Y>/<Z>
CIEuvY:<u>/<v>/<Y>
CIExyY:<x>/<y>/<Y>
CIELab:<L>/<a>/<b>
CIELuv:<L>/<u>/<v>
TekHVC:<H>/<V>/<C>

   All of the values (C, H, V, X, Y, Z, a, b, u, v, y, x) are
   floating-point values. The syntax for these values is an
   optional plus or minus sign, a string of digits possibly
   containing a decimal point, and an optional exponent field
   consisting of an ``E'' or ``e'' followed by an optional plus or
   minus followed by a string of digits.

Color Conversion Contexts and Gamut Mapping

   When Xlib converts device-independent color specifications into
   device-dependent specifications and vice versa, it uses
   knowledge about the color limitations of the screen hardware.
   This information, typically called the device profile, is
   available in a Color Conversion Context (CCC).

   Because a specified color may be outside the color gamut of the
   target screen and the white point associated with the color
   specification may differ from the white point inherent to the
   screen, Xlib applies gamut mapping when it encounters certain
   conditions:
     * Gamut compression occurs when conversion of
       device-independent color specifications to device-dependent
       color specifications results in a color out of the target
       screen's gamut.
     * White adjustment occurs when the inherent white point of
       the screen differs from the white point assumed by the
       client.

   Gamut handling methods are stored as callbacks in the CCC,
   which in turn are used by the color space conversion routines.
   Client data is also stored in the CCC for each callback. The
   CCC also contains the white point the client assumes to be
   associated with color specifications (that is, the Client White
   Point). The client can specify the gamut handling callbacks and
   client data as well as the Client White Point. Xlib does not
   preclude the X client from performing other forms of gamut
   handling (for example, gamut expansion); however, Xlib does not
   provide direct support for gamut handling other than white
   adjustment and gamut compression.

   Associated with each colormap is an initial CCC transparently
   generated by Xlib. Therefore, when you specify a colormap as an
   argument to an Xlib function, you are indirectly specifying a
   CCC. There is a default CCC associated with each screen. Newly
   created CCCs inherit attributes from the default CCC, so the
   default CCC attributes can be modified to affect new CCCs.

   Xcms functions in which gamut mapping can occur return Status
   and have specific status values defined for them, as follows:
     * XcmsFailure indicates that the function failed.
     * XcmsSuccess indicates that the function succeeded. In
       addition, if the function performed any color conversion,
       the colors did not need to be compressed.
     * XcmsSuccessWithCompression indicates the function performed
       color conversion and at least one of the colors needed to
       be compressed. The gamut compression method is determined
       by the gamut compression procedure in the CCC that is
       specified directly as a function argument or in the CCC
       indirectly specified by means of the colormap argument.

Creating, Copying, and Destroying Colormaps

   To create a colormap for a screen, use XCreateColormap.

   Colormap XCreateColormap(Display *display, Window w, Visual
   *visual, int alloc);

   display

   Specifies the connection to the X server.

   w

   Specifies the window on whose screen you want to create a
   colormap.

   visual

   Specifies a visual type supported on the screen. If the visual
   type is not one supported by the screen, a BadMatch error
   results.

   alloc

   Specifies the colormap entries to be allocated. You can pass
   AllocNone or AllocAll.

   The XCreateColormap function creates a colormap of the
   specified visual type for the screen on which the specified
   window resides and returns the colormap ID associated with it.
   Note that the specified window is only used to determine the
   screen.

   The initial values of the colormap entries are undefined for
   the visual classes GrayScale, PseudoColor, and DirectColor. For
   StaticGray, StaticColor, and TrueColor, the entries have
   defined values, but those values are specific to the visual and
   are not defined by X. For StaticGray, StaticColor, and
   TrueColor, alloc must be AllocNone, or a BadMatch error
   results. For the other visual classes, if alloc is AllocNone,
   the colormap initially has no allocated entries, and clients
   can allocate them. For information about the visual types, see
   section 3.1.

   If alloc is AllocAll, the entire colormap is allocated
   writable. The initial values of all allocated entries are
   undefined. For GrayScale and PseudoColor, the effect is as if
   an XAllocColorCells call returned all pixel values from zero to
   N - 1, where N is the colormap entries value in the specified
   visual. For DirectColor, the effect is as if an
   XAllocColorPlanes call returned a pixel value of zero and
   red_mask, green_mask, and blue_mask values containing the same
   bits as the corresponding masks in the specified visual.
   However, in all cases, none of these entries can be freed by
   using XFreeColors.

   XCreateColormap can generate BadAlloc, BadMatch, BadValue, and
   BadWindow errors.

   To create a new colormap when the allocation out of a
   previously shared colormap has failed because of resource
   exhaustion, use XCopyColormapAndFree.

   Colormap XCopyColormapAndFree(Display *display, Colormap
   colormap);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   The XCopyColormapAndFree function creates a colormap of the
   same visual type and for the same screen as the specified
   colormap and returns the new colormap ID. It also moves all of
   the client's existing allocation from the specified colormap to
   the new colormap with their color values intact and their
   read-only or writable characteristics intact and frees those
   entries in the specified colormap. Color values in other
   entries in the new colormap are undefined. If the specified
   colormap was created by the client with alloc set to AllocAll,
   the new colormap is also created with AllocAll, all color
   values for all entries are copied from the specified colormap,
   and then all entries in the specified colormap are freed. If
   the specified colormap was not created by the client with
   AllocAll, the allocations to be moved are all those pixels and
   planes that have been allocated by the client using
   XAllocColor, XAllocNamedColor, XAllocColorCells, or
   XAllocColorPlanes and that have not been freed since they were
   allocated.

   XCopyColormapAndFree can generate BadAlloc and BadColor errors.

   To destroy a colormap, use XFreeColormap.

   XFreeColormap(Display *display, Colormap colormap);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap that you want to destroy.

   The XFreeColormap function deletes the association between the
   colormap resource ID and the colormap and frees the colormap
   storage. However, this function has no effect on the default
   colormap for a screen. If the specified colormap is an
   installed map for a screen, it is uninstalled (see
   XUninstallColormap). If the specified colormap is defined as
   the colormap for a window (by XCreateWindow,
   XSetWindowColormap, or XChangeWindowAttributes), XFreeColormap
   changes the colormap associated with the window to None and
   generates a ColormapNotify event. X does not define the colors
   displayed for a window with a colormap of None.

   XFreeColormap can generate a BadColor error.

Mapping Color Names to Values

   To map a color name to an RGB value, use XLookupColor.

   Status XLookupColor(Display *display, Colormap colormap, char
   *color_name, XColor *exact_def_return, XColor
   *screen_def_return);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   color_name

   Specifies the color name string (for example, red) whose color
   definition structure you want returned.

   exact_def_return

   Returns the exact RGB values.

   screen_def_return

   Returns the closest RGB values provided by the hardware.

   The XLookupColor function looks up the string name of a color
   with respect to the screen associated with the specified
   colormap. It returns both the exact color values and the
   closest values provided by the screen with respect to the
   visual type of the specified colormap. If the color name is not
   in the Host Portable Character Encoding, the result is
   implementation-dependent. Use of uppercase or lowercase does
   not matter. XLookupColor returns nonzero if the name is
   resolved; otherwise, it returns zero.

   XLookupColor can generate a BadColor error.

   To map a color name to the exact RGB value, use XParseColor.

   Status XParseColor(Display *display, Colormap colormap, char
   *spec, XColor *exact_def_return);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   spec

   Specifies the color name string; case is ignored.

   exact_def_return

   Returns the exact color value for later use and sets the DoRed,
   DoGreen, and DoBlue flags.

   The XParseColor function looks up the string name of a color
   with respect to the screen associated with the specified
   colormap. It returns the exact color value. If the color name
   is not in the Host Portable Character Encoding, the result is
   implementation-dependent. Use of uppercase or lowercase does
   not matter. XParseColor returns nonzero if the name is
   resolved; otherwise, it returns zero.

   XParseColor can generate a BadColor error.

   To map a color name to a value in an arbitrary color space, use
   XcmsLookupColor.

   Status XcmsLookupColor(Display *display, Colormap colormap,
   char *color_string, XcmsColor *color_exact_return, XcmsColor
   *color_screen_return, XcmsColorFormat result_format);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   color_string

   Specifies the color string(St.

   color_exact_return

   Returns the color specification parsed from the color string or
   parsed from the corresponding string found in a color-name
   database.

   color_screen_return

   Returns the color that can be reproduced on the screen.

   result_format

   Specifies the color format for the returned color
   specifications (color_screen_return and color_exact_return
   arguments). If the format is XcmsUndefinedFormat and the color
   string contains a numerical color specification, the
   specification is returned in the format used in that numerical
   color specification. If the format is XcmsUndefinedFormat and
   the color string contains a color name, the specification is
   returned in the format used to store the color in the database.

   The XcmsLookupColor function looks up the string name of a
   color with respect to the screen associated with the specified
   colormap. It returns both the exact color values and the
   closest values provided by the screen with respect to the
   visual type of the specified colormap. The values are returned
   in the format specified by result_format. If the color name is
   not in the Host Portable Character Encoding, the result is
   implementation-dependent. Use of uppercase or lowercase does
   not matter. XcmsLookupColor returns XcmsSuccess or
   XcmsSuccessWithCompression if the name is resolved; otherwise,
   it returns XcmsFailure. If XcmsSuccessWithCompression is
   returned, the color specification returned in
   color_screen_return is the result of gamut compression.

Allocating and Freeing Color Cells

   There are two ways of allocating color cells: explicitly as
   read-only entries, one pixel value at a time, or read/write,
   where you can allocate a number of color cells and planes
   simultaneously. A read-only cell has its RGB value set by the
   server. Read/write cells do not have defined colors initially;
   functions described in the next section must be used to store
   values into them. Although it is possible for any client to
   store values into a read/write cell allocated by another
   client, read/write cells normally should be considered private
   to the client that allocated them.

   Read-only colormap cells are shared among clients. The server
   counts each allocation and freeing of the cell by clients. When
   the last client frees a shared cell, the cell is finally
   deallocated. If a single client allocates the same read-only
   cell multiple times, the server counts each such allocation,
   not just the first one.

   To allocate a read-only color cell with an RGB value, use
   XAllocColor.

   Status XAllocColor(Display *display, Colormap colormap, XColor
   *screen_in_out);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   screen_in_out

   Specifies and returns the values actually used in the colormap.

   The XAllocColor function allocates a read-only colormap entry
   corresponding to the closest RGB value supported by the
   hardware. XAllocColor returns the pixel value of the color
   closest to the specified RGB elements supported by the hardware
   and returns the RGB value actually used. The corresponding
   colormap cell is read-only. In addition, XAllocColor returns
   nonzero if it succeeded or zero if it failed. Multiple clients
   that request the same effective RGB value can be assigned the
   same read-only entry, thus allowing entries to be shared. When
   the last client deallocates a shared cell, it is deallocated.
   XAllocColor does not use or affect the flags in the XColor
   structure.

   XAllocColor can generate a BadColor error. delim %%

   To allocate a read-only color cell with a color in arbitrary
   format, use XcmsAllocColor.

   Status XcmsAllocColor(Display *display, Colormap colormap,
   XcmsColor *color_in_out, XcmsColorFormat result_format);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   color_in_out

   Specifies the color to allocate and returns the pixel and color
   that is actually used in the colormap.

   result_format

   Specifies the color format for the returned color
   specification.

   The XcmsAllocColor function is similar to XAllocColor except
   the color can be specified in any format. The XcmsAllocColor
   function ultimately calls XAllocColor to allocate a read-only
   color cell (colormap entry) with the specified color.
   XcmsAllocColor first converts the color specified to an RGB
   value and then passes this to XAllocColor. XcmsAllocColor
   returns the pixel value of the color cell and the color
   specification actually allocated. This returned color
   specification is the result of converting the RGB value
   returned by XAllocColor into the format specified with the
   result_format argument. If there is no interest in a returned
   color specification, unnecessary computation can be bypassed if
   result_format is set to XcmsRGBFormat. The corresponding
   colormap cell is read-only. If this routine returns
   XcmsFailure, the color_in_out color specification is left
   unchanged.

   XcmsAllocColor can generate a BadColor error.

   To allocate a read-only color cell using a color name and
   return the closest color supported by the hardware in RGB
   format, use XAllocNamedColor.

   Status XAllocNamedColor(Display *display, Colormap colormap,
   char *color_name, XColor *screen_def_return, XColor
   *exact_def_return);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   color_name

   Specifies the color name string (for example, red) whose color
   definition structure you want returned.

   screen_def_return

   Returns the closest RGB values provided by the hardware.

   exact_def_return

   Returns the exact RGB values.

   The XAllocNamedColor function looks up the named color with
   respect to the screen that is associated with the specified
   colormap. It returns both the exact database definition and the
   closest color supported by the screen. The allocated color cell
   is read-only. The pixel value is returned in screen_def_return.
   If the color name is not in the Host Portable Character
   Encoding, the result is implementation-dependent. Use of
   uppercase or lowercase does not matter. If screen_def_return
   and exact_def_return point to the same structure, the pixel
   field will be set correctly, but the color values are
   undefined. XAllocNamedColor returns nonzero if a cell is
   allocated; otherwise, it returns zero.

   XAllocNamedColor can generate a BadColor error.

   To allocate a read-only color cell using a color name and
   return the closest color supported by the hardware in an
   arbitrary format, use XcmsAllocNamedColor.

   Status XcmsAllocNamedColor(Display *display, Colormap colormap,
   char *color_string, XcmsColor *color_screen_return, XcmsColor
   *color_exact_return, XcmsColorFormat result_format);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   color_string

   Specifies the color string whose color definition structure is
   to be returned.

   color_screen_return

   Returns the pixel value of the color cell and color
   specification that actually is stored for that cell.

   color_exact_return

   Returns the color specification parsed from the color string or
   parsed from the corresponding string found in a color-name
   database.

   result_format

   Specifies the color format for the returned color
   specifications (color_screen_return and color_exact_return
   arguments). If the format is XcmsUndefinedFormat and the color
   string contains a numerical color specification, the
   specification is returned in the format used in that numerical
   color specification. If the format is XcmsUndefinedFormat and
   the color string contains a color name, the specification is
   returned in the format used to store the color in the database.

   The XcmsAllocNamedColor function is similar to XAllocNamedColor
   except that the color returned can be in any format specified.
   This function ultimately calls XAllocColor to allocate a
   read-only color cell with the color specified by a color
   string. The color string is parsed into an XcmsColor structure
   (see XcmsLookupColor), converted to an RGB value, and finally
   passed to XAllocColor. If the color name is not in the Host
   Portable Character Encoding, the result is
   implementation-dependent. Use of uppercase or lowercase does
   not matter.

   This function returns both the color specification as a result
   of parsing (exact specification) and the actual color
   specification stored (screen specification). This screen
   specification is the result of converting the RGB value
   returned by XAllocColor into the format specified in
   result_format. If there is no interest in a returned color
   specification, unnecessary computation can be bypassed if
   result_format is set to XcmsRGBFormat. If color_screen_return
   and color_exact_return point to the same structure, the pixel
   field will be set correctly, but the color values are
   undefined.

   XcmsAllocNamedColor can generate a BadColor error.

   To allocate read/write color cell and color plane combinations
   for a PseudoColor model, use XAllocColorCells.

   Status XAllocColorCells(Display *display, Colormap colormap,
   Bool contig, unsigned long plane_masks_return[], unsigned int
   nplanes, unsigned long pixels_return[], unsigned int npixels);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   contig

   Specifies a Boolean value that indicates whether the planes
   must be contiguous.

   plane_mask_return

   Returns an array of plane masks.

   nplanes

   Specifies the number of plane masks that are to be returned in
   the plane masks array.

   pixels_return

   Returns an array of pixel values.

   npixels

   Specifies the number of pixel values that are to be returned in
   the pixels_return array.

   The XAllocColorCells function allocates read/write color cells.
   The number of colors must be positive and the number of planes
   nonnegative, or a BadValue error results. If ncolors and
   nplanes are requested, then ncolors pixels and nplane plane
   masks are returned. No mask will have any bits set to 1 in
   common with any other mask or with any of the pixels. By ORing
   together each pixel with zero or more masks, ncolors ×
   2^nplanes distinct pixels can be produced. All of these are
   allocated writable by the request. For GrayScale or
   PseudoColor, each mask has exactly one bit set to 1. For
   DirectColor, each has exactly three bits set to 1. If contig is
   True and if all masks are ORed together, a single contiguous
   set of bits set to 1 will be formed for GrayScale or
   PseudoColor and three contiguous sets of bits set to 1 (one
   within each pixel subfield) for DirectColor. The RGB values of
   the allocated entries are undefined. XAllocColorCells returns
   nonzero if it succeeded or zero if it failed.

   XAllocColorCells can generate BadColor and BadValue errors.

   To allocate read/write color resources for a DirectColor model,
   use XAllocColorPlanes.

   Status XAllocColorPlanes(Display *display, Colormap colormap,
   Bool contig, unsigned long pixels_return[], int ncolors, int
   nreds, int ngreens, int nblues, unsigned long *rmask_return,
   unsigned long *gmask_return, unsigned long *bmask_return);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   contig

   Specifies a Boolean value that indicates whether the planes
   must be contiguous.

   pixels_return

   Returns an array of pixel values. XAllocColorPlanes returns the
   pixel values in this array.

   ncolors

   Specifies the number of pixel values that are to be returned in
   the pixels_return array.

   nreds

   ngreens

   nblues

   Specify the number of red, green, and blue planes. The value
   you pass must be nonnegative.

   rmask_return

   gmask_return

   bmask_return

   Return bit masks for the red, green, and blue planes.

   The specified ncolors must be positive; and nreds, ngreens, and
   nblues must be nonnegative, or a BadValue error results. If
   ncolors colors, nreds reds, ngreens greens, and nblues blues
   are requested, ncolors pixels are returned; and the masks have
   nreds, ngreens, and nblues bits set to 1, respectively. If
   contig is True, each mask will have a contiguous set of bits
   set to 1. No mask will have any bits set to 1 in common with
   any other mask or with any of the pixels. For DirectColor, each
   mask will lie within the corresponding pixel subfield. By ORing
   together subsets of masks with each pixel value, ncolors ×
   2^(nreds+ngreens+nblues) distinct pixel values can be produced.
   All of these are allocated by the request. However, in the
   colormap, there are only ncolors × 2^nreds independent red
   entries, ncolors × 2^ngreens independent green entries, and
   ncolors × 2^nblues independent blue entries. This is true even
   for PseudoColor. When the colormap entry of a pixel value is
   changed (using XStoreColors, XStoreColor, or XStoreNamedColor),
   the pixel is decomposed according to the masks, and the
   corresponding independent entries are updated.
   XAllocColorPlanes returns nonzero if it succeeded or zero if it
   failed.

   XAllocColorPlanes can generate BadColor and BadValue errors.

   To free colormap cells, use XFreeColors.

   XFreeColors(Display *display, Colormap colormap, unsigned long
   pixels[], int npixels, unsigned long planes);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   pixels

   Specifies an array of pixel values that map to the cells in the
   specified colormap.

   npixels

   Specifies the number of pixels.

   planes

   Specifies the planes you want to free.

   The XFreeColors function frees the cells represented by pixels
   whose values are in the pixels array. The planes argument
   should not have any bits set to 1 in common with any of the
   pixels. The set of all pixels is produced by ORing together
   subsets of the planes argument with the pixels. The request
   frees all of these pixels that were allocated by the client
   (using XAllocColor, XAllocNamedColor, XAllocColorCells, and
   XAllocColorPlanes). Note that freeing an individual pixel
   obtained from XAllocColorPlanes may not actually allow it to be
   reused until all of its related pixels are also freed.
   Similarly, a read-only entry is not actually freed until it has
   been freed by all clients, and if a client allocates the same
   read-only entry multiple times, it must free the entry that
   many times before the entry is actually freed.

   All specified pixels that are allocated by the client in the
   colormap are freed, even if one or more pixels produce an
   error. If a specified pixel is not a valid index into the
   colormap, a BadValue error results. If a specified pixel is not
   allocated by the client (that is, is unallocated or is only
   allocated by another client) or if the colormap was created
   with all entries writable (by passing AllocAll to
   XCreateColormap), a BadAccess error results. If more than one
   pixel is in error, the one that gets reported is arbitrary.

   XFreeColors can generate BadAccess, BadColor, and BadValue
   errors.

Modifying and Querying Colormap Cells

   To store an RGB value in a single colormap cell, use
   XStoreColor.

   XStoreColor(Display *display, Colormap colormap, XColor
   *color);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   color

   Specifies the pixel and RGB values.

   The XStoreColor function changes the colormap entry of the
   pixel value specified in the pixel member of the XColor
   structure. You specified this value in the pixel member of the
   XColor structure. This pixel value must be a read/write cell
   and a valid index into the colormap. If a specified pixel is
   not a valid index into the colormap, a BadValue error results.
   XStoreColor also changes the red, green, and/or blue color
   components. You specify which color components are to be
   changed by setting DoRed, DoGreen, and/or DoBlue in the flags
   member of the XColor structure. If the colormap is an installed
   map for its screen, the changes are visible immediately.

   XStoreColor can generate BadAccess, BadColor, and BadValue
   errors.

   To store multiple RGB values in multiple colormap cells, use
   XStoreColors.

   XStoreColors(Display *display, Colormap colormap, XColor
   color[], int ncolors);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   color

   Specifies an array of color definition structures to be stored.

   ncolors

   Specifies the number of XColor structures in the color
   definition array.

   The XStoreColors function changes the colormap entries of the
   pixel values specified in the pixel members of the XColor
   structures. You specify which color components are to be
   changed by setting DoRed, DoGreen, and/or DoBlue in the flags
   member of the XColor structures. If the colormap is an
   installed map for its screen, the changes are visible
   immediately. XStoreColors changes the specified pixels if they
   are allocated writable in the colormap by any client, even if
   one or more pixels generates an error. If a specified pixel is
   not a valid index into the colormap, a BadValue error results.
   If a specified pixel either is unallocated or is allocated
   read-only, a BadAccess error results. If more than one pixel is
   in error, the one that gets reported is arbitrary.

   XStoreColors can generate BadAccess, BadColor, and BadValue
   errors.

   To store a color of arbitrary format in a single colormap cell,
   use XcmsStoreColor.

   Status XcmsStoreColor(Display *display, Colormap colormap,
   XcmsColor *color);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   color

   Specifies the color cell and the color to store. Values
   specified in this XcmsColor structure remain unchanged on
   return.

   The XcmsStoreColor function converts the color specified in the
   XcmsColor structure into RGB values. It then uses this RGB
   specification in an XColor structure, whose three flags (DoRed,
   DoGreen, and DoBlue) are set, in a call to XStoreColor to
   change the color cell specified by the pixel member of the
   XcmsColor structure. This pixel value must be a valid index for
   the specified colormap, and the color cell specified by the
   pixel value must be a read/write cell. If the pixel value is
   not a valid index, a BadValue error results. If the color cell
   is unallocated or is allocated read-only, a BadAccess error
   results. If the colormap is an installed map for its screen,
   the changes are visible immediately.

   Note that XStoreColor has no return value; therefore, an
   XcmsSuccess return value from this function indicates that the
   conversion to RGB succeeded and the call to XStoreColor was
   made. To obtain the actual color stored, use XcmsQueryColor.
   Because of the screen's hardware limitations or gamut
   compression, the color stored in the colormap may not be
   identical to the color specified.

   XcmsStoreColor can generate BadAccess, BadColor, and BadValue
   errors.

   To store multiple colors of arbitrary format in multiple
   colormap cells, use XcmsStoreColors.

   Status XcmsStoreColors(Display *display, Colormap colormap,
   XcmsColor colors[], int ncolors, Bool
   compression_flags_return[]);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   colors

   Specifies the color specification array of XcmsColor
   structures, each specifying a color cell and the color to store
   in that cell. Values specified in the array remain unchanged
   upon return.

   ncolors

   Specifies the number of XcmsColor structures in the
   color-specification array.

   compression_flags_return

   Returns an array of Boolean values indicating compression
   status. If a non-NULL pointer is supplied, each element of the
   array is set to True if the corresponding color was compressed
   and False otherwise. Pass NULL if the compression status is not
   useful.

   The XcmsStoreColors function converts the colors specified in
   the array of XcmsColor structures into RGB values and then uses
   these RGB specifications in XColor structures, whose three
   flags (DoRed, DoGreen, and DoBlue) are set, in a call to
   XStoreColors to change the color cells specified by the pixel
   member of the corresponding XcmsColor structure. Each pixel
   value must be a valid index for the specified colormap, and the
   color cell specified by each pixel value must be a read/write
   cell. If a pixel value is not a valid index, a BadValue error
   results. If a color cell is unallocated or is allocated
   read-only, a BadAccess error results. If more than one pixel is
   in error, the one that gets reported is arbitrary. If the
   colormap is an installed map for its screen, the changes are
   visible immediately.

   Note that XStoreColors has no return value; therefore, an
   XcmsSuccess return value from this function indicates that
   conversions to RGB succeeded and the call to XStoreColors was
   made. To obtain the actual colors stored, use XcmsQueryColors.
   Because of the screen's hardware limitations or gamut
   compression, the colors stored in the colormap may not be
   identical to the colors specified.

   XcmsStoreColors can generate BadAccess, BadColor, and BadValue
   errors.

   To store a color specified by name in a single colormap cell,
   use XStoreNamedColor.

   XStoreNamedColor(Display *display, Colormap colormap, char
   *color, unsigned long pixel, int flags);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   color

   Specifies the color name string (for example, red).

   pixel

   Specifies the entry in the colormap.

   flags

   Specifies which red, green, and blue components are set.

   The XStoreNamedColor function looks up the named color with
   respect to the screen associated with the colormap and stores
   the result in the specified colormap. The pixel argument
   determines the entry in the colormap. The flags argument
   determines which of the red, green, and blue components are
   set. You can set this member to the bitwise inclusive OR of the
   bits DoRed, DoGreen, and DoBlue. If the color name is not in
   the Host Portable Character Encoding, the result is
   implementation-dependent. Use of uppercase or lowercase does
   not matter. If the specified pixel is not a valid index into
   the colormap, a BadValue error results. If the specified pixel
   either is unallocated or is allocated read-only, a BadAccess
   error results.

   XStoreNamedColor can generate BadAccess, BadColor, BadName, and
   BadValue errors.

   The XQueryColor and XQueryColors functions take pixel values in
   the pixel member of XColor structures and store in the
   structures the RGB values for those pixels from the specified
   colormap. The values returned for an unallocated entry are
   undefined. These functions also set the flags member in the
   XColor structure to all three colors. If a pixel is not a valid
   index into the specified colormap, a BadValue error results. If
   more than one pixel is in error, the one that gets reported is
   arbitrary.

   To query the RGB value of a single colormap cell, use
   XQueryColor.

   XQueryColor(Display *display, Colormap colormap, XColor
   *def_in_out);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   def_in_out

   Specifies and returns the RGB values for the pixel specified in
   the structure.

   The XQueryColor function returns the current RGB value for the
   pixel in the XColor structure and sets the DoRed, DoGreen, and
   DoBlue flags.

   XQueryColor can generate BadColor and BadValue errors.

   To query the RGB values of multiple colormap cells, use
   XQueryColors.

   XQueryColors(Display *display, Colormap colormap, XColor
   defs_in_out[], int ncolors);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   defs_in_out

   Specifies and returns an array of color definition structures
   for the pixel specified in the structure.

   ncolors

   Specifies the number of XColor structures in the color
   definition array.

   The XQueryColors function returns the RGB value for each pixel
   in each XColor structure and sets the DoRed, DoGreen, and
   DoBlue flags in each structure.

   XQueryColors can generate BadColor and BadValue errors.

   To query the color of a single colormap cell in an arbitrary
   format, use XcmsQueryColor.

   Status XcmsQueryColor(Display *display, Colormap colormap,
   XcmsColor *color_in_out, XcmsColorFormat result_format);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   color_in_out

   Specifies the pixel member that indicates the color cell to
   query. The color specification stored for the color cell is
   returned in this XcmsColor structure.

   result_format

   Specifies the color format for the returned color
   specification.

   The XcmsQueryColor function obtains the RGB value for the pixel
   value in the pixel member of the specified XcmsColor structure
   and then converts the value to the target format as specified
   by the result_format argument. If the pixel is not a valid
   index in the specified colormap, a BadValue error results.

   XcmsQueryColor can generate BadColor and BadValue errors.

   To query the color of multiple colormap cells in an arbitrary
   format, use XcmsQueryColors.

   Status XcmsQueryColors(Display *display, Colormap colormap,
   XcmsColor colors_in_out[], unsigned int ncolors,
   XcmsColorFormat result_format);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   colors_in_out

   Specifies an array of XcmsColor structures, each pixel member
   indicating the color cell to query. The color specifications
   for the color cells are returned in these structures.

   ncolors

   Specifies the number of XcmsColor structures in the
   color-specification array.

   result_format

   Specifies the color format for the returned color
   specification.

   The XcmsQueryColors function obtains the RGB values for pixel
   values in the pixel members of XcmsColor structures and then
   converts the values to the target format as specified by the
   result_format argument. If a pixel is not a valid index into
   the specified colormap, a BadValue error results. If more than
   one pixel is in error, the one that gets reported is arbitrary.

   XcmsQueryColors can generate BadColor and BadValue errors.

Color Conversion Context Functions

   This section describes functions to create, modify, and query
   Color Conversion Contexts (CCCs).

   Associated with each colormap is an initial CCC transparently
   generated by Xlib. Therefore, when you specify a colormap as an
   argument to a function, you are indirectly specifying a CCC.
   The CCC attributes that can be modified by the X client are:
     * Client White Point
     * Gamut compression procedure and client data
     * White point adjustment procedure and client data

   The initial values for these attributes are implementation
   specific. The CCC attributes for subsequently created CCCs can
   be defined by changing the CCC attributes of the default CCC.
   There is a default CCC associated with each screen.

Getting and Setting the Color Conversion Context of a Colormap

   To obtain the CCC associated with a colormap, use
   XcmsCCCOfColormap.

   XcmsCCC XcmsCCCOfColormap(Display *display, Colormap colormap);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   The XcmsCCCOfColormap function returns the CCC associated with
   the specified colormap. Once obtained, the CCC attributes can
   be queried or modified. Unless the CCC associated with the
   specified colormap is changed with XcmsSetCCCOfColormap, this
   CCC is used when the specified colormap is used as an argument
   to color functions.

   To change the CCC associated with a colormap, use
   XcmsSetCCCOfColormap.

   XcmsCCC XcmsSetCCCOfColormap(Display *display, Colormap
   colormap, XcmsCCC ccc);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   ccc

   Specifies the CCC.

   The XcmsSetCCCOfColormap function changes the CCC associated
   with the specified colormap. It returns the CCC previously
   associated with the colormap. If they are not used again in the
   application, CCCs should be freed by calling XcmsFreeCCC.
   Several colormaps may share the same CCC without restriction;
   this includes the CCCs generated by Xlib with each colormap.
   Xlib, however, creates a new CCC with each new colormap.

Obtaining the Default Color Conversion Context

   You can change the default CCC attributes for subsequently
   created CCCs by changing the CCC attributes of the default CCC.
   A default CCC is associated with each screen.

   To obtain the default CCC for a screen, use XcmsDefaultCCC.

   XcmsCCC XcmsDefaultCCC(Display *display, int screen_number);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   The XcmsDefaultCCC function returns the default CCC for the
   specified screen. Its visual is the default visual of the
   screen. Its initial gamut compression and white point
   adjustment procedures as well as the associated client data are
   implementation specific.

Color Conversion Context Macros

   Applications should not directly modify any part of the
   XcmsCCC. The following lists the C language macros, their
   corresponding function equivalents for other language bindings,
   and what data they both can return.

   DisplayOfCCC(XcmsCCC ccc);

   Display *XcmsDisplayOfCCC(XcmsCCC ccc);

   ccc

   Specifies the CCC.

   Both return the display associated with the specified CCC.

   VisualOfCCC(XcmsCCC ccc);

   Visual *XcmsVisualOfCCC(XcmsCCC ccc);

   ccc

   Specifies the CCC.

   Both return the visual associated with the specified CCC.

   ScreenNumberOfCCC(XcmsCCC ccc);

   int XcmsScreenNumberOfCCC(XcmsCCC ccc);

   ccc

   Specifies the CCC.

   Both return the number of the screen associated with the
   specified CCC.

   ScreenWhitePointOfCCC(XcmsCCC ccc);

   XcmsColor XcmsScreenWhitePointOfCCC(XcmsCCC ccc);

   ccc

   Specifies the CCC.

   Both return the white point of the screen associated with the
   specified CCC.

   ClientWhitePointOfCCC(XcmsCCC ccc);

   XcmsColor *XcmsClientWhitePointOfCCC(XcmsCCC ccc);

   ccc

   Specifies the CCC.

   Both return the Client White Point of the specified CCC.

Modifying Attributes of a Color Conversion Context

   To set the Client White Point in the CCC, use
   XcmsSetWhitePoint.

   Status XcmsSetWhitePoint(XcmsCCC ccc, XcmsColor *color);

   ccc

   Specifies the CCC.

   color

   Specifies the new Client White Point.

   The XcmsSetWhitePoint function changes the Client White Point
   in the specified CCC. Note that the pixel member is ignored and
   that the color specification is left unchanged upon return. The
   format for the new white point must be XcmsCIEXYZFormat,
   XcmsCIEuvYFormat, XcmsCIExyYFormat, or XcmsUndefinedFormat. If
   the color argument is NULL, this function sets the format
   component of the Client White Point specification to
   XcmsUndefinedFormat, indicating that the Client White Point is
   assumed to be the same as the Screen White Point.

   This function returns nonzero status if the format for the new
   white point is valid; otherwise, it returns zero.

   To set the gamut compression procedure and corresponding client
   data in a specified CCC, use XcmsSetCompressionProc.

   XcmsCompressionProc XcmsSetCompressionProc(XcmsCCC ccc,
   XcmsCompressionProc compression_proc, XPointer client_data);

   ccc

   Specifies the CCC.

   compression_proc

   Specifies the gamut compression procedure that is to be applied
   when a color lies outside the screen's color gamut. If NULL is
   specified and a function using this CCC must convert a color
   specification to a device-dependent format and encounters a
   color that lies outside the screen's color gamut, that function
   will return XcmsFailure.

   client_data

   Specifies client data for gamut compression procedure or NULL.

   The XcmsSetCompressionProc function first sets the gamut
   compression procedure and client data in the specified CCC with
   the newly specified procedure and client data and then returns
   the old procedure.

   To set the white point adjustment procedure and corresponding
   client data in a specified CCC, use XcmsSetWhiteAdjustProc.

   XcmsWhiteAdjustProc XcmsSetWhiteAdjustProc(XcmsCCC ccc,
   XcmsWhiteAdjustProc white_adjust_proc, XPointer client_data);

   ccc

   Specifies the CCC.

   white_adjust_proc

   Specifies the white point adjustment procedure.

   client_data

   Specifies client data for white point adjustment procedure or
   NULL.

   The XcmsSetWhiteAdjustProc function first sets the white point
   adjustment procedure and client data in the specified CCC with
   the newly specified procedure and client data and then returns
   the old procedure.

Creating and Freeing a Color Conversion Context

   You can explicitly create a CCC within your application by
   calling XcmsCreateCCC. These created CCCs can then be used by
   those functions that explicitly call for a CCC argument. Old
   CCCs that will not be used by the application should be freed
   using XcmsFreeCCC.

   To create a CCC, use XcmsCreateCCC.

   XcmsCCC XcmsCreateCCC(Display *display, int screen_number,
   Visual *visual, XcmsColor *client_white_point,
   XcmsCompressionProc compression_proc, XPointer
   compression_client_data, XcmsWhiteAdjustProc white_adjust_proc,
   XPointer white_adjust_client_data);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   visual

   Specifies the visual type.

   client_white_point

   Specifies the Client White Point. If NULL is specified, the
   Client White Point is to be assumed to be the same as the
   Screen White Point. Note that the pixel member is ignored.

   compression_proc

   Specifies the gamut compression procedure that is to be applied
   when a color lies outside the screen's color gamut. If NULL is
   specified and a function using this CCC must convert a color
   specification to a device-dependent format and encounters a
   color that lies outside the screen's color gamut, that function
   will return XcmsFailure.

   compression_client_data

   Specifies client data for use by the gamut compression
   procedure or NULL.

   white_adjust_proc

   Specifies the white adjustment procedure that is to be applied
   when the Client White Point differs from the Screen White
   Point. NULL indicates that no white point adjustment is
   desired.

   white_adjust_client_data

   Specifies client data for use with the white point adjustment
   procedure or NULL.

   The XcmsCreateCCC function creates a CCC for the specified
   display, screen, and visual.

   To free a CCC, use XcmsFreeCCC.

   void XcmsFreeCCC(XcmsCCC ccc);

   ccc

   Specifies the CCC.

   The XcmsFreeCCC function frees the memory used for the
   specified CCC. Note that default CCCs and those currently
   associated with colormaps are ignored.

Converting between Color Spaces

   To convert an array of color specifications in arbitrary color
   formats to a single destination format, use XcmsConvertColors.

   Status XcmsConvertColors(XcmsCCC ccc, XcmsColor
   colors_in_out[], unsigned int ncolors, XcmsColorFormat
   target_format, Bool compression_flags_return[]);

   ccc

   Specifies the CCC. If conversion is between device-independent
   color spaces only (for example, TekHVC to CIELuv), the CCC is
   necessary only to specify the Client White Point.

   colors_in_out

   Specifies an array of color specifications. Pixel members are
   ignored and remain unchanged upon return.

   ncolors

   Specifies the number of XcmsColor structures in the
   color-specification array.

   target_format

   Specifies the target color specification format.

   compression_flags_return

   Returns an array of Boolean values indicating compression
   status. If a non-NULL pointer is supplied, each element of the
   array is set to True if the corresponding color was compressed
   and False otherwise. Pass NULL if the compression status is not
   useful.

   The XcmsConvertColors function converts the color
   specifications in the specified array of XcmsColor structures
   from their current format to a single target format, using the
   specified CCC. When the return value is XcmsFailure, the
   contents of the color specification array are left unchanged.

   The array may contain a mixture of color specification formats
   (for example, 3 CIE XYZ, 2 CIE Luv, and so on). When the array
   contains both device-independent and device-dependent color
   specifications and the target_format argument specifies a
   device-dependent format (for example, XcmsRGBiFormat,
   XcmsRGBFormat), all specifications are converted to CIE XYZ
   format and then to the target device-dependent format.

Callback Functions

   This section describes the gamut compression and white point
   adjustment callbacks.

   The gamut compression procedure specified in the CCC is called
   when an attempt to convert a color specification from
   XcmsCIEXYZ to a device-dependent format (typically XcmsRGBi)
   results in a color that lies outside the screen's color gamut.
   If the gamut compression procedure requires client data, this
   data is passed via the gamut compression client data in the
   CCC.

   During color specification conversion between
   device-independent and device-dependent color spaces, if a
   white point adjustment procedure is specified in the CCC, it is
   triggered when the Client White Point and Screen White Point
   differ. If required, the client data is obtained from the CCC.

Prototype Gamut Compression Procedure

   The gamut compression callback interface must adhere to the
   following:

   typedef Status(*XcmsCompressionProc)(XcmsCCC ccc, XcmsColor
   colors_in_out[], unsigned int ncolors, unsigned int index, Bool
   compression_flags_return[]);

   ccc

   Specifies the CCC.

   colors_in_out

   Specifies an array of color specifications. Pixel members
   should be ignored and must remain unchanged upon return.

   ncolors

   Specifies the number of XcmsColor structures in the
   color-specification array.

   index

   Specifies the index into the array of XcmsColor structures for
   the encountered color specification that lies outside the
   screen's color gamut. Valid values are 0 (for the first
   element) to ncolors - 1.

   compression_flags_return

   Returns an array of Boolean values for indicating compression
   status. If a non-NULL pointer is supplied and a color at a
   given index is compressed, then True should be stored at the
   corresponding index in this array; otherwise, the array should
   not be modified.

   When implementing a gamut compression procedure, consider the
   following rules and assumptions:
     * The gamut compression procedure can attempt to compress one
       or multiple specifications at a time.
     * When called, elements 0 to index - 1 in the color
       specification array can be assumed to fall within the
       screen's color gamut. In addition, these color
       specifications are already in some device-dependent format
       (typically XcmsRGBi). If any modifications are made to
       these color specifications, they must be in their initial
       device-dependent format upon return.
     * When called, the element in the color specification array
       specified by the index argument contains the color
       specification outside the screen's color gamut encountered
       by the calling routine. In addition, this color
       specification can be assumed to be in XcmsCIEXYZ. Upon
       return, this color specification must be in XcmsCIEXYZ.
     * When called, elements from index to ncolors - 1 in the
       color specification array may or may not fall within the
       screen's color gamut. In addition, these color
       specifications can be assumed to be in XcmsCIEXYZ. If any
       modifications are made to these color specifications, they
       must be in XcmsCIEXYZ upon return.
     * The color specifications passed to the gamut compression
       procedure have already been adjusted to the Screen White
       Point. This means that at this point the color
       specification's white point is the Screen White Point.
     * If the gamut compression procedure uses a
       device-independent color space not initially accessible for
       use in the color management system, use XcmsAddColorSpace
       to ensure that it is added.

Supplied Gamut Compression Procedures

   The following equations are useful in describing gamut
   compression functions: delim %%

%CIELab~Psychometric~Chroma ~=~ sqrt(a_star sup 2 ~+~ b_star sup 2 )%

%CIELab~Psychometric~Hue ~=~ tan sup -1 left [ b_star over a_star right
]%

%CIELuv~Psychometric~Chroma ~=~ sqrt(u_star sup 2 ~+~ v_star sup 2 )%

%CIELuv~Psychometric~Hue ~=~ tan sup -1 left [ v_star over u_star right
]%

   The gamut compression callback procedures provided by Xlib are
   as follows:
     * XcmsCIELabClipL
     * This brings the encountered out-of-gamut color
       specification into the screen's color gamut by reducing or
       increasing CIE metric lightness (L*) in the CIE L*a*b*
       color space until the color is within the gamut. If the
       Psychometric Chroma of the color specification is beyond
       maximum for the Psychometric Hue Angle, then while
       maintaining the same Psychometric Hue Angle, the color will
       be clipped to the CIE L*a*b* coordinates of maximum
       Psychometric Chroma. See XcmsCIELabQueryMaxC. No client
       data is necessary.
     * XcmsCIELabClipab
     * This brings the encountered out-of-gamut color
       specification into the screen's color gamut by reducing
       Psychometric Chroma, while maintaining Psychometric Hue
       Angle, until the color is within the gamut. No client data
       is necessary.
     * XcmsCIELabClipLab
     * This brings the encountered out-of-gamut color
       specification into the screen's color gamut by replacing it
       with CIE L*a*b* coordinates that fall within the color
       gamut while maintaining the original Psychometric Hue Angle
       and whose vector to the original coordinates is the
       shortest attainable. No client data is necessary.
     * XcmsCIELuvClipL
     * This brings the encountered out-of-gamut color
       specification into the screen's color gamut by reducing or
       increasing CIE metric lightness (L*) in the CIE L*u*v*
       color space until the color is within the gamut. If the
       Psychometric Chroma of the color specification is beyond
       maximum for the Psychometric Hue Angle, then, while
       maintaining the same Psychometric Hue Angle, the color will
       be clipped to the CIE L*u*v* coordinates of maximum
       Psychometric Chroma. See XcmsCIELuvQueryMaxC. No client
       data is necessary.
     * XcmsCIELuvClipuv
     * This brings the encountered out-of-gamut color
       specification into the screen's color gamut by reducing
       Psychometric Chroma, while maintaining Psychometric Hue
       Angle, until the color is within the gamut. No client data
       is necessary.
     * XcmsCIELuvClipLuv
     * This brings the encountered out-of-gamut color
       specification into the screen's color gamut by replacing it
       with CIE L*u*v* coordinates that fall within the color
       gamut while maintaining the original Psychometric Hue Angle
       and whose vector to the original coordinates is the
       shortest attainable. No client data is necessary.
     * XcmsTekHVCClipV
     * This brings the encountered out-of-gamut color
       specification into the screen's color gamut by reducing or
       increasing the Value dimension in the TekHVC color space
       until the color is within the gamut. If Chroma of the color
       specification is beyond maximum for the particular Hue,
       then, while maintaining the same Hue, the color will be
       clipped to the Value and Chroma coordinates that represent
       maximum Chroma for that particular Hue. No client data is
       necessary.
     * XcmsTekHVCClipC
     * This brings the encountered out-of-gamut color
       specification into the screen's color gamut by reducing the
       Chroma dimension in the TekHVC color space until the color
       is within the gamut. No client data is necessary.
     * XcmsTekHVCClipVC
     * This brings the encountered out-of-gamut color
       specification into the screen's color gamut by replacing it
       with TekHVC coordinates that fall within the color gamut
       while maintaining the original Hue and whose vector to the
       original coordinates is the shortest attainable. No client
       data is necessary.

Prototype White Point Adjustment Procedure

   The white point adjustment procedure interface must adhere to
   the following:

   typedef Status (*XcmsWhiteAdjustProc)(XcmsCCC ccc, XcmsColor
   *initial_white_point, XcmsColor *target_white_point,
   XcmsColorFormat target_format, XcmsColor colors_in_out[],
   unsigned int ncolors, Bool compression_flags_return[]);

   ccc

   Specifies the CCC.

   initial_white_point

   Specifies the initial white point.

   target_white_point

   Specifies the target white point.

   target_format

   Specifies the target color specification format.

   colors_in_out

   Specifies an array of color specifications. Pixel members
   should be ignored and must remain unchanged upon return.

   ncolors

   Specifies the number of XcmsColor structures in the
   color-specification array.

   compression_flags_return

   Returns an array of Boolean values for indicating compression
   status. If a non-NULL pointer is supplied and a color at a
   given index is compressed, then True should be stored at the
   corresponding index in this array; otherwise, the array should
   not be modified.

Supplied White Point Adjustment Procedures

   White point adjustment procedures provided by Xlib are as
   follows:
     * XcmsCIELabWhiteShiftColors
     * This uses the CIE L*a*b* color space for adjusting the
       chromatic character of colors to compensate for the
       chromatic differences between the source and destination
       white points. This procedure simply converts the color
       specifications to XcmsCIELab using the source white point
       and then converts to the target specification format using
       the destination's white point. No client data is necessary.
     * XcmsCIELuvWhiteShiftColors
     * This uses the CIE L*u*v* color space for adjusting the
       chromatic character of colors to compensate for the
       chromatic differences between the source and destination
       white points. This procedure simply converts the color
       specifications to XcmsCIELuv using the source white point
       and then converts to the target specification format using
       the destination's white point. No client data is necessary.
     * XcmsTekHVCWhiteShiftColors
     * This uses the TekHVC color space for adjusting the
       chromatic character of colors to compensate for the
       chromatic differences between the source and destination
       white points. This procedure simply converts the color
       specifications to XcmsTekHVC using the source white point
       and then converts to the target specification format using
       the destination's white point. An advantage of this
       procedure over those previously described is an attempt to
       minimize hue shift. No client data is necessary.

   From an implementation point of view, these white point
   adjustment procedures convert the color specifications to a
   device-independent but white-point-dependent color space (for
   example, CIE L*u*v*, CIE L*a*b*, TekHVC) using one white point
   and then converting those specifications to the target color
   space using another white point. In other words, the
   specification goes in the color space with one white point but
   comes out with another white point, resulting in a chromatic
   shift based on the chromatic displacement between the initial
   white point and target white point. The CIE color spaces that
   are assumed to be white-point-independent are CIE u'v'Y, CIE
   XYZ, and CIE xyY. When developing a custom white point
   adjustment procedure that uses a device-independent color space
   not initially accessible for use in the color management
   system, use XcmsAddColorSpace to ensure that it is added.

   As an example, if the CCC specifies a white point adjustment
   procedure and if the Client White Point and Screen White Point
   differ, the XcmsAllocColor function will use the white point
   adjustment procedure twice:
     * Once to convert to XcmsRGB
     * A second time to convert from XcmsRGB

   For example, assume the specification is in XcmsCIEuvY and the
   adjustment procedure is XcmsCIELuvWhiteShiftColors. During
   conversion to XcmsRGB, the call to XcmsAllocColor results in
   the following series of color specification conversions:
     * From XcmsCIEuvY to XcmsCIELuv using the Client White Point
     * From XcmsCIELuv to XcmsCIEuvY using the Screen White Point
     * From XcmsCIEuvY to XcmsCIEXYZ (CIE u'v'Y and XYZ are
       white-point-independent color spaces)
     * From XcmsCIEXYZ to XcmsRGBi
     * From XcmsRGBi to XcmsRGB

   The resulting RGB specification is passed to XAllocColor, and
   the RGB specification returned by XAllocColor is converted back
   to XcmsCIEuvY by reversing the color conversion sequence.

Gamut Querying Functions

   This section describes the gamut querying functions that Xlib
   provides. These functions allow the client to query the
   boundary of the screen's color gamut in terms of the CIE
   L*a*b*, CIE L*u*v*, and TekHVC color spaces. Functions are also
   provided that allow you to query the color specification of:
     * White (full-intensity red, green, and blue)
     * Red (full-intensity red while green and blue are zero)
     * Green (full-intensity green while red and blue are zero)
     * Blue (full-intensity blue while red and green are zero)
     * Black (zero-intensity red, green, and blue)

   The white point associated with color specifications passed to
   and returned from these gamut querying functions is assumed to
   be the Screen White Point. This is a reasonable assumption,
   because the client is trying to query the screen's color gamut.

   The following naming convention is used for the Max and Min
   functions:

Xcms<color_space>QueryMax<dimensions>

Xcms<color_space>QueryMin<dimensions>

   The <dimensions> consists of a letter or letters that identify
   the dimensions of the color space that are not fixed. For
   example, XcmsTekHVCQueryMaxC is given a fixed Hue and Value for
   which maximum Chroma is found.

Red, Green, and Blue Queries

   To obtain the color specification for black (zero-intensity
   red, green, and blue), use XcmsQueryBlack.

   Status XcmsQueryBlack(XcmsCCC ccc, XcmsColorFormat
   target_format, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   target_format

   Specifies the target color specification format.

   color_return

   Returns the color specification in the specified target format
   for zero-intensity red, green, and blue. The white point
   associated with the returned color specification is the Screen
   White Point. The value returned in the pixel member is
   undefined.

   The XcmsQueryBlack function returns the color specification in
   the specified target format for zero-intensity red, green, and
   blue.

   To obtain the color specification for blue (full-intensity blue
   while red and green are zero), use XcmsQueryBlue.

   Status XcmsQueryBlue(XcmsCCC ccc, XcmsColorFormat
   target_format, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   target_format

   Specifies the target color specification format.

   color_return

   Returns the color specification in the specified target format
   for full-intensity blue while red and green are zero. The white
   point associated with the returned color specification is the
   Screen White Point. The value returned in the pixel member is
   undefined.

   The XcmsQueryBlue function returns the color specification in
   the specified target format for full-intensity blue while red
   and green are zero.

   To obtain the color specification for green (full-intensity
   green while red and blue are zero), use XcmsQueryGreen.

   Status XcmsQueryGreen(XcmsCCC ccc, XcmsColorFormat
   target_format, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   target_format

   Specifies the target color specification format.

   color_return

   Returns the color specification in the specified target format
   for full-intensity green while red and blue are zero. The white
   point associated with the returned color specification is the
   Screen White Point. The value returned in the pixel member is
   undefined.

   The XcmsQueryGreen function returns the color specification in
   the specified target format for full-intensity green while red
   and blue are zero.

   To obtain the color specification for red (full-intensity red
   while green and blue are zero), use XcmsQueryRed.

   Status XcmsQueryRed(XcmsCCC ccc, XcmsColorFormat target_format,
   XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   target_format

   Specifies the target color specification format.

   color_return

   Returns the color specification in the specified target format
   for full-intensity red while green and blue are zero. The white
   point associated with the returned color specification is the
   Screen White Point. The value returned in the pixel member is
   undefined.

   The XcmsQueryRed function returns the color specification in
   the specified target format for full-intensity red while green
   and blue are zero.

   To obtain the color specification for white (full-intensity
   red, green, and blue), use XcmsQueryWhite.

   Status XcmsQueryWhite(XcmsCCC ccc, XcmsColorFormat
   target_format, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   target_format

   Specifies the target color specification format.

   color_return

   Returns the color specification in the specified target format
   for full-intensity red, green, and blue. The white point
   associated with the returned color specification is the Screen
   White Point. The value returned in the pixel member is
   undefined.

   The XcmsQueryWhite function returns the color specification in
   the specified target format for full-intensity red, green, and
   blue.

CIELab Queries

   The following equations are useful in describing the CIELab
   query functions: delim %%

%CIELab~Psychometric~Chroma ~=~ sqrt(a_star sup 2 ~+~ b_star sup 2 )%

%CIELab~Psychometric~Hue ~=~ tan sup -1 left [ b_star over a_star right
]%

   To obtain the CIE L*a*b* coordinates of maximum Psychometric
   Chroma for a given Psychometric Hue Angle and CIE metric
   lightness (L*), use XcmsCIELabQueryMaxC.

   Status XcmsCIELabQueryMaxC(XcmsCCC ccc, XcmsFloat hue_angle,
   XcmsFloat L_star, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue_angle

   Specifies the hue angle (in degrees) at which to find maximum
   chroma.

   L_star

   Specifies the lightness (L*) at which to find maximum chroma.

   color_return

   Returns the CIE L*a*b* coordinates of maximum chroma
   displayable by the screen for the given hue angle and
   lightness. The white point associated with the returned color
   specification is the Screen White Point. The value returned in
   the pixel member is undefined.

   The XcmsCIELabQueryMaxC function, given a hue angle and
   lightness, finds the point of maximum chroma displayable by the
   screen. It returns this point in CIE L*a*b* coordinates.

   To obtain the CIE L*a*b* coordinates of maximum CIE metric
   lightness (L*) for a given Psychometric Hue Angle and
   Psychometric Chroma, use XcmsCIELabQueryMaxL.

   Status XcmsCIELabQueryMaxL(XcmsCCC ccc, XcmsFloat hue_angle,
   XcmsFloat chroma, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue_angle

   Specifies the hue angle (in degrees) at which to find maximum
   lightness.

   chroma

   Specifies the chroma at which to find maximum lightness.

   color_return

   Returns the CIE L*a*b* coordinates of maximum lightness
   displayable by the screen for the given hue angle and chroma.
   The white point associated with the returned color
   specification is the Screen White Point. The value returned in
   the pixel member is undefined.

   The XcmsCIELabQueryMaxL function, given a hue angle and chroma,
   finds the point in CIE L*a*b* color space of maximum lightness
   (L*) displayable by the screen. It returns this point in CIE
   L*a*b* coordinates. An XcmsFailure return value usually
   indicates that the given chroma is beyond maximum for the given
   hue angle.

   To obtain the CIE L*a*b* coordinates of maximum Psychometric
   Chroma for a given Psychometric Hue Angle, use
   XcmsCIELabQueryMaxLC.

   Status XcmsCIELabQueryMaxLC(XcmsCCC ccc, XcmsFloat hue_angle,
   XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue_angle

   Specifies the hue angle (in degrees) at which to find maximum
   chroma.

   color_return

   Returns the CIE L*a*b* coordinates of maximum chroma
   displayable by the screen for the given hue angle. The white
   point associated with the returned color specification is the
   Screen White Point. The value returned in the pixel member is
   undefined.

   The XcmsCIELabQueryMaxLC function, given a hue angle, finds the
   point of maximum chroma displayable by the screen. It returns
   this point in CIE L*a*b* coordinates.

   To obtain the CIE L*a*b* coordinates of minimum CIE metric
   lightness (L*) for a given Psychometric Hue Angle and
   Psychometric Chroma, use XcmsCIELabQueryMinL.

   Status XcmsCIELabQueryMinL(XcmsCCC ccc, XcmsFloat hue_angle,
   XcmsFloat chroma, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue_angle

   Specifies the hue angle (in degrees) at which to find minimum
   lightness.

   chroma

   Specifies the chroma at which to find minimum lightness.

   color_return

   Returns the CIE L*a*b* coordinates of minimum lightness
   displayable by the screen for the given hue angle and chroma.
   The white point associated with the returned color
   specification is the Screen White Point. The value returned in
   the pixel member is undefined.

   The XcmsCIELabQueryMinL function, given a hue angle and chroma,
   finds the point of minimum lightness (L*) displayable by the
   screen. It returns this point in CIE L*a*b* coordinates. An
   XcmsFailure return value usually indicates that the given
   chroma is beyond maximum for the given hue angle.

CIELuv Queries

   The following equations are useful in describing the CIELuv
   query functions: delim %%

%CIELuv~Psychometric~Chroma ~=~ sqrt(u_star sup 2 ~+~ v_star sup 2 )%

%CIELuv~Psychometric~Hue ~=~ tan sup -1 left [ v_star over u_star right
]%

   To obtain the CIE L*u*v* coordinates of maximum Psychometric
   Chroma for a given Psychometric Hue Angle and CIE metric
   lightness (L*), use XcmsCIELuvQueryMaxC.

   Status XcmsCIELuvQueryMaxC(XcmsCCC ccc, XcmsFloat hue_angle,
   XcmsFloat L_star, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue_angle

   Specifies the hue angle (in degrees) at which to find maximum
   chroma.

   L_star

   Specifies the lightness (L*) at which to find maximum chroma.

   color_return

   Returns the CIE L*u*v* coordinates of maximum chroma
   displayable by the screen for the given hue angle and
   lightness. The white point associated with the returned color
   specification is the Screen White Point. The value returned in
   the pixel member is undefined.

   The XcmsCIELuvQueryMaxC function, given a hue angle and
   lightness, finds the point of maximum chroma displayable by the
   screen. It returns this point in CIE L*u*v* coordinates.

   To obtain the CIE L*u*v* coordinates of maximum CIE metric
   lightness (L*) for a given Psychometric Hue Angle and
   Psychometric Chroma, use XcmsCIELuvQueryMaxL.

   Status XcmsCIELuvQueryMaxL(XcmsCCC ccc, XcmsFloat hue_angle,
   XcmsFloat chroma, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue_angle

   Specifies the hue angle (in degrees) at which to find maximum
   lightness.

   L_star

   Specifies the lightness (L*) at which to find maximum
   lightness.

   color_return

   Returns the CIE L*u*v* coordinates of maximum lightness
   displayable by the screen for the given hue angle and chroma.
   The white point associated with the returned color
   specification is the Screen White Point. The value returned in
   the pixel member is undefined.

   The XcmsCIELuvQueryMaxL function, given a hue angle and chroma,
   finds the point in CIE L*u*v* color space of maximum lightness
   (L*) displayable by the screen. It returns this point in CIE
   L*u*v* coordinates. An XcmsFailure return value usually
   indicates that the given chroma is beyond maximum for the given
   hue angle.

   To obtain the CIE L*u*v* coordinates of maximum Psychometric
   Chroma for a given Psychometric Hue Angle, use
   XcmsCIELuvQueryMaxLC.

   Status XcmsCIELuvQueryMaxLC(XcmsCCC ccc, XcmsFloat hue_angle,
   XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue_angle

   Specifies the hue angle (in degrees) at which to find maximum
   chroma.

   color_return

   Returns the CIE L*u*v* coordinates of maximum chroma
   displayable by the screen for the given hue angle. The white
   point associated with the returned color specification is the
   Screen White Point. The value returned in the pixel member is
   undefined.

   The XcmsCIELuvQueryMaxLC function, given a hue angle, finds the
   point of maximum chroma displayable by the screen. It returns
   this point in CIE L*u*v* coordinates.

   To obtain the CIE L*u*v* coordinates of minimum CIE metric
   lightness (L*) for a given Psychometric Hue Angle and
   Psychometric Chroma, use XcmsCIELuvQueryMinL.

   Status XcmsCIELuvQueryMinL(XcmsCCC ccc, XcmsFloat hue_angle,
   XcmsFloat chroma, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue_angle

   Specifies the hue angle (in degrees) at which to find minimum
   lightness.

   chroma

   Specifies the chroma at which to find minimum lightness.

   color_return

   Returns the CIE L*u*v* coordinates of minimum lightness
   displayable by the screen for the given hue angle and chroma.
   The white point associated with the returned color
   specification is the Screen White Point. The value returned in
   the pixel member is undefined.

   The XcmsCIELuvQueryMinL function, given a hue angle and chroma,
   finds the point of minimum lightness (L*) displayable by the
   screen. It returns this point in CIE L*u*v* coordinates. An
   XcmsFailure return value usually indicates that the given
   chroma is beyond maximum for the given hue angle.

TekHVC Queries

   To obtain the maximum Chroma for a given Hue and Value, use
   XcmsTekHVCQueryMaxC.

   Status XcmsTekHVCQueryMaxC(XcmsCCC ccc, XcmsFloat hue,
   XcmsFloat value, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue

   Specifies the Hue in which to find the maximum Chroma.

   value

   Specifies the Value in which to find the maximum Chroma.

   color_return

   Returns the maximum Chroma along with the actual Hue and Value
   at which the maximum Chroma was found. The white point
   associated with the returned color specification is the Screen
   White Point. The value returned in the pixel member is
   undefined.

   The XcmsTekHVCQueryMaxC function, given a Hue and Value,
   determines the maximum Chroma in TekHVC color space displayable
   by the screen. It returns the maximum Chroma along with the
   actual Hue and Value at which the maximum Chroma was found.

   To obtain the maximum Value for a given Hue and Chroma, use
   XcmsTekHVCQueryMaxV.

   Status XcmsTekHVCQueryMaxV(XcmsCCC ccc, XcmsFloat hue,
   XcmsFloat chroma, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue

   Specifies the Hue in which to find the maximum Value.

   chroma

   Specifies the chroma at which to find maximum Value.

   color_return

   Returns the maximum Value along with the Hue and Chroma at
   which the maximum Value was found. The white point associated
   with the returned color specification is the Screen White
   Point. The value returned in the pixel member is undefined.

   The XcmsTekHVCQueryMaxV function, given a Hue and Chroma,
   determines the maximum Value in TekHVC color space displayable
   by the screen. It returns the maximum Value and the actual Hue
   and Chroma at which the maximum Value was found.

   To obtain the maximum Chroma and Value at which it is reached
   for a specified Hue, use XcmsTekHVCQueryMaxVC.

   Status XcmsTekHVCQueryMaxVC(XcmsCCC ccc, XcmsFloat hue,
   XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue

   Specifies the Hue in which to find the maximum Chroma.

   color_return

   Returns the color specification in XcmsTekHVC for the maximum
   Chroma, the Value at which that maximum Chroma is reached, and
   the actual Hue at which the maximum Chroma was found. The white
   point associated with the returned color specification is the
   Screen White Point. The value returned in the pixel member is
   undefined.

   The XcmsTekHVCQueryMaxVC function, given a Hue, determines the
   maximum Chroma in TekHVC color space displayable by the screen
   and the Value at which that maximum Chroma is reached. It
   returns the maximum Chroma, the Value at which that maximum
   Chroma is reached, and the actual Hue for which the maximum
   Chroma was found.

   To obtain a specified number of TekHVC specifications such that
   they contain maximum Values for a specified Hue and the Chroma
   at which the maximum Values are reached, use
   XcmsTekHVCQueryMaxVSamples.

   Status XcmsTekHVCQueryMaxVSamples(XcmsCCC ccc, XcmsFloat hue,
   XcmsColor colors_return[], unsigned int nsamples);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue

   Specifies the Hue for maximum Chroma/Value samples.

   nsamples

   Specifies the number of samples.

   colors_return

   Returns nsamples of color specifications in XcmsTekHVC such
   that the Chroma is the maximum attainable for the Value and
   Hue. The white point associated with the returned color
   specification is the Screen White Point. The value returned in
   the pixel member is undefined.

   The XcmsTekHVCQueryMaxVSamples returns nsamples of maximum
   Value, the Chroma at which that maximum Value is reached, and
   the actual Hue for which the maximum Chroma was found. These
   sample points may then be used to plot the maximum Value/Chroma
   boundary of the screen's color gamut for the specified Hue in
   TekHVC color space.

   To obtain the minimum Value for a given Hue and Chroma, use
   XcmsTekHVCQueryMinV.

   Status XcmsTekHVCQueryMinV(XcmsCCC ccc, XcmsFloat hue,
   XcmsFloat chroma, XcmsColor *color_return);

   ccc

   Specifies the CCC. The CCC's Client White Point and white point
   adjustment procedures are ignored.

   hue

   Specifies the Hue in which to find the minimum Value.

   value

   Specifies the Value in which to find the minimum Value.

   color_return

   Returns the minimum Value and the actual Hue and Chroma at
   which the minimum Value was found. The white point associated
   with the returned color specification is the Screen White
   Point. The value returned in the pixel member is undefined.

   The XcmsTekHVCQueryMinV function, given a Hue and Chroma,
   determines the minimum Value in TekHVC color space displayable
   by the screen. It returns the minimum Value and the actual Hue
   and Chroma at which the minimum Value was found.

Color Management Extensions

   The Xlib color management facilities can be extended in two
   ways:
     * Device-Independent Color Spaces
     * Device-independent color spaces that are derivable to CIE
       XYZ space can be added using the XcmsAddColorSpace
       function.
     * Color Characterization Function Set
     * A Color Characterization Function Set consists of
       device-dependent color spaces and their functions that
       convert between these color spaces and the CIE XYZ color
       space, bundled together for a specific class of output
       devices. A function set can be added using the
       XcmsAddFunctionSet function.

Color Spaces

   The CIE XYZ color space serves as the hub for all conversions
   between device-independent and device-dependent color spaces.
   Therefore, the knowledge to convert an XcmsColor structure to
   and from CIE XYZ format is associated with each color space.
   For example, conversion from CIE L*u*v* to RGB requires the
   knowledge to convert from CIE L*u*v* to CIE XYZ and from CIE
   XYZ to RGB. This knowledge is stored as an array of functions
   that, when applied in series, will convert the XcmsColor
   structure to or from CIE XYZ format. This color specification
   conversion mechanism facilitates the addition of color spaces.

   Of course, when converting between only device-independent
   color spaces or only device-dependent color spaces, shortcuts
   are taken whenever possible. For example, conversion from
   TekHVC to CIE L*u*v* is performed by intermediate conversion to
   CIE u*v*Y and then to CIE L*u*v*, thus bypassing conversion
   between CIE u*v*Y and CIE XYZ.

Adding Device-Independent Color Spaces

   To add a device-independent color space, use XcmsAddColorSpace.

   Status XcmsAddColorSpace(XcmsColorSpace *color_space);

   color_space

   Specifies the device-independent color space to add.

   The XcmsAddColorSpace function makes a device-independent color
   space (actually an XcmsColorSpace structure) accessible by the
   color management system. Because format values for unregistered
   color spaces are assigned at run time, they should be treated
   as private to the client. If references to an unregistered
   color space must be made outside the client (for example,
   storing color specifications in a file using the unregistered
   color space), then reference should be made by color space
   prefix (see XcmsFormatOfPrefix and XcmsPrefixOfFormat).

   If the XcmsColorSpace structure is already accessible in the
   color management system, XcmsAddColorSpace returns XcmsSuccess.

   Note that added XcmsColorSpaces must be retained for reference
   by Xlib.

Querying Color Space Format and Prefix

   To obtain the format associated with the color space associated
   with a specified color string prefix, use XcmsFormatOfPrefix.

   XcmsColorFormat XcmsFormatOfPrefix(char *prefix);

   prefix

   Specifies the string that contains the color space prefix.

   The XcmsFormatOfPrefix function returns the format for the
   specified color space prefix (for example, the string
   ``CIEXYZ''). The prefix is case-insensitive. If the color space
   is not accessible in the color management system,
   XcmsFormatOfPrefix returns XcmsUndefinedFormat.

   To obtain the color string prefix associated with the color
   space specified by a color format, use XcmsPrefixOfFormat.

   char *XcmsPrefixOfFormat(XcmsColorFormat format);

   format

   Specifies the color specification format.

   The XcmsPrefixOfFormat function returns the string prefix
   associated with the color specification encoding specified by
   the format argument. Otherwise, if no encoding is found, it
   returns NULL. The returned string must be treated as read-only.

Creating Additional Color Spaces

   Color space specific information necessary for color space
   conversion and color string parsing is stored in an
   XcmsColorSpace structure. Therefore, a new structure containing
   this information is required for each additional color space.
   In the case of device-independent color spaces, a handle to
   this new structure (that is, by means of a global variable) is
   usually made accessible to the client program for use with the
   XcmsAddColorSpace function.

   If a new XcmsColorSpace structure specifies a color space not
   registered with the X Consortium, they should be treated as
   private to the client because format values for unregistered
   color spaces are assigned at run time. If references to an
   unregistered color space must be made outside the client (for
   example, storing color specifications in a file using the
   unregistered color space), then reference should be made by
   color space prefix (see XcmsFormatOfPrefix and
   XcmsPrefixOfFormat).



typedef (*XcmsConversionProc)();
typedef XcmsConversionProc *XcmsFuncListPtr;
                /* A NULL terminated list of function pointers*/

typedef struct _XcmsColorSpace {
        char *prefix;
        XcmsColorFormat format;
        XcmsParseStringProc parseString;
        XcmsFuncListPtr to_CIEXYZ;
        XcmsFuncListPtr from_CIEXYZ;
        int inverse_flag;
} XcmsColorSpace;

   The prefix member specifies the prefix that indicates a color
   string is in this color space's string format. For example, the
   strings ``ciexyz'' or ``CIEXYZ'' for CIE XYZ, and ``rgb'' or
   ``RGB'' for RGB. The prefix is case insensitive. The format
   member specifies the color specification format. Formats for
   unregistered color spaces are assigned at run time. The
   parseString member contains a pointer to the function that can
   parse a color string into an XcmsColor structure. This function
   returns an integer (int): nonzero if it succeeded and zero
   otherwise. The to_CIEXYZ and from_CIEXYZ members contain
   pointers, each to a NULL terminated list of function pointers.
   When the list of functions is executed in series, it will
   convert the color specified in an XcmsColor structure from/to
   the current color space format to/from the CIE XYZ format. Each
   function returns an integer (int): nonzero if it succeeded and
   zero otherwise. The white point to be associated with the
   colors is specified explicitly, even though white points can be
   found in the CCC. The inverse_flag member, if nonzero,
   specifies that for each function listed in to_CIEXYZ, its
   inverse function can be found in from_CIEXYZ such that:

Given:  n = number of functions in each list

for each i, such that 0 <= i < n
    from_CIEXYZ[n - i - 1] is the inverse of to_CIEXYZ[i].

   This allows Xlib to use the shortest conversion path, thus
   bypassing CIE XYZ if possible (for example, TekHVC to CIE
   L*u*v*).

Parse String Callback

   The callback in the XcmsColorSpace structure for parsing a
   color string for the particular color space must adhere to the
   following software interface specification:

   Status XcmsParseStringProc(char *color_string, XcmsColor
   *color_return);

   color_string

   Specifies the color string to parse.

   color_return

   Returns the color specification in the color space's format.

Color Specification Conversion Callback

   Callback functions in the XcmsColorSpace structure for
   converting a color specification between device-independent
   spaces must adhere to the following software interface
   specification:

   Status ConversionProc(XcmsCCC ccc, XcmsColor *white_point,
   XcmsColor *colors_in_out, unsigned int ncolors);

   ccc

   Specifies the CCC.

   white_point

   Specifies the white point associated with color specifications.
   The pixel member should be ignored, and the entire structure
   remain unchanged upon return.

   colors_in_out

   Specifies an array of color specifications. Pixel members
   should be ignored and must remain unchanged upon return.

   ncolors

   Specifies the number of XcmsColor structures in the
   color-specification array.

   Callback functions in the XcmsColorSpace structure for
   converting a color specification to or from a device-dependent
   space must adhere to the following software interface
   specification:

   Status ConversionProc(XcmsCCC ccc, XcmsColor *colors_in_out,
   unsigned int ncolors, Bool compression_flags_return[]);

   ccc

   Specifies the CCC.

   colors_in_out

   Specifies an array of color specifications. Pixel members
   should be ignored and must remain unchanged upon return.

   ncolors

   Specifies the number of XcmsColor structures in the
   color-specification array.

   compression_flags_return

   Returns an array of Boolean values for indicating compression
   status. If a non-NULL pointer is supplied and a color at a
   given index is compressed, then True should be stored at the
   corresponding index in this array; otherwise, the array should
   not be modified.

   Conversion functions are available globally for use by other
   color spaces. The conversion functions provided by Xlib are:
   Function           Converts from    Converts to
   XcmsCIELabToCIEXYZ XcmsCIELabFormat XcmsCIEXYZFormat
   XcmsCIELuvToCIEuvY XcmsCIELuvFormat XcmsCIEuvYFormat
   XcmsCIEXYZToCIELab XcmsCIEXYZFormat XcmsCIELabFormat
   XcmsCIEXYZToCIEuvY XcmsCIEXYZFormat XcmsCIEuvYFormat
   XcmsCIEXYZToCIExyY XcmsCIEXYZFormat XcmsCIExyYFormat
   XcmsCIEXYZToRGBi   XcmsCIEXYZFormat XcmsRGBiFormat
   XcmsCIEuvYToCIELuv XcmsCIEuvYFormat XcmsCIELabFormat
   XcmsCIEuvYToCIEXYZ XcmsCIEuvYFormat XcmsCIEXYZFormat
   XcmsCIEuvYToTekHVC XcmsCIEuvYFormat XcmsTekHVCFormat
   XcmsCIExyYToCIEXYZ XcmsCIExyYFormat XcmsCIEXYZFormat
   XcmsRGBToRGBi      XcmsRGBFormat    XcmsRGBiFormat
   XcmsRGBiToCIEXYZ   XcmsRGBiFormat   XcmsCIEXYZFormat
   XcmsRGBiToRGB      XcmsRGBiFormat   XcmsRGBFormat
   XcmsTekHVCToCIEuvY XcmsTekHVCFormat XcmsCIEuvYFormat

Function Sets

   Functions to convert between device-dependent color spaces and
   CIE XYZ may differ for different classes of output devices (for
   example, color versus gray monitors). Therefore, the notion of
   a Color Characterization Function Set has been developed. A
   function set consists of device-dependent color spaces and the
   functions that convert color specifications between these
   device-dependent color spaces and the CIE XYZ color space
   appropriate for a particular class of output devices. The
   function set also contains a function that reads color
   characterization data off root window properties. It is this
   characterization data that will differ between devices within a
   class of output devices. For details about how color
   characterization data is stored in root window properties, see
   the section on Device Color Characterization in the
   Inter-Client Communication Conventions Manual. The LINEAR_RGB
   function set is provided by Xlib and will support most color
   monitors. Function sets may require data that differs from
   those needed for the LINEAR_RGB function set. In that case, its
   corresponding data may be stored on different root window
   properties.

Adding Function Sets

   To add a function set, use XcmsAddFunctionSet.

   Status XcmsAddFunctionSet(XcmsFunctionSet *function_set);

   function_set

   Specifies the function set to add.

   The XcmsAddFunctionSet function adds a function set to the
   color management system. If the function set uses
   device-dependent XcmsColorSpace structures not accessible in
   the color management system, XcmsAddFunctionSet adds them. If
   an added XcmsColorSpace structure is for a device-dependent
   color space not registered with the X Consortium, they should
   be treated as private to the client because format values for
   unregistered color spaces are assigned at run time. If
   references to an unregistered color space must be made outside
   the client (for example, storing color specifications in a file
   using the unregistered color space), then reference should be
   made by color space prefix (see XcmsFormatOfPrefix and
   XcmsPrefixOfFormat).

   Additional function sets should be added before any calls to
   other Xlib routines are made. If not, the XcmsPerScrnInfo
   member of a previously created XcmsCCC does not have the
   opportunity to initialize with the added function set.

Creating Additional Function Sets

   The creation of additional function sets should be required
   only when an output device does not conform to existing
   function sets or when additional device-dependent color spaces
   are necessary. A function set consists primarily of a
   collection of device-dependent XcmsColorSpace structures and a
   means to read and store a screen's color characterization data.
   This data is stored in an XcmsFunctionSet structure. A handle
   to this structure (that is, by means of global variable) is
   usually made accessible to the client program for use with
   XcmsAddFunctionSet.

   If a function set uses new device-dependent XcmsColorSpace
   structures, they will be transparently processed into the color
   management system. Function sets can share an XcmsColorSpace
   structure for a device-dependent color space. In addition,
   multiple XcmsColorSpace structures are allowed for a
   device-dependent color space; however, a function set can
   reference only one of them. These XcmsColorSpace structures
   will differ in the functions to convert to and from CIE XYZ,
   thus tailored for the specific function set.



typedef struct _XcmsFunctionSet {
        XcmsColorSpace **DDColorSpaces;
        XcmsScreenInitProc screenInitProc;
        XcmsScreenFreeProc screenFreeProc;
} XcmsFunctionSet;

   The DDColorSpaces member is a pointer to a NULL terminated list
   of pointers to XcmsColorSpace structures for the
   device-dependent color spaces that are supported by the
   function set. The screenInitProc member is set to the callback
   procedure (see the following interface specification) that
   initializes the XcmsPerScrnInfo structure for a particular
   screen.

   The screen initialization callback must adhere to the following
   software interface specification:

   typedef Status (*XcmsScreenInitProc)(Display *display, int
   screen_number, ScmsPerScrnInfo *screen_info);

   display

   Specifies the connection to the X server.

   screen_number

   Specifies the appropriate screen number on the host server.

   screen_info

   Specifies the XcmsPerScrnInfo structure, which contains the per
   screen information.

   The screen initialization callback in the XcmsFunctionSet
   structure fetches the color characterization data (device
   profile) for the specified screen, typically off properties on
   the screen's root window. It then initializes the specified
   XcmsPerScrnInfo structure. If successful, the procedure fills
   in the XcmsPerScrnInfo structure as follows:
     * It sets the screenData member to the address of the created
       device profile data structure (contents known only by the
       function set).
     * It next sets the screenWhitePoint member.
     * It next sets the functionSet member to the address of the
       XcmsFunctionSet structure.
     * It then sets the state member to XcmsInitSuccess and
       finally returns XcmsSuccess.

   If unsuccessful, the procedure sets the state member to
   XcmsInitFailure and returns XcmsFailure.

   The XcmsPerScrnInfo structure contains:



typedef struct _XcmsPerScrnInfo {
        XcmsColor screenWhitePoint;
        XPointer functionSet;
        XPointer screenData;
        unsigned char state;
        char pad[3];
} XcmsPerScrnInfo;

   The screenWhitePoint member specifies the white point inherent
   to the screen. The functionSet member specifies the appropriate
   function set. The screenData member specifies the device
   profile. The state member is set to one of the following:
     * XcmsInitNone indicates initialization has not been
       previously attempted.
     * XcmsInitFailure indicates initialization has been
       previously attempted but failed.
     * XcmsInitSuccess indicates initialization has been
       previously attempted and succeeded.

   The screen free callback must adhere to the following software
   interface specification:

   typedef void (*XcmsScreenFreeProc)(XPointer screenData);

   screenData

   Specifies the data to be freed.

   This function is called to free the screenData stored in an
   XcmsPerScrnInfo structure.

Chapter 7. Graphics Context Functions

   Table of Contents

   Manipulating Graphics Context/State
   Using Graphics Context Convenience Routines

        Setting the Foreground, Background, Function, or Plane
                Mask

        Setting the Line Attributes and Dashes
        Setting the Fill Style and Fill Rule
        Setting the Fill Tile and Stipple
        Setting the Current Font
        Setting the Clip Region
        Setting the Arc Mode, Subwindow Mode, and Graphics
                Exposure

   A number of resources are used when performing graphics
   operations in X. Most information about performing graphics
   (for example, foreground color, background color, line style,
   and so on) is stored in resources called graphics contexts
   (GCs). Most graphics operations (see chapter 8) take a GC as an
   argument. Although in theory the X protocol permits sharing of
   GCs between applications, it is expected that applications will
   use their own GCs when performing operations. Sharing of GCs is
   highly discouraged because the library may cache GC state.

   Graphics operations can be performed to either windows or
   pixmaps, which collectively are called drawables. Each drawable
   exists on a single screen. A GC is created for a specific
   screen and drawable depth and can only be used with drawables
   of matching screen and depth.

   This chapter discusses how to:
     * Manipulate graphics context/state
     * Use graphics context convenience functions

Manipulating Graphics Context/State

   Most attributes of graphics operations are stored in GCs. These
   include line width, line style, plane mask, foreground,
   background, tile, stipple, clipping region, end style, join
   style, and so on. Graphics operations (for example, drawing
   lines) use these values to determine the actual drawing
   operation. Extensions to X may add additional components to
   GCs. The contents of a GC are private to Xlib.

   Xlib implements a write-back cache for all elements of a GC
   that are not resource IDs to allow Xlib to implement the
   transparent coalescing of changes to GCs. For example, a call
   to XSetForeground of a GC followed by a call to
   XSetLineAttributes results in only a single-change GC protocol
   request to the server. GCs are neither expected nor encouraged
   to be shared between client applications, so this write-back
   caching should present no problems. Applications cannot share
   GCs without external synchronization. Therefore, sharing GCs
   between applications is highly discouraged.

   To set an attribute of a GC, set the appropriate member of the
   XGCValues structure and OR in the corresponding value bitmask
   in your subsequent calls to XCreateGC. The symbols for the
   value mask bits and the XGCValues structure are:
/* GC attribute value mask bits */

#define     GCFunction              (1L<<0)
#define     GCPlaneMask             (1L<<1)
#define     GCForeground            (1L<<2)
#define     GCBackground            (1L<<3)
#define     GCLineWidth             (1L<<4)
#define     GCLineStyle             (1L<<5)
#define     GCCapStyle              (1L<<6)
#define     GCJoinStyle             (1L<<7)
#define     GCFillStyle             (1L<<8)
#define     GCFillRule              (1L<<9)
#define     GCTile                  (1L<<10)
#define     GCStipple               (1L<<11)
#define     GCTileStipXOrigin       (1L<<12)
#define     GCTileStipYOrigin       (1L<<13)
#define     GCFont                  (1L<<14)
#define     GCSubwindowMode         (1L<<15)
#define     GCGraphicsExposures     (1L<<16)
#define     GCClipXOrigin           (1L<<17)
#define     GCClipYOrigin           (1L<<18)
#define     GCClipMask              (1L<<19)
#define     GCDashOffset            (1L<<20)
#define     GCDashList              (1L<<21)
#define     GCArcMode               (1L<<22)



/* Values */

typedef struct {
     int function;                 /* logical operation */
     unsigned long plane_mask;     /* plane mask */
     unsigned long foreground;     /* foreground pixel */
     unsigned long background;     /* background pixel */
     int line_width;               /* line width (in pixels) */
     int line_style;               /* LineSolid, LineOnOffDash, LineDoub
leDash */
     int cap_style;                /* CapNotLast, CapButt, CapRound, Cap
Projecting */
     int join_style;               /* JoinMiter, JoinRound, JoinBevel */
     int fill_style;               /* FillSolid, FillTiled, FillStippled
 FillOpaqueStippled*/
     int fill_rule;                /* EvenOddRule, WindingRule */
     int arc_mode;                 /* ArcChord, ArcPieSlice */
     Pixmap tile;                  /* tile pixmap for tiling operations
*/
     Pixmap stipple;               /* stipple 1 plane pixmap for stippli
ng */
     int ts_x_origin;              /* offset for tile or stipple operati
ons */
     int ts_y_origin
     Font font;                    /* default text font for text operati
ons */
     int subwindow_mode;           /* ClipByChildren, IncludeInferiors *
/
     Bool graphics_exposures;      /* boolean, should exposures be gener
ated */
     int clip_x_origin;            /* origin for clipping */
     int clip_y_origin;
     Pixmap clip_mask;             /* bitmap clipping; other calls for r
ects */
     int dash_offset;              /* patterned/dashed line information
*/
     char dashes;
} XGCValues;

   The default GC values are:
   Component          Default
   function           GXcopy
   plane_mask         All ones
   foreground         0
   background         1
   line_width         0
   line_style         LineSolid
   cap_style          CapButt
   join_style         JoinMiter
   fill_style         FillSolid
   fill_rule          EvenOddRule
   arc_mode           ArcPieSlice
   tile

   Pixmap of unspecified size filled with foreground pixel

   (that is, client specified pixel if any, else 0)

   (subsequent changes to foreground do not affect this pixmap)
   stipple            Pixmap of unspecified size filled with ones
   ts_x_origin        0
   ts_y_origin        0
   font               <implementation dependent>
   subwindow_mode     ClipByChildren
   graphics_exposures True
   clip_x_origin      0
   clip_y_origin      0
   clip_mask          None
   dash_offset        0
   dashes             4 (that is, the list [4, 4])

   Note that foreground and background are not set to any values
   likely to be useful in a window.

   The function attributes of a GC are used when you update a
   section of a drawable (the destination) with bits from
   somewhere else (the source). The function in a GC defines how
   the new destination bits are to be computed from the source
   bits and the old destination bits. GXcopy is typically the most
   useful because it will work on a color display, but special
   applications may use other functions, particularly in concert
   with particular planes of a color display. The 16 GC functions,
   defined in <X11/X.h>, are:
   Function Name  Value Operation
   GXclear        0x0   0
   GXand          0x1   src AND dst
   GXandReverse   0x2   src AND NOT dst
   GXcopy         0x3   src
   GXandInverted  0x4   (NOT src) AND dst
   GXnoop         0x5   dst
   GXxor          0x6   src XOR dst
   GXor           0x7   src OR dst
   GXnor          0x8   (NOT src) AND (NOT dst)
   GXequiv        0x9   (NOT src) XOR dst
   GXinvert       0xa   NOT dst
   GXorReverse    0xb   src OR (NOT dst)
   GXcopyInverted 0xc   NOT src
   GXorInverted   0xd   (NOT src) OR dst
   GXnand         0xe   (NOT src) OR (NOT dst)
   GXset          0xf   1

   Many graphics operations depend on either pixel values or
   planes in a GC. The planes attribute is of type long, and it
   specifies which planes of the destination are to be modified,
   one bit per plane. A monochrome display has only one plane and
   will be the least significant bit of the word. As planes are
   added to the display hardware, they will occupy more
   significant bits in the plane mask.

   In graphics operations, given a source and destination pixel,
   the result is computed bitwise on corresponding bits of the
   pixels. That is, a Boolean operation is performed in each bit
   plane. The plane_mask restricts the operation to a subset of
   planes. A macro constant AllPlanes can be used to refer to all
   planes of the screen simultaneously. The result is computed by
   the following:

((src FUNC dst) AND plane-mask) OR (dst AND (NOT plane-mask))

   Range checking is not performed on the values for foreground,
   background, or plane_mask. They are simply truncated to the
   appropriate number of bits. The line-width is measured in
   pixels and either can be greater than or equal to one (wide
   line) or can be the special value zero (thin line).

   Wide lines are drawn centered on the path described by the
   graphics request. Unless otherwise specified by the join-style
   or cap-style, the bounding box of a wide line with endpoints
   [x1, y1], [x2, y2] and width w is a rectangle with vertices at
   the following real coordinates:



[x1-(w*sn/2), y1+(w*cs/2)], [x1+(w*sn/2), y1-(w*cs/2)],
[x2-(w*sn/2), y2+(w*cs/2)], [x2+(w*sn/2), y2-(w*cs/2)]

   Here sn is the sine of the angle of the line, and cs is the
   cosine of the angle of the line. A pixel is part of the line
   and so is drawn if the center of the pixel is fully inside the
   bounding box (which is viewed as having infinitely thin edges).
   If the center of the pixel is exactly on the bounding box, it
   is part of the line if and only if the interior is immediately
   to its right (x increasing direction). Pixels with centers on a
   horizontal edge are a special case and are part of the line if
   and only if the interior or the boundary is immediately below
   (y increasing direction) and the interior or the boundary is
   immediately to the right (x increasing direction).

   Thin lines (zero line-width) are one-pixel-wide lines drawn
   using an unspecified, device-dependent algorithm. There are
   only two constraints on this algorithm.
     * If a line is drawn unclipped from [x1,y1] to [x2,y2] and if
       another line is drawn unclipped from [x1+dx,y1+dy] to
       [x2+dx,y2+dy], a point [x,y] is touched by drawing the
       first line if and only if the point [x+dx,y+dy] is touched
       by drawing the second line.
     * The effective set of points comprising a line cannot be
       affected by clipping. That is, a point is touched in a
       clipped line if and only if the point lies inside the
       clipping region and the point would be touched by the line
       when drawn unclipped.

   A wide line drawn from [x1,y1] to [x2,y2] always draws the same
   pixels as a wide line drawn from [x2,y2] to [x1,y1], not
   counting cap-style and join-style. It is recommended that this
   property be true for thin lines, but this is not required. A
   line-width of zero may differ from a line-width of one in which
   pixels are drawn. This permits the use of many manufacturers'
   line drawing hardware, which may run many times faster than the
   more precisely specified wide lines.

   In general, drawing a thin line will be faster than drawing a
   wide line of width one. However, because of their different
   drawing algorithms, thin lines may not mix well aesthetically
   with wide lines. If it is desirable to obtain precise and
   uniform results across all displays, a client should always use
   a line-width of one rather than a line-width of zero.

   The line-style defines which sections of a line are drawn:

   LineSolid

   The full path of the line is drawn.

   LineDoubleDash

   The full path of the line is drawn, but the even dashes are
   filled differently from the odd dashes (see fill-style) with
   CapButt style used where even and odd dashes meet.

   LineOnOffDash

   Only the even dashes are drawn, and cap-style applies to all
   internal ends of the individual dashes, except CapNotLast is
   treated as CapButt.

   The cap-style defines how the endpoints of a path are drawn:

   CapNotLast

   This is equivalent to CapButt except that for a line-width of
   zero the final endpoint is not drawn.

   CapButt

   The line is square at the endpoint (perpendicular to the slope
   of the line) with no projection beyond.

   CapRound

   The line has a circular arc with the diameter equal to the
   line-width, centered on the endpoint. (This is equivalent to
   CapButt for line-width of zero).

   CapProjecting

   The line is square at the end, but the path continues beyond
   the endpoint for a distance equal to half the line-width. (This
   is equivalent to CapButt for line-width of zero).

   The join-style defines how corners are drawn for wide lines:

   JoinMiter

   The outer edges of two lines extend to meet at an angle.
   However, if the angle is less than 11 degrees, then a JoinBevel
   join-style is used instead.

   JoinRound

   The corner is a circular arc with the diameter equal to the
   line-width, centered on the joinpoint.

   JoinBevel

   The corner has CapButt endpoint styles with the triangular
   notch filled.

   For a line with coincident endpoints (x1=x2, y1=y2), when the
   cap-style is applied to both endpoints, the semantics depends
   on the line-width and the cap-style:
   CapNotLast thin The results are device dependent, but the
   desired effect is that nothing is drawn.
   CapButt thin The results are device dependent, but the desired
   effect is that a single pixel is drawn.
   CapRound thin The results are the same as for CapButt /thin.
   CapProjecting thin The results are the same as for CapButt
   /thin.
   CapButt wide Nothing is drawn.
   CapRound wide The closed path is a circle, centered at the
   endpoint, and with the diameter equal to the line-width.
   CapProjecting wide The closed path is a square, aligned with
   the coordinate axes, centered at the endpoint, and with the
   sides equal to the line-width.

   For a line with coincident endpoints (x1=x2, y1=y2), when the
   join-style is applied at one or both endpoints, the effect is
   as if the line was removed from the overall path. However, if
   the total path consists of or is reduced to a single point
   joined with itself, the effect is the same as when the
   cap-style is applied at both endpoints.

   The tile/stipple represents an infinite two-dimensional plane,
   with the tile/stipple replicated in all dimensions. When that
   plane is superimposed on the drawable for use in a graphics
   operation, the upper-left corner of some instance of the
   tile/stipple is at the coordinates within the drawable
   specified by the tile/stipple origin. The tile/stipple and clip
   origins are interpreted relative to the origin of whatever
   destination drawable is specified in a graphics request. The
   tile pixmap must have the same root and depth as the GC, or a
   BadMatch error results. The stipple pixmap must have depth one
   and must have the same root as the GC, or a BadMatch error
   results. For stipple operations where the fill-style is
   FillStippled but not FillOpaqueStippled, the stipple pattern is
   tiled in a single plane and acts as an additional clip mask to
   be ANDed with the clip-mask. Although some sizes may be faster
   to use than others, any size pixmap can be used for tiling or
   stippling.

   The fill-style defines the contents of the source for line,
   text, and fill requests. For all text and fill requests (for
   example, XDrawText, XDrawText16, XFillRectangle, XFillPolygon,
   and XFillArc); for line requests with line-style LineSolid (for
   example, XDrawLine, XDrawSegments, XDrawRectangle, XDrawArc);
   and for the even dashes for line requests with line-style
   LineOnOffDash or LineDoubleDash, the following apply:
   FillSolid Foreground
   FillTiled Tile
   FillOpaqueStippled A tile with the same width and height as
   stipple, but with background everywhere stipple has a zero and
   with foreground everywhere stipple has a one
   FillStippled Foreground masked by stipple

   When drawing lines with line-style LineDoubleDash, the odd
   dashes are controlled by the fill-style in the following
   manner:
   FillSolid          Background
   FillTiled          Same as for even dashes
   FillOpaqueStippled Same as for even dashes
   FillStippled       Background masked by stipple

   Storing a pixmap in a GC might or might not result in a copy
   being made. If the pixmap is later used as the destination for
   a graphics request, the change might or might not be reflected
   in the GC. If the pixmap is used simultaneously in a graphics
   request both as a destination and as a tile or stipple, the
   results are undefined.

   For optimum performance, you should draw as much as possible
   with the same GC (without changing its components). The costs
   of changing GC components relative to using different GCs
   depend on the display hardware and the server implementation.
   It is quite likely that some amount of GC information will be
   cached in display hardware and that such hardware can only
   cache a small number of GCs.

   The dashes value is actually a simplified form of the more
   general patterns that can be set with XSetDashes. Specifying a
   value of N is equivalent to specifying the two-element list [N,
   N] in XSetDashes. The value must be nonzero, or a BadValue
   error results.

   The clip-mask restricts writes to the destination drawable. If
   the clip-mask is set to a pixmap, it must have depth one and
   have the same root as the GC, or a BadMatch error results. If
   clip-mask is set to None, the pixels are always drawn
   regardless of the clip origin. The clip-mask also can be set by
   calling the XSetClipRectangles or XSetRegion functions. Only
   pixels where the clip-mask has a bit set to 1 are drawn. Pixels
   are not drawn outside the area covered by the clip-mask or
   where the clip-mask has a bit set to 0. The clip-mask affects
   all graphics requests. The clip-mask does not clip sources. The
   clip-mask origin is interpreted relative to the origin of
   whatever destination drawable is specified in a graphics
   request.

   You can set the subwindow-mode to ClipByChildren or
   IncludeInferiors. For ClipByChildren, both source and
   destination windows are additionally clipped by all viewable
   InputOutput children. For IncludeInferiors, neither source nor
   destination window is clipped by inferiors. This will result in
   including subwindow contents in the source and drawing through
   subwindow boundaries of the destination. The use of
   IncludeInferiors on a window of one depth with mapped inferiors
   of differing depth is not illegal, but the semantics are
   undefined by the core protocol.

   The fill-rule defines what pixels are inside (drawn) for paths
   given in XFillPolygon requests and can be set to EvenOddRule or
   WindingRule. For EvenOddRule, a point is inside if an infinite
   ray with the point as origin crosses the path an odd number of
   times. For WindingRule, a point is inside if an infinite ray
   with the point as origin crosses an unequal number of clockwise
   and counterclockwise directed path segments. A clockwise
   directed path segment is one that crosses the ray from left to
   right as observed from the point. A counterclockwise segment is
   one that crosses the ray from right to left as observed from
   the point. The case where a directed line segment is coincident
   with the ray is uninteresting because you can simply choose a
   different ray that is not coincident with a segment.

   For both EvenOddRule and WindingRule, a point is infinitely
   small, and the path is an infinitely thin line. A pixel is
   inside if the center point of the pixel is inside and the
   center point is not on the boundary. If the center point is on
   the boundary, the pixel is inside if and only if the polygon
   interior is immediately to its right (x increasing direction).
   Pixels with centers on a horizontal edge are a special case and
   are inside if and only if the polygon interior is immediately
   below (y increasing direction).

   The arc-mode controls filling in the XFillArcs function and can
   be set to ArcPieSlice or ArcChord. For ArcPieSlice, the arcs
   are pie-slice filled. For ArcChord, the arcs are chord filled.

   The graphics-exposure flag controls GraphicsExpose event
   generation for XCopyArea and XCopyPlane requests (and any
   similar requests defined by extensions).

   To create a new GC that is usable on a given screen with a
   depth of drawable, use XCreateGC.

   GC XCreateGC(Display *display, Drawable d, unsigned long
   valuemask, XGCValues *values);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   valuemask

   Specifies which components in the GC are to be set using the
   information in the specified values structure. This argument is
   the bitwise inclusive OR of zero or more of the valid GC
   component mask bits.

   values

   Specifies any values as specified by the valuemask.

   The XCreateGC function creates a graphics context and returns a
   GC. The GC can be used with any destination drawable having the
   same root and depth as the specified drawable. Use with other
   drawables results in a BadMatch error.

   XCreateGC can generate BadAlloc, BadDrawable, BadFont,
   BadMatch, BadPixmap, and BadValue errors.

   To copy components from a source GC to a destination GC, use
   XCopyGC.

   XCopyGC(Display *display, GC src, GC dest, unsigned long
   valuemask);

   display

   Specifies the connection to the X server.

   src

   Specifies the components of the source GC.

   valuemask

   Specifies which components in the GC are to be copied to the
   destination GC. This argument is the bitwise inclusive OR of
   zero or more of the valid GC component mask bits.

   dest

   Specifies the destination GC.

   The XCopyGC function copies the specified components from the
   source GC to the destination GC. The source and destination GCs
   must have the same root and depth, or a BadMatch error results.
   The valuemask specifies which component to copy, as for
   XCreateGC.

   XCopyGC can generate BadAlloc, BadGC, and BadMatch errors.

   To change the components in a given GC, use XChangeGC.

   XChangeGC(Display *display, GC gc, unsigned long valuemask,
   XGCValues *values);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   valuemask

   Specifies which components in the GC are to be changed using
   information in the specified values structure. This argument is
   the bitwise inclusive OR of zero or more of the valid GC
   component mask bits.

   values

   Specifies any values as specified by the valuemask.

   The XChangeGC function changes the components specified by
   valuemask for the specified GC. The values argument contains
   the values to be set. The values and restrictions are the same
   as for XCreateGC. Changing the clip-mask overrides any previous
   XSetClipRectangles request on the context. Changing the
   dash-offset or dash-list overrides any previous XSetDashes
   request on the context. The order in which components are
   verified and altered is server dependent. If an error is
   generated, a subset of the components may have been altered.

   XChangeGC can generate BadAlloc, BadFont, BadGC, BadMatch,
   BadPixmap, and BadValue errors.

   To obtain components of a given GC, use XGetGCValues.

   Status XGetGCValues(Display *display, GC gc, unsigned long
   valuemask, XGCValues *values_return);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   valuemask

   Specifies which components in the GC are to be returned in the
   values_return argument. This argument is the bitwise inclusive
   OR of zero or more of the valid GC component mask bits.

   values_return

   Returns the GC values in the specified XGCValues structure.

   The XGetGCValues function returns the components specified by
   valuemask for the specified GC. If the valuemask contains a
   valid set of GC mask bits (GCFunction, GCPlaneMask,
   GCForeground, GCBackground, GCLineWidth, GCLineStyle,
   GCCapStyle, GCJoinStyle, GCFillStyle, GCFillRule, GCTile,
   GCStipple, GCTileStipXOrigin, GCTileStipYOrigin, GCFont,
   GCSubwindowMode, GCGraphicsExposures, GCClipXOrigin,
   GCClipYOrigin, GCDashOffset, or GCArcMode) and no error occurs,
   XGetGCValues sets the requested components in values_return and
   returns a nonzero status. Otherwise, it returns a zero status.
   Note that the clip-mask and dash-list (represented by the
   GCClipMask and GCDashList bits, respectively, in the valuemask)
   cannot be requested. Also note that an invalid resource ID
   (with one or more of the three most significant bits set to 1)
   will be returned for GCFont, GCTile, and GCStipple if the
   component has never been explicitly set by the client.

   To free a given GC, use XFreeGC.

   XFreeGC(Display *display, GC gc);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   The XFreeGC function destroys the specified GC as well as all
   the associated storage.

   XFreeGC can generate a BadGC error.

   To obtain the GContext resource ID for a given GC, use
   XGContextFromGC.

   GContext XGContextFromGC(GC gc);

   gc

   Specifies the GC for which you want the resource ID.

   Xlib usually defers sending changes to the components of a GC
   to the server until a graphics function is actually called with
   that GC. This permits batching of component changes into a
   single server request. In some circumstances, however, it may
   be necessary for the client to explicitly force sending the
   changes to the server. An example might be when a protocol
   extension uses the GC indirectly, in such a way that the
   extension interface cannot know what GC will be used. To force
   sending GC component changes, use XFlushGC.

   void XFlushGC(Display *display, GC gc);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

Using Graphics Context Convenience Routines

   This section discusses how to set the:
     * Foreground, background, plane mask, or function components
     * Line attributes and dashes components
     * Fill style and fill rule components
     * Fill tile and stipple components
     * Font component
     * Clip region component
     * Arc mode, subwindow mode, and graphics exposure components

Setting the Foreground, Background, Function, or Plane Mask

   To set the foreground, background, plane mask, and function
   components for a given GC, use XSetState.

   XSetState(Display *display, GC gc, unsigned long foreground,
   unsigned long background, int function, unsigned long
   plane_mask);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   foreground

   Specifies the foreground you want to set for the specified GC.

   background

   Specifies the background you want to set for the specified GC.

   function

   Specifies the function you want to set for the specified GC.

   plane_mask

   Specifies the plane mask.

   XSetState can generate BadAlloc, BadGC, and BadValue errors.

   To set the foreground of a given GC, use XSetForeground.

   XSetForeground(Display *display, GC gc, unsigned long
   foreground);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   foreground

   Specifies the foreground you want to set for the specified GC.

   XSetForeground can generate BadAlloc and BadGC errors.

   To set the background of a given GC, use XSetBackground.

   XSetBackground(Display *display, GC gc, unsigned long
   background);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   background

   Specifies the background you want to set for the specified GC.

   XSetBackground can generate BadAlloc and BadGC errors.

   To set the display function in a given GC, use XSetFunction.

   XSetFunction(Display *display, GC gc, int function);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   function

   Specifies the function you want to set for the specified GC.

   XSetFunction can generate BadAlloc, BadGC, and BadValue errors.

   To set the plane mask of a given GC, use XSetPlaneMask.

   XSetPlaneMask(Display *display, GC gc, unsigned long
   plane_mask);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   plane_mask

   Specifies the plane mask.

   XSetPlaneMask can generate BadAlloc and BadGC errors.

Setting the Line Attributes and Dashes

   To set the line drawing components of a given GC, use
   XSetLineAttributes.

   XSetLineAttributes(Display *display, GC gc, unsigned int
   line_width, int line_style, int cap_style, int join_style);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   line_width

   Specifies the line-width you want to set for the specified GC.

   line_style

   Specifies the line-style you want to set for the specified GC.
   You can pass LineSolid, LineOnOffDash, or LineDoubleDash.

   cap_style

   Specifies the line-style and cap-style you want to set for the
   specified GC. You can pass CapNotLast, CapButt, CapRound, or
   CapProjecting.

   join_style

   Specifies the line join-style you want to set for the specified
   GC. You can pass JoinMiter, JoinRound, or JoinBevel.

   XSetLineAttributes can generate BadAlloc, BadGC, and BadValue
   errors.

   To set the dash-offset and dash-list for dashed line styles of
   a given GC, use XSetDashes.

   XSetDashes(Display *display, GC gc, int dash_offset, char
   dash_list[], int n);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   dash_offset

   Specifies the phase of the pattern for the dashed line-style
   you want to set for the specified GC.

   dash_list

   Specifies the dash-list for the dashed line-style you want to
   set for the specified GC.

   n

   Specifies the number of elements in dash_list.

   The XSetDashes function sets the dash-offset and dash-list
   attributes for dashed line styles in the specified GC. There
   must be at least one element in the specified dash_list, or a
   BadValue error results. The initial and alternating elements
   (second, fourth, and so on) of the dash_list are the even
   dashes, and the others are the odd dashes. Each element
   specifies a dash length in pixels. All of the elements must be
   nonzero, or a BadValue error results. Specifying an odd-length
   list is equivalent to specifying the same list concatenated
   with itself to produce an even-length list.

   The dash-offset defines the phase of the pattern, specifying
   how many pixels into the dash-list the pattern should actually
   begin in any single graphics request. Dashing is continuous
   through path elements combined with a join-style but is reset
   to the dash-offset between each sequence of joined lines.

   The unit of measure for dashes is the same for the ordinary
   coordinate system. Ideally, a dash length is measured along the
   slope of the line, but implementations are only required to
   match this ideal for horizontal and vertical lines. Failing the
   ideal semantics, it is suggested that the length be measured
   along the major axis of the line. The major axis is defined as
   the x axis for lines drawn at an angle of between -45 and +45
   degrees or between 135 and 225 degrees from the x axis. For all
   other lines, the major axis is the y axis.

   XSetDashes can generate BadAlloc, BadGC, and BadValue errors.

Setting the Fill Style and Fill Rule

   To set the fill-style of a given GC, use XSetFillStyle.

   XSetFillStyle(Display *display, GC gc, int fill_style);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   fill_style

   Specifies the fill-style you want to set for the specified GC.
   You can pass FillSolid, FillTiled, FillStippled, or
   FillOpaqueStippled.

   XSetFillStyle can generate BadAlloc, BadGC, and BadValue
   errors.

   To set the fill-rule of a given GC, use XSetFillRule.

   XSetFillRule(Display *display, GC gc, int fill_rule);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   fill_rule

   Specifies the fill-rule you want to set for the specified GC.
   You can pass EvenOddRule or WindingRule.

   XSetFillRule can generate BadAlloc, BadGC, and BadValue errors.

Setting the Fill Tile and Stipple

   Some displays have hardware support for tiling or stippling
   with patterns of specific sizes. Tiling and stippling
   operations that restrict themselves to those specific sizes run
   much faster than such operations with arbitrary size patterns.
   Xlib provides functions that you can use to determine the best
   size, tile, or stipple for the display as well as to set the
   tile or stipple shape and the tile or stipple origin.

   To obtain the best size of a tile, stipple, or cursor, use
   XQueryBestSize.

   Status XQueryBestSize(Display *display, int class, Drawable
   which_screen, unsigned int width, unsigned int height, unsigned
   int *width_return, unsigned int *height_return);

   display

   Specifies the connection to the X server.

   class

   Specifies the class that you are interested in. You can pass
   TileShape, CursorShape, or StippleShape.

   which_screen

   Specifies any drawable on the screen.

   width

   height

   Specify the width and height.

   width_return

   height_return

   Return the width and height of the object best supported by the
   display hardware.

   The XQueryBestSize function returns the best or closest size to
   the specified size. For CursorShape, this is the largest size
   that can be fully displayed on the screen specified by
   which_screen. For TileShape, this is the size that can be tiled
   fastest. For StippleShape, this is the size that can be
   stippled fastest. For CursorShape, the drawable indicates the
   desired screen. For TileShape and StippleShape, the drawable
   indicates the screen and possibly the window class and depth.
   An InputOnly window cannot be used as the drawable for
   TileShape or StippleShape, or a BadMatch error results.

   XQueryBestSize can generate BadDrawable, BadMatch, and BadValue
   errors.

   To obtain the best fill tile shape, use XQueryBestTile.

   Status XQueryBestTile(Display *display, Drawable which_screen,
   unsigned int width, unsigned int height, unsigned int
   *width_return, unsigned int *height_return);

   display

   Specifies the connection to the X server.

   which_screen

   Specifies any drawable on the screen.

   width

   height

   Specify the width and height.

   width_return

   height_return

   Return the width and height of the object best supported by the
   display hardware.

   The XQueryBestTile function returns the best or closest size,
   that is, the size that can be tiled fastest on the screen
   specified by which_screen. The drawable indicates the screen
   and possibly the window class and depth. If an InputOnly window
   is used as the drawable, a BadMatch error results.

   XQueryBestTile can generate BadDrawable and BadMatch errors.

   To obtain the best stipple shape, use XQueryBestStipple.

   Status XQueryBestStipple(Display *display, Drawable
   which_screen, unsigned int width, unsigned int height, unsigned
   int *width_return, unsigned int *height_return);

   display

   Specifies the connection to the X server.

   which_screen

   Specifies any drawable on the screen.

   width

   height

   Specify the width and height.

   width_return

   height_return

   Return the width and height of the object best supported by the
   display hardware.

   The XQueryBestStipple function returns the best or closest
   size, that is, the size that can be stippled fastest on the
   screen specified by which_screen. The drawable indicates the
   screen and possibly the window class and depth. If an InputOnly
   window is used as the drawable, a BadMatch error results.

   XQueryBestStipple can generate BadDrawable and BadMatch errors.

   To set the fill tile of a given GC, use XSetTile.

   XSetTile(Display *display, GC gc, Pixmap tile);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   tile

   Specifies the fill tile you want to set for the specified GC.

   The tile and GC must have the same depth, or a BadMatch error
   results.

   XSetTile can generate BadAlloc, BadGC, BadMatch, and BadPixmap
   errors.

   To set the stipple of a given GC, use XSetStipple.

   XSetStipple(Display *display, GC gc, Pixmap stipple);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   stipple

   Specifies the stipple you want to set for the specified GC.

   The stipple must have a depth of one, or a BadMatch error
   results.

   XSetStipple can generate BadAlloc, BadGC, BadMatch, and
   BadPixmap errors.

   To set the tile or stipple origin of a given GC, use
   XSetTSOrigin.

   XSetTSOrigin(Display *display, GC gc, int ts_x_origin, int
   ts_y_origin);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   ts_x_origin

   ts_y_origin

   Specify the x and y coordinates of the tile and stipple origin.

   When graphics requests call for tiling or stippling, the
   parent's origin will be interpreted relative to whatever
   destination drawable is specified in the graphics request.

   XSetTSOrigin can generate BadAlloc and BadGC errors.

Setting the Current Font

   To set the current font of a given GC, use XSetFont.

   XSetFont(Display *display, GC gc, Font font);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   font

   Specifies the font.

   XSetFont can generate BadAlloc, BadFont, and BadGC errors.

Setting the Clip Region

   Xlib provides functions that you can use to set the clip-origin
   and the clip-mask or set the clip-mask to a list of rectangles.

   To set the clip-origin of a given GC, use XSetClipOrigin.

   XSetClipOrigin(Display *display, GC gc, int clip_x_origin, int
   clip_y_origin);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   clip_x_origin

   clip_y_origin

   Specify the x and y coordinates of the clip-mask origin.

   The clip-mask origin is interpreted relative to the origin of
   whatever destination drawable is specified in the graphics
   request.

   XSetClipOrigin can generate BadAlloc and BadGC errors.

   To set the clip-mask of a given GC to the specified pixmap, use
   XSetClipMask.

   XSetClipMask(Display *display, GC gc, Pixmap pixmap);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   pixmap

   Specifies the pixmap or None.

   If the clip-mask is set to None, the pixels are always drawn
   (regardless of the clip-origin).

   XSetClipMask can generate BadAlloc, BadGC, BadMatch, and
   BadPixmap errors.

   To set the clip-mask of a given GC to the specified list of
   rectangles, use XSetClipRectangles.

   XSetClipRectangles(Display *display, GC gc, int clip_x_origin,
   int clip_y_origin, XRectangle rectangles[], int n, int
   ordering);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   clip_x_origin

   clip_y_origin

   Specify the x and y coordinates of the clip-mask origin.

   rectangles

   Specifies an array of rectangles that define the clip-mask.

   n

   Specifies the number of rectangles.

   ordering

   Specifies the ordering relations on the rectangles. You can
   pass Unsorted, YSorted, YXSorted, or YXBanded.

   The XSetClipRectangles function changes the clip-mask in the
   specified GC to the specified list of rectangles and sets the
   clip origin. The output is clipped to remain contained within
   the rectangles. The clip-origin is interpreted relative to the
   origin of whatever destination drawable is specified in a
   graphics request. The rectangle coordinates are interpreted
   relative to the clip-origin. The rectangles should be
   nonintersecting, or the graphics results will be undefined.
   Note that the list of rectangles can be empty, which
   effectively disables output. This is the opposite of passing
   None as the clip-mask in XCreateGC, XChangeGC, and
   XSetClipMask.

   If known by the client, ordering relations on the rectangles
   can be specified with the ordering argument. This may provide
   faster operation by the server. If an incorrect ordering is
   specified, the X server may generate a BadMatch error, but it
   is not required to do so. If no error is generated, the
   graphics results are undefined. Unsorted means the rectangles
   are in arbitrary order. YSorted means that the rectangles are
   nondecreasing in their Y origin. YXSorted additionally
   constrains YSorted order in that all rectangles with an equal Y
   origin are nondecreasing in their X origin. YXBanded
   additionally constrains YXSorted by requiring that, for every
   possible Y scanline, all rectangles that include that scanline
   have an identical Y origins and Y extents.

   XSetClipRectangles can generate BadAlloc, BadGC, BadMatch, and
   BadValue errors.

   Xlib provides a set of basic functions for performing region
   arithmetic. For information about these functions, see section
   16.5.

Setting the Arc Mode, Subwindow Mode, and Graphics Exposure

   To set the arc mode of a given GC, use XSetArcMode.

   XSetArcMode(Display *display, GC gc, int arc_mode);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   arc_mode

   Specifies the arc mode. You can pass ArcChord or ArcPieSlice.

   XSetArcMode can generate BadAlloc, BadGC, and BadValue errors.

   To set the subwindow mode of a given GC, use XSetSubwindowMode.

   XSetSubwindowMode(Display *display, GC gc, int subwindow_mode);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   subwindow_mode

   Specifies the subwindow mode. You can pass ClipByChildren or
   IncludeInferiors.

   XSetSubwindowMode can generate BadAlloc, BadGC, and BadValue
   errors.

   To set the graphics-exposures flag of a given GC, use
   XSetGraphicsExposures.

   XSetGraphicsExposures(Display *display, GC gc, Bool
   graphics_exposures);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   graphics_exposures

   Specifies a Boolean value that indicates whether you want
   GraphicsExpose and NoExpose events to be reported when calling
   XCopyArea and XCopyPlane with this GC.

   XSetGraphicsExposures can generate BadAlloc, BadGC, and
   BadValue errors.

Chapter 8. Graphics Functions

   Table of Contents

   Clearing Areas
   Copying Areas
   Drawing Points, Lines, Rectangles, and Arcs

        Drawing Single and Multiple Points
        Drawing Single and Multiple Lines
        Drawing Single and Multiple Rectangles
        Drawing Single and Multiple Arcs

   Filling Areas

        Filling Single and Multiple Rectangles
        Filling a Single Polygon
        Filling Single and Multiple Arcs

   Font Metrics

        Loading and Freeing Fonts
        Obtaining and Freeing Font Names and Information
        Computing Character String Sizes
        Computing Logical Extents
        Querying Character String Sizes

   Drawing Text

        Drawing Complex Text
        Drawing Text Characters
        Drawing Image Text Characters

   Transferring Images between Client and Server

   Once you have established a connection to a display, you can
   use the Xlib graphics functions to:
     * Clear and copy areas
     * Draw points, lines, rectangles, and arcs
     * Fill areas
     * Manipulate fonts
     * Draw text
     * Transfer images between clients and the server

   If the same drawable and GC is used for each call, Xlib batches
   back-to-back calls to XDrawPoint, XDrawLine, XDrawRectangle,
   XFillArc, and XFillRectangle. Note that this reduces the total
   number of requests sent to the server.

Clearing Areas

   Xlib provides functions that you can use to clear an area or
   the entire window. Because pixmaps do not have defined
   backgrounds, they cannot be filled by using the functions
   described in this section. Instead, to accomplish an analogous
   operation on a pixmap, you should use XFillRectangle, which
   sets the pixmap to a known value.

   To clear a rectangular area of a given window, use XClearArea.

   XClearArea(Display *display, Window w, int x, int y, unsigned
   int width, unsigned int height, Bool exposures);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the window and specify the upper-left corner of the
   rectangle.

   width

   height

   Specify the width and height, which are the dimensions of the
   rectangle.

   exposures

   Specifies a Boolean value that indicates if Expose events are
   to be generated.

   The XClearArea function paints a rectangular area in the
   specified window according to the specified dimensions with the
   window's background pixel or pixmap. The subwindow-mode
   effectively is ClipByChildren. If width is zero, it is replaced
   with the current width of the window minus x. If height is
   zero, it is replaced with the current height of the window
   minus y. If the window has a defined background tile, the
   rectangle clipped by any children is filled with this tile. If
   the window has background None, the contents of the window are
   not changed. In either case, if exposures is True, one or more
   Expose events are generated for regions of the rectangle that
   are either visible or are being retained in a backing store. If
   you specify a window whose class is InputOnly, a BadMatch error
   results.

   XClearArea can generate BadMatch, BadValue, and BadWindow
   errors.

   To clear the entire area in a given window, use XClearWindow.

   XClearWindow(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XClearWindow function clears the entire area in the
   specified window and is equivalent to XClearArea (display, w,
   0, 0, 0, 0, False). If the window has a defined background
   tile, the rectangle is tiled with a plane-mask of all ones and
   GXcopy function. If the window has background None, the
   contents of the window are not changed. If you specify a window
   whose class is InputOnly, a BadMatch error results.

   XClearWindow can generate BadMatch and BadWindow errors.

Copying Areas

   Xlib provides functions that you can use to copy an area or a
   bit plane.

   To copy an area between drawables of the same root and depth,
   use XCopyArea.

   XCopyArea(Display *display, Drawable src, Drawable dest, GC gc,
   int src_x, int src_y, unsigned int width, unsigned int height,
   int dest_x, int dest_y);

   display

   Specifies the connection to the X server.

   src

   dest

   Specify the source and destination rectangles to be combined.

   gc

   Specifies the GC.

   src_x

   src_y

   Specify the x and y coordinates, which are relative to the
   origin of the source rectangle and specify its upper-left
   corner.

   width

   height

   Specify the width and height, which are the dimensions of both
   the source and destination rectangles.

   dest_x

   dest_y

   Specify the x and y coordinates, which are relative to the
   origin of the destination rectangle and specify its upper-left
   corner.

   The XCopyArea function combines the specified rectangle of src
   with the specified rectangle of dest. The drawables must have
   the same root and depth, or a BadMatch error results.

   If regions of the source rectangle are obscured and have not
   been retained in backing store or if regions outside the
   boundaries of the source drawable are specified, those regions
   are not copied. Instead, the following occurs on all
   corresponding destination regions that are either visible or
   are retained in backing store. If the destination is a window
   with a background other than None, corresponding regions of the
   destination are tiled with that background (with plane-mask of
   all ones and GXcopy function). Regardless of tiling or whether
   the destination is a window or a pixmap, if graphics-exposures
   is True, then GraphicsExpose events for all corresponding
   destination regions are generated. If graphics-exposures is
   True but no GraphicsExpose events are generated, a NoExpose
   event is generated. Note that by default graphics-exposures is
   True in new GCs.

   This function uses these GC components: function, plane-mask,
   subwindow-mode, graphics-exposures, clip-x-origin,
   clip-y-origin, and clip-mask.

   XCopyArea can generate BadDrawable, BadGC, and BadMatch errors.

   To copy a single bit plane of a given drawable, use XCopyPlane.

   XCopyPlane(Display *display, Drawable src, Drawable dest, GC
   gc, int src_x, int src_y, unsigned int width, unsigned int
   height, int dest_x, int dest_y, unsigned long plane);

   display

   Specifies the connection to the X server.

   src

   dest

   Specify the source and destination rectangles to be combined.

   gc

   Specifies the GC.

   src_x

   src_y

   Specify the x and y coordinates, which are relative to the
   origin of the source rectangle and specify its upper-left
   corner.

   width

   height

   Specify the width and height, which are the dimensions of both
   the source and destination rectangles.

   dest_x

   dest_y

   Specify the x and y coordinates, which are relative to the
   origin of the destination rectangle and specify its upper-left
   corner.

   plane

   Specifies the bit plane. You must set exactly one bit to 1.

   The XCopyPlane function uses a single bit plane of the
   specified source rectangle combined with the specified GC to
   modify the specified rectangle of dest. The drawables must have
   the same root but need not have the same depth. If the
   drawables do not have the same root, a BadMatch error results.
   If plane does not have exactly one bit set to 1 and the value
   of plane is not less than %2 sup n%, where n is the depth of
   src, a BadValue error results.

   Effectively, XCopyPlane forms a pixmap of the same depth as the
   rectangle of dest and with a size specified by the source
   region. It uses the foreground/background pixels in the GC
   (foreground everywhere the bit plane in src contains a bit set
   to 1, background everywhere the bit plane in src contains a bit
   set to 0) and the equivalent of a CopyArea protocol request is
   performed with all the same exposure semantics. This can also
   be thought of as using the specified region of the source bit
   plane as a stipple with a fill-style of FillOpaqueStippled for
   filling a rectangular area of the destination.

   This function uses these GC components: function, plane-mask,
   foreground, background, subwindow-mode, graphics-exposures,
   clip-x-origin, clip-y-origin, and clip-mask.

   XCopyPlane can generate BadDrawable, BadGC, BadMatch, and
   BadValue errors.

Drawing Points, Lines, Rectangles, and Arcs

   Xlib provides functions that you can use to draw:
     * A single point or multiple points
     * A single line or multiple lines
     * A single rectangle or multiple rectangles
     * A single arc or multiple arcs

   Some of the functions described in the following sections use
   these structures:



typedef struct {
     short x1, y1, x2, y2;
} XSegment;



typedef struct {
     short x, y;
} XPoint;



typedef struct {
     short x, y;
     unsigned short width, height;
} XRectangle;



typedef struct {
     short x, y;
     unsigned short width, height;
     short angle1, angle2;             /* Degrees * 64 */
} XArc;

   All x and y members are signed integers. The width and height
   members are 16-bit unsigned integers. You should be careful not
   to generate coordinates and sizes out of the 16-bit ranges,
   because the protocol only has 16-bit fields for these values.

Drawing Single and Multiple Points

   To draw a single point in a given drawable, use XDrawPoint.

   XDrawPoint(Display *display, Drawable d, GC gc, int x, int y);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates where you want the point drawn.

   To draw multiple points in a given drawable, use XDrawPoints.

   XDrawPoints(Display *display, Drawable d, GC gc, XPoint
   *points, int npoints, int mode);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   points

   Specifies an array of points.

   npoints

   Specifies the number of points in the array.

   mode

   Specifies the coordinate mode. You can pass CoordModeOrigin or
   CoordModePrevious.

   The XDrawPoint function uses the foreground pixel and function
   components of the GC to draw a single point into the specified
   drawable; XDrawPoints draws multiple points this way.
   CoordModeOrigin treats all coordinates as relative to the
   origin, and CoordModePrevious treats all coordinates after the
   first as relative to the previous point. XDrawPoints draws the
   points in the order listed in the array.

   Both functions use these GC components: function, plane-mask,
   foreground, subwindow-mode, clip-x-origin, clip-y-origin, and
   clip-mask.

   XDrawPoint can generate BadDrawable, BadGC, and BadMatch
   errors. XDrawPoints can generate BadDrawable, BadGC, BadMatch,
   and BadValue errors.

Drawing Single and Multiple Lines

   To draw a single line between two points in a given drawable,
   use XDrawLine.

   XDrawLine(Display *display, Drawable d, GC gc, int x1, int y1,
   int x2, int y2);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x1

   y1

   x2

   y2

   Specify the points (x1, y1) and (x2, y2) to be connected.

   To draw multiple lines in a given drawable, use XDrawLines.

   XDrawLines(Display *display, Drawable d, GC gc, XPoint *points,
   int npoints, int mode);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   points

   Specifies an array of points.

   npoints

   Specifies the number of points in the array.

   mode

   Specifies the coordinate mode. You can pass CoordModeOrigin or
   CoordModePrevious.

   To draw multiple, unconnected lines in a given drawable, use
   XDrawSegments.

   XDrawSegments(Display *display, Drawable d, GC gc, XSegment
   *segments, int nsegments);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   segments

   Specifies an array of segments.

   nsegments

   Specifies the number of segments in the array.

   The XDrawLine function uses the components of the specified GC
   to draw a line between the specified set of points (x1, y1) and
   (x2, y2). It does not perform joining at coincident endpoints.
   For any given line, XDrawLine does not draw a pixel more than
   once. If lines intersect, the intersecting pixels are drawn
   multiple times.

   The XDrawLines function uses the components of the specified GC
   to draw npoints-1 lines between each pair of points (point[i],
   point[i+1]) in the array of XPoint structures. It draws the
   lines in the order listed in the array. The lines join
   correctly at all intermediate points, and if the first and last
   points coincide, the first and last lines also join correctly.
   For any given line, XDrawLines does not draw a pixel more than
   once. If thin (zero line-width) lines intersect, the
   intersecting pixels are drawn multiple times. If wide lines
   intersect, the intersecting pixels are drawn only once, as
   though the entire PolyLine protocol request were a single,
   filled shape. CoordModeOrigin treats all coordinates as
   relative to the origin, and CoordModePrevious treats all
   coordinates after the first as relative to the previous point.

   The XDrawSegments function draws multiple, unconnected lines.
   For each segment, XDrawSegments draws a line between (x1, y1)
   and (x2, y2). It draws the lines in the order listed in the
   array of XSegment structures and does not perform joining at
   coincident endpoints. For any given line, XDrawSegments does
   not draw a pixel more than once. If lines intersect, the
   intersecting pixels are drawn multiple times.

   All three functions use these GC components: function,
   plane-mask, line-width, line-style, cap-style, fill-style,
   subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask.
   The XDrawLines function also uses the join-style GC component.
   All three functions also use these GC mode-dependent
   components: foreground, background, tile, stipple,
   tile-stipple-x-origin, tile-stipple-y-origin, dash-offset, and
   dash-list.

   XDrawLine, XDrawLines, and XDrawSegments can generate
   BadDrawable, BadGC, and BadMatch errors. XDrawLines also can
   generate BadValue errors.

Drawing Single and Multiple Rectangles

   To draw the outline of a single rectangle in a given drawable,
   use XDrawRectangle.

   XDrawRectangle(Display *display, Drawable d, GC gc, int x, int
   y, unsigned int width, unsigned int height);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates, which specify the upper-left
   corner of the rectangle.

   width

   height

   Specify the width and height, which specify the dimensions of
   the rectangle.

   To draw the outline of multiple rectangles in a given drawable,
   use XDrawRectangles.

   XDrawRectangles(Display *display, Drawable d, GC gc, XRectangle
   rectangles[], int nrectangles);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   rectangles

   Specifies an array of rectangles.

   nrectangles

   Specifies the number of rectangles in the array.

   The XDrawRectangle and XDrawRectangles functions draw the
   outlines of the specified rectangle or rectangles as if a
   five-point PolyLine protocol request were specified for each
   rectangle:
     * [x,y] [x+width,y] [x+width,y+height] [x,y+height] [x,y]

   For the specified rectangle or rectangles, these functions do
   not draw a pixel more than once. XDrawRectangles draws the
   rectangles in the order listed in the array. If rectangles
   intersect, the intersecting pixels are drawn multiple times.

   Both functions use these GC components: function, plane-mask,
   line-width, line-style, cap-style, join-style, fill-style,
   subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask.
   They also use these GC mode-dependent components: foreground,
   background, tile, stipple, tile-stipple-x-origin,
   tile-stipple-y-origin, dash-offset, and dash-list.

   XDrawRectangle and XDrawRectangles can generate BadDrawable,
   BadGC, and BadMatch errors.

Drawing Single and Multiple Arcs

   To draw a single arc in a given drawable, use XDrawArc.

   XDrawArc(Display *display, Drawable d, GC gc, int x, int y,
   unsigned int width, unsigned int height, int angle1, int
   angle2);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the drawable and specify the upper-left corner of the
   bounding rectangle.

   width

   height

   Specify the width and height, which are the major and minor
   axes of the arc.

   angle1

   Specifies the start of the arc relative to the three-o'clock
   position from the center, in units of degrees * 64.

   angle2

   Specifies the path and extent of the arc relative to the start
   of the arc, in units of degrees * 64.

   To draw multiple arcs in a given drawable, use XDrawArcs.

   XDrawArcs(Display *display, Drawable d, GC gc, XArc *arcs, int
   narcs);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   arcs

   Specifies an array of arcs.

   narcs

   Specifies the number of arcs in the array.

   delim %% XDrawArc draws a single circular or elliptical arc,
   and XDrawArcs draws multiple circular or elliptical arcs. Each
   arc is specified by a rectangle and two angles. The center of
   the circle or ellipse is the center of the rectangle, and the
   major and minor axes are specified by the width and height.
   Positive angles indicate counterclockwise motion, and negative
   angles indicate clockwise motion. If the magnitude of angle2 is
   greater than 360 degrees, XDrawArc or XDrawArcs truncates it to
   360 degrees.

   For an arc specified as %[ ~x, ~y, ~width , ~height, ~angle1,
   ~angle2 ]%, the origin of the major and minor axes is at % [ x
   +^ {width over 2} , ~y +^ {height over 2} ]%, and the
   infinitely thin path describing the entire circle or ellipse
   intersects the horizontal axis at % [ x, ~y +^ {height over 2}
   ]% and % [ x +^ width , ~y +^ { height over 2 }] % and
   intersects the vertical axis at % [ x +^ { width over 2 } , ~y
   ]% and % [ x +^ { width over 2 }, ~y +^ height ]%. These
   coordinates can be fractional and so are not truncated to
   discrete coordinates. The path should be defined by the ideal
   mathematical path. For a wide line with line-width lw, the
   bounding outlines for filling are given by the two infinitely
   thin paths consisting of all points whose perpendicular
   distance from the path of the circle/ellipse is equal to lw/2
   (which may be a fractional value). The cap-style and join-style
   are applied the same as for a line corresponding to the tangent
   of the circle/ellipse at the endpoint.

   For an arc specified as % [ ~x, ~y, ~width, ~height, ~angle1,
   ~angle2 ]%, the angles must be specified in the effectively
   skewed coordinate system of the ellipse (for a circle, the
   angles and coordinate systems are identical). The relationship
   between these angles and angles expressed in the normal
   coordinate system of the screen (as measured with a protractor)
   is as follows:

% roman "skewed-angle" ~ = ~ atan left ( tan ( roman "normal-angle" )
 * width over height right ) +^ adjust%

   The skewed-angle and normal-angle are expressed in radians
   (rather than in degrees scaled by 64) in the range % [ 0 , ~2
   pi ]% and where atan returns a value in the range % [ - pi over
   2 , ~pi over 2 ] % and adjust is:



%0%     for normal-angle in the range % [ 0 , ~pi over 2  ]%
%pi%     for normal-angle in the range % [ pi over 2 , ~{3 pi} over 2  ]
%
%2 pi%     for normal-angle in the range % [ {3 pi} over 2 , ~2 pi  ]%

   For any given arc, XDrawArc and XDrawArcs do not draw a pixel
   more than once. If two arcs join correctly and if the
   line-width is greater than zero and the arcs intersect,
   XDrawArc and XDrawArcs do not draw a pixel more than once.
   Otherwise, the intersecting pixels of intersecting arcs are
   drawn multiple times. Specifying an arc with one endpoint and a
   clockwise extent draws the same pixels as specifying the other
   endpoint and an equivalent counterclockwise extent, except as
   it affects joins.

   If the last point in one arc coincides with the first point in
   the following arc, the two arcs will join correctly. If the
   first point in the first arc coincides with the last point in
   the last arc, the two arcs will join correctly. By specifying
   one axis to be zero, a horizontal or vertical line can be
   drawn. Angles are computed based solely on the coordinate
   system and ignore the aspect ratio.

   Both functions use these GC components: function, plane-mask,
   line-width, line-style, cap-style, join-style, fill-style,
   subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask.
   They also use these GC mode-dependent components: foreground,
   background, tile, stipple, tile-stipple-x-origin,
   tile-stipple-y-origin, dash-offset, and dash-list.

   XDrawArc and XDrawArcs can generate BadDrawable, BadGC, and
   BadMatch errors.

Filling Areas

   Xlib provides functions that you can use to fill:
     * A single rectangle or multiple rectangles
     * A single polygon
     * A single arc or multiple arcs

Filling Single and Multiple Rectangles

   To fill a single rectangular area in a given drawable, use
   XFillRectangle.

   XFillRectangle(Display *display, Drawable d, GC gc, int x, int
   y, unsigned int width, unsigned int height);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the drawable and specify the upper-left corner of the
   rectangle.

   width

   height

   Specify the width and height, which are the dimensions of the
   rectangle to be filled.

   To fill multiple rectangular areas in a given drawable, use
   XFillRectangles.

   XFillRectangles(Display *display, Drawable d, GC gc, XRectangle
   *rectangles, int nrectangles);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   rectangles

   Specifies an array of rectangles.

   nrectangles

   Specifies the number of rectangles in the array.

   The XFillRectangle and XFillRectangles functions fill the
   specified rectangle or rectangles as if a four-point
   FillPolygon protocol request were specified for each rectangle:

[x,y] [x+width,y] [x+width,y+height] [x,y+height]

   Each function uses the x and y coordinates, width and height
   dimensions, and GC you specify.

   XFillRectangles fills the rectangles in the order listed in the
   array. For any given rectangle, XFillRectangle and
   XFillRectangles do not draw a pixel more than once. If
   rectangles intersect, the intersecting pixels are drawn
   multiple times.

   Both functions use these GC components: function, plane-mask,
   fill-style, subwindow-mode, clip-x-origin, clip-y-origin, and
   clip-mask. They also use these GC mode-dependent components:
   foreground, background, tile, stipple, tile-stipple-x-origin,
   and tile-stipple-y-origin.

   XFillRectangle and XFillRectangles can generate BadDrawable,
   BadGC, and BadMatch errors.

Filling a Single Polygon

   To fill a polygon area in a given drawable, use XFillPolygon.

   XFillPolygon(Display *display, Drawable d, GC gc, XPoint
   *points, int npoints, int shape, int mode);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   points

   Specifies an array of points.

   npoints

   Specifies the number of points in the array.

   shape

   Specifies a shape that helps the server to improve performance.
   You can pass Complex, Convex, or Nonconvex.

   mode

   Specifies the coordinate mode. You can pass CoordModeOrigin or
   CoordModePrevious.

   XFillPolygon fills the region closed by the specified path. The
   path is closed automatically if the last point in the list does
   not coincide with the first point. XFillPolygon does not draw a
   pixel of the region more than once. CoordModeOrigin treats all
   coordinates as relative to the origin, and CoordModePrevious
   treats all coordinates after the first as relative to the
   previous point.

   Depending on the specified shape, the following occurs:
     * If shape is Complex, the path may self-intersect. Note that
       contiguous coincident points in the path are not treated as
       self-intersection.
     * If shape is Convex, for every pair of points inside the
       polygon, the line segment connecting them does not
       intersect the path. If known by the client, specifying
       Convex can improve performance. If you specify Convex for a
       path that is not convex, the graphics results are
       undefined.
     * If shape is Nonconvex, the path does not self-intersect,
       but the shape is not wholly convex. If known by the client,
       specifying Nonconvex instead of Complex may improve
       performance. If you specify Nonconvex for a
       self-intersecting path, the graphics results are undefined.

   The fill-rule of the GC controls the filling behavior of
   self-intersecting polygons.

   This function uses these GC components: function, plane-mask,
   fill-style, fill-rule, subwindow-mode, clip-x-origin,
   clip-y-origin, and clip-mask. It also uses these GC
   mode-dependent components: foreground, background, tile,
   stipple, tile-stipple-x-origin, and tile-stipple-y-origin.

   XFillPolygon can generate BadDrawable, BadGC, BadMatch, and
   BadValue errors.

Filling Single and Multiple Arcs

   To fill a single arc in a given drawable, use XFillArc.

   XFillArc(Display *display, Drawable d, GC gc, int x, int y,
   unsigned int width, unsigned int height, int angle1, int
   angle2);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the drawable and specify the upper-left corner of the
   bounding rectangle.

   width

   height

   Specify the width and height, which are the major and minor
   axes of the arc.

   angle1

   Specifies the start of the arc relative to the three-o'clock
   position from the center, in units of degrees * 64.

   angle2

   Specifies the path and extent of the arc relative to the start
   of the arc, in units of degrees * 64.

   To fill multiple arcs in a given drawable, use XFillArcs.

   XFillArcs(Display *display, Drawable d, GC gc, XArc *arcs, int
   narcs);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   arcs

   Specifies an array of arcs.

   narcs

   Specifies the number of arcs in the array.

   For each arc, XFillArc or XFillArcs fills the region closed by
   the infinitely thin path described by the specified arc and,
   depending on the arc-mode specified in the GC, one or two line
   segments. For ArcChord, the single line segment joining the
   endpoints of the arc is used. For ArcPieSlice, the two line
   segments joining the endpoints of the arc with the center point
   are used. XFillArcs fills the arcs in the order listed in the
   array. For any given arc, XFillArc and XFillArcs do not draw a
   pixel more than once. If regions intersect, the intersecting
   pixels are drawn multiple times.

   Both functions use these GC components: function, plane-mask,
   fill-style, arc-mode, subwindow-mode, clip-x-origin,
   clip-y-origin, and clip-mask. They also use these GC
   mode-dependent components: foreground, background, tile,
   stipple, tile-stipple-x-origin, and tile-stipple-y-origin.

   XFillArc and XFillArcs can generate BadDrawable, BadGC, and
   BadMatch errors.

Font Metrics

   A font is a graphical description of a set of characters that
   are used to increase efficiency whenever a set of small,
   similar sized patterns are repeatedly used.

   This section discusses how to:
     * Load and free fonts
     * Obtain and free font names
     * Compute character string sizes
     * Compute logical extents
     * Query character string sizes

   The X server loads fonts whenever a program requests a new
   font. The server can cache fonts for quick lookup. Fonts are
   global across all screens in a server. Several levels are
   possible when dealing with fonts. Most applications simply use
   XLoadQueryFont to load a font and query the font metrics.

   Characters in fonts are regarded as masks. Except for image
   text requests, the only pixels modified are those in which bits
   are set to 1 in the character. This means that it makes sense
   to draw text using stipples or tiles (for example, many menus
   gray-out unusable entries).

   The XFontStruct structure contains all of the information for
   the font and consists of the font-specific information as well
   as a pointer to an array of XCharStruct structures for the
   characters contained in the font. The XFontStruct, XFontProp,
   and XCharStruct structures contain:



typedef struct {
     short lbearing;               /* origin to left edge of raster */
     short rbearing;               /* origin to right edge of raster */
     short width;                  /* advance to next char's origin */
     short ascent;                 /* baseline to top edge of raster */
     short descent;                /* baseline to bottom edge of raster
*/
     unsigned short attributes;    /* per char flags (not predefined) */
} XCharStruct;



typedef struct {
     Atom     name;
     unsigned long card32;
} XFontProp;



typedef struct {     /* normal 16 bit characters are two bytes */
    unsigned char byte1;
    unsigned char byte2;
} XChar2b;



typedef struct {
     XExtData *ext_data;               /* hook for extension to hang dat
a */
     Font fid;                         /* Font id for this font */
     unsigned direction;               /* hint about the direction font
is painted */
     unsigned min_char_or_byte2;       /* first character */
     unsigned max_char_or_byte2;       /* last character */
     unsigned min_byte1;               /* first row that exists */
     unsigned max_byte1;               /* last row that exists */
     Bool all_chars_exist;             /* flag if all characters have no
nzero size */
     unsigned default_char;            /* char to print for undefined ch
aracter */
     int n_properties;                 /* how many properties there are
*/
     XFontProp *properties;            /* pointer to array of additional
 properties */
     XCharStruct min_bounds;           /* minimum bounds over all existi
ng char */
     XCharStruct max_bounds;           /* maximum bounds over all existi
ng char */
     XCharStruct *per_char;            /* first_char to last_char inform
ation */
     int ascent;                       /* logical extent above baseline
for spacing */
     int descent;                      /* logical descent below baseline
 for spacing */
} XFontStruct;

   X supports single byte/character, two bytes/character matrix,
   and 16-bit character text operations. Note that any of these
   forms can be used with a font, but a single byte/character text
   request can only specify a single byte (that is, the first row
   of a 2-byte font). You should view 2-byte fonts as a
   two-dimensional matrix of defined characters: byte1 specifies
   the range of defined rows and byte2 defines the range of
   defined columns of the font. Single byte/character fonts have
   one row defined, and the byte2 range specified in the structure
   defines a range of characters.

   The bounding box of a character is defined by the XCharStruct
   of that character. When characters are absent from a font, the
   default_char is used. When fonts have all characters of the
   same size, only the information in the XFontStruct min and max
   bounds are used.

   The members of the XFontStruct have the following semantics:
     * The direction member can be either FontLeftToRight or
       FontRightToLeft. It is just a hint as to whether most
       XCharStruct elements have a positive (FontLeftToRight) or a
       negative (FontRightToLeft) character width metric. The core
       protocol defines no support for vertical text.
     * If the min_byte1 and max_byte1 members are both zero,
       min_char_or_byte2 specifies the linear character index
       corresponding to the first element of the per_char array,
       and max_char_or_byte2 specifies the linear character index
       of the last element.
     * If either min_byte1 or max_byte1 are nonzero, both
       min_char_or_byte2 and max_char_or_byte2 are less than 256,
       and the 2-byte character index values corresponding to the
       per_char array element N (counting from 0) are:
     * byte1 = N/D + min_byte1 byte2 = N\\D + min_char_or_byte2
     * where:
     * D = max_char_or_byte2 - min_char_or_byte2 + 1 / = integer
       division \\ = integer modulus
     * If the per_char pointer is NULL, all glyphs between the
       first and last character indexes inclusive have the same
       information, as given by both min_bounds and max_bounds.
     * If all_chars_exist is True, all characters in the per_char
       array have nonzero bounding boxes.
     * The default_char member specifies the character that will
       be used when an undefined or nonexistent character is
       printed. The default_char is a 16-bit character (not a
       2-byte character). For a font using 2-byte matrix format,
       the default_char has byte1 in the most-significant byte and
       byte2 in the least significant byte. If the default_char
       itself specifies an undefined or nonexistent character, no
       printing is performed for an undefined or nonexistent
       character.
     * The min_bounds and max_bounds members contain the most
       extreme values of each individual XCharStruct component
       over all elements of this array (and ignore nonexistent
       characters). The bounding box of the font (the smallest
       rectangle enclosing the shape obtained by superimposing all
       of the characters at the same origin [x,y]) has its
       upper-left coordinate at:
     [x + min_bounds.lbearing, y - max_bounds.ascent]

     * Its width is:
     max_bounds.rbearing - min_bounds.lbearing

     * Its height is:
     max_bounds.ascent + max_bounds.descent

     * The ascent member is the logical extent of the font above
       the baseline that is used for determining line spacing.
       Specific characters may extend beyond this.
     * The descent member is the logical extent of the font at or
       below the baseline that is used for determining line
       spacing. Specific characters may extend beyond this.
     * If the baseline is at Y-coordinate y, the logical extent of
       the font is inclusive between the Y-coordinate values (y -
       font.ascent) and (y + font.descent - 1). Typically, the
       minimum interline spacing between rows of text is given by
       ascent + descent.

   For a character origin at [x,y], the bounding box of a
   character (that is, the smallest rectangle that encloses the
   character's shape) described in terms of XCharStruct components
   is a rectangle with its upper-left corner at:

[x + lbearing, y - ascent]

   Its width is:

rbearing - lbearing

   Its height is:

ascent + descent

   The origin for the next character is defined to be:

[x + width, y]

   The lbearing member defines the extent of the left edge of the
   character ink from the origin. The rbearing member defines the
   extent of the right edge of the character ink from the origin.
   The ascent member defines the extent of the top edge of the
   character ink from the origin. The descent member defines the
   extent of the bottom edge of the character ink from the origin.
   The width member defines the logical width of the character.

   Note that the baseline (the y position of the character origin)
   is logically viewed as being the scanline just below
   nondescending characters. When descent is zero, only pixels
   with Y-coordinates less than y are drawn, and the origin is
   logically viewed as being coincident with the left edge of a
   nonkerned character. When lbearing is zero, no pixels with
   X-coordinate less than x are drawn. Any of the XCharStruct
   metric members could be negative. If the width is negative, the
   next character will be placed to the left of the current
   origin.

   The X protocol does not define the interpretation of the
   attributes member in the XCharStruct structure. A nonexistent
   character is represented with all members of its XCharStruct
   set to zero.

   A font is not guaranteed to have any properties. The
   interpretation of the property value (for example, long or
   unsigned long) must be derived from a priori knowledge of the
   property. A basic set of font properties is specified in the X
   Consortium standard X Logical Font Description Conventions.

Loading and Freeing Fonts

   Xlib provides functions that you can use to load fonts, get
   font information, unload fonts, and free font information. A
   few font functions use a GContext resource ID or a font ID
   interchangeably.

   To load a given font, use XLoadFont.

   Font XLoadFont(Display *display, char *name);

   display

   Specifies the connection to the X server.

   name

   Specifies the name of the font, which is a null-terminated
   string.

   The XLoadFont function loads the specified font and returns its
   associated font ID. If the font name is not in the Host
   Portable Character Encoding, the result is
   implementation-dependent. Use of uppercase or lowercase does
   not matter. When the characters ``?'' and ``*'' are used in a
   font name, a pattern match is performed and any matching font
   is used. In the pattern, the ``?'' character will match any
   single character, and the ``*'' character will match any number
   of characters. A structured format for font names is specified
   in the X Consortium standard X Logical Font Description
   Conventions. If XLoadFont was unsuccessful at loading the
   specified font, a BadName error results. Fonts are not
   associated with a particular screen and can be stored as a
   component of any GC. When the font is no longer needed, call
   XUnloadFont.

   XLoadFont can generate BadAlloc and BadName errors.

   To return information about an available font, use XQueryFont.

   XFontStruct *XQueryFont(Display *display, XID font_ID);

   display

   Specifies the connection to the X server.

   font_ID

   Specifies the font ID or the GContext ID.

   The XQueryFont function returns a pointer to the XFontStruct
   structure, which contains information associated with the font.
   You can query a font or the font stored in a GC. The font ID
   stored in the XFontStruct structure will be the GContext ID,
   and you need to be careful when using this ID in other
   functions (see XGContextFromGC). If the font does not exist,
   XQueryFont returns NULL. To free this data, use XFreeFontInfo.

   To perform a XLoadFont and XQueryFont in a single operation,
   use XLoadQueryFont.

   XFontStruct *XLoadQueryFont(Display *display, char *name);

   display

   Specifies the connection to the X server.

   name

   Specifies the name of the font, which is a null-terminated
   string.

   The XLoadQueryFont function provides the most common way for
   accessing a font. XLoadQueryFont both opens (loads) the
   specified font and returns a pointer to the appropriate
   XFontStruct structure. If the font name is not in the Host
   Portable Character Encoding, the result is
   implementation-dependent. If the font does not exist,
   XLoadQueryFont returns NULL.

   XLoadQueryFont can generate a BadAlloc error.

   To unload the font and free the storage used by the font
   structure that was allocated by XQueryFont or XLoadQueryFont,
   use XFreeFont.

   XFreeFont(Display *display, XFontStruct *font_struct);

   display

   Specifies the connection to the X server.

   font_struct

   Specifies the storage associated with the font.

   The XFreeFont function deletes the association between the font
   resource ID and the specified font and frees the XFontStruct
   structure. The font itself will be freed when no other resource
   references it. The data and the font should not be referenced
   again.

   XFreeFont can generate a BadFont error.

   To return a given font property, use XGetFontProperty.

   Bool XGetFontProperty(XFontStruct *font_struct, Atom atom,
   unsigned long *value_return);

   font_struct

   Specifies the storage associated with the font.

   atom

   Specifies the atom for the property name you want returned.

   value_return

   Returns the value of the font property.

   Given the atom for that property, the XGetFontProperty function
   returns the value of the specified font property.
   XGetFontProperty also returns False if the property was not
   defined or True if it was defined. A set of predefined atoms
   exists for font properties, which can be found in
   <X11/Xatom.h>. This set contains the standard properties
   associated with a font. Although it is not guaranteed, it is
   likely that the predefined font properties will be present.

   To unload a font that was loaded by XLoadFont, use XUnloadFont.

   XUnloadFont(Display *display, Font font);

   display

   Specifies the connection to the X server.

   font

   Specifies the font.

   The XUnloadFont function deletes the association between the
   font resource ID and the specified font. The font itself will
   be freed when no other resource references it. The font should
   not be referenced again.

   XUnloadFont can generate a BadFont error.

Obtaining and Freeing Font Names and Information

   You obtain font names and information by matching a wildcard
   specification when querying a font type for a list of available
   sizes and so on.

   To return a list of the available font names, use XListFonts.

   char **XListFonts(Display *display, char *pattern, int
   maxnames, int *actual_count_return);

   display

   Specifies the connection to the X server.

   pattern

   Specifies the null-terminated pattern string that can contain
   wildcard characters.

   maxnames

   Specifies the maximum number of names to be returned.

   actual_count_return

   Returns the actual number of font names.

   The XListFonts function returns an array of available font
   names (as controlled by the font search path; see XSetFontPath)
   that match the string you passed to the pattern argument. The
   pattern string can contain any characters, but each asterisk
   (*) is a wildcard for any number of characters, and each
   question mark (?) is a wildcard for a single character. If the
   pattern string is not in the Host Portable Character Encoding,
   the result is implementation-dependent. Use of uppercase or
   lowercase does not matter. Each returned string is
   null-terminated. If the data returned by the server is in the
   Latin Portable Character Encoding, then the returned strings
   are in the Host Portable Character Encoding. Otherwise, the
   result is implementation-dependent. If there are no matching
   font names, XListFonts returns NULL. The client should call
   XFreeFontNames when finished with the result to free the
   memory.

   To free a font name array, use XFreeFontNames.

   XFreeFontNames(char *list[]);

   list

   Specifies the array of strings you want to free.

   The XFreeFontNames function frees the array and strings
   returned by XListFonts or XListFontsWithInfo.

   To obtain the names and information about available fonts, use
   XListFontsWithInfo.

   char **XListFontsWithInfo(Display *display, char *pattern, int
   maxnames, int *count_return, XFontStruct **info_return);

   display

   Specifies the connection to the X server.

   pattern

   Specifies the null-terminated pattern string that can contain
   wildcard characters.

   maxnames

   Specifies the maximum number of names to be returned.

   count_return

   Returns the actual number of matched font names.

   info_return

   Returns the font information.

   The XListFontsWithInfo function returns a list of font names
   that match the specified pattern and their associated font
   information. The list of names is limited to size specified by
   maxnames. The information returned for each font is identical
   to what XLoadQueryFont would return except that the
   per-character metrics are not returned. The pattern string can
   contain any characters, but each asterisk (*) is a wildcard for
   any number of characters, and each question mark (?) is a
   wildcard for a single character. If the pattern string is not
   in the Host Portable Character Encoding, the result is
   implementation-dependent. Use of uppercase or lowercase does
   not matter. Each returned string is null-terminated. If the
   data returned by the server is in the Latin Portable Character
   Encoding, then the returned strings are in the Host Portable
   Character Encoding. Otherwise, the result is
   implementation-dependent. If there are no matching font names,
   XListFontsWithInfo returns NULL.

   To free only the allocated name array, the client should call
   XFreeFontNames. To free both the name array and the font
   information array or to free just the font information array,
   the client should call XFreeFontInfo.

   To free font structures and font names, use XFreeFontInfo.

   XFreeFontInfo(char **names, XFontStruct *free_info, int
   actual_count);

   names

   Specifies the list of font names.

   free_info

   Specifies the font information.

   actual_count

   Specifies the actual number of font names.

   The XFreeFontInfo function frees a font structure or an array
   of font structures and optionally an array of font names. If
   NULL is passed for names, no font names are freed. If a font
   structure for an open font (returned by XLoadQueryFont) is
   passed, the structure is freed, but the font is not closed; use
   XUnloadFont to close the font.

Computing Character String Sizes

   Xlib provides functions that you can use to compute the width,
   the logical extents, and the server information about 8-bit and
   2-byte text strings. The width is computed by adding the
   character widths of all the characters. It does not matter if
   the font is an 8-bit or 2-byte font. These functions return the
   sum of the character metrics in pixels.

   To determine the width of an 8-bit character string, use
   XTextWidth.

   int XTextWidth(XFontStruct *font_struct, char *string, int
   count);

   font_struct

   Specifies the font used for the width computation.

   string

   Specifies the character string.

   count

   Specifies the character count in the specified string.

   To determine the width of a 2-byte character string, use
   XTextWidth16.

   int XTextWidth16(XFontStruct *font_struct, XChar2b *string, int
   count);

   font_struct

   Specifies the font used for the width computation.

   string

   Specifies the character string.

   count

   Specifies the character count in the specified string.

Computing Logical Extents

   To compute the bounding box of an 8-bit character string in a
   given font, use XTextExtents.

   XTextExtents(XFontStruct *font_struct, char *string, int
   nchars, int *direction_return, int *font_ascent_return, int
   *font_descent_return, XCharStruct *overall_return);

   font_struct

   Specifies the XFontStruct structure.

   string

   Specifies the character string.

   nchars

   Specifies the number of characters in the character string.

   direction_return

   Returns the value of the direction hint (FontLeftToRight or
   FontRightToLeft).

   font_ascent_return

   Returns the font ascent.

   font_descent_return

   Returns the font descent.

   overall_return

   Returns the overall size in the specified XCharStruct
   structure.

   To compute the bounding box of a 2-byte character string in a
   given font, use XTextExtents16.

   XTextExtents16(XFontStruct *font_struct, XChar2b *string, int
   nchars, int *direction_return, int *font_ascent_return, int
   *font_descent_return, XCharStruct *overall_return);

   font_struct

   Specifies the XFontStruct structure.

   string

   Specifies the character string.

   nchars

   Specifies the number of characters in the character string.

   direction_return

   Returns the value of the direction hint (FontLeftToRight or
   FontRightToLeft).

   font_ascent_return

   Returns the font ascent.

   font_descent_return

   Returns the font descent.

   overall_return

   Returns the overall size in the specified XCharStruct
   structure.

   The XTextExtents and XTextExtents16 functions perform the size
   computation locally and, thereby, avoid the round-trip overhead
   of XQueryTextExtents and XQueryTextExtents16. Both functions
   return an XCharStruct structure, whose members are set to the
   values as follows.

   The ascent member is set to the maximum of the ascent metrics
   of all characters in the string. The descent member is set to
   the maximum of the descent metrics. The width member is set to
   the sum of the character-width metrics of all characters in the
   string. For each character in the string, let W be the sum of
   the character-width metrics of all characters preceding it in
   the string. Let L be the left-side-bearing metric of the
   character plus W. Let R be the right-side-bearing metric of the
   character plus W. The lbearing member is set to the minimum L
   of all characters in the string. The rbearing member is set to
   the maximum R.

   For fonts defined with linear indexing rather than 2-byte
   matrix indexing, each XChar2b structure is interpreted as a
   16-bit number with byte1 as the most significant byte. If the
   font has no defined default character, undefined characters in
   the string are taken to have all zero metrics.

Querying Character String Sizes

   To query the server for the bounding box of an 8-bit character
   string in a given font, use XQueryTextExtents.

   XQueryTextExtents(Display *display, XID font_ID, char *string,
   int nchars, int *direction_return, int *font_ascent_return, int
   *font_descent_return, XCharStruct *overall_return);

   display

   Specifies the connection to the X server.

   font_ID

   Specifies either the font ID or the GContext ID that contains
   the font.

   string

   Specifies the character string.

   nchars

   Specifies the number of characters in the character string.

   direction_return

   Returns the value of the direction hint (FontLeftToRight or
   FontRightToLeft).

   font_ascent_return

   Returns the font ascent.

   font_descent_return

   Returns the font descent.

   overall_return

   Returns the overall size in the specified XCharStruct
   structure.

   To query the server for the bounding box of a 2-byte character
   string in a given font, use XQueryTextExtents16.

   XQueryTextExtents16(Display *display, XID font_ID, XChar2b
   *string, int nchars, int *direction_return, int
   *font_ascent_return, int *font_descent_return, XCharStruct
   *overall_return);

   display

   Specifies the connection to the X server.

   font_ID

   Specifies either the font ID or the GContext ID that contains
   the font.

   string

   Specifies the character string.

   nchars

   Specifies the number of characters in the character string.

   direction_return

   Returns the value of the direction hint (FontLeftToRight or
   FontRightToLeft).

   font_ascent_return

   Returns the font ascent.

   font_descent_return

   Returns the font descent.

   overall_return

   Returns the overall size in the specified XCharStruct
   structure.

   The XQueryTextExtents and XQueryTextExtents16 functions return
   the bounding box of the specified 8-bit and 16-bit character
   string in the specified font or the font contained in the
   specified GC. These functions query the X server and,
   therefore, suffer the round-trip overhead that is avoided by
   XTextExtents and XTextExtents16. Both functions return a
   XCharStruct structure, whose members are set to the values as
   follows.

   The ascent member is set to the maximum of the ascent metrics
   of all characters in the string. The descent member is set to
   the maximum of the descent metrics. The width member is set to
   the sum of the character-width metrics of all characters in the
   string. For each character in the string, let W be the sum of
   the character-width metrics of all characters preceding it in
   the string. Let L be the left-side-bearing metric of the
   character plus W. Let R be the right-side-bearing metric of the
   character plus W. The lbearing member is set to the minimum L
   of all characters in the string. The rbearing member is set to
   the maximum R.

   For fonts defined with linear indexing rather than 2-byte
   matrix indexing, each XChar2b structure is interpreted as a
   16-bit number with byte1 as the most significant byte. If the
   font has no defined default character, undefined characters in
   the string are taken to have all zero metrics.

   Characters with all zero metrics are ignored. If the font has
   no defined default_char, the undefined characters in the string
   are also ignored.

   XQueryTextExtents and XQueryTextExtents16 can generate BadFont
   and BadGC errors.

Drawing Text

   This section discusses how to draw:
     * Complex text
     * Text characters
     * Image text characters

   The fundamental text functions XDrawText and XDrawText16 use
   the following structures:



typedef struct {
     char *chars;     /* pointer to string */
     int nchars;      /* number of characters */
     int delta;       /* delta between strings */
     Font font;       /* Font to print it in, None don't change */
} XTextItem;



typedef struct {
     XChar2b *chars;     /* pointer to two-byte characters */
     int nchars;         /* number of characters */
     int delta;         /* delta between strings */
     Font font;         /* font to print it in, None don't change */
} XTextItem16;

   If the font member is not None, the font is changed before
   printing and also is stored in the GC. If an error was
   generated during text drawing, the previous items may have been
   drawn. The baseline of the characters are drawn starting at the
   x and y coordinates that you pass in the text drawing
   functions.

   For example, consider the background rectangle drawn by
   XDrawImageString. If you want the upper-left corner of the
   background rectangle to be at pixel coordinate (x,y), pass the
   (x,y + ascent) as the baseline origin coordinates to the text
   functions. The ascent is the font ascent, as given in the
   XFontStruct structure. If you want the lower-left corner of the
   background rectangle to be at pixel coordinate (x,y), pass the
   (x,y - descent + 1) as the baseline origin coordinates to the
   text functions. The descent is the font descent, as given in
   the XFontStruct structure.

Drawing Complex Text

   To draw 8-bit characters in a given drawable, use XDrawText.

   XDrawText(Display *display, Drawable d, GC gc, int x, int y,
   XTextItem *items, int nitems);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the specified drawable and define the origin of the
   first character.

   items

   Specifies an array of text items.

   nitems

   Specifies the number of text items in the array.

   To draw 2-byte characters in a given drawable, use XDrawText16.

   XDrawText16(Display *display, Drawable d, GC gc, int x, int y,
   XTextItem16 *items, int nitems);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the specified drawable and define the origin of the
   first character.

   items

   Specifies an array of text items.

   nitems

   Specifies the number of text items in the array.

   The XDrawText16 function is similar to XDrawText except that it
   uses 2-byte or 16-bit characters. Both functions allow complex
   spacing and font shifts between counted strings.

   Each text item is processed in turn. A font member other than
   None in an item causes the font to be stored in the GC and used
   for subsequent text. A text element delta specifies an
   additional change in the position along the x axis before the
   string is drawn. The delta is always added to the character
   origin and is not dependent on any characteristics of the font.
   Each character image, as defined by the font in the GC, is
   treated as an additional mask for a fill operation on the
   drawable. The drawable is modified only where the font
   character has a bit set to 1. If a text item generates a
   BadFont error, the previous text items may have been drawn.

   For fonts defined with linear indexing rather than 2-byte
   matrix indexing, each XChar2b structure is interpreted as a
   16-bit number with byte1 as the most significant byte.

   Both functions use these GC components: function, plane-mask,
   fill-style, font, subwindow-mode, clip-x-origin, clip-y-origin,
   and clip-mask. They also use these GC mode-dependent
   components: foreground, background, tile, stipple,
   tile-stipple-x-origin, and tile-stipple-y-origin.

   XDrawText and XDrawText16 can generate BadDrawable, BadFont,
   BadGC, and BadMatch errors.

Drawing Text Characters

   To draw 8-bit characters in a given drawable, use XDrawString.

   XDrawString(Display *display, Drawable d, GC gc, int x, int y,
   char *string, int length);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the specified drawable and define the origin of the
   first character.

   string

   Specifies the character string.

   length

   Specifies the number of characters in the string argument.

   To draw 2-byte characters in a given drawable, use
   XDrawString16.

   XDrawString16(Display *display, Drawable d, GC gc, int x, int
   y, XChar2b *string, int length);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the specified drawable and define the origin of the
   first character.

   string

   Specifies the character string.

   length

   Specifies the number of characters in the string argument.

   Each character image, as defined by the font in the GC, is
   treated as an additional mask for a fill operation on the
   drawable. The drawable is modified only where the font
   character has a bit set to 1. For fonts defined with 2-byte
   matrix indexing and used with XDrawString16, each byte is used
   as a byte2 with a byte1 of zero.

   Both functions use these GC components: function, plane-mask,
   fill-style, font, subwindow-mode, clip-x-origin, clip-y-origin,
   and clip-mask. They also use these GC mode-dependent
   components: foreground, background, tile, stipple,
   tile-stipple-x-origin, and tile-stipple-y-origin.

   XDrawString and XDrawString16 can generate BadDrawable, BadGC,
   and BadMatch errors.

Drawing Image Text Characters

   Some applications, in particular terminal emulators, need to
   print image text in which both the foreground and background
   bits of each character are painted. This prevents annoying
   flicker on many displays.

   To draw 8-bit image text characters in a given drawable, use
   XDrawImageString.

   XDrawImageString(Display *display, Drawable d, GC gc, int x,
   int y, char *string, int length);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the specified drawable and define the origin of the
   first character.

   string

   Specifies the character string.

   length

   Specifies the number of characters in the string argument.

   To draw 2-byte image text characters in a given drawable, use
   XDrawImageString16.

   XDrawImageString16(Display *display, Drawable d, GC gc, int x,
   int y, XChar2b *string, int length);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the specified drawable and define the origin of the
   first character.

   string

   Specifies the character string.

   length

   Specifies the number of characters in the string argument.

   The XDrawImageString16 function is similar to XDrawImageString
   except that it uses 2-byte or 16-bit characters. Both functions
   also use both the foreground and background pixels of the GC in
   the destination.

   The effect is first to fill a destination rectangle with the
   background pixel defined in the GC and then to paint the text
   with the foreground pixel. The upper-left corner of the filled
   rectangle is at:

[x, y - font-ascent]

   The width is:

overall-width

   The height is:

font-ascent + font-descent

   The overall-width, font-ascent, and font-descent are as would
   be returned by XQueryTextExtents using gc and string. The
   function and fill-style defined in the GC are ignored for these
   functions. The effective function is GXcopy, and the effective
   fill-style is FillSolid.

   For fonts defined with 2-byte matrix indexing and used with
   XDrawImageString, each byte is used as a byte2 with a byte1 of
   zero.

   Both functions use these GC components: plane-mask, foreground,
   background, font, subwindow-mode, clip-x-origin, clip-y-origin,
   and clip-mask.

   XDrawImageString and XDrawImageString16 can generate
   BadDrawable, BadGC, and BadMatch errors.

Transferring Images between Client and Server

   Xlib provides functions that you can use to transfer images
   between a client and the server. Because the server may require
   diverse data formats, Xlib provides an image object that fully
   describes the data in memory and that provides for basic
   operations on that data. You should reference the data through
   the image object rather than referencing the data directly.
   However, some implementations of the Xlib library may
   efficiently deal with frequently used data formats by replacing
   functions in the procedure vector with special case functions.
   Supported operations include destroying the image, getting a
   pixel, storing a pixel, extracting a subimage of an image, and
   adding a constant to an image (see section 16.8).

   All the image manipulation functions discussed in this section
   make use of the XImage structure, which describes an image as
   it exists in the client's memory.



typedef struct _XImage {
     int width, height;         /* size of image */
     int xoffset;               /* number of pixels offset in X directio
n */
     int format;                /* XYBitmap, XYPixmap, ZPixmap */
     char *data;                /* pointer to image data */
     int byte_order;            /* data byte order, LSBFirst, MSBFirst *
/
     int bitmap_unit;           /* quant. of scanline 8, 16, 32 */
     int bitmap_bit_order;      /* LSBFirst, MSBFirst */
     int bitmap_pad;            /* 8, 16, 32 either XY or ZPixmap */
     int depth;                 /* depth of image */
     int bytes_per_line;        /* accelerator to next scanline */
     int bits_per_pixel;        /* bits per pixel (ZPixmap) */
     unsigned long red_mask;    /* bits in z arrangement */
     unsigned long green_mask;
     unsigned long blue_mask;
     XPointer obdata;           /* hook for the object routines to hang
on */
     struct funcs {             /* image manipulation routines */
          struct _XImage *(*create_image)();
          int             (*destroy_image)();
          unsigned long   (*get_pixel)();
          int             (*put_pixel)();
          struct _XImage  *(*sub_image)();
          int            (*add_pixel)();
     } f;
} XImage;

   To initialize the image manipulation routines of an image
   structure, use XInitImage.

   Status XInitImage(XImage *image);

   ximage

   Specifies the image.

   The XInitImage function initializes the internal image
   manipulation routines of an image structure, based on the
   values of the various structure members. All fields other than
   the manipulation routines must already be initialized. If the
   bytes_per_line member is zero, XInitImage will assume the image
   data is contiguous in memory and set the bytes_per_line member
   to an appropriate value based on the other members; otherwise,
   the value of bytes_per_line is not changed. All of the
   manipulation routines are initialized to functions that other
   Xlib image manipulation functions need to operate on the type
   of image specified by the rest of the structure.

   This function must be called for any image constructed by the
   client before passing it to any other Xlib function. Image
   structures created or returned by Xlib do not need to be
   initialized in this fashion.

   This function returns a nonzero status if initialization of the
   structure is successful. It returns zero if it detected some
   error or inconsistency in the structure, in which case the
   image is not changed.

   To combine an image with a rectangle of a drawable on the
   display, use XPutImage.

   XPutImage(Display *display, Drawable d, GC gc, XImage *image,
   int src_x, int src_y, int dest_x, int dest_y, unsigned int
   width, unsigned int height);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   image

   Specifies the image you want combined with the rectangle.

   src_x

   Specifies the offset in X from the left edge of the image
   defined by the XImage structure.

   src_y

   Specifies the offset in Y from the top edge of the image
   defined by the XImage structure.

   dest_x

   dest_y

   Specify the x and y coordinates, which are relative to the
   origin of the drawable and are the coordinates of the subimage.

   width

   height

   Specify the width and height of the subimage, which define the
   dimensions of the rectangle.

   The XPutImage function combines an image with a rectangle of
   the specified drawable. The section of the image defined by the
   src_x, src_y, width, and height arguments is drawn on the
   specified part of the drawable. If XYBitmap format is used, the
   depth of the image must be one, or a BadMatch error results.
   The foreground pixel in the GC defines the source for the one
   bits in the image, and the background pixel defines the source
   for the zero bits. For XYPixmap and ZPixmap, the depth of the
   image must match the depth of the drawable, or a BadMatch error
   results.

   If the characteristics of the image (for example, byte_order
   and bitmap_unit) differ from what the server requires,
   XPutImage automatically makes the appropriate conversions.

   This function uses these GC components: function, plane-mask,
   subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask. It
   also uses these GC mode-dependent components: foreground and
   background.

   XPutImage can generate BadDrawable, BadGC, BadMatch, and
   BadValue errors.

   To return the contents of a rectangle in a given drawable on
   the display, use XGetImage. This function specifically supports
   rudimentary screen dumps.

   XImage *XGetImage(Display *display, Drawable d, int x, int y,
   unsigned int width, unsigned int height, unsigned long
   plane_mask, int format);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the drawable and define the upper-left corner of the
   rectangle.

   width

   height

   Specify the width and height of the subimage, which define the
   dimensions of the rectangle.

   plane_mask

   Specifies the plane mask.

   format

   Specifies the format for the image. You can pass XYPixmap or
   ZPixmap.

   The XGetImage function returns a pointer to an XImage
   structure. This structure provides you with the contents of the
   specified rectangle of the drawable in the format you specify.
   If the format argument is XYPixmap, the image contains only the
   bit planes you passed to the plane_mask argument. If the
   plane_mask argument only requests a subset of the planes of the
   display, the depth of the returned image will be the number of
   planes requested. If the format argument is ZPixmap, XGetImage
   returns as zero the bits in all planes not specified in the
   plane_mask argument. The function performs no range checking on
   the values in plane_mask and ignores extraneous bits.

   XGetImage returns the depth of the image to the depth member of
   the XImage structure. The depth of the image is as specified
   when the drawable was created, except when getting a subset of
   the planes in XYPixmap format, when the depth is given by the
   number of bits set to 1 in plane_mask.

   If the drawable is a pixmap, the given rectangle must be wholly
   contained within the pixmap, or a BadMatch error results. If
   the drawable is a window, the window must be viewable, and it
   must be the case that if there were no inferiors or overlapping
   windows, the specified rectangle of the window would be fully
   visible on the screen and wholly contained within the outside
   edges of the window, or a BadMatch error results. Note that the
   borders of the window can be included and read with this
   request. If the window has backing-store, the backing-store
   contents are returned for regions of the window that are
   obscured by noninferior windows. If the window does not have
   backing-store, the returned contents of such obscured regions
   are undefined. The returned contents of visible regions of
   inferiors of a different depth than the specified window's
   depth are also undefined. The pointer cursor image is not
   included in the returned contents. If a problem occurs,
   XGetImage returns NULL.

   XGetImage can generate BadDrawable, BadMatch, and BadValue
   errors.

   To copy the contents of a rectangle on the display to a
   location within a preexisting image structure, use
   XGetSubImage.

   XImage *XGetSubImage(Display *display, Drawable d, int x, int
   y, unsigned int width, unsigned int height, unsigned long
   plane_mask, int format, XImage *dest_image, int dest_x, int
   dest_y);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   x

   y

   Specify the x and y coordinates, which are relative to the
   origin of the drawable and define the upper-left corner of the
   rectangle.

   width

   height

   Specify the width and height of the subimage, which define the
   dimensions of the rectangle.

   plane_mask

   Specifies the plane mask.

   format

   Specifies the format for the image. You can pass XYPixmap or
   ZPixmap.

   dest_image

   Specifies the destination image.

   dest_x

   dest_y

   Specify the x and y coordinates, which are relative to the
   origin of the destination rectangle, specify its upper-left
   corner, and determine where the subimage is placed in the
   destination image.

   The XGetSubImage function updates dest_image with the specified
   subimage in the same manner as XGetImage. If the format
   argument is XYPixmap, the image contains only the bit planes
   you passed to the plane_mask argument. If the format argument
   is ZPixmap, XGetSubImage returns as zero the bits in all planes
   not specified in the plane_mask argument. The function performs
   no range checking on the values in plane_mask and ignores
   extraneous bits. As a convenience, XGetSubImage returns a
   pointer to the same XImage structure specified by dest_image.

   The depth of the destination XImage structure must be the same
   as that of the drawable. If the specified subimage does not fit
   at the specified location on the destination image, the right
   and bottom edges are clipped. If the drawable is a pixmap, the
   given rectangle must be wholly contained within the pixmap, or
   a BadMatch error results. If the drawable is a window, the
   window must be viewable, and it must be the case that if there
   were no inferiors or overlapping windows, the specified
   rectangle of the window would be fully visible on the screen
   and wholly contained within the outside edges of the window, or
   a BadMatch error results. If the window has backing-store, then
   the backing-store contents are returned for regions of the
   window that are obscured by noninferior windows. If the window
   does not have backing-store, the returned contents of such
   obscured regions are undefined. The returned contents of
   visible regions of inferiors of a different depth than the
   specified window's depth are also undefined. If a problem
   occurs, XGetSubImage returns NULL.

   XGetSubImage can generate BadDrawable, BadGC, BadMatch, and
   BadValue errors.

Chapter 9. Window and Session Manager Functions

   Table of Contents

   Changing the Parent of a Window
   Controlling the Lifetime of a Window
   Managing Installed Colormaps
   Setting and Retrieving the Font Search Path
   Grabbing the Server
   Killing Clients
   Controlling the Screen Saver
   Controlling Host Access

        Adding, Getting, or Removing Hosts
        Changing, Enabling, or Disabling Access Control

   Although it is difficult to categorize functions as exclusively
   for an application, a window manager, or a session manager, the
   functions in this chapter are most often used by window
   managers and session managers. It is not expected that these
   functions will be used by most application programs. Xlib
   provides management functions to:
     * Change the parent of a window
     * Control the lifetime of a window
     * Manage installed colormaps
     * Set and retrieve the font search path
     * Grab the server
     * Kill a client
     * Control the screen saver
     * Control host access

Changing the Parent of a Window

   To change a window's parent to another window on the same
   screen, use XReparentWindow. There is no way to move a window
   between screens.

   XReparentWindow(Display *display, Window w, Window parent, int
   x, int y);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   parent

   Specifies the parent window.

   x

   y

   Specify the x and y coordinates of the position in the new
   parent window.

   If the specified window is mapped, XReparentWindow
   automatically performs an UnmapWindow request on it, removes it
   from its current position in the hierarchy, and inserts it as
   the child of the specified parent. The window is placed in the
   stacking order on top with respect to sibling windows.

   After reparenting the specified window, XReparentWindow causes
   the X server to generate a ReparentNotify event. The
   override_redirect member returned in this event is set to the
   window's corresponding attribute. Window manager clients
   usually should ignore this window if this member is set to
   True. Finally, if the specified window was originally mapped,
   the X server automatically performs a MapWindow request on it.

   The X server performs normal exposure processing on formerly
   obscured windows. The X server might not generate Expose events
   for regions from the initial UnmapWindow request that are
   immediately obscured by the final MapWindow request. A BadMatch
   error results if:
     * The new parent window is not on the same screen as the old
       parent window.
     * The new parent window is the specified window or an
       inferior of the specified window.
     * The new parent is InputOnly, and the window is not.
     * The specified window has a ParentRelative background, and
       the new parent window is not the same depth as the
       specified window.

   XReparentWindow can generate BadMatch and BadWindow errors.

Controlling the Lifetime of a Window

   The save-set of a client is a list of other clients' windows
   that, if they are inferiors of one of the client's windows at
   connection close, should not be destroyed and should be
   remapped if they are unmapped. For further information about
   close-connection processing, see section 2.6. To allow an
   application's window to survive when a window manager that has
   reparented a window fails, Xlib provides the save-set functions
   that you can use to control the longevity of subwindows that
   are normally destroyed when the parent is destroyed. For
   example, a window manager that wants to add decoration to a
   window by adding a frame might reparent an application's
   window. When the frame is destroyed, the application's window
   should not be destroyed but be returned to its previous place
   in the window hierarchy.

   The X server automatically removes windows from the save-set
   when they are destroyed.

   To add or remove a window from the client's save-set, use
   XChangeSaveSet.

   XChangeSaveSet(Display *display, Window w, int change_mode);

   display

   Specifies the connection to the X server.

   w

   Specifies the window that you want to add to or delete from the
   client's save-set.

   change_mode

   Specifies the mode. You can pass SetModeInsert or
   SetModeDelete.

   Depending on the specified mode, XChangeSaveSet either inserts
   or deletes the specified window from the client's save-set. The
   specified window must have been created by some other client,
   or a BadMatch error results.

   XChangeSaveSet can generate BadMatch, BadValue, and BadWindow
   errors.

   To add a window to the client's save-set, use XAddToSaveSet.

   XAddToSaveSet(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window that you want to add to the client's
   save-set.

   The XAddToSaveSet function adds the specified window to the
   client's save-set. The specified window must have been created
   by some other client, or a BadMatch error results.

   XAddToSaveSet can generate BadMatch and BadWindow errors.

   To remove a window from the client's save-set, use
   XRemoveFromSaveSet.

   XRemoveFromSaveSet(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window that you want to delete from the client's
   save-set.

   The XRemoveFromSaveSet function removes the specified window
   from the client's save-set. The specified window must have been
   created by some other client, or a BadMatch error results.

   XRemoveFromSaveSet can generate BadMatch and BadWindow errors.

Managing Installed Colormaps

   The X server maintains a list of installed colormaps. Windows
   using these colormaps are guaranteed to display with correct
   colors; windows using other colormaps may or may not display
   with correct colors. Xlib provides functions that you can use
   to install a colormap, uninstall a colormap, and obtain a list
   of installed colormaps.

   At any time, there is a subset of the installed maps that is
   viewed as an ordered list and is called the required list. The
   length of the required list is at most M, where M is the
   minimum number of installed colormaps specified for the screen
   in the connection setup. The required list is maintained as
   follows. When a colormap is specified to XInstallColormap, it
   is added to the head of the list; the list is truncated at the
   tail, if necessary, to keep its length to at most M. When a
   colormap is specified to XUninstallColormap and it is in the
   required list, it is removed from the list. A colormap is not
   added to the required list when it is implicitly installed by
   the X server, and the X server cannot implicitly uninstall a
   colormap that is in the required list.

   To install a colormap, use XInstallColormap.

   XInstallColormap(Display *display, Colormap colormap);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   The XInstallColormap function installs the specified colormap
   for its associated screen. All windows associated with this
   colormap immediately display with true colors. You associated
   the windows with this colormap when you created them by calling
   XCreateWindow, XCreateSimpleWindow, XChangeWindowAttributes, or
   XSetWindowColormap.

   If the specified colormap is not already an installed colormap,
   the X server generates a ColormapNotify event on each window
   that has that colormap. In addition, for every other colormap
   that is installed as a result of a call to XInstallColormap,
   the X server generates a ColormapNotify event on each window
   that has that colormap.

   XInstallColormap can generate a BadColor error.

   To uninstall a colormap, use XUninstallColormap.

   XUninstallColormap(Display *display, Colormap colormap);

   display

   Specifies the connection to the X server.

   colormap

   Specifies the colormap.

   The XUninstallColormap function removes the specified colormap
   from the required list for its screen. As a result, the
   specified colormap might be uninstalled, and the X server might
   implicitly install or uninstall additional colormaps. Which
   colormaps get installed or uninstalled is server dependent
   except that the required list must remain installed.

   If the specified colormap becomes uninstalled, the X server
   generates a ColormapNotify event on each window that has that
   colormap. In addition, for every other colormap that is
   installed or uninstalled as a result of a call to
   XUninstallColormap, the X server generates a ColormapNotify
   event on each window that has that colormap.

   XUninstallColormap can generate a BadColor error.

   To obtain a list of the currently installed colormaps for a
   given screen, use XListInstalledColormaps.

   Colormap *XListInstalledColormaps(Display *display, Window w,
   int *num_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window that determines the screen.

   num_return

   Returns the number of currently installed colormaps.

   The XListInstalledColormaps function returns a list of the
   currently installed colormaps for the screen of the specified
   window. The order of the colormaps in the list is not
   significant and is no explicit indication of the required list.
   When the allocated list is no longer needed, free it by using
   XFree.

   XListInstalledColormaps can generate a BadWindow error.

Setting and Retrieving the Font Search Path

   The set of fonts available from a server depends on a font
   search path. Xlib provides functions to set and retrieve the
   search path for a server.

   To set the font search path, use XSetFontPath.

   XSetFontPath(Display *display, char **directories, int ndirs);

   display

   Specifies the connection to the X server.

   directories

   Specifies the directory path used to look for a font. Setting
   the path to the empty list restores the default path defined
   for the X server.

   ndirs

   Specifies the number of directories in the path.

   The XSetFontPath function defines the directory search path for
   font lookup. There is only one search path per X server, not
   one per client. The encoding and interpretation of the strings
   are implementation-dependent, but typically they specify
   directories or font servers to be searched in the order listed.
   An X server is permitted to cache font information internally;
   for example, it might cache an entire font from a file and not
   check on subsequent opens of that font to see if the underlying
   font file has changed. However, when the font path is changed,
   the X server is guaranteed to flush all cached information
   about fonts for which there currently are no explicit resource
   IDs allocated. The meaning of an error from this request is
   implementation-dependent.

   XSetFontPath can generate a BadValue error.

   To get the current font search path, use XGetFontPath.

   char **XGetFontPath(Display *display, int *npaths_return);

   display

   Specifies the connection to the X server.

   npaths_return

   Returns the number of strings in the font path array.

   The XGetFontPath function allocates and returns an array of
   strings containing the search path. The contents of these
   strings are implementation-dependent and are not intended to be
   interpreted by client applications. When it is no longer
   needed, the data in the font path should be freed by using
   XFreeFontPath.

   To free data returned by XGetFontPath, use XFreeFontPath.

   XFreeFontPath(char **list);

   list

   Specifies the array of strings you want to free.

   The XFreeFontPath function frees the data allocated by
   XGetFontPath.

Grabbing the Server

   Xlib provides functions that you can use to grab and ungrab the
   server. These functions can be used to control processing of
   output on other connections by the window system server. While
   the server is grabbed, no processing of requests or close downs
   on any other connection will occur. A client closing its
   connection automatically ungrabs the server. Although grabbing
   the server is highly discouraged, it is sometimes necessary.

   To grab the server, use XGrabServer.

   XGrabServer(Display *display);

   display

   Specifies the connection to the X server.

   The XGrabServer function disables processing of requests and
   close downs on all other connections than the one this request
   arrived on. You should not grab the X server any more than is
   absolutely necessary.

   To ungrab the server, use XUngrabServer.

   XUngrabServer(Display *display);

   display

   Specifies the connection to the X server.

   The XUngrabServer function restarts processing of requests and
   close downs on other connections. You should avoid grabbing the
   X server as much as possible.

Killing Clients

   Xlib provides a function to cause the connection to a client to
   be closed and its resources to be destroyed. To destroy a
   client, use XKillClient.

   XKillClient(Display *display, XID resource);

   display

   Specifies the connection to the X server.

   resource

   Specifies any resource associated with the client that you want
   to destroy or AllTemporary.

   The XKillClient function forces a close down of the client that
   created the resource if a valid resource is specified. If the
   client has already terminated in either RetainPermanent or
   RetainTemporary mode, all of the client's resources are
   destroyed. If AllTemporary is specified, the resources of all
   clients that have terminated in RetainTemporary are destroyed
   (see section 2.5). This permits implementation of window
   manager facilities that aid debugging. A client can set its
   close-down mode to RetainTemporary. If the client then crashes,
   its windows would not be destroyed. The programmer can then
   inspect the application's window tree and use the window
   manager to destroy the zombie windows.

   XKillClient can generate a BadValue error.

Controlling the Screen Saver

   Xlib provides functions that you can use to set or reset the
   mode of the screen saver, to force or activate the screen
   saver, or to obtain the current screen saver values.

   To set the screen saver mode, use XSetScreenSaver.

   XSetScreenSaver(Display *display, int timeout, int interval,
   int prefer_blanking, int allow_exposures);

   display

   Specifies the connection to the X server.

   timeout

   Specifies the timeout, in seconds, until the screen saver turns
   on.

   interval

   Specifies the interval, in seconds, between screen saver
   alterations.

   prefer_blanking

   Specifies how to enable screen blanking. You can pass
   DontPreferBlanking, PreferBlanking, or DefaultBlanking.

   allow_exposures

   Specifies the screen save control values. You can pass
   DontAllowExposures, AllowExposures, or DefaultExposures.

   Timeout and interval are specified in seconds. A timeout of 0
   disables the screen saver (but an activated screen saver is not
   deactivated), and a timeout of -1 restores the default. Other
   negative values generate a BadValue error. If the timeout value
   is nonzero, XSetScreenSaver enables the screen saver. An
   interval of 0 disables the random-pattern motion. If no input
   from devices (keyboard, mouse, and so on) is generated for the
   specified number of timeout seconds once the screen saver is
   enabled, the screen saver is activated.

   For each screen, if blanking is preferred and the hardware
   supports video blanking, the screen simply goes blank.
   Otherwise, if either exposures are allowed or the screen can be
   regenerated without sending Expose events to clients, the
   screen is tiled with the root window background tile randomly
   re-origined each interval seconds. Otherwise, the screens'
   state do not change, and the screen saver is not activated. The
   screen saver is deactivated, and all screen states are restored
   at the next keyboard or pointer input or at the next call to
   XForceScreenSaver with mode ScreenSaverReset.

   If the server-dependent screen saver method supports periodic
   change, the interval argument serves as a hint about how long
   the change period should be, and zero hints that no periodic
   change should be made. Examples of ways to change the screen
   include scrambling the colormap periodically, moving an icon
   image around the screen periodically, or tiling the screen with
   the root window background tile, randomly re-origined
   periodically.

   XSetScreenSaver can generate a BadValue error.

   To force the screen saver on or off, use XForceScreenSaver.

   XForceScreenSaver(Display *display, int mode);

   display

   Specifies the connection to the X server.

   mode

   Specifies the mode that is to be applied. You can pass
   ScreenSaverActive or ScreenSaverReset.

   If the specified mode is ScreenSaverActive and the screen saver
   currently is deactivated, XForceScreenSaver activates the
   screen saver even if the screen saver had been disabled with a
   timeout of zero. If the specified mode is ScreenSaverReset and
   the screen saver currently is enabled, XForceScreenSaver
   deactivates the screen saver if it was activated, and the
   activation timer is reset to its initial state (as if device
   input had been received).

   XForceScreenSaver can generate a BadValue error.

   To activate the screen saver, use XActivateScreenSaver.

   XActivateScreenSaver(Display *display);

   display

   Specifies the connection to the X server.

   To reset the screen saver, use XResetScreenSaver.

   XResetScreenSaver(Display *display);

   display

   Specifies the connection to the X server.

   To get the current screen saver values, use XGetScreenSaver.

   XGetScreenSaver(Display *display, int *timeout_return, int
   *interval_return, int *prefer_blanking_return, int
   *allow_exposures_return);

   display

   Specifies the connection to the X server.

   timeout_return

   Returns the timeout, in seconds, until the screen saver turns
   on.

   interval_return

   Returns the interval between screen saver invocations.

   prefer_blanking_return

   Returns the current screen blanking preference
   (DontPreferBlanking, PreferBlanking, or DefaultBlanking).

   allow_exposures_return

   Returns the current screen save control value
   (DontAllowExposures, AllowExposures, or DefaultExposures).

Controlling Host Access

   This section discusses how to:
     * Add, get, or remove hosts from the access control list
     * Change, enable, or disable access

   X does not provide any protection on a per-window basis. If you
   find out the resource ID of a resource, you can manipulate it.
   To provide some minimal level of protection, however,
   connections are permitted only from machines you trust. This is
   adequate on single-user workstations but obviously breaks down
   on timesharing machines. Although provisions exist in the X
   protocol for proper connection authentication, the lack of a
   standard authentication server leaves host-level access control
   as the only common mechanism.

   The initial set of hosts allowed to open connections typically
   consists of:
     * The host the window system is running on.
     * On POSIX-conformant systems, each host listed in the
       /etc/X?.hosts file. The ? indicates the number of the
       display. This file should consist of host names separated
       by newlines. DECnet nodes must terminate in :: to
       distinguish them from Internet hosts.

   If a host is not in the access control list when the access
   control mechanism is enabled and if the host attempts to
   establish a connection, the server refuses the connection. To
   change the access list, the client must reside on the same host
   as the server and/or must have been granted permission in the
   initial authorization at connection setup.

   Servers also can implement other access control policies in
   addition to or in place of this host access facility. For
   further information about other access control implementations,
   see X Window System Protocol.

Adding, Getting, or Removing Hosts

   Xlib provides functions that you can use to add, get, or remove
   hosts from the access control list. All the host access control
   functions use the XHostAddress structure, which contains:



typedef struct {
     int family;        /* for example FamilyInternet */
     int length;        /* length of address, in bytes */
     char *address;     /* pointer to where to find the address */
} XHostAddress;

   The family member specifies which protocol address family to
   use (for example, TCP/IP or DECnet) and can be FamilyInternet,
   FamilyInternet6, FamilyServerInterpreted, FamilyDECnet, or
   FamilyChaos. The length member specifies the length of the
   address in bytes. The address member specifies a pointer to the
   address.

   For TCP/IP, the address should be in network byte order. For IP
   version 4 addresses, the family should be FamilyInternet and
   the length should be 4 bytes. For IP version 6 addresses, the
   family should be FamilyInternet6 and the length should be 16
   bytes.

   For the DECnet family, the server performs no automatic
   swapping on the address bytes. A Phase IV address is 2 bytes
   long. The first byte contains the least significant 8 bits of
   the node number. The second byte contains the most significant
   2 bits of the node number in the least significant 2 bits of
   the byte and the area in the most significant 6 bits of the
   byte.

   For the ServerInterpreted family, the length is ignored and the
   address member is a pointer to a XServerInterpretedAddress
   structure, which contains:



typedef struct {
     int typelength;     /* length of type string, in bytes */
     int valuelength;    /* length of value string, in bytes */
     char *type;         /* pointer to where to find the type string */
     char *value;        /* pointer to where to find the address */
} XServerInterpretedAddress;

   The type and value members point to strings representing the
   type and value of the server interpreted entry. These strings
   may not be NULL-terminated so care should be used when
   accessing them. The typelength and valuelength members specify
   the length in byte of the type and value strings.

   To add a single host, use XAddHost.

   XAddHost(Display *display, XHostAddress *host);

   display

   Specifies the connection to the X server.

   host

   Specifies the host that is to be added.

   The XAddHost function adds the specified host to the access
   control list for that display. The server must be on the same
   host as the client issuing the command, or a BadAccess error
   results.

   XAddHost can generate BadAccess and BadValue errors.

   To add multiple hosts at one time, use XAddHosts.

   XAddHosts(Display *display, XHostAddress *hosts, int
   num_hosts);

   display

   Specifies the connection to the X server.

   hosts

   Specifies each host that is to be added.

   num_hosts

   Specifies the number of hosts.

   The XAddHosts function adds each specified host to the access
   control list for that display. The server must be on the same
   host as the client issuing the command, or a BadAccess error
   results.

   XAddHosts can generate BadAccess and BadValue errors.

   To obtain a host list, use XListHosts.

   XHostAddress *XListHosts(Display *display, int *nhosts_return,
   Bool *state_return);

   display

   Specifies the connection to the X server.

   nhosts_return

   Returns the number of hosts currently in the access control
   list.

   state_return

   Returns the state of the access control.

   The XListHosts function returns the current access control list
   as well as whether the use of the list at connection setup was
   enabled or disabled. XListHosts allows a program to find out
   what machines can make connections. It also returns a pointer
   to a list of host structures that were allocated by the
   function. When no longer needed, this memory should be freed by
   calling XFree.

   To remove a single host, use XRemoveHost.

   XRemoveHost(Display *display, XHostAddress *host);

   display

   Specifies the connection to the X server.

   host

   Specifies the host that is to be removed.

   The XRemoveHost function removes the specified host from the
   access control list for that display. The server must be on the
   same host as the client process, or a BadAccess error results.
   If you remove your machine from the access list, you can no
   longer connect to that server, and this operation cannot be
   reversed unless you reset the server.

   XRemoveHost can generate BadAccess and BadValue errors.

   To remove multiple hosts at one time, use XRemoveHosts.

   XRemoveHosts(Display *display, XHostAddress *hosts, int
   num_hosts);

   display

   Specifies the connection to the X server.

   hosts

   Specifies each host that is to be removed.

   num_hosts

   Specifies the number of hosts.

   The XRemoveHosts function removes each specified host from the
   access control list for that display. The X server must be on
   the same host as the client process, or a BadAccess error
   results. If you remove your machine from the access list, you
   can no longer connect to that server, and this operation cannot
   be reversed unless you reset the server.

   XRemoveHosts can generate BadAccess and BadValue errors.

Changing, Enabling, or Disabling Access Control

   Xlib provides functions that you can use to enable, disable, or
   change access control.

   For these functions to execute successfully, the client
   application must reside on the same host as the X server and/or
   have been given permission in the initial authorization at
   connection setup.

   To change access control, use XSetAccessControl.

   XSetAccessControl(Display *display, int mode);

   display

   Specifies the connection to the X server.

   mode

   Specifies the mode. You can pass EnableAccess or DisableAccess.

   The XSetAccessControl function either enables or disables the
   use of the access control list at each connection setup.

   XSetAccessControl can generate BadAccess and BadValue errors.

   To enable access control, use XEnableAccessControl.

   XEnableAccessControl(Display *display);

   display

   Specifies the connection to the X server.

   The XEnableAccessControl function enables the use of the access
   control list at each connection setup.

   XEnableAccessControl can generate a BadAccess error.

   To disable access control, use XDisableAccessControl.

   XDisableAccessControl(Display *display);

   display

   Specifies the connection to the X server.

   The XDisableAccessControl function disables the use of the
   access control list at each connection setup.

   XDisableAccessControl can generate a BadAccess error.

Chapter 10. Events

   Table of Contents

   Event Types
   Event Structures
   Event Masks
   Event Processing Overview
   Keyboard and Pointer Events

        Pointer Button Events
        Keyboard and Pointer Events

   Window Entry/Exit Events

        Normal Entry/Exit Events
        Grab and Ungrab Entry/Exit Events

   Input Focus Events

        Normal Focus Events and Focus Events While Grabbed
        Focus Events Generated by Grabs

   Key Map State Notification Events
   Exposure Events

        Expose Events
        GraphicsExpose and NoExpose Events

   Window State Change Events

        CirculateNotify Events
        ConfigureNotify Events
        CreateNotify Events
        DestroyNotify Events
        GravityNotify Events
        MapNotify Events
        MappingNotify Events
        ReparentNotify Events
        UnmapNotify Events
        VisibilityNotify Events

   Structure Control Events

        CirculateRequest Events
        ConfigureRequest Events
        MapRequest Events
        ResizeRequest Events

   Colormap State Change Events
   Client Communication Events

        ClientMessage Events
        PropertyNotify Events
        SelectionClear Events
        SelectionRequest Events
        SelectionNotify Events

   A client application communicates with the X server through the
   connection you establish with the XOpenDisplay function. A
   client application sends requests to the X server over this
   connection. These requests are made by the Xlib functions that
   are called in the client application. Many Xlib functions cause
   the X server to generate events, and the user's typing or
   moving the pointer can generate events asynchronously. The X
   server returns events to the client on the same connection.

   This chapter discusses the following topics associated with
   events:
     * Event types
     * Event structures
     * Event masks
     * Event processing

   Functions for handling events are dealt with in the next
   chapter.

Event Types

   An event is data generated asynchronously by the X server as a
   result of some device activity or as side effects of a request
   sent by an Xlib function. Device-related events propagate from
   the source window to ancestor windows until some client
   application has selected that event type or until the event is
   explicitly discarded. The X server generally sends an event to
   a client application only if the client has specifically asked
   to be informed of that event type, typically by setting the
   event-mask attribute of the window. The mask can also be set
   when you create a window or by changing the window's
   event-mask. You can also mask out events that would propagate
   to ancestor windows by manipulating the do-not-propagate mask
   of the window's attributes. However, MappingNotify events are
   always sent to all clients.

   An event type describes a specific event generated by the X
   server. For each event type, a corresponding constant name is
   defined in <X11/X.h>, which is used when referring to an event
   type. The following table lists the event category and its
   associated event type or types. The processing associated with
   these events is discussed in section 10.5.

   Event Category Event Type
   Keyboard events KeyPress, KeyRelease
   Pointer events ButtonPress, ButtonRelease, MotionNotify
   Window crossing events EnterNotify, LeaveNotify
   Input focus events FocusIn, FocusOut
   Keymap state notification event KeymapNotify
   Exposure events Expose, GraphicsExpose, NoExpose
   Structure control events CirculateRequest, ConfigureRequest,
   MapRequest, ResizeRequest
   Window state notification events CirculateNotify,
   ConfigureNotify, CreateNotify, DestroyNotify, GravityNotify,
   MapNotify, MappingNotify, ReparentNotify, UnmapNotify,
   VisibilityNotify
   Colormap state notification event ColormapNotify
   Client communication events ClientMessage, PropertyNotify,
   SelectionClear, SelectionNotify, SelectionRequest

Event Structures

   For each event type, a corresponding structure is declared in
   <X11/Xlib.h>. All the event structures have the following
   common members:



typedef struct {
     int           type;
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        window;
} XAnyEvent;

   The type member is set to the event type constant name that
   uniquely identifies it. For example, when the X server reports
   a GraphicsExpose event to a client application, it sends an
   XGraphicsExposeEvent structure with the type member set to
   GraphicsExpose. The display member is set to a pointer to the
   display the event was read on. The send_event member is set to
   True if the event came from a SendEvent protocol request. The
   serial member is set from the serial number reported in the
   protocol but expanded from the 16-bit least-significant bits to
   a full 32-bit value. The window member is set to the window
   that is most useful to toolkit dispatchers.

   The X server can send events at any time in the input stream.
   Xlib stores any events received while waiting for a reply in an
   event queue for later use. Xlib also provides functions that
   allow you to check events in the event queue (see section
   11.3).

   In addition to the individual structures declared for each
   event type, the XEvent structure is a union of the individual
   structures declared for each event type. Depending on the type,
   you should access members of each event by using the XEvent
   union.



typedef union _XEvent {
     int                            type;          /* must not be change
d */
     XAnyEvent                      xany;
     XKeyEvent                      xkey;
     XButtonEvent                   xbutton;
     XMotionEvent                   xmotion;
     XCrossingEvent                 xcrossing;
     XFocusChangeEvent              xfocus;
     XExposeEvent                   xexpose;
     XGraphicsExposeEvent           xgraphicsexpose;
     XNoExposeEvent                 xnoexpose;
     XVisibilityEvent               xvisibility;
     XCreateWindowEvent             xcreatewindow;
     XDestroyWindowEvent            xdestroywindow;
     XUnmapEvent                    xunmap;
     XMapEvent                      xmap;
     XMapRequestEvent               xmaprequest;
     XReparentEvent                 xreparent;
     XConfigureEvent                xconfigure;
     XGravityEvent                  xgravity;
     XResizeRequestEvent            xresizerequest;
     XConfigureRequestEvent         xconfigurerequest;
     XCirculateEvent                xcirculate;
     XCirculateRequestEvent         xcirculaterequest;
     XPropertyEvent                 xproperty;
     XSelectionClearEvent           xselectionclear;
     XSelectionRequestEvent         xselectionrequest;
     XSelectionEvent                xselection;
     XColormapEvent                 xcolormap;
     XClientMessageEvent            xclient;
     XMappingEvent                  xmapping;
     XErrorEvent                    xerror;
     XKeymapEvent                   xkeymap;
     long                           pad[24];
} XEvent;

   An XEvent structure's first entry always is the type member,
   which is set to the event type. The second member always is the
   serial number of the protocol request that generated the event.
   The third member always is send_event, which is a Bool that
   indicates if the event was sent by a different client. The
   fourth member always is a display, which is the display that
   the event was read from. Except for keymap events, the fifth
   member always is a window, which has been carefully selected to
   be useful to toolkit dispatchers. To avoid breaking toolkits,
   the order of these first five entries is not to change. Most
   events also contain a time member, which is the time at which
   an event occurred. In addition, a pointer to the generic event
   must be cast before it is used to access any other information
   in the structure.

Event Masks

   Clients select event reporting of most events relative to a
   window. To do this, pass an event mask to an Xlib
   event-handling function that takes an event_mask argument. The
   bits of the event mask are defined in <X11/X.h>. Each bit in
   the event mask maps to an event mask name, which describes the
   event or events you want the X server to return to a client
   application.

   Unless the client has specifically asked for them, most events
   are not reported to clients when they are generated. Unless the
   client suppresses them by setting graphics-exposures in the GC
   to False, GraphicsExpose and NoExpose are reported by default
   as a result of XCopyPlane and XCopyArea. SelectionClear,
   SelectionRequest, SelectionNotify, or ClientMessage cannot be
   masked. Selection-related events are only sent to clients
   cooperating with selections (see section 4.5). When the
   keyboard or pointer mapping is changed, MappingNotify is always
   sent to clients.

   The following table lists the event mask constants you can pass
   to the event_mask argument and the circumstances in which you
   would want to specify the event mask:
   Event Mask Circumstances
   NoEventMask No events wanted
   KeyPressMask Keyboard down events wanted
   KeyReleaseMask Keyboard up events wanted
   ButtonPressMask Pointer button down events wanted
   ButtonReleaseMask Pointer button up events wanted
   EnterWindowMask Pointer window entry events wanted
   LeaveWindowMask Pointer window leave events wanted
   PointerMotionMask Pointer motion events wanted
   PointerMotionHintMask Pointer motion hints wanted
   Button1MotionMask Pointer motion while button 1 down
   Button2MotionMask Pointer motion while button 2 down
   Button3MotionMask Pointer motion while button 3 down
   Button4MotionMask Pointer motion while button 4 down
   Button5MotionMask Pointer motion while button 5 down
   ButtonMotionMask Pointer motion while any button down
   KeymapStateMask Keyboard state wanted at window entry and focus
   in
   ExposureMask Any exposure wanted
   VisibilityChangeMask Any change in visibility wanted
   StructureNotifyMask Any change in window structure wanted
   ResizeRedirectMask Redirect resize of this window
   SubstructureNotifyMask Substructure notification wanted
   SubstructureRedirectMask Redirect structure requests on
   children
   FocusChangeMask Any change in input focus wanted
   PropertyChangeMask Any change in property wanted
   ColormapChangeMask Any change in colormap wanted
   OwnerGrabButtonMask Automatic grabs should activate with
   owner_events set to True

Event Processing Overview

   The event reported to a client application during event
   processing depends on which event masks you provide as the
   event-mask attribute for a window. For some event masks, there
   is a one-to-one correspondence between the event mask constant
   and the event type constant. For example, if you pass the event
   mask ButtonPressMask, the X server sends back only ButtonPress
   events. Most events contain a time member, which is the time at
   which an event occurred.

   In other cases, one event mask constant can map to several
   event type constants. For example, if you pass the event mask
   SubstructureNotifyMask, the X server can send back
   CirculateNotify, ConfigureNotify, CreateNotify, DestroyNotify,
   GravityNotify, MapNotify, ReparentNotify, or UnmapNotify
   events.

   In another case, two event masks can map to one event type. For
   example, if you pass either PointerMotionMask or
   ButtonMotionMask, the X server sends back a MotionNotify event.

   The following table lists the event mask, its associated event
   type or types, and the structure name associated with the event
   type. Some of these structures actually are typedefs to a
   generic structure that is shared between two event types. Note
   that N.A. appears in columns for which the information is not
   applicable.
   Event Mask Event Type Structure Generic Structure

   ButtonMotionMask

   Button1MotionMask

   Button2MotionMask

   Button3MotionMask

   Button4MotionMask

   Button5MotionMask
   MotionNotify XPointerMovedEvent XMotionEvent
   ButtonPressMask ButtonPress XButtonPressedEvent XButtonEvent
   ButtonReleaseMask ButtonRelease XButtonReleasedEvent
   XButtonEvent
   ColormapChangeMask ColormapNotify XColormapEvent
   EnterWindowMask EnterNotify XEnterWindowEvent XCrossingEvent
   LeaveWindowMask LeaveNotify XLeaveWindowEvent XCrossingEvent
   ExposureMask Expose XExposeEvent
   GCGraphicsExposures in GC GraphicsExpose XGraphicsExposeEvent
   NoExpose XNoExposeEvent
   FocusChangeMask FocusIn XFocusInEvent XFocusChangeEvent
   FocusOut XFocusOutEvent XFocusChangeEvent
   KeymapStateMask KeymapNotify XKeymapEvent
   KeyPressMask KeyPress XKeyPressedEvent XKeyEvent
   KeyReleaseMask KeyRelease XKeyReleasedEvent XKeyEvent
   OwnerGrabButtonMask N.A. N.A.
   PointerMotionMask MotionNotify XPointerMovedEvent XMotionEvent
   PointerMotionHintMask N.A. N.A.
   PropertyChangeMask PropertyNotify XPropertyEvent
   ResizeRedirectMask ResizeRequest XResizeRequestEvent
   StructureNotifyMask CirculateNotify XCirculateEvent
   ConfigureNotify XConfigureEvent
   DestroyNotify XDestroyWindowEvent
   GravityNotify XGravityEvent
   MapNotify XMapEvent
   ReparentNotify XReparentEvent
   UnmapNotify XUnmapEvent
   SubstructureNotifyMask CirculateNotify XCirculateEvent
   ConfigureNotify XConfigureEvent
   CreateNotify XCreateWindowEvent
   DestroyNotify XDestroyWindowEvent
   GravityNotify XGravityEvent
   MapNotify XMapEvent
   ReparentNotify XReparentEvent
   UnmapNotify XUnmapEvent
   SubstructureRedirectMask CirculateRequest
   XCirculateRequestEvent
   ConfigureRequest XConfigureRequestEvent
   MapRequest XMapRequestEvent
   N.A. ClientMessage XClientMessageEvent
   N.A. MappingNotify XMappingEvent
   N.A. SelectionClear XSelectionClearEvent
   N.A. SelectionNotify XSelectionEvent
   N.A. SelectionRequest XSelectionRequestEvent
   VisibilityChangeMask VisibilityNotify XVisibilityEvent

   The sections that follow describe the processing that occurs
   when you select the different event masks. The sections are
   organized according to these processing categories:
     * Keyboard and pointer events
     * Window crossing events
     * Input focus events
     * Keymap state notification events
     * Exposure events
     * Window state notification events
     * Structure control events
     * Colormap state notification events
     * Client communication events

Keyboard and Pointer Events

   This section discusses:
     * Pointer button events
     * Keyboard and pointer events

Pointer Button Events

   The following describes the event processing that occurs when a
   pointer button press is processed with the pointer in some
   window w and when no active pointer grab is in progress.

   The X server searches the ancestors of w from the root down,
   looking for a passive grab to activate. If no matching passive
   grab on the button exists, the X server automatically starts an
   active grab for the client receiving the event and sets the
   last-pointer-grab time to the current server time. The effect
   is essentially equivalent to an XGrabButton with these client
   passed arguments:
   Argument Value
   w The event window
   event_mask The client's selected pointer events on the event
   window
   pointer_mode GrabModeAsync
   keyboard_mode GrabModeAsync
   owner_events True, if the client has selected
   OwnerGrabButtonMask on the event window, otherwise False
   confine_to None
   cursor None

   The active grab is automatically terminated when the logical
   state of the pointer has all buttons released. Clients can
   modify the active grab by calling XUngrabPointer and
   XChangeActivePointerGrab.

Keyboard and Pointer Events

   This section discusses the processing that occurs for the
   keyboard events KeyPress and KeyRelease and the pointer events
   ButtonPress, ButtonRelease, and MotionNotify. For information
   about the keyboard event-handling utilities, see chapter 11.

   The X server reports KeyPress or KeyRelease events to clients
   wanting information about keys that logically change state.
   Note that these events are generated for all keys, even those
   mapped to modifier bits. The X server reports ButtonPress or
   ButtonRelease events to clients wanting information about
   buttons that logically change state.

   The X server reports MotionNotify events to clients wanting
   information about when the pointer logically moves. The X
   server generates this event whenever the pointer is moved and
   the pointer motion begins and ends in the window. The
   granularity of MotionNotify events is not guaranteed, but a
   client that selects this event type is guaranteed to receive at
   least one event when the pointer moves and then rests.

   The generation of the logical changes lags the physical changes
   if device event processing is frozen.

   To receive KeyPress, KeyRelease, ButtonPress, and ButtonRelease
   events, set KeyPressMask, KeyReleaseMask, ButtonPressMask, and
   ButtonReleaseMask bits in the event-mask attribute of the
   window.

   To receive MotionNotify events, set one or more of the
   following event masks bits in the event-mask attribute of the
   window.
     * Button1MotionMask - Button5MotionMask
     * The client application receives MotionNotify events only
       when one or more of the specified buttons is pressed.
     * ButtonMotionMask
     * The client application receives MotionNotify events only
       when at least one button is pressed.
     * PointerMotionMask
     * The client application receives MotionNotify events
       independent of the state of the pointer buttons.
     * PointerMotionHintMask
     * If PointerMotionHintMask is selected in combination with
       one or more of the above masks, the X server is free to
       send only one MotionNotify event (with the is_hint member
       of the XPointerMovedEvent structure set to NotifyHint) to
       the client for the event window, until either the key or
       button state changes, the pointer leaves the event window,
       or the client calls XQueryPointer or . The server still may
       send MotionNotify events without is_hint set to NotifyHint.

   The source of the event is the viewable window that the pointer
   is in. The window used by the X server to report these events
   depends on the window's position in the window hierarchy and
   whether any intervening window prohibits the generation of
   these events. Starting with the source window, the X server
   searches up the window hierarchy until it locates the first
   window specified by a client as having an interest in these
   events. If one of the intervening windows has its
   do-not-propagate-mask set to prohibit generation of the event
   type, the events of those types will be suppressed. Clients can
   modify the actual window used for reporting by performing
   active grabs and, in the case of keyboard events, by using the
   focus window.

   The structures for these event types contain:
typedef struct {
     int            type;            /* ButtonPress or ButtonRelease */
     unsigned long  serial;          /* # of last request processed by s
erver */
     Bool           send_event;      /* true if this came from a SendEve
nt request */
     Display        *display;        /* Display the event was read from
*/
     Window         window;          /* ``event'' window it is reported
relative to */
     Window         root;            /* root window that the event occur
red on */
     Window         subwindow;       /* child window */
     Time           time;            /* milliseconds */
     int            x, y;            /* pointer x, y coordinates in even
t window */
     int            x_root, y_root;  /* coordinates relative to root */
     unsigned int   state;           /* key or button mask */
     unsigned int   button;          /* detail */
     Bool           same_screen;     /* same screen flag */
} XButtonEvent;
typedef XButtonEvent XButtonPressedEvent;
typedef XButtonEvent XButtonReleasedEvent;

typedef struct {
     int            type;            /* KeyPress or KeyRelease */
     unsigned long  serial;          /* # of last request processed by s
erver */
     Bool           send_event;      /* true if this came from a SendEve
nt request */
     Display        *display;        /* Display the event was read from
*/
     Window         window;          /* ``event'' window it is reported
relative to */
     Window         root;            /* root window that the event occur
red on */
     Window         subwindow;       /* child window */
     Time           time;            /* milliseconds */
     int            x, y;            /* pointer x, y coordinates in even
t window */
     int            x_root, y_root;  /* coordinates relative to root */
     unsigned int   state;           /* key or button mask */
     unsigned int   keycode;         /* detail */
     Bool           same_screen;     /* same screen flag */
} XKeyEvent;
typedef XKeyEvent XKeyPressedEvent;
typedef XKeyEvent XKeyReleasedEvent;

typedef struct {
     int            type;              /* MotionNotify */
     unsigned long  serial;            /* # of last request processed by
 server */
     Bool           send_event;        /* true if this came from a SendE
vent request */
     Display        *display;          /* Display the event was read fro
m */
     Window         window;            /* ``event'' window reported rela
tive to */
     Window         root;              /* root window that the event occ
urred on */
     Window         subwindow;         /* child window */
     Time           time;              /* milliseconds */
     int            x, y;              /* pointer x, y coordinates in ev
ent window */
     int            x_root, y_root;    /* coordinates relative to root *
/
     unsigned int   state;             /* key or button mask */
     char           is_hint;           /* detail */
     Bool           same_screen;       /* same screen flag */
} XMotionEvent;
typedef XMotionEvent XPointerMovedEvent;

   These structures have the following common members: window,
   root, subwindow, time, x, y, x_root, y_root, state, and
   same_screen. The window member is set to the window on which
   the event was generated and is referred to as the event window.
   As long as the conditions previously discussed are met, this is
   the window used by the X server to report the event. The root
   member is set to the source window's root window. The x_root
   and y_root members are set to the pointer's coordinates
   relative to the root window's origin at the time of the event.

   The same_screen member is set to indicate whether the event
   window is on the same screen as the root window and can be
   either True or False. If True, the event and root windows are
   on the same screen. If False, the event and root windows are
   not on the same screen.

   If the source window is an inferior of the event window, the
   subwindow member of the structure is set to the child of the
   event window that is the source window or the child of the
   event window that is an ancestor of the source window.
   Otherwise, the X server sets the subwindow member to None. The
   time member is set to the time when the event was generated and
   is expressed in milliseconds.

   If the event window is on the same screen as the root window,
   the x and y members are set to the coordinates relative to the
   event window's origin. Otherwise, these members are set to
   zero.

   The state member is set to indicate the logical state of the
   pointer buttons and modifier keys just prior to the event,
   which is the bitwise inclusive OR of one or more of the button
   or modifier key masks: Button1Mask, Button2Mask, Button3Mask,
   Button4Mask, Button5Mask, ShiftMask, LockMask, ControlMask,
   Mod1Mask, Mod2Mask, Mod3Mask, Mod4Mask, and Mod5Mask.

   Each of these structures also has a member that indicates the
   detail. For the XKeyPressedEvent and XKeyReleasedEvent
   structures, this member is called a keycode. It is set to a
   number that represents a physical key on the keyboard. The
   keycode is an arbitrary representation for any key on the
   keyboard (see sections 12.7 and 16.1).

   For the XButtonPressedEvent and XButtonReleasedEvent
   structures, this member is called button. It represents the
   pointer button that changed state and can be the Button1,
   Button2, Button3, Button4, or Button5 value. For the
   XPointerMovedEvent structure, this member is called is_hint. It
   can be set to NotifyNormal or NotifyHint.

   Some of the symbols mentioned in this section have fixed
   values, as follows:
   Symbol            Value
   Button1MotionMask (1L<<8)
   Button2MotionMask (1L<<9)
   Button3MotionMask (1L<<10)
   Button4MotionMask (1L<<11)
   Button5MotionMask (1L<<12)
   Button1Mask       (1<<8)
   Button2Mask       (1<<9)
   Button3Mask       (1<<10)
   Button4Mask       (1<<11)
   Button5Mask       (1<<12)
   ShiftMask         (1<<0)
   LockMask          (1<<1)
   ControlMask       (1<<2)
   Mod1Mask          (1<<3)
   Mod2Mask          (1<<4)
   Mod3Mask          (1<<5)
   Mod4Mask          (1<<6)
   Mod5Mask          (1<<7)
   Button1           1
   Button2           2
   Button3           3
   Button4           4
   Button5           5

Window Entry/Exit Events

   This section describes the processing that occurs for the
   window crossing events EnterNotify and LeaveNotify. If a
   pointer motion or a window hierarchy change causes the pointer
   to be in a different window than before, the X server reports
   EnterNotify or LeaveNotify events to clients who have selected
   for these events. All EnterNotify and LeaveNotify events caused
   by a hierarchy change are generated after any hierarchy event
   (UnmapNotify, MapNotify, ConfigureNotify, GravityNotify,
   CirculateNotify) caused by that change; however, the X protocol
   does not constrain the ordering of EnterNotify and LeaveNotify
   events with respect to FocusOut, VisibilityNotify, and Expose
   events.

   This contrasts with MotionNotify events, which are also
   generated when the pointer moves but only when the pointer
   motion begins and ends in a single window. An EnterNotify or
   LeaveNotify event also can be generated when some client
   application calls XGrabPointer and XUngrabPointer.

   To receive EnterNotify or LeaveNotify events, set the
   EnterWindowMask or LeaveWindowMask bits of the event-mask
   attribute of the window.

   The structure for these event types contains:


typedef struct {
     int           type;           /* EnterNotify or LeaveNotify */
     unsigned long serial;         /* # of last request processed by ser
ver */
     Bool          send_event;     /* true if this came from a SendEvent
 request */
     Display       *display;       /* Display the event was read from */
     Window        window;         /* ``event'' window reported relative
 to */
     Window        root;           /* root window that the event occurre
d on */
     Window        subwindow;      /* child window */
     Time          time;           /* milliseconds */
     int           x, y;           /* pointer x, y coordinates in event
window */
     int           x_root, y_root; /* coordinates relative to root */
     int           mode;           /* NotifyNormal, NotifyGrab, NotifyUn
grab */
     int           detail;
                   /*
                    * NotifyAncestor, NotifyVirtual, NotifyInferior,
                    * NotifyNonlinear,NotifyNonlinearVirtual
                    */
     Bool          same_screen;    /* same screen flag */
     Bool          focus;          /* boolean focus */
     unsigned int  state;          /* key or button mask */
} XCrossingEvent;
typedef XCrossingEvent XEnterWindowEvent;
typedef XCrossingEvent XLeaveWindowEvent;

   The window member is set to the window on which the EnterNotify
   or LeaveNotify event was generated and is referred to as the
   event window. This is the window used by the X server to report
   the event, and is relative to the root window on which the
   event occurred. The root member is set to the root window of
   the screen on which the event occurred.

   For a LeaveNotify event, if a child of the event window
   contains the initial position of the pointer, the subwindow
   component is set to that child. Otherwise, the X server sets
   the subwindow member to None. For an EnterNotify event, if a
   child of the event window contains the final pointer position,
   the subwindow component is set to that child or None.

   The time member is set to the time when the event was generated
   and is expressed in milliseconds. The x and y members are set
   to the coordinates of the pointer position in the event window.
   This position is always the pointer's final position, not its
   initial position. If the event window is on the same screen as
   the root window, x and y are the pointer coordinates relative
   to the event window's origin. Otherwise, x and y are set to
   zero. The x_root and y_root members are set to the pointer's
   coordinates relative to the root window's origin at the time of
   the event.

   The same_screen member is set to indicate whether the event
   window is on the same screen as the root window and can be
   either True or False. If True, the event and root windows are
   on the same screen. If False, the event and root windows are
   not on the same screen.

   The focus member is set to indicate whether the event window is
   the focus window or an inferior of the focus window. The X
   server can set this member to either True or False. If True,
   the event window is the focus window or an inferior of the
   focus window. If False, the event window is not the focus
   window or an inferior of the focus window.

   The state member is set to indicate the state of the pointer
   buttons and modifier keys just prior to the event. The X server
   can set this member to the bitwise inclusive OR of one or more
   of the button or modifier key masks: Button1Mask, Button2Mask,
   Button3Mask, Button4Mask, Button5Mask, ShiftMask, LockMask,
   ControlMask, Mod1Mask, Mod2Mask, Mod3Mask, Mod4Mask, Mod5Mask.

   The mode member is set to indicate whether the events are
   normal events, pseudo-motion events when a grab activates, or
   pseudo-motion events when a grab deactivates. The X server can
   set this member to NotifyNormal, NotifyGrab, or NotifyUngrab.

   The detail member is set to indicate the notify detail and can
   be NotifyAncestor, NotifyVirtual, NotifyInferior,
   NotifyNonlinear, or NotifyNonlinearVirtual.

Normal Entry/Exit Events

   EnterNotify and LeaveNotify events are generated when the
   pointer moves from one window to another window. Normal events
   are identified by XEnterWindowEvent or XLeaveWindowEvent
   structures whose mode member is set to NotifyNormal.
     * When the pointer moves from window A to window B and A is
       an inferior of B, the X server does the following:
     * It generates a LeaveNotify event on window A, with the
       detail member of the XLeaveWindowEvent structure set to
       NotifyAncestor.
     * It generates a LeaveNotify event on each window between
       window A and window B, exclusive, with the detail member of
       each XLeaveWindowEvent structure set to NotifyVirtual.
     * It generates an EnterNotify event on window B, with the
       detail member of the XEnterWindowEvent structure set to
       NotifyInferior.
     * When the pointer moves from window A to window B and B is
       an inferior of A, the X server does the following:
     * It generates a LeaveNotify event on window A, with the
       detail member of the XLeaveWindowEvent structure set to
       NotifyInferior.
     * It generates an EnterNotify event on each window between
       window A and window B, exclusive, with the detail member of
       each XEnterWindowEvent structure set to NotifyVirtual.
     * It generates an EnterNotify event on window B, with the
       detail member of the XEnterWindowEvent structure set to
       NotifyAncestor.
     * When the pointer moves from window A to window B and window
       C is their least common ancestor, the X server does the
       following:
     * It generates a LeaveNotify event on window A, with the
       detail member of the XLeaveWindowEvent structure set to
       NotifyNonlinear.
     * It generates a LeaveNotify event on each window between
       window A and window C, exclusive, with the detail member of
       each XLeaveWindowEvent structure set to
       NotifyNonlinearVirtual.
     * It generates an EnterNotify event on each window between
       window C and window B, exclusive, with the detail member of
       each XEnterWindowEvent structure set to
       NotifyNonlinearVirtual.
     * It generates an EnterNotify event on window B, with the
       detail member of the XEnterWindowEvent structure set to
       NotifyNonlinear.
     * When the pointer moves from window A to window B on
       different screens, the X server does the following:
     * It generates a LeaveNotify event on window A, with the
       detail member of the XLeaveWindowEvent structure set to
       NotifyNonlinear.
     * If window A is not a root window, it generates a
       LeaveNotify event on each window above window A up to and
       including its root, with the detail member of each
       XLeaveWindowEvent structure set to NotifyNonlinearVirtual.
     * If window B is not a root window, it generates an
       EnterNotify event on each window from window B's root down
       to but not including window B, with the detail member of
       each XEnterWindowEvent structure set to
       NotifyNonlinearVirtual.
     * It generates an EnterNotify event on window B, with the
       detail member of the XEnterWindowEvent structure set to
       NotifyNonlinear.

Grab and Ungrab Entry/Exit Events

   Pseudo-motion mode EnterNotify and LeaveNotify events are
   generated when a pointer grab activates or deactivates. Events
   in which the pointer grab activates are identified by
   XEnterWindowEvent or XLeaveWindowEvent structures whose mode
   member is set to NotifyGrab. Events in which the pointer grab
   deactivates are identified by XEnterWindowEvent or
   XLeaveWindowEvent structures whose mode member is set to
   NotifyUngrab (see XGrabPointer).
     * When a pointer grab activates after any initial warp into a
       confine_to window and before generating any actual
       ButtonPress event that activates the grab, G is the
       grab_window for the grab, and P is the window the pointer
       is in, the X server does the following:
     * It generates EnterNotify and LeaveNotify events (see
       section 10.6.1) with the mode members of the
       XEnterWindowEvent and XLeaveWindowEvent structures set to
       NotifyGrab. These events are generated as if the pointer
       were to suddenly warp from its current position in P to
       some position in G. However, the pointer does not warp, and
       the X server uses the pointer position as both the initial
       and final positions for the events.
     * When a pointer grab deactivates after generating any actual
       ButtonRelease event that deactivates the grab, G is the
       grab_window for the grab, and P is the window the pointer
       is in, the X server does the following:
     * It generates EnterNotify and LeaveNotify events (see
       section 10.6.1) with the mode members of the
       XEnterWindowEvent and XLeaveWindowEvent structures set to
       NotifyUngrab. These events are generated as if the pointer
       were to suddenly warp from some position in G to its
       current position in P. However, the pointer does not warp,
       and the X server uses the current pointer position as both
       the initial and final positions for the events.

Input Focus Events

   This section describes the processing that occurs for the input
   focus events FocusIn and FocusOut. The X server can report
   FocusIn or FocusOut events to clients wanting information about
   when the input focus changes. The keyboard is always attached
   to some window (typically, the root window or a top-level
   window), which is called the focus window. The focus window and
   the position of the pointer determine the window that receives
   keyboard input. Clients may need to know when the input focus
   changes to control highlighting of areas on the screen.

   To receive FocusIn or FocusOut events, set the FocusChangeMask
   bit in the event-mask attribute of the window.

   The structure for these event types contains:


typedef struct {
     int           type;       /* FocusIn or FocusOut */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        window;     /* window of event */
     int           mode;       /* NotifyNormal, NotifyGrab, NotifyUngrab
 */
     int           detail;
                   /*
                    * NotifyAncestor, NotifyVirtual, NotifyInferior,
                    * NotifyNonlinear,NotifyNonlinearVirtual, NotifyPoin
ter,
                    * NotifyPointerRoot, NotifyDetailNone
                    */
} XFocusChangeEvent;
typedef XFocusChangeEvent XFocusInEvent;
typedef XFocusChangeEvent XFocusOutEvent;

   The window member is set to the window on which the FocusIn or
   FocusOut event was generated. This is the window used by the X
   server to report the event. The mode member is set to indicate
   whether the focus events are normal focus events, focus events
   while grabbed, focus events when a grab activates, or focus
   events when a grab deactivates. The X server can set the mode
   member to NotifyNormal, NotifyWhileGrabbed, NotifyGrab, or
   NotifyUngrab.

   All FocusOut events caused by a window unmap are generated
   after any UnmapNotify event; however, the X protocol does not
   constrain the ordering of FocusOut events with respect to
   generated EnterNotify, LeaveNotify, VisibilityNotify, and
   Expose events.

   Depending on the event mode, the detail member is set to
   indicate the notify detail and can be NotifyAncestor,
   NotifyVirtual, NotifyInferior, NotifyNonlinear,
   NotifyNonlinearVirtual, NotifyPointer, NotifyPointerRoot, or
   NotifyDetailNone.

Normal Focus Events and Focus Events While Grabbed

   Normal focus events are identified by XFocusInEvent or
   XFocusOutEvent structures whose mode member is set to
   NotifyNormal. Focus events while grabbed are identified by
   XFocusInEvent or XFocusOutEvent structures whose mode member is
   set to NotifyWhileGrabbed. The X server processes normal focus
   and focus events while grabbed according to the following:
     * When the focus moves from window A to window B, A is an
       inferior of B, and the pointer is in window P, the X server
       does the following:
     * It generates a FocusOut event on window A, with the detail
       member of the XFocusOutEvent structure set to
       NotifyAncestor.
     * It generates a FocusOut event on each window between window
       A and window B, exclusive, with the detail member of each
       XFocusOutEvent structure set to NotifyVirtual.
     * It generates a FocusIn event on window B, with the detail
       member of the XFocusOutEvent structure set to
       NotifyInferior.
     * If window P is an inferior of window B but window P is not
       window A or an inferior or ancestor of window A, it
       generates a FocusIn event on each window below window B,
       down to and including window P, with the detail member of
       each XFocusInEvent structure set to NotifyPointer.
     * When the focus moves from window A to window B, B is an
       inferior of A, and the pointer is in window P, the X server
       does the following:
     * If window P is an inferior of window A but P is not an
       inferior of window B or an ancestor of B, it generates a
       FocusOut event on each window from window P up to but not
       including window A, with the detail member of each
       XFocusOutEvent structure set to NotifyPointer.
     * It generates a FocusOut event on window A, with the detail
       member of the XFocusOutEvent structure set to
       NotifyInferior.
     * It generates a FocusIn event on each window between window
       A and window B, exclusive, with the detail member of each
       XFocusInEvent structure set to NotifyVirtual.
     * It generates a FocusIn event on window B, with the detail
       member of the XFocusInEvent structure set to
       NotifyAncestor.
     * When the focus moves from window A to window B, window C is
       their least common ancestor, and the pointer is in window
       P, the X server does the following:
     * If window P is an inferior of window A, it generates a
       FocusOut event on each window from window P up to but not
       including window A, with the detail member of the
       XFocusOutEvent structure set to NotifyPointer.
     * It generates a FocusOut event on window A, with the detail
       member of the XFocusOutEvent structure set to
       NotifyNonlinear.
     * It generates a FocusOut event on each window between window
       A and window C, exclusive, with the detail member of each
       XFocusOutEvent structure set to NotifyNonlinearVirtual.
     * It generates a FocusIn event on each window between C and
       B, exclusive, with the detail member of each XFocusInEvent
       structure set to NotifyNonlinearVirtual.
     * It generates a FocusIn event on window B, with the detail
       member of the XFocusInEvent structure set to
       NotifyNonlinear.
     * If window P is an inferior of window B, it generates a
       FocusIn event on each window below window B down to and
       including window P, with the detail member of the
       XFocusInEvent structure set to NotifyPointer.
     * When the focus moves from window A to window B on different
       screens and the pointer is in window P, the X server does
       the following:
     * If window P is an inferior of window A, it generates a
       FocusOut event on each window from window P up to but not
       including window A, with the detail member of each
       XFocusOutEvent structure set to NotifyPointer.
     * It generates a FocusOut event on window A, with the detail
       member of the XFocusOutEvent structure set to
       NotifyNonlinear.
     * If window A is not a root window, it generates a FocusOut
       event on each window above window A up to and including its
       root, with the detail member of each XFocusOutEvent
       structure set to NotifyNonlinearVirtual.
     * If window B is not a root window, it generates a FocusIn
       event on each window from window B's root down to but not
       including window B, with the detail member of each
       XFocusInEvent structure set to NotifyNonlinearVirtual.
     * It generates a FocusIn event on window B, with the detail
       member of each XFocusInEvent structure set to
       NotifyNonlinear.
     * If window P is an inferior of window B, it generates a
       FocusIn event on each window below window B down to and
       including window P, with the detail member of each
       XFocusInEvent structure set to NotifyPointer.
     * When the focus moves from window A to PointerRoot (events
       sent to the window under the pointer) or None (discard),
       and the pointer is in window P, the X server does the
       following:
     * If window P is an inferior of window A, it generates a
       FocusOut event on each window from window P up to but not
       including window A, with the detail member of each
       XFocusOutEvent structure set to NotifyPointer.
     * It generates a FocusOut event on window A, with the detail
       member of the XFocusOutEvent structure set to
       NotifyNonlinear.
     * If window A is not a root window, it generates a FocusOut
       event on each window above window A up to and including its
       root, with the detail member of each XFocusOutEvent
       structure set to NotifyNonlinearVirtual.
     * It generates a FocusIn event on the root window of all
       screens, with the detail member of each XFocusInEvent
       structure set to NotifyPointerRoot (or NotifyDetailNone).
     * If the new focus is PointerRoot, it generates a FocusIn
       event on each window from window P's root down to and
       including window P, with the detail member of each
       XFocusInEvent structure set to NotifyPointer.
     * When the focus moves from PointerRoot (events sent to the
       window under the pointer) or None to window A, and the
       pointer is in window P, the X server does the following:
     * If the old focus is PointerRoot, it generates a FocusOut
       event on each window from window P up to and including
       window P's root, with the detail member of each
       XFocusOutEvent structure set to NotifyPointer.
     * It generates a FocusOut event on all root windows, with the
       detail member of each XFocusOutEvent structure set to
       NotifyPointerRoot (or NotifyDetailNone).
     * If window A is not a root window, it generates a FocusIn
       event on each window from window A's root down to but not
       including window A, with the detail member of each
       XFocusInEvent structure set to NotifyNonlinearVirtual.
     * It generates a FocusIn event on window A, with the detail
       member of the XFocusInEvent structure set to
       NotifyNonlinear.
     * If window P is an inferior of window A, it generates a
       FocusIn event on each window below window A down to and
       including window P, with the detail member of each
       XFocusInEvent structure set to NotifyPointer.
     * When the focus moves from PointerRoot (events sent to the
       window under the pointer) to None (or vice versa), and the
       pointer is in window P, the X server does the following:
     * If the old focus is PointerRoot, it generates a FocusOut
       event on each window from window P up to and including
       window P's root, with the detail member of each
       XFocusOutEvent structure set to NotifyPointer.
     * It generates a FocusOut event on all root windows, with the
       detail member of each XFocusOutEvent structure set to
       either NotifyPointerRoot or NotifyDetailNone.
     * It generates a FocusIn event on all root windows, with the
       detail member of each XFocusInEvent structure set to
       NotifyDetailNone or NotifyPointerRoot.
     * If the new focus is PointerRoot, it generates a FocusIn
       event on each window from window P's root down to and
       including window P, with the detail member of each
       XFocusInEvent structure set to NotifyPointer.

Focus Events Generated by Grabs

   Focus events in which the keyboard grab activates are
   identified by XFocusInEvent or XFocusOutEvent structures whose
   mode member is set to NotifyGrab. Focus events in which the
   keyboard grab deactivates are identified by XFocusInEvent or
   XFocusOutEvent structures whose mode member is set to
   NotifyUngrab (see XGrabKeyboard).
     * When a keyboard grab activates before generating any actual
       KeyPress event that activates the grab, G is the
       grab_window, and F is the current focus, the X server does
       the following:
     * It generates FocusIn and FocusOut events, with the mode
       members of the XFocusInEvent and XFocusOutEvent structures
       set to NotifyGrab. These events are generated as if the
       focus were to change from F to G.
     * When a keyboard grab deactivates after generating any
       actual KeyRelease event that deactivates the grab, G is the
       grab_window, and F is the current focus, the X server does
       the following:
     * It generates FocusIn and FocusOut events, with the mode
       members of the XFocusInEvent and XFocusOutEvent structures
       set to NotifyUngrab. These events are generated as if the
       focus were to change from G to F.

Key Map State Notification Events

   The X server can report KeymapNotify events to clients that
   want information about changes in their keyboard state.

   To receive KeymapNotify events, set the KeymapStateMask bit in
   the event-mask attribute of the window. The X server generates
   this event immediately after every EnterNotify and FocusIn
   event.

   The structure for this event type contains:



/* generated on EnterWindow and FocusIn when KeymapState selected */
typedef struct {
     int            type;           /* KeymapNotify */
     unsigned long  serial;         /* # of last request processed by se
rver */
     Bool           send_event;     /* true if this came from a SendEven
t request */
     Display        *display;       /* Display the event was read from *
/
     Window         window;
     char           key_vector[32];
} XKeymapEvent;

   The window member is not used but is present to aid some
   toolkits. The key_vector member is set to the bit vector of the
   keyboard. Each bit set to 1 indicates that the corresponding
   key is currently pressed. The vector is represented as 32
   bytes. Byte N (from 0) contains the bits for keys 8N to 8N + 7
   with the least significant bit in the byte representing key 8N.

Exposure Events

   The X protocol does not guarantee to preserve the contents of
   window regions when the windows are obscured or reconfigured.
   Some implementations may preserve the contents of windows.
   Other implementations are free to destroy the contents of
   windows when exposed. X expects client applications to assume
   the responsibility for restoring the contents of an exposed
   window region. (An exposed window region describes a formerly
   obscured window whose region becomes visible.) Therefore, the X
   server sends Expose events describing the window and the region
   of the window that has been exposed. A naive client application
   usually redraws the entire window. A more sophisticated client
   application redraws only the exposed region.

Expose Events

   The X server can report Expose events to clients wanting
   information about when the contents of window regions have been
   lost. The circumstances in which the X server generates Expose
   events are not as definite as those for other events. However,
   the X server never generates Expose events on windows whose
   class you specified as InputOnly. The X server can generate
   Expose events when no valid contents are available for regions
   of a window and either the regions are visible, the regions are
   viewable and the server is (perhaps newly) maintaining backing
   store on the window, or the window is not viewable but the
   server is (perhaps newly) honoring the window's backing-store
   attribute of Always or WhenMapped. The regions decompose into
   an (arbitrary) set of rectangles, and an Expose event is
   generated for each rectangle. For any given window, the X
   server guarantees to report contiguously all of the regions
   exposed by some action that causes Expose events, such as
   raising a window.

   To receive Expose events, set the ExposureMask bit in the
   event-mask attribute of the window.

   The structure for this event type contains:



typedef struct {
     int           type;           /* Expose */
     unsigned long serial;         /* # of last request processed by ser
ver */
     Bool          send_event;     /* true if this came from a SendEvent
 request */
     Display       *display;       /* Display the event was read from */
     Window        window;
     int           x, y;
     int           width, height;
     int           count;          /* if nonzero, at least this many mor
e */
} XExposeEvent;

   The window member is set to the exposed (damaged) window. The x
   and y members are set to the coordinates relative to the
   window's origin and indicate the upper-left corner of the
   rectangle. The width and height members are set to the size
   (extent) of the rectangle. The count member is set to the
   number of Expose events that are to follow. If count is zero,
   no more Expose events follow for this window. However, if count
   is nonzero, at least that number of Expose events (and possibly
   more) follow for this window. Simple applications that do not
   want to optimize redisplay by distinguishing between subareas
   of its window can just ignore all Expose events with nonzero
   counts and perform full redisplays on events with zero counts.

GraphicsExpose and NoExpose Events

   The X server can report GraphicsExpose events to clients
   wanting information about when a destination region could not
   be computed during certain graphics requests: XCopyArea or
   XCopyPlane. The X server generates this event whenever a
   destination region could not be computed because of an obscured
   or out-of-bounds source region. In addition, the X server
   guarantees to report contiguously all of the regions exposed by
   some graphics request (for example, copying an area of a
   drawable to a destination drawable).

   The X server generates a NoExpose event whenever a graphics
   request that might produce a GraphicsExpose event does not
   produce any. In other words, the client is really asking for a
   GraphicsExpose event but instead receives a NoExpose event.

   To receive GraphicsExpose or NoExpose events, you must first
   set the graphics-exposure attribute of the graphics context to
   True. You also can set the graphics-expose attribute when
   creating a graphics context using XCreateGC or by calling
   XSetGraphicsExposures.

   The structures for these event types contain:



typedef struct {
     int            type;           /* GraphicsExpose */
     unsigned long  serial;         /* # of last request processed by se
rver */
     Bool           send_event;     /* true if this came from a SendEven
t request */
     Display        *display;       /* Display the event was read from *
/
     Drawable       drawable;
     int            x, y;
     int            width, height;
     int            count;          /* if nonzero, at least this many mo
re */
     int            major_code;     /* core is CopyArea or CopyPlane */
     int            minor_code;     /* not defined in the core */
} XGraphicsExposeEvent;



typedef struct {
     int           type;         /* NoExpose */
     unsigned long serial;       /* # of last request processed by serve
r */
     Bool          send_event;   /* true if this came from a SendEvent r
equest */
     Display       *display;     /* Display the event was read from */
     Drawable      drawable;
     int           major_code;   /* core is CopyArea or CopyPlane */
     int           minor_code;   /* not defined in the core */
} XNoExposeEvent;

   Both structures have these common members: drawable,
   major_code, and minor_code. The drawable member is set to the
   drawable of the destination region on which the graphics
   request was to be performed. The major_code member is set to
   the graphics request initiated by the client and can be either
   X_CopyArea or X_CopyPlane. If it is X_CopyArea, a call to
   XCopyArea initiated the request. If it is X_CopyPlane, a call
   to XCopyPlane initiated the request. These constants are
   defined in <X11/Xproto.h>. The minor_code member, like the
   major_code member, indicates which graphics request was
   initiated by the client. However, the minor_code member is not
   defined by the core X protocol and will be zero in these cases,
   although it may be used by an extension.

   The XGraphicsExposeEvent structure has these additional
   members: x, y, width, height, and count. The x and y members
   are set to the coordinates relative to the drawable's origin
   and indicate the upper-left corner of the rectangle. The width
   and height members are set to the size (extent) of the
   rectangle. The count member is set to the number of
   GraphicsExpose events to follow. If count is zero, no more
   GraphicsExpose events follow for this window. However, if count
   is nonzero, at least that number of GraphicsExpose events (and
   possibly more) are to follow for this window.

Window State Change Events

   The following sections discuss:
     * CirculateNotify events
     * ConfigureNotify events
     * CreateNotify events
     * DestroyNotify events
     * GravityNotify events
     * MapNotify events
     * MappingNotify events
     * ReparentNotify events
     * UnmapNotify events
     * VisibilityNotify events

CirculateNotify Events

   The X server can report CirculateNotify events to clients
   wanting information about when a window changes its position in
   the stack. The X server generates this event type whenever a
   window is actually restacked as a result of a client
   application calling XCirculateSubwindows,
   XCirculateSubwindowsUp, or XCirculateSubwindowsDown.

   To receive CirculateNotify events, set the StructureNotifyMask
   bit in the event-mask attribute of the window or the
   SubstructureNotifyMask bit in the event-mask attribute of the
   parent window (in which case, circulating any child generates
   an event).

   The structure for this event type contains:



typedef struct {
     int type;     /* CirculateNotify */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool send_event;     /* true if this came from a SendEvent request
*/
     Display *display;     /* Display the event was read from */
     Window event;
     Window window;
     int place;     /* PlaceOnTop, PlaceOnBottom */
} XCirculateEvent;

   The event member is set either to the restacked window or to
   its parent, depending on whether StructureNotify or
   SubstructureNotify was selected. The window member is set to
   the window that was restacked. The place member is set to the
   window's position after the restack occurs and is either
   PlaceOnTop or PlaceOnBottom. If it is PlaceOnTop, the window is
   now on top of all siblings. If it is PlaceOnBottom, the window
   is now below all siblings.

ConfigureNotify Events

   The X server can report ConfigureNotify events to clients
   wanting information about actual changes to a window's state,
   such as size, position, border, and stacking order. The X
   server generates this event type whenever one of the following
   configure window requests made by a client application actually
   completes:
     * A window's size, position, border, and/or stacking order is
       reconfigured by calling XConfigureWindow.
     * The window's position in the stacking order is changed by
       calling XLowerWindow, XRaiseWindow, or XRestackWindows.
     * A window is moved by calling XMoveWindow.
     * A window's size is changed by calling XResizeWindow.
     * A window's size and location is changed by calling
       XMoveResizeWindow.
     * A window is mapped and its position in the stacking order
       is changed by calling XMapRaised.
     * A window's border width is changed by calling
       XSetWindowBorderWidth.

   To receive ConfigureNotify events, set the StructureNotifyMask
   bit in the event-mask attribute of the window or the
   SubstructureNotifyMask bit in the event-mask attribute of the
   parent window (in which case, configuring any child generates
   an event).

   The structure for this event type contains:


typedef struct {
     int           type;       /* ConfigureNotify */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        event;
     Window        window;
     int           x, y;
     int           width, height;
     int           border_width;
     Window        above;
     Bool          override_redirect;
} XConfigureEvent;

   The event member is set either to the reconfigured window or to
   its parent, depending on whether StructureNotify or
   SubstructureNotify was selected. The window member is set to
   the window whose size, position, border, and/or stacking order
   was changed.

   The x and y members are set to the coordinates relative to the
   parent window's origin and indicate the position of the
   upper-left outside corner of the window. The width and height
   members are set to the inside size of the window, not including
   the border. The border_width member is set to the width of the
   window's border, in pixels.

   The above member is set to the sibling window and is used for
   stacking operations. If the X server sets this member to None,
   the window whose state was changed is on the bottom of the
   stack with respect to sibling windows. However, if this member
   is set to a sibling window, the window whose state was changed
   is placed on top of this sibling window.

   The override_redirect member is set to the override-redirect
   attribute of the window. Window manager clients normally should
   ignore this window if the override_redirect member is True.

CreateNotify Events

   The X server can report CreateNotify events to clients wanting
   information about creation of windows. The X server generates
   this event whenever a client application creates a window by
   calling XCreateWindow or XCreateSimpleWindow.

   To receive CreateNotify events, set the SubstructureNotifyMask
   bit in the event-mask attribute of the window. Creating any
   children then generates an event.

   The structure for the event type contains:



typedef struct {
     int           type;               /* CreateNotify */
     unsigned long serial;             /* # of last request processed by
 server */
     Bool          send_event;         /* true if this came from a SendE
vent request */
     Display       *display;           /* Display the event was read fro
m */
     Window        parent;             /* parent of the window */
     Window        window;             /* window id of window created */
     int           x, y;               /* window location */
     int           width, height;      /* size of window */
     int           border_width;       /* border width */
     Bool          override_redirect;  /* creation should be overridden
*/
} XCreateWindowEvent;

   The parent member is set to the created window's parent. The
   window member specifies the created window. The x and y members
   are set to the created window's coordinates relative to the
   parent window's origin and indicate the position of the
   upper-left outside corner of the created window. The width and
   height members are set to the inside size of the created window
   (not including the border) and are always nonzero. The
   border_width member is set to the width of the created window's
   border, in pixels. The override_redirect member is set to the
   override-redirect attribute of the window. Window manager
   clients normally should ignore this window if the
   override_redirect member is True.

DestroyNotify Events

   The X server can report DestroyNotify events to clients wanting
   information about which windows are destroyed. The X server
   generates this event whenever a client application destroys a
   window by calling XDestroyWindow or XDestroySubwindows.

   The ordering of the DestroyNotify events is such that for any
   given window, DestroyNotify is generated on all inferiors of
   the window before being generated on the window itself. The X
   protocol does not constrain the ordering among siblings and
   across subhierarchies.

   To receive DestroyNotify events, set the StructureNotifyMask
   bit in the event-mask attribute of the window or the
   SubstructureNotifyMask bit in the event-mask attribute of the
   parent window (in which case, destroying any child generates an
   event).

   The structure for this event type contains:



typedef struct {
     int           type;       /* DestroyNotify */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        event;
     Window        window;
} XDestroyWindowEvent;

   The event member is set either to the destroyed window or to
   its parent, depending on whether StructureNotify or
   SubstructureNotify was selected. The window member is set to
   the window that is destroyed.

GravityNotify Events

   The X server can report GravityNotify events to clients wanting
   information about when a window is moved because of a change in
   the size of its parent. The X server generates this event
   whenever a client application actually moves a child window as
   a result of resizing its parent by calling XConfigureWindow,
   XMoveResizeWindow, or XResizeWindow.

   To receive GravityNotify events, set the StructureNotifyMask
   bit in the event-mask attribute of the window or the
   SubstructureNotifyMask bit in the event-mask attribute of the
   parent window (in which case, any child that is moved because
   its parent has been resized generates an event).

   The structure for this event type contains:



typedef struct {
     int           type;       /* GravityNotify */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        event;
     Window        window;
     int           x, y;
} XGravityEvent;

   The event member is set either to the window that was moved or
   to its parent, depending on whether StructureNotify or
   SubstructureNotify was selected. The window member is set to
   the child window that was moved. The x and y members are set to
   the coordinates relative to the new parent window's origin and
   indicate the position of the upper-left outside corner of the
   window.

MapNotify Events

   The X server can report MapNotify events to clients wanting
   information about which windows are mapped. The X server
   generates this event type whenever a client application changes
   the window's state from unmapped to mapped by calling
   XMapWindow, XMapRaised, XMapSubwindows, XReparentWindow, or as
   a result of save-set processing.

   To receive MapNotify events, set the StructureNotifyMask bit in
   the event-mask attribute of the window or the
   SubstructureNotifyMask bit in the event-mask attribute of the
   parent window (in which case, mapping any child generates an
   event).

   The structure for this event type contains:



typedef struct {
     int           type;                  /* MapNotify */
     unsigned long serial;                /* # of last request processed
 by server */
     Bool          send_event;            /* true if this came from a Se
ndEvent request */
     Display       *display;              /* Display the event was read
from */
     Window        event;
     Window        window;
     Bool          override_redirect;     /* boolean, is override set...
 */
} XMapEvent;

   The event member is set either to the window that was mapped or
   to its parent, depending on whether StructureNotify or
   SubstructureNotify was selected. The window member is set to
   the window that was mapped. The override_redirect member is set
   to the override-redirect attribute of the window. Window
   manager clients normally should ignore this window if the
   override-redirect attribute is True, because these events
   usually are generated from pop-ups, which override structure
   control.

MappingNotify Events

   The X server reports MappingNotify events to all clients. There
   is no mechanism to express disinterest in this event. The X
   server generates this event type whenever a client application
   successfully calls:
     * XSetModifierMapping to indicate which KeyCodes are to be
       used as modifiers
     * XChangeKeyboardMapping to change the keyboard mapping
     * XSetPointerMapping to set the pointer mapping

   The structure for this event type contains:



typedef struct {
     int           type;           /* MappingNotify */
     unsigned long serial;         /* # of last request processed by ser
ver */
     Bool          send_event;     /* true if this came from a SendEvent
 request */
     Display       *display;       /* Display the event was read from */
     Window        window;         /* unused */
     int           request;        /* one of MappingModifier, MappingKey
board,
                   MappingPointer  */
     int           first_keycode;  /* first keycode */
     int           count;          /* defines range of change w. first_k
eycode*/
} XMappingEvent;

   The request member is set to indicate the kind of mapping
   change that occurred and can be MappingModifier,
   MappingKeyboard, or MappingPointer. If it is MappingModifier,
   the modifier mapping was changed. If it is MappingKeyboard, the
   keyboard mapping was changed. If it is MappingPointer, the
   pointer button mapping was changed. The first_keycode and count
   members are set only if the request member was set to
   MappingKeyboard. The number in first_keycode represents the
   first number in the range of the altered mapping, and count
   represents the number of keycodes altered.

   To update the client application's knowledge of the keyboard,
   you should call XRefreshKeyboardMapping.

ReparentNotify Events

   The X server can report ReparentNotify events to clients
   wanting information about changing a window's parent. The X
   server generates this event whenever a client application calls
   XReparentWindow and the window is actually reparented.

   To receive ReparentNotify events, set the StructureNotifyMask
   bit in the event-mask attribute of the window or the
   SubstructureNotifyMask bit in the event-mask attribute of
   either the old or the new parent window (in which case,
   reparenting any child generates an event).

   The structure for this event type contains:



typedef struct {
     int           type;       /* ReparentNotify */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        event;
     Window        window;
     Window        parent;
     int           x, y;
     Bool          override_redirect;
} XReparentEvent;

   The event member is set either to the reparented window or to
   the old or the new parent, depending on whether StructureNotify
   or SubstructureNotify was selected. The window member is set to
   the window that was reparented. The parent member is set to the
   new parent window. The x and y members are set to the
   reparented window's coordinates relative to the new parent
   window's origin and define the upper-left outer corner of the
   reparented window. The override_redirect member is set to the
   override-redirect attribute of the window specified by the
   window member. Window manager clients normally should ignore
   this window if the override_redirect member is True.

UnmapNotify Events

   The X server can report UnmapNotify events to clients wanting
   information about which windows are unmapped. The X server
   generates this event type whenever a client application changes
   the window's state from mapped to unmapped.

   To receive UnmapNotify events, set the StructureNotifyMask bit
   in the event-mask attribute of the window or the
   SubstructureNotifyMask bit in the event-mask attribute of the
   parent window (in which case, unmapping any child window
   generates an event).

   The structure for this event type contains:



typedef struct {
     int           type;       /* UnmapNotify */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        event;
     Window        window;
     Bool          from_configure;
} XUnmapEvent;

   The event member is set either to the unmapped window or to its
   parent, depending on whether StructureNotify or
   SubstructureNotify was selected. This is the window used by the
   X server to report the event. The window member is set to the
   window that was unmapped. The from_configure member is set to
   True if the event was generated as a result of a resizing of
   the window's parent when the window itself had a win_gravity of
   UnmapGravity.

VisibilityNotify Events

   The X server can report VisibilityNotify events to clients
   wanting any change in the visibility of the specified window. A
   region of a window is visible if someone looking at the screen
   can actually see it. The X server generates this event whenever
   the visibility changes state. However, this event is never
   generated for windows whose class is InputOnly.

   All VisibilityNotify events caused by a hierarchy change are
   generated after any hierarchy event (UnmapNotify, MapNotify,
   ConfigureNotify, GravityNotify, CirculateNotify) caused by that
   change. Any VisibilityNotify event on a given window is
   generated before any Expose events on that window, but it is
   not required that all VisibilityNotify events on all windows be
   generated before all Expose events on all windows. The X
   protocol does not constrain the ordering of VisibilityNotify
   events with respect to FocusOut, EnterNotify, and LeaveNotify
   events.

   To receive VisibilityNotify events, set the
   VisibilityChangeMask bit in the event-mask attribute of the
   window.

   The structure for this event type contains:



typedef struct {
     int           type;       /* VisibilityNotify */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        window;
     int           state;
} XVisibilityEvent;

   The window member is set to the window whose visibility state
   changes. The state member is set to the state of the window's
   visibility and can be VisibilityUnobscured,
   VisibilityPartiallyObscured, or VisibilityFullyObscured. The X
   server ignores all of a window's subwindows when determining
   the visibility state of the window and processes
   VisibilityNotify events according to the following:
     * When the window changes state from partially obscured,
       fully obscured, or not viewable to viewable and completely
       unobscured, the X server generates the event with the state
       member of the XVisibilityEvent structure set to
       VisibilityUnobscured.
     * When the window changes state from viewable and completely
       unobscured or not viewable to viewable and partially
       obscured, the X server generates the event with the state
       member of the XVisibilityEvent structure set to
       VisibilityPartiallyObscured.
     * When the window changes state from viewable and completely
       unobscured, viewable and partially obscured, or not
       viewable to viewable and fully obscured, the X server
       generates the event with the state member of the
       XVisibilityEvent structure set to VisibilityFullyObscured.

Structure Control Events

   This section discusses:
     * CirculateRequest events
     * ConfigureRequest events
     * MapRequest events
     * ResizeRequest events

CirculateRequest Events

   The X server can report CirculateRequest events to clients
   wanting information about when another client initiates a
   circulate window request on a specified window. The X server
   generates this event type whenever a client initiates a
   circulate window request on a window and a subwindow actually
   needs to be restacked. The client initiates a circulate window
   request on the window by calling XCirculateSubwindows,
   XCirculateSubwindowsUp, or XCirculateSubwindowsDown.

   To receive CirculateRequest events, set the
   SubstructureRedirectMask in the event-mask attribute of the
   window. Then, in the future, the circulate window request for
   the specified window is not executed, and thus, any subwindow's
   position in the stack is not changed. For example, suppose a
   client application calls XCirculateSubwindowsUp to raise a
   subwindow to the top of the stack. If you had selected
   SubstructureRedirectMask on the window, the X server reports to
   you a CirculateRequest event and does not raise the subwindow
   to the top of the stack.

   The structure for this event type contains:



typedef struct {
     int           type;       /* CirculateRequest */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        parent;
     Window        window;
     int place;                /* PlaceOnTop, PlaceOnBottom */
} XCirculateRequestEvent;

   The parent member is set to the parent window. The window
   member is set to the subwindow to be restacked. The place
   member is set to what the new position in the stacking order
   should be and is either PlaceOnTop or PlaceOnBottom. If it is
   PlaceOnTop, the subwindow should be on top of all siblings. If
   it is PlaceOnBottom, the subwindow should be below all
   siblings.

ConfigureRequest Events

   The X server can report ConfigureRequest events to clients
   wanting information about when a different client initiates a
   configure window request on any child of a specified window.
   The configure window request attempts to reconfigure a window's
   size, position, border, and stacking order. The X server
   generates this event whenever a different client initiates a
   configure window request on a window by calling
   XConfigureWindow, XLowerWindow, XRaiseWindow, XMapRaised,
   XMoveResizeWindow, XMoveWindow, XResizeWindow, XRestackWindows,
   or XSetWindowBorderWidth.

   To receive ConfigureRequest events, set the
   SubstructureRedirectMask bit in the event-mask attribute of the
   window. ConfigureRequest events are generated when a
   ConfigureWindow protocol request is issued on a child window by
   another client. For example, suppose a client application calls
   XLowerWindow to lower a window. If you had selected
   SubstructureRedirectMask on the parent window and if the
   override-redirect attribute of the window is set to False, the
   X server reports a ConfigureRequest event to you and does not
   lower the specified window.

   The structure for this event type contains:



typedef struct {
     int           type;         /* ConfigureRequest */
     unsigned long serial;       /* # of last request processed by serve
r */
     Bool          send_event;   /* true if this came from a SendEvent r
equest */
     Display       *display;     /* Display the event was read from */
     Window        parent;
     Window        window;
     int           x, y;
     int           width, height;
     int           border_width;
     Window        above;
     int           detail;       /* Above, Below, TopIf, BottomIf, Oppos
ite */
     unsigned long value_mask;
} XConfigureRequestEvent;

   The parent member is set to the parent window. The window
   member is set to the window whose size, position, border width,
   and/or stacking order is to be reconfigured. The value_mask
   member indicates which components were specified in the
   ConfigureWindow protocol request. The corresponding values are
   reported as given in the request. The remaining values are
   filled in from the current geometry of the window, except in
   the case of above (sibling) and detail (stack-mode), which are
   reported as None and Above, respectively, if they are not given
   in the request.

MapRequest Events

   The X server can report MapRequest events to clients wanting
   information about a different client's desire to map windows. A
   window is considered mapped when a map window request
   completes. The X server generates this event whenever a
   different client initiates a map window request on an unmapped
   window whose override_redirect member is set to False. Clients
   initiate map window requests by calling XMapWindow, XMapRaised,
   or XMapSubwindows.

   To receive MapRequest events, set the SubstructureRedirectMask
   bit in the event-mask attribute of the window. This means
   another client's attempts to map a child window by calling one
   of the map window request functions is intercepted, and you are
   sent a MapRequest instead. For example, suppose a client
   application calls XMapWindow to map a window. If you (usually a
   window manager) had selected SubstructureRedirectMask on the
   parent window and if the override-redirect attribute of the
   window is set to False, the X server reports a MapRequest event
   to you and does not map the specified window. Thus, this event
   gives your window manager client the ability to control the
   placement of subwindows.

   The structure for this event type contains:



typedef struct {
     int           type;       /* MapRequest */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        parent;
     Window        window;
} XMapRequestEvent;

   The parent member is set to the parent window. The window
   member is set to the window to be mapped.

ResizeRequest Events

   The X server can report ResizeRequest events to clients wanting
   information about another client's attempts to change the size
   of a window. The X server generates this event whenever some
   other client attempts to change the size of the specified
   window by calling XConfigureWindow, XResizeWindow, or
   XMoveResizeWindow.

   To receive ResizeRequest events, set the ResizeRedirect bit in
   the event-mask attribute of the window. Any attempts to change
   the size by other clients are then redirected.

   The structure for this event type contains:



typedef struct {
     int           type;        /* ResizeRequest */
     unsigned long serial;      /* # of last request processed by server
 */
     Bool          send_event;  /* true if this came from a SendEvent re
quest */
     Display       *display;    /* Display the event was read from */
     Window        window;
     int           width, height;
} XResizeRequestEvent;

   The window member is set to the window whose size another
   client attempted to change. The width and height members are
   set to the inside size of the window, excluding the border.

Colormap State Change Events

   The X server can report ColormapNotify events to clients
   wanting information about when the colormap changes and when a
   colormap is installed or uninstalled. The X server generates
   this event type whenever a client application:
     * Changes the colormap member of the XSetWindowAttributes
       structure by calling XChangeWindowAttributes,
       XFreeColormap, or XSetWindowColormap
     * Installs or uninstalls the colormap by calling
       XInstallColormap or XUninstallColormap

   To receive ColormapNotify events, set the ColormapChangeMask
   bit in the event-mask attribute of the window.

   The structure for this event type contains:



typedef struct {
     int           type;       /* ColormapNotify */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        window;
     Colormap      colormap;   /* colormap or None */
     Bool          new;
     int           state;      /* ColormapInstalled, ColormapUninstalled
 */
} XColormapEvent;

   The window member is set to the window whose associated
   colormap is changed, installed, or uninstalled. For a colormap
   that is changed, installed, or uninstalled, the colormap member
   is set to the colormap associated with the window. For a
   colormap that is changed by a call to XFreeColormap, the
   colormap member is set to None. The new member is set to
   indicate whether the colormap for the specified window was
   changed or installed or uninstalled and can be True or False.
   If it is True, the colormap was changed. If it is False, the
   colormap was installed or uninstalled. The state member is
   always set to indicate whether the colormap is installed or
   uninstalled and can be ColormapInstalled or
   ColormapUninstalled.

Client Communication Events

   This section discusses:
     * ClientMessage events
     * PropertyNotify events
     * SelectionClear events
     * SelectionNotify events
     * SelectionRequest events

ClientMessage Events

   The X server generates ClientMessage events only when a client
   calls the function XSendEvent.

   The structure for this event type contains:



typedef struct {
     int           type;           /* ClientMessage */
     unsigned long serial;         /* # of last request processed by ser
ver */
     Bool          send_event;     /* true if this came from a SendEvent
 request */
     Display       *display;       /* Display the event was read from */
     Window        window;
     Atom          message_type;
     int           format;
     union         {
                     char  b[20];
                     short s[10];
                     long  l[5];
                   } data;
} XClientMessageEvent;

   The message_type member is set to an atom that indicates how
   the data should be interpreted by the receiving client. The
   format member is set to 8, 16, or 32 and specifies whether the
   data should be viewed as a list of bytes, shorts, or longs. The
   data member is a union that contains the members b, s, and l.
   The b, s, and l members represent data of twenty 8-bit values,
   ten 16-bit values, and five 32-bit values. Particular message
   types might not make use of all these values. The X server
   places no interpretation on the values in the window,
   message_type, or data members.

PropertyNotify Events

   The X server can report PropertyNotify events to clients
   wanting information about property changes for a specified
   window.

   To receive PropertyNotify events, set the PropertyChangeMask
   bit in the event-mask attribute of the window.

   The structure for this event type contains:



typedef struct {
     int           type;       /* PropertyNotify */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        window;
     Atom atom;
     Time time;
     int state;                /* PropertyNewValue or PropertyDelete */
} XPropertyEvent;

   The window member is set to the window whose associated
   property was changed. The atom member is set to the property's
   atom and indicates which property was changed or desired. The
   time member is set to the server time when the property was
   changed. The state member is set to indicate whether the
   property was changed to a new value or deleted and can be
   PropertyNewValue or PropertyDelete. The state member is set to
   PropertyNewValue when a property of the window is changed using
   XChangeProperty or XRotateWindowProperties (even when adding
   zero-length data using XChangeProperty) and when replacing all
   or part of a property with identical data using XChangeProperty
   or XRotateWindowProperties. The state member is set to
   PropertyDelete when a property of the window is deleted using
   XDeleteProperty or, if the delete argument is True,
   XGetWindowProperty.

SelectionClear Events

   The X server reports SelectionClear events to the client losing
   ownership of a selection. The X server generates this event
   type when another client asserts ownership of the selection by
   calling XSetSelectionOwner.

   The structure for this event type contains:



typedef struct {
     int           type;       /* SelectionClear */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        window;
     Atom          selection;
     Time          time;
} XSelectionClearEvent;

   The selection member is set to the selection atom. The time
   member is set to the last change time recorded for the
   selection. The window member is the window that was specified
   by the current owner (the owner losing the selection) in its
   XSetSelectionOwner call.

SelectionRequest Events

   The X server reports SelectionRequest events to the owner of a
   selection. The X server generates this event whenever a client
   requests a selection conversion by calling XConvertSelection
   for the owned selection.

   The structure for this event type contains:



typedef struct {
     int           type;       /* SelectionRequest */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        owner;
     Window        requestor;
     Atom          selection;
     Atom          target;
     Atom          property;
     Time          time;
} XSelectionRequestEvent;

   The owner member is set to the window that was specified by the
   current owner in its XSetSelectionOwner call. The requestor
   member is set to the window requesting the selection. The
   selection member is set to the atom that names the selection.
   For example, PRIMARY is used to indicate the primary selection.
   The target member is set to the atom that indicates the type
   the selection is desired in. The property member can be a
   property name or None. The time member is set to the timestamp
   or CurrentTime value from the ConvertSelection request.

   The owner should convert the selection based on the specified
   target type and send a SelectionNotify event back to the
   requestor. A complete specification for using selections is
   given in the X Consortium standard Inter-Client Communication
   Conventions Manual.

SelectionNotify Events

   This event is generated by the X server in response to a
   ConvertSelection protocol request when there is no owner for
   the selection. When there is an owner, it should be generated
   by the owner of the selection by using XSendEvent. The owner of
   a selection should send this event to a requestor when a
   selection has been converted and stored as a property or when a
   selection conversion could not be performed (which is indicated
   by setting the property member to None).

   If None is specified as the property in the ConvertSelection
   protocol request, the owner should choose a property name,
   store the result as that property on the requestor window, and
   then send a SelectionNotify giving that actual property name.

   The structure for this event type contains:



typedef struct {
     int           type;       /* SelectionNotify */
     unsigned long serial;     /* # of last request processed by server
*/
     Bool          send_event; /* true if this came from a SendEvent req
uest */
     Display       *display;   /* Display the event was read from */
     Window        requestor;
     Atom          selection;
     Atom          target;
     Atom          property;   /* atom or None */
     Time          time;
} XSelectionEvent;

   The requestor member is set to the window associated with the
   requestor of the selection. The selection member is set to the
   atom that indicates the selection. For example, PRIMARY is used
   for the primary selection. The target member is set to the atom
   that indicates the converted type. For example, PIXMAP is used
   for a pixmap. The property member is set to the atom that
   indicates which property the result was stored on. If the
   conversion failed, the property member is set to None. The time
   member is set to the time the conversion took place and can be
   a timestamp or CurrentTime.

Chapter 11. Event Handling Functions

   Table of Contents

   Selecting Events
   Handling the Output Buffer
   Event Queue Management
   Manipulating the Event Queue

        Returning the Next Event
        Selecting Events Using a Predicate Procedure
        Selecting Events Using a Window or Event Mask

   Putting an Event Back into the Queue
   Sending Events to Other Applications
   Getting Pointer Motion History
   Handling Protocol Errors

        Enabling or Disabling Synchronization
        Using the Default Error Handlers

   This chapter discusses the Xlib functions you can use to:
     * Select events
     * Handle the output buffer and the event queue
     * Select events from the event queue
     * Send and get events
     * Handle protocol errors

Note

   Some toolkits use their own event-handling functions and do not
   allow you to interchange these event-handling functions with
   those in Xlib. For further information, see the documentation
   supplied with the toolkit.

   Most applications simply are event loops: they wait for an
   event, decide what to do with it, execute some amount of code
   that results in changes to the display, and then wait for the
   next event.

Selecting Events

   There are two ways to select the events you want reported to
   your client application. One way is to set the event_mask
   member of the XSetWindowAttributes structure when you call
   XCreateWindow and XChangeWindowAttributes. Another way is to
   use XSelectInput.

   XSelectInput(Display *display, Window w, long event_mask);

   display

   Specifies the connection to the X server.

   w

   Specifies the window whose events you are interested in.

   event_mask

   Specifies the event mask.

   The XSelectInput function requests that the X server report the
   events associated with the specified event mask. Initially, X
   will not report any of these events. Events are reported
   relative to a window. If a window is not interested in a device
   event, it usually propagates to the closest ancestor that is
   interested, unless the do_not_propagate mask prohibits it.

   Setting the event-mask attribute of a window overrides any
   previous call for the same window but not for other clients.
   Multiple clients can select for the same events on the same
   window with the following restrictions:
     * Multiple clients can select events on the same window
       because their event masks are disjoint. When the X server
       generates an event, it reports it to all interested
       clients.
     * Only one client at a time can select CirculateRequest,
       ConfigureRequest, or MapRequest events, which are
       associated with the event mask SubstructureRedirectMask.
     * Only one client at a time can select a ResizeRequest event,
       which is associated with the event mask ResizeRedirectMask.
     * Only one client at a time can select a ButtonPress event,
       which is associated with the event mask ButtonPressMask.

   The server reports the event to all interested clients.

   XSelectInput can generate a BadWindow error.

Handling the Output Buffer

   The output buffer is an area used by Xlib to store requests.
   The functions described in this section flush the output buffer
   if the function would block or not return an event. That is,
   all requests residing in the output buffer that have not yet
   been sent are transmitted to the X server. These functions
   differ in the additional tasks they might perform.

   To flush the output buffer, use XFlush.

   XFlush(Display *display);

   display

   Specifies the connection to the X server.

   The XFlush function flushes the output buffer. Most client
   applications need not use this function because the output
   buffer is automatically flushed as needed by calls to XPending,
   XNextEvent, and XWindowEvent. Events generated by the server
   may be enqueued into the library's event queue.

   To flush the output buffer and then wait until all requests
   have been processed, use XSync.

   XSync(Display *display, Bool discard);

   display

   Specifies the connection to the X server.

   discard

   Specifies a Boolean value that indicates whether XSync discards
   all events on the event queue.

   The XSync function flushes the output buffer and then waits
   until all requests have been received and processed by the X
   server. Any errors generated must be handled by the error
   handler. For each protocol error received by Xlib, XSync calls
   the client application's error handling routine (see section
   11.8.2). Any events generated by the server are enqueued into
   the library's event queue.

   Finally, if you passed False, XSync does not discard the events
   in the queue. If you passed True, XSync discards all events in
   the queue, including those events that were on the queue before
   XSync was called. Client applications seldom need to call
   XSync.

Event Queue Management

   Xlib maintains an event queue. However, the operating system
   also may be buffering data in its network connection that is
   not yet read into the event queue.

   To check the number of events in the event queue, use
   XEventsQueued.

   int XEventsQueued(Display *display, int mode);

   display

   Specifies the connection to the X server.

   mode

   Specifies the mode. You can pass QueuedAlready,
   QueuedAfterFlush, or QueuedAfterReading.

   If mode is QueuedAlready, XEventsQueued returns the number of
   events already in the event queue (and never performs a system
   call). If mode is QueuedAfterFlush, XEventsQueued returns the
   number of events already in the queue if the number is nonzero.
   If there are no events in the queue, XEventsQueued flushes the
   output buffer, attempts to read more events out of the
   application's connection, and returns the number read. If mode
   is QueuedAfterReading, XEventsQueued returns the number of
   events already in the queue if the number is nonzero. If there
   are no events in the queue, XEventsQueued attempts to read more
   events out of the application's connection without flushing the
   output buffer and returns the number read.

   XEventsQueued always returns immediately without I/O if there
   are events already in the queue. XEventsQueued with mode
   QueuedAfterFlush is identical in behavior to XPending.
   XEventsQueued with mode QueuedAlready is identical to the
   XQLength function.

   To return the number of events that are pending, use XPending.

   int XPending(Display *display);

   display

   Specifies the connection to the X server.

   The XPending function returns the number of events that have
   been received from the X server but have not been removed from
   the event queue. XPending is identical to XEventsQueued with
   the mode QueuedAfterFlush specified.

Manipulating the Event Queue

   Xlib provides functions that let you manipulate the event
   queue. This section discusses how to:
     * Obtain events, in order, and remove them from the queue
     * Peek at events in the queue without removing them
     * Obtain events that match the event mask or the arbitrary
       predicate procedures that you provide

Returning the Next Event

   To get the next event and remove it from the queue, use
   XNextEvent.

   XNextEvent(Display *display, XEvent *event_return);

   display

   Specifies the connection to the X server.

   event_return

   Returns the next event in the queue.

   The XNextEvent function copies the first event from the event
   queue into the specified XEvent structure and then removes it
   from the queue. If the event queue is empty, XNextEvent flushes
   the output buffer and blocks until an event is received.

   To peek at the event queue, use XPeekEvent.

   XPeekEvent(Display *display, XEvent *event_return);

   display

   Specifies the connection to the X server.

   event_return

   Returns a copy of the matched event's associated structure.

   The XPeekEvent function returns the first event from the event
   queue, but it does not remove the event from the queue. If the
   queue is empty, XPeekEvent flushes the output buffer and blocks
   until an event is received. It then copies the event into the
   client-supplied XEvent structure without removing it from the
   event queue.

Selecting Events Using a Predicate Procedure

   Each of the functions discussed in this section requires you to
   pass a predicate procedure that determines if an event matches
   what you want. Your predicate procedure must decide if the
   event is useful without calling any Xlib functions. If the
   predicate directly or indirectly causes the state of the event
   queue to change, the result is not defined. If Xlib has been
   initialized for threads, the predicate is called with the
   display locked and the result of a call by the predicate to any
   Xlib function that locks the display is not defined unless the
   caller has first called XLockDisplay.

   The predicate procedure and its associated arguments are:

   Bool(Display *display, XEvent *event, XPointer arg);

   display

   Specifies the connection to the X server.

   event

   Specifies the XEvent structure.

   arg

   Specifies the argument passed in from the XIfEvent,
   XCheckIfEvent, or XPeekIfEvent function.

   The predicate procedure is called once for each event in the
   queue until it finds a match. After finding a match, the
   predicate procedure must return True. If it did not find a
   match, it must return False.

   To check the event queue for a matching event and, if found,
   remove the event from the queue, use XIfEvent.

   XIfEvent(Display *display, XEvent *event_return, Bool
   (*predicate)(), XPointer arg);

   display

   Specifies the connection to the X server.

   event_return

   Returns the matched event's associated structure.

   predicate

   Specifies the procedure that is to be called to determine if
   the next event in the queue matches what you want.

   arg

   Specifies the user-supplied argument that will be passed to the
   predicate procedure.

   The XIfEvent function completes only when the specified
   predicate procedure returns True for an event, which indicates
   an event in the queue matches. XIfEvent flushes the output
   buffer if it blocks waiting for additional events. XIfEvent
   removes the matching event from the queue and copies the
   structure into the client-supplied XEvent structure.

   To check the event queue for a matching event without blocking,
   use XCheckIfEvent.

   Bool XCheckIfEvent(Display *display, XEvent *event_return, Bool
   (*predicate)(), XPointer arg);

   display

   Specifies the connection to the X server.

   event_return

   Returns a copy of the matched event's associated structure.

   predicate

   Specifies the procedure that is to be called to determine if
   the next event in the queue matches what you want.

   arg

   Specifies the user-supplied argument that will be passed to the
   predicate procedure.

   When the predicate procedure finds a match, XCheckIfEvent
   copies the matched event into the client-supplied XEvent
   structure and returns True. (This event is removed from the
   queue.) If the predicate procedure finds no match,
   XCheckIfEvent returns False, and the output buffer will have
   been flushed. All earlier events stored in the queue are not
   discarded.

   To check the event queue for a matching event without removing
   the event from the queue, use XPeekIfEvent.

   XPeekIfEvent(Display *display, XEvent *event_return, Bool
   (*predicate)(), XPointer arg);

   display

   Specifies the connection to the X server.

   event_return

   Returns a copy of the matched event's associated structure.

   predicate

   Specifies the procedure that is to be called to determine if
   the next event in the queue matches what you want.

   arg

   Specifies the user-supplied argument that will be passed to the
   predicate procedure.

   The XPeekIfEvent function returns only when the specified
   predicate procedure returns True for an event. After the
   predicate procedure finds a match, XPeekIfEvent copies the
   matched event into the client-supplied XEvent structure without
   removing the event from the queue. XPeekIfEvent flushes the
   output buffer if it blocks waiting for additional events.

Selecting Events Using a Window or Event Mask

   The functions discussed in this section let you select events
   by window or event types, allowing you to process events out of
   order.

   To remove the next event that matches both a window and an
   event mask, use XWindowEvent.

   XWindowEvent(Display *display, Window w, long event_mask,
   XEvent *event_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window whose events you are interested in.

   event_mask

   Specifies the event mask.

   event_return

   Returns the matched event's associated structure.

   The XWindowEvent function searches the event queue for an event
   that matches both the specified window and event mask. When it
   finds a match, XWindowEvent removes that event from the queue
   and copies it into the specified XEvent structure. The other
   events stored in the queue are not discarded. If a matching
   event is not in the queue, XWindowEvent flushes the output
   buffer and blocks until one is received.

   To remove the next event that matches both a window and an
   event mask (if any), use XCheckWindowEvent. This function is
   similar to XWindowEvent except that it never blocks and it
   returns a Bool indicating if the event was returned.

   Bool XCheckWindowEvent(Display *display, Window w, long
   event_mask, XEvent *event_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window whose events you are interested in.

   event_mask

   Specifies the event mask.

   event_return

   Returns the matched event's associated structure.

   The XCheckWindowEvent function searches the event queue and
   then the events available on the server connection for the
   first event that matches the specified window and event mask.
   If it finds a match, XCheckWindowEvent removes that event,
   copies it into the specified XEvent structure, and returns
   True. The other events stored in the queue are not discarded.
   If the event you requested is not available, XCheckWindowEvent
   returns False, and the output buffer will have been flushed.

   To remove the next event that matches an event mask, use
   XMaskEvent.

   XMaskEvent(Display *display, long event_mask, XEvent
   *event_return);

   display

   Specifies the connection to the X server.

   event_mask

   Specifies the event mask.

   event_return

   Returns the matched event's associated structure.

   The XMaskEvent function searches the event queue for the events
   associated with the specified mask. When it finds a match,
   XMaskEvent removes that event and copies it into the specified
   XEvent structure. The other events stored in the queue are not
   discarded. If the event you requested is not in the queue,
   XMaskEvent flushes the output buffer and blocks until one is
   received.

   To return and remove the next event that matches an event mask
   (if any), use XCheckMaskEvent. This function is similar to
   XMaskEvent except that it never blocks and it returns a Bool
   indicating if the event was returned.

   Bool XCheckMaskEvent(Display *display, long event_mask, XEvent
   *event_return);

   display

   Specifies the connection to the X server.

   event_mask

   Specifies the event mask.

   event_return

   Returns the matched event's associated structure.

   The XCheckMaskEvent function searches the event queue and then
   any events available on the server connection for the first
   event that matches the specified mask. If it finds a match,
   XCheckMaskEvent removes that event, copies it into the
   specified XEvent structure, and returns True. The other events
   stored in the queue are not discarded. If the event you
   requested is not available, XCheckMaskEvent returns False, and
   the output buffer will have been flushed.

   To return and remove the next event in the queue that matches
   an event type, use XCheckTypedEvent.

   Bool XCheckTypedEvent(Display *display, int event_type, XEvent
   *event_return);

   display

   Specifies the connection to the X server.

   event_type

   Specifies the event type to be compared.

   event_return

   Returns the matched event's associated structure.

   The XCheckTypedEvent function searches the event queue and then
   any events available on the server connection for the first
   event that matches the specified type. If it finds a match,
   XCheckTypedEvent removes that event, copies it into the
   specified XEvent structure, and returns True. The other events
   in the queue are not discarded. If the event is not available,
   XCheckTypedEvent returns False, and the output buffer will have
   been flushed.

   To return and remove the next event in the queue that matches
   an event type and a window, use XCheckTypedWindowEvent.

   Bool XCheckTypedWindowEvent(Display *display, Window w, int
   event_type, XEvent *event_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   event_type

   Specifies the event type to be compared.

   event_return

   Returns the matched event's associated structure.

   The XCheckTypedWindowEvent function searches the event queue
   and then any events available on the server connection for the
   first event that matches the specified type and window. If it
   finds a match, XCheckTypedWindowEvent removes the event from
   the queue, copies it into the specified XEvent structure, and
   returns True. The other events in the queue are not discarded.
   If the event is not available, XCheckTypedWindowEvent returns
   False, and the output buffer will have been flushed.

Putting an Event Back into the Queue

   To push an event back into the event queue, use XPutBackEvent.

   XPutBackEvent(Display *display, XEvent *event);

   display

   Specifies the connection to the X server.

   event

   Specifies the event.

   The XPutBackEvent function pushes an event back onto the head
   of the display's event queue by copying the event into the
   queue. This can be useful if you read an event and then decide
   that you would rather deal with it later. There is no limit to
   the number of times in succession that you can call
   XPutBackEvent.

Sending Events to Other Applications

   To send an event to a specified window, use XSendEvent. This
   function is often used in selection processing. For example,
   the owner of a selection should use XSendEvent to send a
   SelectionNotify event to a requestor when a selection has been
   converted and stored as a property.

   Status XSendEvent(Display *display, Window w, Bool propagate,
   long event_mask, XEvent *event_send);

   display

   Specifies the connection to the X server.

   w

   Specifies the window the event is to be sent to, or
   PointerWindow, or InputFocus.

   propagate

   Specifies a Boolean value.

   event_mask

   Specifies the event mask.

   event_send

   Specifies the event that is to be sent.

   The XSendEvent function identifies the destination window,
   determines which clients should receive the specified events,
   and ignores any active grabs. This function requires you to
   pass an event mask. For a discussion of the valid event mask
   names, see section 10.3. This function uses the w argument to
   identify the destination window as follows:
     * If w is PointerWindow, the destination window is the window
       that contains the pointer.
     * If w is InputFocus and if the focus window contains the
       pointer, the destination window is the window that contains
       the pointer; otherwise, the destination window is the focus
       window.

   To determine which clients should receive the specified events,
   XSendEvent uses the propagate argument as follows:
     * If event_mask is the empty set, the event is sent to the
       client that created the destination window. If that client
       no longer exists, no event is sent.
     * If propagate is False, the event is sent to every client
       selecting on destination any of the event types in the
       event_mask argument.
     * If propagate is True and no clients have selected on
       destination any of the event types in event-mask, the
       destination is replaced with the closest ancestor of
       destination for which some client has selected a type in
       event-mask and for which no intervening window has that
       type in its do-not-propagate-mask. If no such window exists
       or if the window is an ancestor of the focus window and
       InputFocus was originally specified as the destination, the
       event is not sent to any clients. Otherwise, the event is
       reported to every client selecting on the final destination
       any of the types specified in event_mask.

   The event in the XEvent structure must be one of the core
   events or one of the events defined by an extension (or a
   BadValue error results) so that the X server can correctly
   byte-swap the contents as necessary. The contents of the event
   are otherwise unaltered and unchecked by the X server except to
   force send_event to True in the forwarded event and to set the
   serial number in the event correctly; therefore these fields
   and the display field are ignored by XSendEvent.

   XSendEvent returns zero if the conversion to wire protocol
   format failed and returns nonzero otherwise.

   XSendEvent can generate BadValue and BadWindow errors.

Getting Pointer Motion History

   Some X server implementations will maintain a more complete
   history of pointer motion than is reported by event
   notification. The pointer position at each pointer hardware
   interrupt may be stored in a buffer for later retrieval. This
   buffer is called the motion history buffer. For example, a few
   applications, such as paint programs, want to have a precise
   history of where the pointer traveled. However, this historical
   information is highly excessive for most applications.

   To determine the approximate maximum number of elements in the
   motion buffer, use XDisplayMotionBufferSize.

   unsigned long(Display *display);

   display

   Specifies the connection to the X server.

   The server may retain the recent history of the pointer motion
   and do so to a finer granularity than is reported by
   MotionNotify events. The function makes this history available.

   To get the motion history for a specified window and time, use
   .

   XTimeCoord *XGetMotionEvents(Display *display, Window w, Time
   start, Time stop, int *nevents_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   start

   stop

   Specify the time interval in which the events are returned from
   the motion history buffer. You can pass a timestamp or
   CurrentTime.

   nevents_return

   Returns the number of events from the motion history buffer.

   The function returns all events in the motion history buffer
   that fall between the specified start and stop times,
   inclusive, and that have coordinates that lie within the
   specified window (including its borders) at its present
   placement. If the server does not support motion history, if
   the start time is later than the stop time, or if the start
   time is in the future, no events are returned; returns NULL. If
   the stop time is in the future, it is equivalent to specifying
   CurrentTime. The return type for this function is a structure
   defined as follows:



typedef struct {
        Time time;
        short x, y;
} XTimeCoord;

   The time member is set to the time, in milliseconds. The x and
   y members are set to the coordinates of the pointer and are
   reported relative to the origin of the specified window. To
   free the data returned from this call, use XFree.

   can generate a BadWindow error.

Handling Protocol Errors

   Xlib provides functions that you can use to enable or disable
   synchronization and to use the default error handlers.

Enabling or Disabling Synchronization

   When debugging X applications, it often is very convenient to
   require Xlib to behave synchronously so that errors are
   reported as they occur. The following function lets you disable
   or enable synchronous behavior. Note that graphics may occur 30
   or more times more slowly when synchronization is enabled. On
   POSIX-conformant systems, there is also a global variable
   _Xdebug that, if set to nonzero before starting a program under
   a debugger, will force synchronous library behavior.

   After completing their work, all Xlib functions that generate
   protocol requests call what is known as an after function. sets
   which function is to be called.

   int(Display *display, int (*procedure)());

   display

   Specifies the connection to the X server.

   procedure

   Specifies the procedure to be called.

   The specified procedure is called with only a display pointer.
   returns the previous after function.

   To enable or disable synchronization, use XSynchronize.

   int(Display *display, Bool onoff);

   display

   Specifies the connection to the X server.

   onoff

   Specifies a Boolean value that indicates whether to enable or
   disable synchronization.

   The XSynchronize function returns the previous after function.
   If onoff is True, XSynchronize turns on synchronous behavior.
   If onoff is False, XSynchronize turns off synchronous behavior.

Using the Default Error Handlers

   There are two default error handlers in Xlib: one to handle
   typically fatal conditions (for example, the connection to a
   display server dying because a machine crashed) and one to
   handle protocol errors from the X server. These error handlers
   can be changed to user-supplied routines if you prefer your own
   error handling and can be changed as often as you like. If
   either function is passed a NULL pointer, it will reinvoke the
   default handler. The action of the default handlers is to print
   an explanatory message and exit.

   To set the error handler, use XSetErrorHandler.

   int *XSetErrorHandler(int *handler);

   handler

   Specifies the program's supplied error handler.

   Xlib generally calls the program's supplied error handler
   whenever an error is received. It is not called on BadName
   errors from OpenFont, LookupColor, or AllocNamedColor protocol
   requests or on BadFont errors from a QueryFont protocol
   request. These errors generally are reflected back to the
   program through the procedural interface. Because this
   condition is not assumed to be fatal, it is acceptable for your
   error handler to return; the returned value is ignored.
   However, the error handler should not call any functions
   (directly or indirectly) on the display that will generate
   protocol requests or that will look for input events. The
   previous error handler is returned.

   The XErrorEvent structure contains:



typedef struct {
        int type;
        Display *display;       /* Display the event was read from */
        unsigned long serial;           /* serial number of failed reque
st */
        unsigned char error_code;       /* error code of failed request
*/
        unsigned char request_code;     /* Major op-code of failed reque
st */
        unsigned char minor_code;       /* Minor op-code of failed reque
st */
        XID resourceid;         /* resource id */
} XErrorEvent;

   The serial member is the number of requests, starting from one,
   sent over the network connection since it was opened. It is the
   number that was the value of NextRequest immediately before the
   failing call was made. The request_code member is a protocol
   request of the procedure that failed, as defined in
   <X11/Xproto.h>. The following error codes can be returned by
   the functions described in this chapter:
   Error Code Description
   BadAccess

   A client attempts to grab a key/button combination already
   grabbed by another client.

   A client attempts to free a colormap entry that it had not
   already allocated or to free an entry in a colormap that was
   created with all entries writable.

   A client attempts to store into a read-only or unallocated
   colormap entry.

   A client attempts to modify the access control list from other
   than the local (or otherwise authorized) host.

   A client attempts to select an event type that another client
   has already selected.
   BadAlloc The server fails to allocate the requested resource.
   Note that the explicit listing of BadAlloc errors in requests
   only covers allocation errors at a very coarse level and is not
   intended to (nor can it in practice hope to) cover all cases of
   a server running out of allocation space in the middle of
   service. The semantics when a server runs out of allocation
   space are left unspecified, but a server may generate a
   BadAlloc error on any request for this reason, and clients
   should be prepared to receive such errors and handle or discard
   them.
   BadAtom A value for an atom argument does not name a defined
   atom.
   BadColor A value for a colormap argument does not name a
   defined colormap.
   BadCursor A value for a cursor argument does not name a defined
   cursor.
   BadDrawable A value for a drawable argument does not name a
   defined window or pixmap.
   BadFont A value for a font argument does not name a defined
   font (or, in some cases, GContext).
   BadGC A value for a GContext argument does not name a defined
   GContext.
   BadIDChoice The value chosen for a resource identifier either
   is not included in the range assigned to the client or is
   already in use. Under normal circumstances, this cannot occur
   and should be considered a server or Xlib error.
   BadImplementation The server does not implement some aspect of
   the request. A server that generates this error for a core
   request is deficient. As such, this error is not listed for any
   of the requests, but clients should be prepared to receive such
   errors and handle or discard them.
   BadLength

   The length of a request is shorter or longer than that required
   to contain the arguments. This is an internal Xlib or server
   error.

   The length of a request exceeds the maximum length accepted by
   the server.
   BadMatch

   In a graphics request, the root and depth of the graphics
   context do not match those of the drawable.

   An InputOnly window is used as a drawable.

   Some argument or pair of arguments has the correct type and
   range, but it fails to match in some other way required by the
   request.

   An InputOnly window lacks this attribute.
   BadName A font or color of the specified name does not exist.
   BadPixmap A value for a pixmap argument does not name a defined
   pixmap.
   BadRequest The major or minor opcode does not specify a valid
   request. This usually is an Xlib or server error.
   BadValue Some numeric value falls outside of the range of
   values accepted by the request. Unless a specific range is
   specified for an argument, the full range defined by the
   argument's type is accepted. Any argument defined as a set of
   alternatives typically can generate this error (due to the
   encoding).
   BadWindow A value for a window argument does not name a defined
   window.

Note

   The BadAtom, BadColor, BadCursor, BadDrawable, BadFont, BadGC,
   BadPixmap, and BadWindow errors are also used when the argument
   type is extended by a set of fixed alternatives.

   To obtain textual descriptions of the specified error code, use
   XGetErrorText.

   XGetErrorText(Display *display, int code, char *buffer_return,
   int length);

   display

   Specifies the connection to the X server.

   code

   Specifies the error code for which you want to obtain a
   description.

   buffer_return

   Returns the error description.

   length

   Specifies the size of the buffer.

   The XGetErrorText function copies a null-terminated string
   describing the specified error code into the specified buffer.
   The returned text is in the encoding of the current locale. It
   is recommended that you use this function to obtain an error
   description because extensions to Xlib may define their own
   error codes and error strings.

   To obtain error messages from the error database, use
   XGetErrorDatabaseText.

   XGetErrorDatabaseText(Display *display, char *name, char
   *message, char *default_string, char *buffer_return, int
   length);

   display

   Specifies the connection to the X server.

   name

   Specifies the name of the application.

   message

   Specifies the type of the error message.

   default_string

   Specifies the default error message if none is found in the
   database.

   buffer_return

   Returns the error description.

   length

   Specifies the size of the buffer.

   The XGetErrorDatabaseText function returns a null-terminated
   message (or the default message) from the error message
   database. Xlib uses this function internally to look up its
   error messages. The text in the default_string argument is
   assumed to be in the encoding of the current locale, and the
   text stored in the buffer_return argument is in the encoding of
   the current locale.

   The name argument should generally be the name of your
   application. The message argument should indicate which type of
   error message you want. If the name and message are not in the
   Host Portable Character Encoding, the result is
   implementation-dependent. Xlib uses three predefined
   ``application names'' to report errors. In these names,
   uppercase and lowercase matter.

   XProtoError

   The protocol error number is used as a string for the message
   argument.

   XlibMessage

   These are the message strings that are used internally by the
   library.

   XRequest

   For a core protocol request, the major request protocol number
   is used for the message argument. For an extension request, the
   extension name (as given by InitExtension) followed by a period
   (.) and the minor request protocol number is used for the
   message argument. If no string is found in the error database,
   the default_string is returned to the buffer argument.

   To report an error to the user when the requested display does
   not exist, use XDisplayName.

   char *XDisplayName(char *string);

   string

   Specifies the character string.

   The XDisplayName function returns the name of the display that
   XOpenDisplay would attempt to use. If a NULL string is
   specified, XDisplayName looks in the environment for the
   display and returns the display name that XOpenDisplay would
   attempt to use. This makes it easier to report to the user
   precisely which display the program attempted to open when the
   initial connection attempt failed.

   To handle fatal I/O errors, use XSetIOErrorHandler.

   int(int(*handler)(Display *));

   handler

   Specifies the program's supplied error handler.

   The XSetIOErrorHandler sets the fatal I/O error handler. Xlib
   calls the program's supplied error handler if any sort of
   system call error occurs (for example, the connection to the
   server was lost). This is assumed to be a fatal condition, and
   the called routine should not return. If the I/O error handler
   does return, the client process exits.

   Note that the previous error handler is returned.

Chapter 12. Input Device Functions

   Table of Contents

   Pointer Grabbing
   Keyboard Grabbing
   Resuming Event Processing
   Moving the Pointer
   Controlling Input Focus
   Manipulating the Keyboard and Pointer Settings
   Manipulating the Keyboard Encoding

   You can use the Xlib input device functions to:
     * Grab the pointer and individual buttons on the pointer
     * Grab the keyboard and individual keys on the keyboard
     * Resume event processing
     * Move the pointer
     * Set the input focus
     * Manipulate the keyboard and pointer settings
     * Manipulate the keyboard encoding

Pointer Grabbing

   Xlib provides functions that you can use to control input from
   the pointer, which usually is a mouse. Usually, as soon as
   keyboard and mouse events occur, the X server delivers them to
   the appropriate client, which is determined by the window and
   input focus. The X server provides sufficient control over
   event delivery to allow window managers to support mouse ahead
   and various other styles of user interface. Many of these user
   interfaces depend on synchronous delivery of events. The
   delivery of pointer and keyboard events can be controlled
   independently.

   When mouse buttons or keyboard keys are grabbed, events will be
   sent to the grabbing client rather than the normal client who
   would have received the event. If the keyboard or pointer is in
   asynchronous mode, further mouse and keyboard events will
   continue to be processed. If the keyboard or pointer is in
   synchronous mode, no further events are processed until the
   grabbing client allows them (see XAllowEvents). The keyboard or
   pointer is considered frozen during this interval. The event
   that triggered the grab can also be replayed.

   Note that the logical state of a device (as seen by client
   applications) may lag the physical state if device event
   processing is frozen.

   There are two kinds of grabs: active and passive. An active
   grab occurs when a single client grabs the keyboard and/or
   pointer explicitly (see XGrabPointer and XGrabKeyboard). A
   passive grab occurs when clients grab a particular keyboard key
   or pointer button in a window, and the grab will activate when
   the key or button is actually pressed. Passive grabs are
   convenient for implementing reliable pop-up menus. For example,
   you can guarantee that the pop-up is mapped before the up
   pointer button event occurs by grabbing a button requesting
   synchronous behavior. The down event will trigger the grab and
   freeze further processing of pointer events until you have the
   chance to map the pop-up window. You can then allow further
   event processing. The up event will then be correctly processed
   relative to the pop-up window.

   For many operations, there are functions that take a time
   argument. The X server includes a timestamp in various events.
   One special time, called CurrentTime, represents the current
   server time. The X server maintains the time when the input
   focus was last changed, when the keyboard was last grabbed,
   when the pointer was last grabbed, or when a selection was last
   changed. Your application may be slow reacting to an event. You
   often need some way to specify that your request should not
   occur if another application has in the meanwhile taken control
   of the keyboard, pointer, or selection. By providing the
   timestamp from the event in the request, you can arrange that
   the operation not take effect if someone else has performed an
   operation in the meanwhile.

   A timestamp is a time value, expressed in milliseconds. It
   typically is the time since the last server reset. Timestamp
   values wrap around (after about 49.7 days). The server, given
   its current time is represented by timestamp T, always
   interprets timestamps from clients by treating half of the
   timestamp space as being later in time than T. One timestamp
   value, named CurrentTime, is never generated by the server.
   This value is reserved for use in requests to represent the
   current server time.

   For many functions in this section, you pass pointer event mask
   bits. The valid pointer event mask bits are: ButtonPressMask,
   ButtonReleaseMask, EnterWindowMask, LeaveWindowMask,
   PointerMotionMask, PointerMotionHintMask, Button1MotionMask,
   Button2MotionMask, Button3MotionMask, Button4MotionMask,
   Button5MotionMask, ButtonMotionMask, and KeymapStateMask. For
   other functions in this section, you pass keymask bits. The
   valid keymask bits are: ShiftMask, LockMask, ControlMask,
   Mod1Mask, Mod2Mask, Mod3Mask, Mod4Mask, and Mod5Mask.

   To grab the pointer, use XGrabPointer.

   int XGrabPointer(Display *display, Window grab_window, Bool
   owner_events, unsigned int event_mask, int pointer_mode, int
   keyboard_mode, Window confine_to, Cursor cursor, Time time);

   display

   Specifies the connection to the X server.

   grab_window

   Specifies the grab window.

   owner_events

   Specifies a Boolean value that indicates whether the pointer
   events are to be reported as usual or reported with respect to
   the grab window if selected by the event mask.

   event_mask

   Specifies which pointer events are reported to the client. The
   mask is the bitwise inclusive OR of the valid pointer event
   mask bits.

   pointer_mode

   Specifies further processing of pointer events. You can pass
   GrabModeSync or GrabModeAsync.

   keyboard_mode

   Specifies further processing of keyboard events. You can pass
   GrabModeSync or GrabModeAsync.

   confine_to

   Specifies the window to confine the pointer in or None.

   cursor

   Specifies the cursor that is to be displayed during the grab or
   None.

   time

   Specifies the time. You can pass either a timestamp or
   CurrentTime.

   The XGrabPointer function actively grabs control of the pointer
   and returns GrabSuccess if the grab was successful. Further
   pointer events are reported only to the grabbing client.
   XGrabPointer overrides any active pointer grab by this client.
   If owner_events is False, all generated pointer events are
   reported with respect to grab_window and are reported only if
   selected by event_mask. If owner_events is True and if a
   generated pointer event would normally be reported to this
   client, it is reported as usual. Otherwise, the event is
   reported with respect to the grab_window and is reported only
   if selected by event_mask. For either value of owner_events,
   unreported events are discarded.

   If the pointer_mode is GrabModeAsync, pointer event processing
   continues as usual. If the pointer is currently frozen by this
   client, the processing of events for the pointer is resumed. If
   the pointer_mode is GrabModeSync, the state of the pointer, as
   seen by client applications, appears to freeze, and the X
   server generates no further pointer events until the grabbing
   client calls XAllowEvents or until the pointer grab is
   released. Actual pointer changes are not lost while the pointer
   is frozen; they are simply queued in the server for later
   processing.

   If the keyboard_mode is GrabModeAsync, keyboard event
   processing is unaffected by activation of the grab. If the
   keyboard_mode is GrabModeSync, the state of the keyboard, as
   seen by client applications, appears to freeze, and the X
   server generates no further keyboard events until the grabbing
   client calls XAllowEvents or until the pointer grab is
   released. Actual keyboard changes are not lost while the
   pointer is frozen; they are simply queued in the server for
   later processing.

   If a cursor is specified, it is displayed regardless of what
   window the pointer is in. If None is specified, the normal
   cursor for that window is displayed when the pointer is in
   grab_window or one of its subwindows; otherwise, the cursor for
   grab_window is displayed.

   If a confine_to window is specified, the pointer is restricted
   to stay contained in that window. The confine_to window need
   have no relationship to the grab_window. If the pointer is not
   initially in the confine_to window, it is warped automatically
   to the closest edge just before the grab activates and
   enter/leave events are generated as usual. If the confine_to
   window is subsequently reconfigured, the pointer is warped
   automatically, as necessary, to keep it contained in the
   window.

   The time argument allows you to avoid certain circumstances
   that come up if applications take a long time to respond or if
   there are long network delays. Consider a situation where you
   have two applications, both of which normally grab the pointer
   when clicked on. If both applications specify the timestamp
   from the event, the second application may wake up faster and
   successfully grab the pointer before the first application. The
   first application then will get an indication that the other
   application grabbed the pointer before its request was
   processed.

   XGrabPointer generates EnterNotify and LeaveNotify events.

   Either if grab_window or confine_to window is not viewable or
   if the confine_to window lies completely outside the boundaries
   of the root window, XGrabPointer fails and returns
   GrabNotViewable. If the pointer is actively grabbed by some
   other client, it fails and returns AlreadyGrabbed. If the
   pointer is frozen by an active grab of another client, it fails
   and returns GrabFrozen. If the specified time is earlier than
   the last-pointer-grab time or later than the current X server
   time, it fails and returns GrabInvalidTime. Otherwise, the
   last-pointer-grab time is set to the specified time
   (CurrentTime is replaced by the current X server time).

   XGrabPointer can generate BadCursor, BadValue, and BadWindow
   errors.

   To ungrab the pointer, use XUngrabPointer.

   XUngrabPointer(Display *display, Time time);

   display

   Specifies the connection to the X server.

   time

   Specifies the time. You can pass either a timestamp or
   CurrentTime.

   The XUngrabPointer function releases the pointer and any queued
   events if this client has actively grabbed the pointer from
   XGrabPointer, XGrabButton, or from a normal button press.
   XUngrabPointer does not release the pointer if the specified
   time is earlier than the last-pointer-grab time or is later
   than the current X server time. It also generates EnterNotify
   and LeaveNotify events. The X server performs an UngrabPointer
   request automatically if the event window or confine_to window
   for an active pointer grab becomes not viewable or if window
   reconfiguration causes the confine_to window to lie completely
   outside the boundaries of the root window.

   To change an active pointer grab, use XChangeActivePointerGrab.

   XChangeActivePointerGrab(Display *display, unsigned int
   event_mask, Cursor cursor, Time time);

   display

   Specifies the connection to the X server.

   event_mask

   Specifies which pointer events are reported to the client. The
   mask is the bitwise inclusive OR of the valid pointer event
   mask bits.

   cursor

   Specifies the cursor that is to be displayed or None.

   time

   Specifies the time. You can pass either a timestamp or
   CurrentTime.

   The XChangeActivePointerGrab function changes the specified
   dynamic parameters if the pointer is actively grabbed by the
   client and if the specified time is no earlier than the
   last-pointer-grab time and no later than the current X server
   time. This function has no effect on the passive parameters of
   an XGrabButton. The interpretation of event_mask and cursor is
   the same as described in XGrabPointer.

   XChangeActivePointerGrab can generate BadCursor and BadValue
   errors.

   To grab a pointer button, use XGrabButton.

   XGrabButton(Display *display, unsigned int button, unsigned int
   modifiers, Window grab_window, Bool owner_events, unsigned int
   event_mask, int pointer_mode, int keyboard_mode, Window
   confine_to, Cursor cursor);

   display

   Specifies the connection to the X server.

   button

   Specifies the pointer button that is to be grabbed or
   AnyButton.

   modifiers

   Specifies the set of keymasks or AnyModifier. The mask is the
   bitwise inclusive OR of the valid keymask bits.

   grab_window

   Specifies the grab window.

   owner_events

   Specifies a Boolean value that indicates whether the pointer
   events are to be reported as usual or reported with respect to
   the grab window if selected by the event mask.

   event_mask

   Specifies which pointer events are reported to the client. The
   mask is the bitwise inclusive OR of the valid pointer event
   mask bits.

   pointer_mode

   Specifies further processing of pointer events. You can pass
   GrabModeSync or GrabModeAsync.

   keyboard_mode

   Specifies further processing of keyboard events. You can pass
   GrabModeSync or GrabModeAsync.

   confine_to

   Specifies the window to confine the pointer in or None.

   cursor

   Specifies the cursor that is to be displayed or None.

   The XGrabButton function establishes a passive grab. In the
   future, the pointer is actively grabbed (as for XGrabPointer),
   the last-pointer-grab time is set to the time at which the
   button was pressed (as transmitted in the ButtonPress event),
   and the ButtonPress event is reported if all of the following
   conditions are true:
     * The pointer is not grabbed, and the specified button is
       logically pressed when the specified modifier keys are
       logically down, and no other buttons or modifier keys are
       logically down.
     * The grab_window contains the pointer.
     * The confine_to window (if any) is viewable.
     * A passive grab on the same button/key combination does not
       exist on any ancestor of grab_window.

   The interpretation of the remaining arguments is as for
   XGrabPointer. The active grab is terminated automatically when
   the logical state of the pointer has all buttons released
   (independent of the state of the logical modifier keys).

   Note that the logical state of a device (as seen by client
   applications) may lag the physical state if device event
   processing is frozen.

   This request overrides all previous grabs by the same client on
   the same button/key combinations on the same window. A
   modifiers of AnyModifier is equivalent to issuing the grab
   request for all possible modifier combinations (including the
   combination of no modifiers). It is not required that all
   modifiers specified have currently assigned KeyCodes. A button
   of AnyButton is equivalent to issuing the request for all
   possible buttons. Otherwise, it is not required that the
   specified button currently be assigned to a physical button.

   If some other client has already issued an XGrabButton with the
   same button/key combination on the same window, a BadAccess
   error results. When using AnyModifier or AnyButton, the request
   fails completely, and a BadAccess error results (no grabs are
   established) if there is a conflicting grab for any
   combination. XGrabButton has no effect on an active grab.

   XGrabButton can generate BadCursor, BadValue, and BadWindow
   errors.

   To ungrab a pointer button, use XUngrabButton.

   XUngrabButton(Display *display, unsigned int button, unsigned
   int modifiers, Window grab_window);

   display

   Specifies the connection to the X server.

   button

   Specifies the pointer button that is to be released or
   AnyButton.

   modifiers

   Specifies the set of keymasks or AnyModifier. The mask is the
   bitwise inclusive OR of the valid keymask bits.

   grab_window

   Specifies the grab window.

   The XUngrabButton function releases the passive button/key
   combination on the specified window if it was grabbed by this
   client. A modifiers of AnyModifier is equivalent to issuing the
   ungrab request for all possible modifier combinations,
   including the combination of no modifiers. A button of
   AnyButton is equivalent to issuing the request for all possible
   buttons. XUngrabButton has no effect on an active grab.

   XUngrabButton can generate BadValue and BadWindow errors.

Keyboard Grabbing

   Xlib provides functions that you can use to grab or ungrab the
   keyboard as well as allow events.

   For many functions in this section, you pass keymask bits. The
   valid keymask bits are: ShiftMask, LockMask, ControlMask,
   Mod1Mask, Mod2Mask, Mod3Mask, Mod4Mask, and Mod5Mask.

   To grab the keyboard, use XGrabKeyboard.

   int XGrabKeyboard(Display *display, Window grab_window, Bool
   owner_events, int pointer_mode, int keyboard_mode, Time time);

   display

   Specifies the connection to the X server.

   grab_window

   Specifies the grab window.

   owner_events

   Specifies a Boolean value that indicates whether the keyboard
   events are to be reported as usual.

   pointer_mode

   Specifies further processing of pointer events. You can pass
   GrabModeSync or GrabModeAsync.

   keyboard_mode

   Specifies further processing of keyboard events. You can pass
   GrabModeSync or GrabModeAsync.

   time

   Specifies the time. You can pass either a timestamp or
   CurrentTime.

   The XGrabKeyboard function actively grabs control of the
   keyboard and generates FocusIn and FocusOut events. Further key
   events are reported only to the grabbing client. XGrabKeyboard
   overrides any active keyboard grab by this client. If
   owner_events is False, all generated key events are reported
   with respect to grab_window. If owner_events is True and if a
   generated key event would normally be reported to this client,
   it is reported normally; otherwise, the event is reported with
   respect to the grab_window. Both KeyPress and KeyRelease events
   are always reported, independent of any event selection made by
   the client.

   If the keyboard_mode argument is GrabModeAsync, keyboard event
   processing continues as usual. If the keyboard is currently
   frozen by this client, then processing of keyboard events is
   resumed. If the keyboard_mode argument is GrabModeSync, the
   state of the keyboard (as seen by client applications) appears
   to freeze, and the X server generates no further keyboard
   events until the grabbing client issues a releasing
   XAllowEvents call or until the keyboard grab is released.
   Actual keyboard changes are not lost while the keyboard is
   frozen; they are simply queued in the server for later
   processing.

   If pointer_mode is GrabModeAsync, pointer event processing is
   unaffected by activation of the grab. If pointer_mode is
   GrabModeSync, the state of the pointer (as seen by client
   applications) appears to freeze, and the X server generates no
   further pointer events until the grabbing client issues a
   releasing XAllowEvents call or until the keyboard grab is
   released. Actual pointer changes are not lost while the pointer
   is frozen; they are simply queued in the server for later
   processing.

   If the keyboard is actively grabbed by some other client,
   XGrabKeyboard fails and returns AlreadyGrabbed. If grab_window
   is not viewable, it fails and returns GrabNotViewable. If the
   keyboard is frozen by an active grab of another client, it
   fails and returns GrabFrozen. If the specified time is earlier
   than the last-keyboard-grab time or later than the current X
   server time, it fails and returns GrabInvalidTime. Otherwise,
   the last-keyboard-grab time is set to the specified time
   (CurrentTime is replaced by the current X server time).

   XGrabKeyboard can generate BadValue and BadWindow errors.

   To ungrab the keyboard, use XUngrabKeyboard.

   XUngrabKeyboard(Display *display, Time time);

   display

   Specifies the connection to the X server.

   time

   Specifies the time. You can pass either a timestamp or
   CurrentTime.

   The XUngrabKeyboard function releases the keyboard and any
   queued events if this client has it actively grabbed from
   either XGrabKeyboard or XGrabKey. XUngrabKeyboard does not
   release the keyboard and any queued events if the specified
   time is earlier than the last-keyboard-grab time or is later
   than the current X server time. It also generates FocusIn and
   FocusOut events. The X server automatically performs an
   UngrabKeyboard request if the event window for an active
   keyboard grab becomes not viewable.

   To passively grab a single key of the keyboard, use XGrabKey.

   XGrabKey(Display *display, int keycode, unsigned int modifiers,
   Window grab_window, Bool owner_events, int pointer_mode, int
   keyboard_mode);

   display

   Specifies the connection to the X server.

   keycode

   Specifies the KeyCode or AnyKey.

   modifiers

   Specifies the set of keymasks or AnyModifier. The mask is the
   bitwise inclusive OR of the valid keymask bits.

   grab_window

   Specifies the grab window.

   owner_events

   Specifies a Boolean value that indicates whether the keyboard
   events are to be reported as usual.

   pointer_mode

   Specifies further processing of pointer events. You can pass
   GrabModeSync or GrabModeAsync.

   keyboard_mode

   Specifies further processing of keyboard events. You can pass
   GrabModeSync or GrabModeAsync.

   The XGrabKey function establishes a passive grab on the
   keyboard. In the future, the keyboard is actively grabbed (as
   for XGrabKeyboard), the last-keyboard-grab time is set to the
   time at which the key was pressed (as transmitted in the
   KeyPress event), and the KeyPress event is reported if all of
   the following conditions are true:
     * The keyboard is not grabbed and the specified key (which
       can itself be a modifier key) is logically pressed when the
       specified modifier keys are logically down, and no other
       modifier keys are logically down.
     * Either the grab_window is an ancestor of (or is) the focus
       window, or the grab_window is a descendant of the focus
       window and contains the pointer.
     * A passive grab on the same key combination does not exist
       on any ancestor of grab_window.

   The interpretation of the remaining arguments is as for
   XGrabKeyboard. The active grab is terminated automatically when
   the logical state of the keyboard has the specified key
   released (independent of the logical state of the modifier
   keys).

   Note that the logical state of a device (as seen by client
   applications) may lag the physical state if device event
   processing is frozen.

   A modifiers argument of AnyModifier is equivalent to issuing
   the request for all possible modifier combinations (including
   the combination of no modifiers). It is not required that all
   modifiers specified have currently assigned KeyCodes. A keycode
   argument of AnyKey is equivalent to issuing the request for all
   possible KeyCodes. Otherwise, the specified keycode must be in
   the range specified by min_keycode and max_keycode in the
   connection setup, or a BadValue error results.

   If some other client has issued a XGrabKey with the same key
   combination on the same window, a BadAccess error results. When
   using AnyModifier or AnyKey, the request fails completely, and
   a BadAccess error results (no grabs are established) if there
   is a conflicting grab for any combination.

   XGrabKey can generate BadAccess, BadValue, and BadWindow
   errors.

   To ungrab a key, use XUngrabKey.

   XUngrabKey(Display *display, int keycode, unsigned int
   modifiers, Window grab_window);

   display

   Specifies the connection to the X server.

   keycode

   Specifies the KeyCode or AnyKey.

   modifiers

   Specifies the set of keymasks or AnyModifier. The mask is the
   bitwise inclusive OR of the valid keymask bits.

   grab_window

   Specifies the grab window.

   The XUngrabKey function releases the key combination on the
   specified window if it was grabbed by this client. It has no
   effect on an active grab. A modifiers of AnyModifier is
   equivalent to issuing the request for all possible modifier
   combinations (including the combination of no modifiers). A
   keycode argument of AnyKey is equivalent to issuing the request
   for all possible key codes.

   XUngrabKey can generate BadValue and BadWindow errors.

Resuming Event Processing

   The previous sections discussed grab mechanisms with which
   processing of events by the server can be temporarily
   suspended. This section describes the mechanism for resuming
   event processing.

   To allow further events to be processed when the device has
   been frozen, use XAllowEvents.

   XAllowEvents(Display *display, int event_mode, Time time);

   display

   Specifies the connection to the X server.

   event_mode

   Specifies the event mode. You can pass AsyncPointer,
   SyncPointer, AsyncKeyboard, SyncKeyboard, ReplayPointer,
   ReplayKeyboard, AsyncBoth, or SyncBoth.

   time

   Specifies the time. You can pass either a timestamp or
   CurrentTime.

   The XAllowEvents function releases some queued events if the
   client has caused a device to freeze. It has no effect if the
   specified time is earlier than the last-grab time of the most
   recent active grab for the client or if the specified time is
   later than the current X server time. Depending on the
   event_mode argument, the following occurs:
   AsyncPointer If the pointer is frozen by the client, pointer
   event processing continues as usual. If the pointer is frozen
   twice by the client on behalf of two separate grabs,
   AsyncPointer thaws for both. AsyncPointer has no effect if the
   pointer is not frozen by the client, but the pointer need not
   be grabbed by the client.
   SyncPointer If the pointer is frozen and actively grabbed by
   the client, pointer event processing continues as usual until
   the next ButtonPress or ButtonRelease event is reported to the
   client. At this time, the pointer again appears to freeze.
   However, if the reported event causes the pointer grab to be
   released, the pointer does not freeze. SyncPointer has no
   effect if the pointer is not frozen by the client or if the
   pointer is not grabbed by the client.
   ReplayPointer If the pointer is actively grabbed by the client
   and is frozen as the result of an event having been sent to the
   client (either from the activation of an XGrabButton or from a
   previous XAllowEvents with mode SyncPointer but not from an
   XGrabPointer), the pointer grab is released and that event is
   completely reprocessed. This time, however, the function
   ignores any passive grabs at or above (toward the root of) the
   grab_window of the grab just released. The request has no
   effect if the pointer is not grabbed by the client or if the
   pointer is not frozen as the result of an event.
   AsyncKeyboard If the keyboard is frozen by the client, keyboard
   event processing continues as usual. If the keyboard is frozen
   twice by the client on behalf of two separate grabs,
   AsyncKeyboard thaws for both. AsyncKeyboard has no effect if
   the keyboard is not frozen by the client, but the keyboard need
   not be grabbed by the client.
   SyncKeyboard If the keyboard is frozen and actively grabbed by
   the client, keyboard event processing continues as usual until
   the next KeyPress or KeyRelease event is reported to the
   client. At this time, the keyboard again appears to freeze.
   However, if the reported event causes the keyboard grab to be
   released, the keyboard does not freeze. SyncKeyboard has no
   effect if the keyboard is not frozen by the client or if the
   keyboard is not grabbed by the client.
   ReplayKeyboard If the keyboard is actively grabbed by the
   client and is frozen as the result of an event having been sent
   to the client (either from the activation of an XGrabKey or
   from a previous XAllowEvents with mode SyncKeyboard but not
   from an XGrabKeyboard), the keyboard grab is released and that
   event is completely reprocessed. This time, however, the
   function ignores any passive grabs at or above (toward the root
   of) the grab_window of the grab just released. The request has
   no effect if the keyboard is not grabbed by the client or if
   the keyboard is not frozen as the result of an event.
   SyncBoth If both pointer and keyboard are frozen by the client,
   event processing for both devices continues as usual until the
   next ButtonPress, ButtonRelease, KeyPress, or KeyRelease event
   is reported to the client for a grabbed device (button event
   for the pointer, key event for the keyboard), at which time the
   devices again appear to freeze. However, if the reported event
   causes the grab to be released, then the devices do not freeze
   (but if the other device is still grabbed, then a subsequent
   event for it will still cause both devices to freeze). SyncBoth
   has no effect unless both pointer and keyboard are frozen by
   the client. If the pointer or keyboard is frozen twice by the
   client on behalf of two separate grabs, SyncBoth thaws for both
   (but a subsequent freeze for SyncBoth will only freeze each
   device once).
   AsyncBoth If the pointer and the keyboard are frozen by the
   client, event processing for both devices continues as usual.
   If a device is frozen twice by the client on behalf of two
   separate grabs, AsyncBoth thaws for both. AsyncBoth has no
   effect unless both pointer and keyboard are frozen by the
   client.

   AsyncPointer, SyncPointer, and ReplayPointer have no effect on
   the processing of keyboard events. AsyncKeyboard, SyncKeyboard,
   and ReplayKeyboard have no effect on the processing of pointer
   events. It is possible for both a pointer grab and a keyboard
   grab (by the same or different clients) to be active
   simultaneously. If a device is frozen on behalf of either grab,
   no event processing is performed for the device. It is possible
   for a single device to be frozen because of both grabs. In this
   case, the freeze must be released on behalf of both grabs
   before events can again be processed. If a device is frozen
   twice by a single client, then a single XAllowEvents releases
   both.

   XAllowEvents can generate a BadValue error.

Moving the Pointer

   Although movement of the pointer normally should be left to the
   control of the end user, sometimes it is necessary to move the
   pointer to a new position under program control.

   To move the pointer to an arbitrary point in a window, use
   XWarpPointer.

   XWarpPointer(Display *display, Window src_w, Window dest_w, int
   src_x, int src_y, unsigned int src_width, unsigned int
   src_height, int dest_x, int dest_y);

   display

   Specifies the connection to the X server.

   src_w

   Specifies the source window or None.

   dest_w

   Specifies the destination window or None.

   src_x

   src_y

   src_width

   src_height

   Specify a rectangle in the source window.

   dest_x

   dest_y

   Specify the x and y coordinates within the destination window.

   If dest_w is None, XWarpPointer moves the pointer by the
   offsets (dest_x, dest_y) relative to the current position of
   the pointer. If dest_w is a window, XWarpPointer moves the
   pointer to the offsets (dest_x, dest_y) relative to the origin
   of dest_w. However, if src_w is a window, the move only takes
   place if the window src_w contains the pointer and if the
   specified rectangle of src_w contains the pointer.

   The src_x and src_y coordinates are relative to the origin of
   src_w. If src_height is zero, it is replaced with the current
   height of src_w minus src_y. If src_width is zero, it is
   replaced with the current width of src_w minus src_x.

   There is seldom any reason for calling this function. The
   pointer should normally be left to the user. If you do use this
   function, however, it generates events just as if the user had
   instantaneously moved the pointer from one position to another.
   Note that you cannot use XWarpPointer to move the pointer
   outside the confine_to window of an active pointer grab. An
   attempt to do so will only move the pointer as far as the
   closest edge of the confine_to window.

   XWarpPointer can generate a BadWindow error.

Controlling Input Focus

   Xlib provides functions that you can use to set and get the
   input focus. The input focus is a shared resource, and
   cooperation among clients is required for correct interaction.
   See the Inter-Client Communication Conventions Manual for input
   focus policy.

   To set the input focus, use XSetInputFocus.

   XSetInputFocus(Display *display, Window focus, int revert_to,
   Time time);

   display

   Specifies the connection to the X server.

   focus

   Specifies the window, PointerRoot, or None.

   revert_to

   Specifies where the input focus reverts to if the window
   becomes not viewable. You can pass RevertToParent,
   RevertToPointerRoot, or RevertToNone.

   time

   Specifies the time. You can pass either a timestamp or
   CurrentTime.

   The XSetInputFocus function changes the input focus and the
   last-focus-change time. It has no effect if the specified time
   is earlier than the current last-focus-change time or is later
   than the current X server time. Otherwise, the
   last-focus-change time is set to the specified time
   (CurrentTime is replaced by the current X server time).
   XSetInputFocus causes the X server to generate FocusIn and
   FocusOut events.

   Depending on the focus argument, the following occurs:
     * If focus is None, all keyboard events are discarded until a
       new focus window is set, and the revert_to argument is
       ignored.
     * If focus is a window, it becomes the keyboard's focus
       window. If a generated keyboard event would normally be
       reported to this window or one of its inferiors, the event
       is reported as usual. Otherwise, the event is reported
       relative to the focus window.
     * If focus is PointerRoot, the focus window is dynamically
       taken to be the root window of whatever screen the pointer
       is on at each keyboard event. In this case, the revert_to
       argument is ignored.

   The specified focus window must be viewable at the time
   XSetInputFocus is called, or a BadMatch error results. If the
   focus window later becomes not viewable, the X server evaluates
   the revert_to argument to determine the new focus window as
   follows:
     * If revert_to is RevertToParent, the focus reverts to the
       parent (or the closest viewable ancestor), and the new
       revert_to value is taken to be RevertToNone.
     * If revert_to is RevertToPointerRoot or RevertToNone, the
       focus reverts to PointerRoot or None, respectively. When
       the focus reverts, the X server generates FocusIn and
       FocusOut events, but the last-focus-change time is not
       affected.

   XSetInputFocus can generate BadMatch, BadValue, and BadWindow
   errors.

   To obtain the current input focus, use XGetInputFocus.

   XGetInputFocus(Display *display, Window *focus_return, int
   *revert_to_return);

   display

   Specifies the connection to the X server.

   focus_return

   Returns the focus window, PointerRoot, or None.

   revert_to_return

   Returns the current focus state (RevertToParent,
   RevertToPointerRoot, or RevertToNone).

   The XGetInputFocus function returns the focus window and the
   current focus state.

Manipulating the Keyboard and Pointer Settings

   Xlib provides functions that you can use to change the keyboard
   control, obtain a list of the auto-repeat keys, turn keyboard
   auto-repeat on or off, ring the bell, set or obtain the pointer
   button or keyboard mapping, and obtain a bit vector for the
   keyboard.

   This section discusses the user-preference options of bell, key
   click, pointer behavior, and so on. The default values for many
   of these options are server dependent. Not all implementations
   will actually be able to control all of these parameters.

   The XChangeKeyboardControl function changes control of a
   keyboard and operates on a XKeyboardControl structure:
/* Mask bits for ChangeKeyboardControl */


#define     KBBellPercent           (1L<<0)
#define     KBBellPitch             (1L<<1)
#define     KBBellDuration          (1L<<2)
#define     KBLed                   (1L<<3)
#define     KBLedMode               (1L<<4)
#define     KBKey                   (1L<<5)
#define     KBAutoRepeatMode        (1L<<6)


/* Values */

typedef struct {
int key_click_percent;
int bell_percent;
int bell_pitch;
int bell_duration;
int led;
int led_mode;                /* LedModeOn, LedModeOff */
int key;
int auto_repeat_mode;        /* AutoRepeatModeOff, AutoRepeatModeOn,
                                AutoRepeatModeDefault */
} XKeyboardControl;


   The key_click_percent member sets the volume for key clicks
   between 0 (off) and 100 (loud) inclusive, if possible. A
   setting of -1 restores the default. Other negative values
   generate a BadValue error.

   The bell_percent sets the base volume for the bell between 0
   (off) and 100 (loud) inclusive, if possible. A setting of -1
   restores the default. Other negative values generate a BadValue
   error. The bell_pitch member sets the pitch (specified in Hz)
   of the bell, if possible. A setting of -1 restores the default.
   Other negative values generate a BadValue error. The
   bell_duration member sets the duration of the bell specified in
   milliseconds, if possible. A setting of -1 restores the
   default. Other negative values generate a BadValue error.

   If both the led_mode and led members are specified, the state
   of that LED is changed, if possible. The led_mode member can be
   set to LedModeOn or LedModeOff. If only led_mode is specified,
   the state of all LEDs are changed, if possible. At most 32 LEDs
   numbered from one are supported. No standard interpretation of
   LEDs is defined. If led is specified without led_mode, a
   BadMatch error results.

   If both the auto_repeat_mode and key members are specified, the
   auto_repeat_mode of that key is changed (according to
   AutoRepeatModeOn, AutoRepeatModeOff, or AutoRepeatModeDefault),
   if possible. If only auto_repeat_mode is specified, the global
   auto_repeat_mode for the entire keyboard is changed, if
   possible, and does not affect the per-key settings. If a key is
   specified without an auto_repeat_mode, a BadMatch error
   results. Each key has an individual mode of whether or not it
   should auto-repeat and a default setting for the mode. In
   addition, there is a global mode of whether auto-repeat should
   be enabled or not and a default setting for that mode. When
   global mode is AutoRepeatModeOn, keys should obey their
   individual auto-repeat modes. When global mode is
   AutoRepeatModeOff, no keys should auto-repeat. An
   auto-repeating key generates alternating KeyPress and
   KeyRelease events. When a key is used as a modifier, it is
   desirable for the key not to auto-repeat, regardless of its
   auto-repeat setting.

   A bell generator connected with the console but not directly on
   a keyboard is treated as if it were part of the keyboard. The
   order in which controls are verified and altered is
   server-dependent. If an error is generated, a subset of the
   controls may have been altered.

   XChangeKeyboardControl(Display *display, unsigned long
   value_mask, XKeyboardControl *values);

   display

   Specifies the connection to the X server.

   value_mask

   Specifies which controls to change. This mask is the bitwise
   inclusive OR of the valid control mask bits.

   values

   Specifies one value for each bit set to 1 in the mask.

   The XChangeKeyboardControl function controls the keyboard
   characteristics defined by the XKeyboardControl structure. The
   value_mask argument specifies which values are to be changed.

   XChangeKeyboardControl can generate BadMatch and BadValue
   errors.

   To obtain the current control values for the keyboard, use
   XGetKeyboardControl.

   XGetKeyboardControl(Display *display, XKeyboardState
   *values_return);

   display

   Specifies the connection to the X server.

   values_return

   Returns the current keyboard controls in the specified
   XKeyboardState structure.

   The XGetKeyboardControl function returns the current control
   values for the keyboard to the XKeyboardState structure.



typedef struct {
        int key_click_percent;
        int bell_percent;
        unsigned int bell_pitch, bell_duration;
        unsigned long led_mask;
        int global_auto_repeat;
        char auto_repeats[32];
} XKeyboardState;

   For the LEDs, the least significant bit of led_mask corresponds
   to LED one, and each bit set to 1 in led_mask indicates an LED
   that is lit. The global_auto_repeat member can be set to
   AutoRepeatModeOn or AutoRepeatModeOff. The auto_repeats member
   is a bit vector. Each bit set to 1 indicates that auto-repeat
   is enabled for the corresponding key. The vector is represented
   as 32 bytes. Byte N (from 0) contains the bits for keys 8N to
   8N + 7 with the least significant bit in the byte representing
   key 8N.

   To turn on keyboard auto-repeat, use XAutoRepeatOn.

   XAutoRepeatOn(Display *display);

   display

   Specifies the connection to the X server.

   The XAutoRepeatOn function turns on auto-repeat for the
   keyboard on the specified display.

   To turn off keyboard auto-repeat, use XAutoRepeatOff.

   XAutoRepeatOff(Display *display);

   display

   Specifies the connection to the X server.

   The XAutoRepeatOff function turns off auto-repeat for the
   keyboard on the specified display.

   To ring the bell, use XBell.

   XBell(Display *display, int percent);

   display

   Specifies the connection to the X server.

   percent

   Specifies the volume for the bell, which can range from -100 to
   100 inclusive.

   The XBell function rings the bell on the keyboard on the
   specified display, if possible. The specified volume is
   relative to the base volume for the keyboard. If the value for
   the percent argument is not in the range -100 to 100 inclusive,
   a BadValue error results. The volume at which the bell rings
   when the percent argument is nonnegative is:
     * base - [(base * percent) / 100] + percent

   The volume at which the bell rings when the percent argument is
   negative is:
     * base + [(base * percent) / 100]

   To change the base volume of the bell, use
   XChangeKeyboardControl.

   XBell can generate a BadValue error.

   To obtain a bit vector that describes the state of the
   keyboard, use XQueryKeymap.

   XQueryKeymap(Display *display, char keys_return[32]);

   display

   Specifies the connection to the X server.

   keys_return

   Returns an array of bytes that identifies which keys are
   pressed down. Each bit represents one key of the keyboard.

   The XQueryKeymap function returns a bit vector for the logical
   state of the keyboard, where each bit set to 1 indicates that
   the corresponding key is currently pressed down. The vector is
   represented as 32 bytes. Byte N (from 0) contains the bits for
   keys 8N to 8N + 7 with the least significant bit in the byte
   representing key 8N.

   Note that the logical state of a device (as seen by client
   applications) may lag the physical state if device event
   processing is frozen.

   To set the mapping of the pointer buttons, use
   XSetPointerMapping.

   int XSetPointerMapping(Display *display, unsignedchar map[],
   int nmap);

   display

   Specifies the connection to the X server.

   map

   Specifies the mapping list.

   nmap

   Specifies the number of items in the mapping list.

   The XSetPointerMapping function sets the mapping of the
   pointer. If it succeeds, the X server generates a MappingNotify
   event, and XSetPointerMapping returns MappingSuccess. Element
   map[i] defines the logical button number for the physical
   button i+1. The length of the list must be the same as
   XGetPointerMapping would return, or a BadValue error results. A
   zero element disables a button, and elements are not restricted
   in value by the number of physical buttons. However, no two
   elements can have the same nonzero value, or a BadValue error
   results. If any of the buttons to be altered are logically in
   the down state, XSetPointerMapping returns MappingBusy, and the
   mapping is not changed.

   XSetPointerMapping can generate a BadValue error.

   To get the pointer mapping, use XGetPointerMapping.

   int XGetPointerMapping(Display *display, unsignedchar
   map_return[], int nmap);

   display

   Specifies the connection to the X server.

   map_return

   Returns the mapping list.

   nmap

   Specifies the number of items in the mapping list.

   The XGetPointerMapping function returns the current mapping of
   the pointer. Pointer buttons are numbered starting from one.
   XGetPointerMapping returns the number of physical buttons
   actually on the pointer. The nominal mapping for a pointer is
   map[i]=i+1. The nmap argument specifies the length of the array
   where the pointer mapping is returned, and only the first nmap
   elements are returned in map_return.

   To control the pointer's interactive feel, use
   XChangePointerControl.

   XChangePointerControl(Display *display, Bool do_accel, Bool
   do_threshold, int accel_numerator, int accel_denominator, int
   threshold);

   display

   Specifies the connection to the X server.

   do_accel

   Specifies a Boolean value that controls whether the values for
   the accel_numerator or accel_denominator are used.

   do_threshold

   Specifies a Boolean value that controls whether the value for
   the threshold is used.

   accel_numerator

   Specifies the numerator for the acceleration multiplier.

   accel_denominator

   Specifies the denominator for the acceleration multiplier.

   threshold

   Specifies the acceleration threshold.

   The XChangePointerControl function defines how the pointing
   device moves. The acceleration, expressed as a fraction, is a
   multiplier for movement. For example, specifying 3/1 means the
   pointer moves three times as fast as normal. The fraction may
   be rounded arbitrarily by the X server. Acceleration only takes
   effect if the pointer moves more than threshold pixels at once
   and only applies to the amount beyond the value in the
   threshold argument. Setting a value to -1 restores the default.
   The values of the do_accel and do_threshold arguments must be
   True for the pointer values to be set, or the parameters are
   unchanged. Negative values (other than -1) generate a BadValue
   error, as does a zero value for the accel_denominator argument.

   XChangePointerControl can generate a BadValue error.

   To get the current pointer parameters, use XGetPointerControl.

   XGetPointerControl(Display *display, int
   *accel_numerator_return, int *accel_denominator_return, int
   *threshold_return);

   display

   Specifies the connection to the X server.

   accel_numerator_return

   Returns the numerator for the acceleration multiplier.

   accel_denominator_return

   Returns the denominator for the acceleration multiplier.

   threshold_return

   Returns the acceleration threshold.

   The XGetPointerControl function returns the pointer's current
   acceleration multiplier and acceleration threshold.

Manipulating the Keyboard Encoding

   A KeyCode represents a physical (or logical) key. KeyCodes lie
   in the inclusive range [8,255]. A KeyCode value carries no
   intrinsic information, although server implementors may attempt
   to encode geometry (for example, matrix) information in some
   fashion so that it can be interpreted in a server-dependent
   fashion. The mapping between keys and KeyCodes cannot be
   changed.

   A KeySym is an encoding of a symbol on the cap of a key. The
   set of defined KeySyms includes the ISO Latin character sets
   (1-4), Katakana, Arabic, Cyrillic, Greek, Technical, Special,
   Publishing, APL, Hebrew, Thai, Korean and a miscellany of keys
   found on keyboards (Return, Help, Tab, and so on). To the
   extent possible, these sets are derived from international
   standards. In areas where no standards exist, some of these
   sets are derived from Digital Equipment Corporation standards.
   The list of defined symbols can be found in <X11/keysymdef.h>.
   Unfortunately, some C preprocessors have limits on the number
   of defined symbols. If you must use KeySyms not in the Latin
   1-4, Greek, and miscellaneous classes, you may have to define a
   symbol for those sets. Most applications usually only include
   <X11/keysym.h>, which defines symbols for ISO Latin 1-4, Greek,
   and miscellaneous.

   A list of KeySyms is associated with each KeyCode. The list is
   intended to convey the set of symbols on the corresponding key.
   If the list (ignoring trailing NoSymbol entries) is a single
   KeySym ``K'', then the list is treated as if it were the list
   ``K NoSymbol K NoSymbol''. If the list (ignoring trailing
   NoSymbol entries) is a pair of KeySyms ``K1 K2'', then the list
   is treated as if it were the list ``K1 K2 K1 K2''. If the list
   (ignoring trailing NoSymbol entries) is a triple of KeySyms
   ``K1 K2 K3'', then the list is treated as if it were the list
   ``K1 K2 K3 NoSymbol''. When an explicit ``void'' element is
   desired in the list, the value VoidSymbol can be used.

   The first four elements of the list are split into two groups
   of KeySyms. Group 1 contains the first and second KeySyms;
   Group 2 contains the third and fourth KeySyms. Within each
   group, if the second element of the group is NoSymbol, then the
   group should be treated as if the second element were the same
   as the first element, except when the first element is an
   alphabetic KeySym ``K'' for which both lowercase and uppercase
   forms are defined. In that case, the group should be treated as
   if the first element were the lowercase form of ``K'' and the
   second element were the uppercase form of ``K''.

   The standard rules for obtaining a KeySym from a KeyPress event
   make use of only the Group 1 and Group 2 KeySyms; no
   interpretation of other KeySyms in the list is given. Which
   group to use is determined by the modifier state. Switching
   between groups is controlled by the KeySym named MODE SWITCH,
   by attaching that KeySym to some KeyCode and attaching that
   KeyCode to any one of the modifiers Mod1 through Mod5. This
   modifier is called the group modifier. For any KeyCode, Group 1
   is used when the group modifier is off, and Group 2 is used
   when the group modifier is on.

   The Lock modifier is interpreted as CapsLock when the KeySym
   named XK_Caps_Lock is attached to some KeyCode and that KeyCode
   is attached to the Lock modifier. The Lock modifier is
   interpreted as ShiftLock when the KeySym named XK_Shift_Lock is
   attached to some KeyCode and that KeyCode is attached to the
   Lock modifier. If the Lock modifier could be interpreted as
   both CapsLock and ShiftLock, the CapsLock interpretation is
   used.

   The operation of keypad keys is controlled by the KeySym named
   XK_Num_Lock, by attaching that KeySym to some KeyCode and
   attaching that KeyCode to any one of the modifiers Mod1 through
   Mod5. This modifier is called the numlock modifier. The
   standard KeySyms with the prefix ``XK_KP_'' in their name are
   called keypad KeySyms; these are KeySyms with numeric value in
   the hexadecimal range 0xFF80 to 0xFFBD inclusive. In addition,
   vendor-specific KeySyms in the hexadecimal range 0x11000000 to
   0x1100FFFF are also keypad KeySyms.

   Within a group, the choice of KeySym is determined by applying
   the first rule that is satisfied from the following list:
     * The numlock modifier is on and the second KeySym is a
       keypad KeySym. In this case, if the Shift modifier is on,
       or if the Lock modifier is on and is interpreted as
       ShiftLock, then the first KeySym is used, otherwise the
       second KeySym is used.
     * The Shift and Lock modifiers are both off. In this case,
       the first KeySym is used.
     * The Shift modifier is off, and the Lock modifier is on and
       is interpreted as CapsLock. In this case, the first KeySym
       is used, but if that KeySym is lowercase alphabetic, then
       the corresponding uppercase KeySym is used instead.
     * The Shift modifier is on, and the Lock modifier is on and
       is interpreted as CapsLock. In this case, the second KeySym
       is used, but if that KeySym is lowercase alphabetic, then
       the corresponding uppercase KeySym is used instead.
     * The Shift modifier is on, or the Lock modifier is on and is
       interpreted as ShiftLock, or both. In this case, the second
       KeySym is used.

   No spatial geometry of the symbols on the key is defined by
   their order in the KeySym list, although a geometry might be
   defined on a server-specific basis. The X server does not use
   the mapping between KeyCodes and KeySyms. Rather, it merely
   stores it for reading and writing by clients.

   To obtain the legal KeyCodes for a display, use
   XDisplayKeycodes.

   XDisplayKeycodes(Display *display, int *min_keycodes_return,
   int *max_keycodes_return);

   display

   Specifies the connection to the X server.

   min_keycodes_return

   Returns the minimum number of KeyCodes.

   max_keycodes_return

   Returns the maximum number of KeyCodes.

   The XDisplayKeycodes function returns the min-keycodes and
   max-keycodes supported by the specified display. The minimum
   number of KeyCodes returned is never less than 8, and the
   maximum number of KeyCodes returned is never greater than 255.
   Not all KeyCodes in this range are required to have
   corresponding keys.

   To obtain the symbols for the specified KeyCodes, use
   XGetKeyboardMapping.

   KeySym *XGetKeyboardMapping(Display *display, KeyCode
   first_keycode, int keycode_count, int
   *keysyms_per_keycode_return);

   display

   Specifies the connection to the X server.

   first_keycode

   Specifies the first KeyCode that is to be returned.

   keycode_count

   Specifies the number of KeyCodes that are to be returned.

   keysyms_per_keycode_return

   Returns the number of KeySyms per KeyCode.

   The XGetKeyboardMapping function returns the symbols for the
   specified number of KeyCodes starting with first_keycode. The
   value specified in first_keycode must be greater than or equal
   to min_keycode as returned by XDisplayKeycodes, or a BadValue
   error results. In addition, the following expression must be
   less than or equal to max_keycode as returned by
   XDisplayKeycodes:

first_keycode + keycode_count - 1

   If this is not the case, a BadValue error results. The number
   of elements in the KeySyms list is:

keycode_count * keysyms_per_keycode_return

   KeySym number N, counting from zero, for KeyCode K has the
   following index in the list, counting from zero:
(K - first_code) * keysyms_per_code_return + N

   The X server arbitrarily chooses the keysyms_per_keycode_return
   value to be large enough to report all requested symbols. A
   special KeySym value of NoSymbol is used to fill in unused
   elements for individual KeyCodes. To free the storage returned
   by XGetKeyboardMapping, use XFree.

   XGetKeyboardMapping can generate a BadValue error.

   To change the keyboard mapping, use XChangeKeyboardMapping.

   XChangeKeyboardMapping(Display *display, int first_keycode, int
   keysyms_per_keycode, KeySym *keysyms, int num_codes);

   display

   Specifies the connection to the X server.

   first_keycode

   Specifies the first KeyCode that is to be changed.

   keysyms_per_keycode

   Specifies the number of KeySyms per KeyCode.

   keysyms

   Specifies an array of KeySyms.

   num_codes

   Specifies the number of KeyCodes that are to be changed.

   The XChangeKeyboardMapping function defines the symbols for the
   specified number of KeyCodes starting with first_keycode. The
   symbols for KeyCodes outside this range remain unchanged. The
   number of elements in keysyms must be:

num_codes * keysyms_per_keycode

   The specified first_keycode must be greater than or equal to
   min_keycode returned by XDisplayKeycodes, or a BadValue error
   results. In addition, the following expression must be less
   than or equal to max_keycode as returned by XDisplayKeycodes,
   or a BadValue error results:

first_keycode + num_codes - 1

   KeySym number N, counting from zero, for KeyCode K has the
   following index in keysyms, counting from zero:

(K - first_keycode) * keysyms_per_keycode + N

   The specified keysyms_per_keycode can be chosen arbitrarily by
   the client to be large enough to hold all desired symbols. A
   special KeySym value of NoSymbol should be used to fill in
   unused elements for individual KeyCodes. It is legal for
   NoSymbol to appear in nontrailing positions of the effective
   list for a KeyCode. XChangeKeyboardMapping generates a
   MappingNotify event.

   There is no requirement that the X server interpret this
   mapping. It is merely stored for reading and writing by
   clients.

   XChangeKeyboardMapping can generate BadAlloc and BadValue
   errors.

   The next six functions make use of the XModifierKeymap data
   structure, which contains:



typedef struct {
        int max_keypermod;      /* This server's max number of keys per
modifier */
        KeyCode *modifiermap;   /* An 8 by max_keypermod array of the mo
difiers */
} XModifierKeymap;

   To create an XModifierKeymap structure, use XNewModifiermap.

   XModifierKeymap *XNewModifiermap(int max_keys_per_mod);

   max_keys_per_mod

   Specifies the number of KeyCode entries preallocated to the
   modifiers in the map.

   The XNewModifiermap function returns a pointer to
   XModifierKeymap structure for later use.

   To add a new entry to an XModifierKeymap structure, use
   XInsertModifiermapEntry.

   XModifierKeymap *XInsertModifiermapEntry(XModifierKeymap
   *modmap, KeyCode keycode_entry, int modifier);

   modmap

   Specifies the XModifierKeymap structure.

   keycode_entry

   Specifies the KeyCode.

   modifier

   Specifies the modifier.

   The XInsertModifiermapEntry function adds the specified KeyCode
   to the set that controls the specified modifier and returns the
   resulting XModifierKeymap structure (expanded as needed).

   To delete an entry from an XModifierKeymap structure, use
   XDeleteModifiermapEntry.

   XModifierKeymap *XDeleteModifiermapEntry(XModifierKeymap
   *modmap, KeyCode keycode_entry, int modifier);

   modmap

   Specifies the XModifierKeymap structure.

   keycode_entry

   Specifies the KeyCode.

   modifier

   Specifies the modifier.

   The XDeleteModifiermapEntry function deletes the specified
   KeyCode from the set that controls the specified modifier and
   returns a pointer to the resulting XModifierKeymap structure.

   To destroy an XModifierKeymap structure, use XFreeModifiermap.

   XFreeModifiermap(XModifierKeymap *modmap);

   modmap

   Specifies the XModifierKeymap structure.

   The XFreeModifiermap function frees the specified
   XModifierKeymap structure.

   To set the KeyCodes to be used as modifiers, use
   XSetModifierMapping.

   int XSetModifierMapping(Display *display, XModifierKeymap
   *modmap);

   display

   Specifies the connection to the X server.

   modmap

   Specifies the XModifierKeymap structure.

   The XSetModifierMapping function specifies the KeyCodes of the
   keys (if any) that are to be used as modifiers. If it succeeds,
   the X server generates a MappingNotify event, and
   XSetModifierMapping returns MappingSuccess. X permits at most 8
   modifier keys. If more than 8 are specified in the
   XModifierKeymap structure, a BadLength error results.

   The modifiermap member of the XModifierKeymap structure
   contains 8 sets of max_keypermod KeyCodes, one for each
   modifier in the order Shift, Lock, Control, Mod1, Mod2, Mod3,
   Mod4, and Mod5. Only nonzero KeyCodes have meaning in each set,
   and zero KeyCodes are ignored. In addition, all of the nonzero
   KeyCodes must be in the range specified by min_keycode and
   max_keycode in the Display structure, or a BadValue error
   results.

   An X server can impose restrictions on how modifiers can be
   changed, for example, if certain keys do not generate up
   transitions in hardware, if auto-repeat cannot be disabled on
   certain keys, or if multiple modifier keys are not supported.
   If some such restriction is violated, the status reply is
   MappingFailed, and none of the modifiers are changed. If the
   new KeyCodes specified for a modifier differ from those
   currently defined and any (current or new) keys for that
   modifier are in the logically down state, XSetModifierMapping
   returns MappingBusy, and none of the modifiers is changed.

   XSetModifierMapping can generate BadAlloc and BadValue errors.

   To obtain the KeyCodes used as modifiers, use
   XGetModifierMapping.

   XModifierKeymap *XGetModifierMapping(Display *display);

   display

   Specifies the connection to the X server.

   The XGetModifierMapping function returns a pointer to a newly
   created XModifierKeymap structure that contains the keys being
   used as modifiers. The structure should be freed after use by
   calling XFreeModifiermap. If only zero values appear in the set
   for any modifier, that modifier is disabled.

Chapter 13. Locales and Internationalized Text Functions

   Table of Contents

   X Locale Management
   Locale and Modifier Dependencies
   Variable Argument Lists
   Output Methods

        Output Method Overview
        Output Method Functions
        X Output Method Values
        Output Context Functions
        Output Context Values
        Creating and Freeing a Font Set
        Obtaining Font Set Metrics
        Drawing Text Using Font Sets

   Input Methods

        Input Method Overview
        Input Method Management
        Input Method Functions
        Input Method Values
        Input Context Functions
        Input Context Values
        Input Method Callback Semantics
        Event Filtering
        Getting Keyboard Input
        Input Method Conventions

   String Constants

   An internationalized application is one that is adaptable to
   the requirements of different native languages, local customs,
   and character string encodings. The process of adapting the
   operation to a particular native language, local custom, or
   string encoding is called localization. A goal of
   internationalization is to permit localization without program
   source modifications or recompilation.

   As one of the localization mechanisms, Xlib provides an X Input
   Method (XIM) functional interface for internationalized text
   input and an X Output Method (XOM) functional interface for
   internationalized text output.

   Internationalization in X is based on the concept of a locale.
   A locale defines the localized behavior of a program at run
   time. Locales affect Xlib in its:
     * Encoding and processing of input method text
     * Encoding of resource files and values
     * Encoding and imaging of text strings
     * Encoding and decoding for inter-client text communication

   o Encoding and decoding for inter-client text communication
   Characters from various languages are represented in a computer
   using an encoding. Different languages have different
   encodings, and there are even different encodings for the same
   characters in the same language.

   This chapter defines support for localized text imaging and
   text input and describes the locale mechanism that controls all
   locale-dependent Xlib functions. Sets of functions are provided
   for multibyte (char *) text as well as wide character (wchar_t)
   text in the form supported by the host C language environment.
   The multibyte and wide character functions are equivalent
   except for the form of the text argument.

   The Xlib internationalization functions are not meant to
   provide support for multilingual applications (mixing multiple
   languages within a single piece of text), but they make it
   possible to implement applications that work in limited fashion
   with more than one language in independent contexts.

   The remainder of this chapter discusses:
     * X locale management
     * Locale and modifier dependencies
     * Variable argument lists
     * Output methods
     * Input methods
     * String constants

X Locale Management

   X supports one or more of the locales defined by the host
   environment. On implementations that conform to the ANSI C
   library, the locale announcement method is setlocale. This
   function configures the locale operation of both the host C
   library and Xlib. The operation of Xlib is governed by the
   LC_CTYPE category; this is called the current locale. An
   implementation is permitted to provide implementation-dependent
   mechanisms for announcing the locale in addition to setlocale.

   On implementations that do not conform to the ANSI C library,
   the locale announcement method is Xlib
   implementation-dependent.

   The mechanism by which the semantic operation of Xlib is
   defined for a specific locale is implementation-dependent.

   X is not required to support all the locales supported by the
   host. To determine if the current locale is supported by X, use
   XSupportsLocale.

   Bool XSupportsLocale(void);

   The XSupportsLocale function returns True if Xlib functions are
   capable of operating under the current locale. If it returns
   False, Xlib locale-dependent functions for which the
   XLocaleNotSupported return status is defined will return
   XLocaleNotSupported. Other Xlib locale-dependent routines will
   operate in the ``C'' locale.

   The client is responsible for selecting its locale and X
   modifiers. Clients should provide a means for the user to
   override the clients' locale selection at client invocation.
   Most single-display X clients operate in a single locale for
   both X and the host processing environment. They will configure
   the locale by calling three functions: the host locale
   configuration function, XSupportsLocale, and
   XSetLocaleModifiers.

   The semantics of certain categories of X internationalization
   capabilities can be configured by setting modifiers. Modifiers
   are named by implementation-dependent and locale-specific
   strings. The only standard use for this capability at present
   is selecting one of several styles of keyboard input method.

   To configure Xlib locale modifiers for the current locale, use
   XSetLocaleModifiers.

   char *XSetLocaleModifiers(char *modifier_list);

   modifier_list

   Specifies the modifiers.

   The XSetLocaleModifiers function sets the X modifiers for the
   current locale setting. The modifier_list argument is a
   null-terminated string of the form ``{@category=value}'', that
   is, having zero or more concatenated ``@category=value''
   entries, where category is a category name and value is the
   (possibly empty) setting for that category. The values are
   encoded in the current locale. Category names are restricted to
   the POSIX Portable Filename Character Set.

   The local host X locale modifiers announcer (on POSIX-compliant
   systems, the XMODIFIERS environment variable) is appended to
   the modifier_list to provide default values on the local host.
   If a given category appears more than once in the list, the
   first setting in the list is used. If a given category is not
   included in the full modifier list, the category is set to an
   implementation-dependent default for the current locale. An
   empty value for a category explicitly specifies the
   implementation-dependent default.

   If the function is successful, it returns a pointer to a
   string. The contents of the string are such that a subsequent
   call with that string (in the same locale) will restore the
   modifiers to the same settings. If modifier_list is a NULL
   pointer, XSetLocaleModifiers also returns a pointer to such a
   string, and the current locale modifiers are not changed.

   If invalid values are given for one or more modifier categories
   supported by the locale, a NULL pointer is returned, and none
   of the current modifiers are changed.

   At program startup, the modifiers that are in effect are
   unspecified until the first successful call to set them.
   Whenever the locale is changed, the modifiers that are in
   effect become unspecified until the next successful call to set
   them. Clients should always call XSetLocaleModifiers with a
   non-NULL modifier_list after setting the locale before they
   call any locale-dependent Xlib routine.

   The only standard modifier category currently defined is
   ``im'', which identifies the desired input method. The values
   for input method are not standardized. A single locale may use
   multiple input methods, switching input method under user
   control. The modifier may specify the initial input method in
   effect or an ordered list of input methods. Multiple input
   methods may be specified in a single im value string in an
   implementation-dependent manner.

   The returned modifiers string is owned by Xlib and should not
   be modified or freed by the client. It may be freed by Xlib
   after the current locale or modifiers are changed. Until freed,
   it will not be modified by Xlib.

   The recommended procedure for clients initializing their locale
   and modifiers is to obtain locale and modifier announcers
   separately from one of the following prioritized sources:
     * A command line option
     * A resource
     * The empty string ("")

   The first of these that is defined should be used. Note that
   when a locale command line option or locale resource is
   defined, the effect should be to set all categories to the
   specified locale, overriding any category-specific settings in
   the local host environment.

Locale and Modifier Dependencies

   The internationalized Xlib functions operate in the current
   locale configured by the host environment and X locale
   modifiers set by XSetLocaleModifiers or in the locale and
   modifiers configured at the time some object supplied to the
   function was created. For each locale-dependent function, the
   following table describes the locale (and modifiers)
   dependency:
   Locale from Affects the Function In
   Locale Query/Configuration:
   setlocale XSupportsLocale Locale queried
   XSetLocaleModifiers Locale modified
   Resources:
   setlocale

   XrmGetFileDatabase

   XrmGetStringDatabase
   Locale of XrmDatabase
   XrmDatabase

   XrmPutFileDatabase

   XrmLocaleOfDatabase
   Locale of XrmDatabase
   Setting Standard Properties:
   setlocale XmbSetWMProperties Encoding of supplied/returned text
   (some WM_ property text in environment locale)
   setlocale

   XmbTextPropertyToTextList

   XwcTextPropertyToTextList

   XmbTextListToTextProperty

   XwcTextListToTextProperty
   Encoding of supplied/returned text
   Text Input:
   setlocale XOpenIM XIM input method selection
   XRegisterIMInstantiateCallback XIM selection
   XUnregisterIMInstantiateCallback XIM selection
   XIM XCreateIC XIC input method configuration
   XLocaleOfIM, and so on Queried locale
   XIC XmbLookupString Keyboard layout
   XwcLookupString Encoding of returned text
   Text Drawing:
   setlocale XOpenOM XOM output method selection
   XCreateFontSet Charsets of fonts in XFontSet
   XOM XCreateOC XOC output method configuration
   XLocaleOfOM, and so on Queried locale
   XFontSet XmbDrawText, Locale of supplied text
   XwcDrawText, and so on Locale of supplied text

   XExtentsOfFontSet, and so on

   XmbTextExtents,

   XwcTextExtents, and so on
   Locale-dependent metrics
   Xlib Errors:
   setlocale

   XGetErrorDatabaseText,

   XGetErrorText, and so on
   Locale of error message

   Clients may assume that a locale-encoded text string returned
   by an X function can be passed to a C library routine, or vice
   versa, if the locale is the same at the two calls.

   All text strings processed by internationalized Xlib functions
   are assumed to begin in the initial state of the encoding of
   the locale, if the encoding is state-dependent.

   All Xlib functions behave as if they do not change the current
   locale or X modifier setting. (This means that if they do
   change locale or call XSetLocaleModifiers with a non-NULL
   argument, they must save and restore the current state on entry
   and exit.) Also, Xlib functions on implementations that conform
   to the ANSI C library do not alter the global state associated
   with the ANSI C functions mblen, mbtowc, wctomb, and strtok.

Variable Argument Lists

   Various functions in this chapter have arguments that conform
   to the ANSI C variable argument list calling convention. Each
   function denoted with an argument of the form ``...'' takes a
   variable-length list of name and value pairs, where each name
   is a string and each value is of type XPointer. A name argument
   that is NULL identifies the end of the list.

   A variable-length argument list may contain a nested list. If
   the name XNVaNestedList is specified in place of an argument
   name, then the following value is interpreted as an
   XVaNestedList value that specifies a list of values logically
   inserted into the original list at the point of declaration. A
   NULL identifies the end of a nested list.

   To allocate a nested variable argument list dynamically, use
   XVaCreateNestedList.

   XVaNestedList XVaCreateNestedList(int dummy);

   dummy

   Specifies an unused argument (required by ANSI C).

   ...

   Specifies the variable length argument list(Al.

   The XVaCreateNestedList function allocates memory and copies
   its arguments into a single list pointer, which may be used as
   a value for arguments requiring a list value. Any entries are
   copied as specified. Data passed by reference is not copied;
   the caller must ensure data remains valid for the lifetime of
   the nested list. The list should be freed using XFree when it
   is no longer needed.

Output Methods

   This section provides discussions of the following X Output
   Method (XOM) topics:
     * Output method overview
     * Output method functions
     * Output method values
     * Output context functions
     * Output context values
     * Creating and freeing a font set
     * Obtaining font set metrics
     * Drawing text using font sets

Output Method Overview

   Locale-dependent text may include one or more text components,
   each of which may require different fonts and character set
   encodings. In some languages, each component might have a
   different drawing direction, and some components might contain
   context-dependent characters that change shape based on
   relationships with neighboring characters.

   When drawing such locale-dependent text, some locale-specific
   knowledge is required; for example, what fonts are required to
   draw the text, how the text can be separated into components,
   and which fonts are selected to draw each component. Further,
   when bidirectional text must be drawn, the internal
   representation order of the text must be changed into the
   visual representation order to be drawn.

   An X Output Method provides a functional interface so that
   clients do not have to deal directly with such locale-dependent
   details. Output methods provide the following capabilities:
     * Creating a set of fonts required to draw locale-dependent
       text.
     * Drawing locale-dependent text with a font set without the
       caller needing to be aware of locale dependencies.
     * Obtaining the escapement and extents in pixels of
       locale-dependent text.
     * Determining if bidirectional or context-dependent drawing
       is required in a specific locale with a specific font set.

   Two different abstractions are used in the representation of
   the output method for clients.

   The abstraction used to communicate with an output method is an
   opaque data structure represented by the XOM data type. The
   abstraction for representing the state of a particular output
   thread is called an output context. The Xlib representation of
   an output context is an XOC, which is compatible with XFontSet
   in terms of its functional interface, but is a broader, more
   generalized abstraction.

Output Method Functions

   To open an output method, use XOpenOM.

   XOM XOpenOM(Display *display, XrmDatabase db, char *res_name,
   char *res_class);

   display

   Specifies the connection to the X server.

   db

   Specifies a pointer to the resource database.

   res_name

   Specifies the full resource name of the application.

   res_class

   Specifies the full class name of the application.

   The XOpenOM function opens an output method matching the
   current locale and modifiers specification. The current locale
   and modifiers are bound to the output method when XOpenOM is
   called. The locale associated with an output method cannot be
   changed.

   The specific output method to which this call will be routed is
   identified on the basis of the current locale and modifiers.
   XOpenOM will identify a default output method corresponding to
   the current locale. That default can be modified using
   XSetLocaleModifiers to set the output method modifier.

   The db argument is the resource database to be used by the
   output method for looking up resources that are private to the
   output method. It is not intended that this database be used to
   look up values that can be set as OC values in an output
   context. If db is NULL, no database is passed to the output
   method.

   The res_name and res_class arguments specify the resource name
   and class of the application. They are intended to be used as
   prefixes by the output method when looking up resources that
   are common to all output contexts that may be created for this
   output method. The characters used for resource names and
   classes must be in the X Portable Character Set. The resources
   looked up are not fully specified if res_name or res_class is
   NULL.

   The res_name and res_class arguments are not assumed to exist
   beyond the call to XOpenOM. The specified resource database is
   assumed to exist for the lifetime of the output method.

   XOpenOM returns NULL if no output method could be opened.

   To close an output method, use XCloseOM.

   Status XCloseOM(XOM om);

   om

   Specifies the output method.

   The XCloseOM function closes the specified output method.

   To set output method attributes, use XSetOMValues.

   char *XSetOMValues(XOM om);

   om

   Specifies the output method.

   ...

   Specifies the variable-length argument list to set XOM values.

   The XSetOMValues function presents a variable argument list
   programming interface for setting properties or features of the
   specified output method. This function returns NULL if it
   succeeds; otherwise, it returns the name of the first argument
   that could not be obtained.

   No standard arguments are currently defined by Xlib.

   To query an output method, use XGetOMValues.

   char *XGetOMValues(XOM om);

   om

   Specifies the output method.

   ...

   Specifies the variable-length argument list to get XOM values.

   The XGetOMValues function presents a variable argument list
   programming interface for querying properties or features of
   the specified output method. This function returns NULL if it
   succeeds; otherwise, it returns the name of the first argument
   that could not be obtained.

   To obtain the display associated with an output method, use
   XDisplayOfOM.

   Display *XDisplayOfOM(XOM om);

   om

   Specifies the output method.

   The XDisplayOfOM function returns the display associated with
   the specified output method.

   To get the locale associated with an output method, use
   XLocaleOfOM.

   char *XLocaleOfOM(XOM om);

   om

   Specifies the output method.

   The XLocaleOfOM returns the locale associated with the
   specified output method.

X Output Method Values

   The following table describes how XOM values are interpreted by
   an output method. The first column lists the XOM values. The
   second column indicates how each of the XOM values are treated
   by a particular output style.

   The following key applies to this table.
   Key Explanation
   G   This value may be read using XGetOMValues.

   XOM Value                     Key
   XNRequiredCharSet             G
   XNQueryOrientation            G
   XNDirectionalDependentDrawing G
   XNContextualDrawing           G

Required Char Set

   The XNRequiredCharSet argument returns the list of charsets
   that are required for loading the fonts needed for the locale.
   The value of the argument is a pointer to a structure of type
   XOMCharSetList.

   The XOMCharSetList structure is defined as follows:


typedef struct {
     int    charset_count;
     char   **charset_list;
} XOMCharSetList;

   The charset_list member is a list of one or more
   null-terminated charset names, and the charset_count member is
   the number of charset names.

   The required charset list is owned by Xlib and should not be
   modified or freed by the client. It will be freed by a call to
   XCloseOM with the associated XOM. Until freed, its contents
   will not be modified by Xlib.

Query Orientation

   The XNQueryOrientation argument returns the global orientation
   of text when drawn. Other than XOMOrientation_LTR_TTB, the set
   of orientations supported is locale-dependent. The value of the
   argument is a pointer to a structure of type XOMOrientation.
   Clients are responsible for freeing the XOMOrientation
   structure by using XFree; this also frees the contents of the
   structure.


typedef struct {
     int          num_orientation;
     XOrientation *orientation;     /* Input Text description */
} XOMOrientation;

typedef enum {
     XOMOrientation_LTR_TTB,
     XOMOrientation_RTL_TTB,
     XOMOrientation_TTB_LTR,
     XOMOrientation_TTB_RTL,
     XOMOrientation_Context
} XOrientation;

   The possible value for XOrientation may be:
     * XOMOrientation_LTR_TTB left-to-right, top-to-bottom global
       orientation
     * XOMOrientation_RTL_TTB right-to-left, top-to-bottom global
       orientation
     * XOMOrientation_TTB_LTR top-to-bottom, left-to-right global
       orientation
     * XOMOrientation_TTB_RTL top-to-bottom, right-to-left global
       orientation
     * XOMOrientation_Context contextual global orientation

Directional Dependent Drawing

   The XNDirectionalDependentDrawing argument indicates whether
   the text rendering functions implement implicit handling of
   directional text. If this value is True, the output method has
   knowledge of directional dependencies and reorders text as
   necessary when rendering text. If this value is False, the
   output method does not implement any directional text handling,
   and all character directions are assumed to be left-to-right.

   Regardless of the rendering order of characters, the origins of
   all characters are on the primary draw direction side of the
   drawing origin.

   This OM value presents functionality identical to the
   XDirectionalDependentDrawing function.

Context Dependent Drawing

   The XNContextualDrawing argument indicates whether the text
   rendering functions implement implicit context-dependent
   drawing. If this value is True, the output method has knowledge
   of context dependencies and performs character shape editing,
   combining glyphs to present a single character as necessary.
   The actual shape editing is dependent on the locale
   implementation and the font set used.

   This OM value presents functionality identical to the
   XContextualDrawing function.

Output Context Functions

   An output context is an abstraction that contains both the data
   required by an output method and the information required to
   display that data. There can be multiple output contexts for
   one output method. The programming interfaces for creating,
   reading, or modifying an output context use a variable argument
   list. The name elements of the argument lists are referred to
   as XOC values. It is intended that output methods be controlled
   by these XOC values. As new XOC values are created, they should
   be registered with the X Consortium. An XOC can be used
   anywhere an XFontSet can be used, and vice versa; XFontSet is
   retained for compatibility with previous releases. The concepts
   of output methods and output contexts include broader, more
   generalized abstraction than font set, supporting complex and
   more intelligent text display, and dealing not only with
   multiple fonts but also with context dependencies. However,
   XFontSet is widely used in several interfaces, so XOC is
   defined as an upward compatible type of XFontSet.

   To create an output context, use XCreateOC.

   XOC XCreateOC(XOM om);

   om

   Specifies the output method.

   ...

   Specifies the variable-length argument list to set XOC values.

   The XCreateOC function creates an output context within the
   specified output method.

   The base font names argument is mandatory at creation time, and
   the output context will not be created unless it is provided.
   All other output context values can be set later.

   XCreateOC returns NULL if no output context could be created.
   NULL can be returned for any of the following reasons:
     * A required argument was not set.
     * A read-only argument was set.
     * An argument name is not recognized.
     * The output method encountered an output method
       implementation-dependent error.

   XCreateOC can generate a BadAtom error.

   To destroy an output context, use XDestroyOC.

   void XDestroyOC(XOC oc);

   oc

   Specifies the output context.

   The XDestroyOC function destroys the specified output context.

   To get the output method associated with an output context, use
   XOMOfOC.

   XOM XOMOfOC(XOC oc);

   oc

   Specifies the output context.

   The XOMOfOC function returns the output method associated with
   the specified output context.

   Xlib provides two functions for setting and reading output
   context values, respectively, XSetOCValues and XGetOCValues.
   Both functions have a variable-length argument list. In that
   argument list, any XOC value's name must be denoted with a
   character string using the X Portable Character Set.

   To set XOC values, use XSetOCValues.

   char *XSetOCValues(XOC oc);

   oc

   Specifies the output context.

   ...

   Specifies the variable-length argument list to set XOC values.

   The XSetOCValues function returns NULL if no error occurred;
   otherwise, it returns the name of the first argument that could
   not be set. An argument might not be set for any of the
   following reasons:
     * The argument is read-only.
     * The argument name is not recognized.
     * An implementation-dependent error occurs.

   Each value to be set must be an appropriate datum, matching the
   data type imposed by the semantics of the argument.

   XSetOCValues can generate a BadAtom error.

   To obtain XOC values, use XGetOCValues.

   char *XGetOCValues(XOC oc);

   oc

   Specifies the output context.

   ...

   Specifies the variable-length argument list to get XOC values.

   The XGetOCValues function returns NULL if no error occurred;
   otherwise, it returns the name of the first argument that could
   not be obtained. An argument might not be obtained for any of
   the following reasons:
     * The argument name is not recognized.
     * An implementation-dependent error occurs.

   Each argument value following a name must point to a location
   where the value is to be stored.

Output Context Values

   The following table describes how XOC values are interpreted by
   an output method. The first column lists the XOC values. The
   second column indicates the alternative interfaces that
   function identically and are provided for compatibility with
   previous releases. The third column indicates how each of the
   XOC values is treated.

   The following keys apply to this table.
   Key Explanation
   C This value must be set with XCreateOC.
   D This value may be set using XCreateOC. If it is not set,a
   default is provided.
   G This value may be read using XGetOCValues.
   S This value must be set using XSetOCValues.

   XOC Value      Alternative Interface Key
   BaseFontName   XCreateFontSet        C-G
   MissingCharSet XCreateFontSet        G
   DefaultString  XCreateFontSet        G
   Orientation    -                     D-S-G
   ResourceName   -                     S-G
   ResourceClass  -                     S-G
   FontInfo       XFontsOfFontSet       G
   OMAutomatic    -                     G

Base Font Name

   The XNBaseFontName argument is a list of base font names that
   Xlib uses to load the fonts needed for the locale. The base
   font names are a comma-separated list. The string is
   null-terminated and is assumed to be in the Host Portable
   Character Encoding; otherwise, the result is
   implementation-dependent. White space immediately on either
   side of a separating comma is ignored.

   Use of XLFD font names permits Xlib to obtain the fonts needed
   for a variety of locales from a single locale-independent base
   font name. The single base font name should name a family of
   fonts whose members are encoded in the various charsets needed
   by the locales of interest.

   An XLFD base font name can explicitly name a charset needed for
   the locale. This allows the user to specify an exact font for
   use with a charset required by a locale, fully controlling the
   font selection.

   If a base font name is not an XLFD name, Xlib will attempt to
   obtain an XLFD name from the font properties for the font. If
   Xlib is successful, the XGetOCValues function will return this
   XLFD name instead of the client-supplied name.

   This argument must be set at creation time and cannot be
   changed. If no fonts exist for any of the required charsets, or
   if the locale definition in Xlib requires that a font exist for
   a particular charset and a font is not found for that charset,
   XCreateOC returns NULL.

   When querying for the XNBaseFontName XOC value, XGetOCValues
   returns a null-terminated string identifying the base font
   names that Xlib used to load the fonts needed for the locale.
   This string is owned by Xlib and should not be modified or
   freed by the client. The string will be freed by a call to
   XDestroyOC with the associated XOC. Until freed, the string
   contents will not be modified by Xlib.

Missing CharSet

   The XNMissingCharSet argument returns the list of required
   charsets that are missing from the font set. The value of the
   argument is a pointer to a structure of type XOMCharSetList.

   If fonts exist for all of the charsets required by the current
   locale, charset_list is set to NULL and charset_count is set to
   zero. If no fonts exist for one or more of the required
   charsets, charset_list is set to a list of one or more
   null-terminated charset names for which no fonts exist, and
   charset_count is set to the number of missing charsets. The
   charsets are from the list of the required charsets for the
   encoding of the locale and do not include any charsets to which
   Xlib may be able to remap a required charset.

   The missing charset list is owned by Xlib and should not be
   modified or freed by the client. It will be freed by a call to
   XDestroyOC with the associated XOC. Until freed, its contents
   will not be modified by Xlib.

Default String

   When a drawing or measuring function is called with an XOC that
   has missing charsets, some characters in the locale will not be
   drawable. The XNDefaultString argument returns a pointer to a
   string that represents the glyphs that are drawn with this XOC
   when the charsets of the available fonts do not include all
   glyphs required to draw a character. The string does not
   necessarily consist of valid characters in the current locale
   and is not necessarily drawn with the fonts loaded for the font
   set, but the client can draw or measure the default glyphs by
   including this string in a string being drawn or measured with
   the XOC.

   If the XNDefaultString argument returned the empty string (""),
   no glyphs are drawn and the escapement is zero. The returned
   string is null-terminated. It is owned by Xlib and should not
   be modified or freed by the client. It will be freed by a call
   to XDestroyOC with the associated XOC. Until freed, its
   contents will not be modified by Xlib.

Orientation

   The XNOrientation argument specifies the current orientation of
   text when drawn. The value of this argument is one of the
   values returned by the XGetOMValues function with the
   XNQueryOrientation argument specified in the XOrientation list.
   The value of the argument is of type XOrientation. When
   XNOrientation is queried, the value specifies the current
   orientation. When XNOrientation is set, a value is used to set
   the current orientation.

   When XOMOrientation_Context is set, the text orientation of the
   text is determined according to an implementation-defined
   method (for example, ISO 6429 control sequences), and the
   initial text orientation for locale-dependent Xlib functions is
   assumed to be XOMOrientation_LTR_TTB.

   The XNOrientation value does not change the prime drawing
   direction for Xlib drawing functions.

Resource Name and Class

   The XNResourceName and XNResourceClass arguments are strings
   that specify the full name and class used by the client to
   obtain resources for the display of the output context. These
   values should be used as prefixes for name and class when
   looking up resources that may vary according to the output
   context. If these values are not set, the resources will not be
   fully specified.

   It is not intended that values that can be set as XOM values be
   set as resources.

   When querying for the XNResourceName or XNResourceClass XOC
   value, XGetOCValues returns a null-terminated string. This
   string is owned by Xlib and should not be modified or freed by
   the client. The string will be freed by a call to XDestroyOC
   with the associated XOC or when the associated value is changed
   via XSetOCValues. Until freed, the string contents will not be
   modified by Xlib.

Font Info

   The XNFontInfo argument specifies a list of one or more
   XFontStruct structures and font names for the fonts used for
   drawing by the given output context. The value of the argument
   is a pointer to a structure of type XOMFontInfo.



typedef struct {
     int         num_font;
     XFontStruct **font_struct_list;
     char        **font_name_list;
} XOMFontInfo;

   A list of pointers to the XFontStruct structures is returned to
   font_struct_list. A list of pointers to null-terminated,
   fully-specified font name strings in the locale of the output
   context is returned to font_name_list. The font_name_list order
   corresponds to the font_struct_list order. The number of
   XFontStruct structures and font names is returned to num_font.

   Because it is not guaranteed that a given character will be
   imaged using a single font glyph, there is no provision for
   mapping a character or default string to the font properties,
   font ID, or direction hint for the font for the character. The
   client may access the XFontStruct list to obtain these values
   for all the fonts currently in use.

   Xlib does not guarantee that fonts are loaded from the server
   at the creation of an XOC. Xlib may choose to cache font data,
   loading it only as needed to draw text or compute text
   dimensions. Therefore, existence of the per_char metrics in the
   XFontStruct structures in the XFontStructSet is undefined.
   Also, note that all properties in the XFontStruct structures
   are in the STRING encoding.

   The client must not free the XOMFontInfo struct itself; it will
   be freed when the XOC is closed.

OM Automatic

   The XNOMAutomatic argument returns whether the associated
   output context was created by XCreateFontSet or not. Because
   the XFreeFontSet function not only destroys the output context
   but also closes the implicit output method associated with it,
   XFreeFontSet should be used with any output context created by
   XCreateFontSet. However, it is possible that a client does not
   know how the output context was created. Before a client
   destroys the output context, it can query whether XNOMAutomatic
   is set to determine whether XFreeFontSet or XDestroyOC should
   be used to destroy the output context.

Creating and Freeing a Font Set

   Xlib international text drawing is done using a set of one or
   more fonts, as needed for the locale of the text. Fonts are
   loaded according to a list of base font names supplied by the
   client and the charsets required by the locale. The XFontSet is
   an opaque type representing the state of a particular output
   thread and is equivalent to the type XOC.

   The XCreateFontSet function is a convenience function for
   creating an output context using only default values. The
   returned XFontSet has an implicitly created XOM. This XOM has
   an OM value XNOMAutomatic automatically set to True so that the
   output context self indicates whether it was created by
   XCreateOC or XCreateFontSet.

   XFontSet XCreateFontSet(Display *display, char
   *base_font_name_list, char ***missing_charset_list_return, int
   *missing_charset_count_return, char **def_string_return);

   display

   Specifies the connection to the X server.

   base_font_name_list

   Specifies the base font names.

   missing_charset_list_return

   Returns the missing charsets.

   missing_charset_count_return

   Returns the number of missing charsets.

   def_string_return

   Returns the string drawn for missing charsets.

   The XCreateFontSet function creates a font set for the
   specified display. The font set is bound to the current locale
   when XCreateFontSet is called. The font set may be used in
   subsequent calls to obtain font and character information and
   to image text in the locale of the font set.

   The base_font_name_list argument is a list of base font names
   that Xlib uses to load the fonts needed for the locale. The
   base font names are a comma-separated list. The string is
   null-terminated and is assumed to be in the Host Portable
   Character Encoding; otherwise, the result is
   implementation-dependent. White space immediately on either
   side of a separating comma is ignored.

   Use of XLFD font names permits Xlib to obtain the fonts needed
   for a variety of locales from a single locale-independent base
   font name. The single base font name should name a family of
   fonts whose members are encoded in the various charsets needed
   by the locales of interest.

   An XLFD base font name can explicitly name a charset needed for
   the locale. This allows the user to specify an exact font for
   use with a charset required by a locale, fully controlling the
   font selection.

   If a base font name is not an XLFD name, Xlib will attempt to
   obtain an XLFD name from the font properties for the font. If
   this action is successful in obtaining an XLFD name, the
   XBaseFontNameListOfFontSet function will return this XLFD name
   instead of the client-supplied name.

   Xlib uses the following algorithm to select the fonts that will
   be used to display text with the XFontSet.

   For each font charset required by the locale, the base font
   name list is searched for the first appearance of one of the
   following cases that names a set of fonts that exist at the
   server:
     * The first XLFD-conforming base font name that specifies the
       required charset or a superset of the required charset in
       its CharSetRegistry and CharSetEncoding fields. The
       implementation may use a base font name whose specified
       charset is a superset of the required charset, for example,
       an ISO8859-1 font for an ASCII charset.
     * The first set of one or more XLFD-conforming base font
       names that specify one or more charsets that can be
       remapped to support the required charset. The Xlib
       implementation may recognize various mappings from a
       required charset to one or more other charsets and use the
       fonts for those charsets. For example, JIS Roman is ASCII
       with tilde and backslash replaced by yen and overbar; Xlib
       may load an ISO8859-1 font to support this character set if
       a JIS Roman font is not available.
     * The first XLFD-conforming font name or the first non-XLFD
       font name for which an XLFD font name can be obtained,
       combined with the required charset (replacing the
       CharSetRegistry and CharSetEncoding fields in the XLFD font
       name). As in case 1, the implementation may use a charset
       that is a superset of the required charset.
     * The first font name that can be mapped in some
       implementation-dependent manner to one or more fonts that
       support imaging text in the charset.

   For example, assume that a locale required the charsets:

ISO8859-1
JISX0208.1983
JISX0201.1976
GB2312-1980.0

   The user could supply a base_font_name_list that explicitly
   specifies the charsets, ensuring that specific fonts are used
   if they exist. For example:

"-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-240-JISX0208.1983-0,\\
-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-120-JISX0201.1976-0,\\
-GB-Fixed-Medium-R-Normal--26-180-100-100-C-240-GB2312-1980.0,\\
-Adobe-Courier-Bold-R-Normal--25-180-75-75-M-150-ISO8859-1"

   Alternatively, the user could supply a base_font_name_list that
   omits the charsets, letting Xlib select font charsets required
   for the locale. For example:

"-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-240,\\
-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-120,\\
-GB-Fixed-Medium-R-Normal--26-180-100-100-C-240,\\
-Adobe-Courier-Bold-R-Normal--25-180-100-100-M-150"

   Alternatively, the user could simply supply a single base font
   name that allows Xlib to select from all available fonts that
   meet certain minimum XLFD property requirements. For example:

"-*-*-*-R-Normal--*-180-100-100-*-*"

   If XCreateFontSet is unable to create the font set, either
   because there is insufficient memory or because the current
   locale is not supported, XCreateFontSet returns NULL,
   missing_charset_list_return is set to NULL, and
   missing_charset_count_return is set to zero. If fonts exist for
   all of the charsets required by the current locale,
   XCreateFontSet returns a valid XFontSet,
   missing_charset_list_return is set to NULL, and
   missing_charset_count_return is set to zero.

   If no font exists for one or more of the required charsets,
   XCreateFontSet sets missing_charset_list_return to a list of
   one or more null-terminated charset names for which no font
   exists and sets missing_charset_count_return to the number of
   missing fonts. The charsets are from the list of the required
   charsets for the encoding of the locale and do not include any
   charsets to which Xlib may be able to remap a required charset.

   If no font exists for any of the required charsets or if the
   locale definition in Xlib requires that a font exist for a
   particular charset and a font is not found for that charset,
   XCreateFontSet returns NULL. Otherwise, XCreateFontSet returns
   a valid XFontSet to font_set.

   When an Xmb/wc drawing or measuring function is called with an
   XFontSet that has missing charsets, some characters in the
   locale will not be drawable. If def_string_return is non-NULL,
   XCreateFontSet returns a pointer to a string that represents
   the glyphs that are drawn with this XFontSet when the charsets
   of the available fonts do not include all font glyphs required
   to draw a codepoint. The string does not necessarily consist of
   valid characters in the current locale and is not necessarily
   drawn with the fonts loaded for the font set, but the client
   can draw and measure the default glyphs by including this
   string in a string being drawn or measured with the XFontSet.

   If the string returned to def_string_return is the empty string
   (""), no glyphs are drawn, and the escapement is zero. The
   returned string is null-terminated. It is owned by Xlib and
   should not be modified or freed by the client. It will be freed
   by a call to XFreeFontSet with the associated XFontSet. Until
   freed, its contents will not be modified by Xlib.

   The client is responsible for constructing an error message
   from the missing charset and default string information and may
   choose to continue operation in the case that some fonts did
   not exist.

   The returned XFontSet and missing charset list should be freed
   with XFreeFontSet and XFreeStringList, respectively. The
   client-supplied base_font_name_list may be freed by the client
   after calling XCreateFontSet.

   To obtain a list of XFontStruct structures and full font names
   given an XFontSet, use XFontsOfFontSet.

   int XFontsOfFontSet(XFontSet font_set, XFontStruct
   ***font_struct_list_return, char ***font_name_list_return);

   font_set

   Specifies the font set.

   font_struct_list_return

   Returns the list of font structs.

   font_name_list_return

   Returns the list of font names.

   The XFontsOfFontSet function returns a list of one or more
   XFontStructs and font names for the fonts used by the Xmb and
   Xwc layers for the given font set. A list of pointers to the
   XFontStruct structures is returned to font_struct_list_return.
   A list of pointers to null-terminated, fully specified font
   name strings in the locale of the font set is returned to
   font_name_list_return. The font_name_list order corresponds to
   the font_struct_list order. The number of XFontStruct
   structures and font names is returned as the value of the
   function.

   Because it is not guaranteed that a given character will be
   imaged using a single font glyph, there is no provision for
   mapping a character or default string to the font properties,
   font ID, or direction hint for the font for the character. The
   client may access the XFontStruct list to obtain these values
   for all the fonts currently in use.

   Xlib does not guarantee that fonts are loaded from the server
   at the creation of an XFontSet. Xlib may choose to cache font
   data, loading it only as needed to draw text or compute text
   dimensions. Therefore, existence of the per_char metrics in the
   XFontStruct structures in the XFontStructSet is undefined.
   Also, note that all properties in the XFontStruct structures
   are in the STRING encoding.

   The XFontStruct and font name lists are owned by Xlib and
   should not be modified or freed by the client. They will be
   freed by a call to XFreeFontSet with the associated XFontSet.
   Until freed, their contents will not be modified by Xlib.

   To obtain the base font name list and the selected font name
   list given an XFontSet, use XBaseFontNameListOfFontSet.

   char *XBaseFontNameListOfFontSet(XFontSet font_set);

   font_set

   Specifies the font set.

   The XBaseFontNameListOfFontSet function returns the original
   base font name list supplied by the client when the XFontSet
   was created. A null-terminated string containing a list of
   comma-separated font names is returned as the value of the
   function. White space may appear immediately on either side of
   separating commas.

   If XCreateFontSet obtained an XLFD name from the font
   properties for the font specified by a non-XLFD base name, the
   XBaseFontNameListOfFontSet function will return the XLFD name
   instead of the non-XLFD base name.

   The base font name list is owned by Xlib and should not be
   modified or freed by the client. It will be freed by a call to
   XFreeFontSet with the associated XFontSet. Until freed, its
   contents will not be modified by Xlib.

   To obtain the locale name given an XFontSet, use
   XLocaleOfFontSet.

   char *XLocaleOfFontSet(XFontSet font_set);

   font_set

   Specifies the font set.

   The XLocaleOfFontSet function returns the name of the locale
   bound to the specified XFontSet, as a null-terminated string.

   The returned locale name string is owned by Xlib and should not
   be modified or freed by the client. It may be freed by a call
   to XFreeFontSet with the associated XFontSet. Until freed, it
   will not be modified by Xlib.

   The XFreeFontSet function is a convenience function for freeing
   an output context. XFreeFontSet also frees its associated XOM
   if the output context was created by XCreateFontSet.

   void XFreeFontSet(Display *display, XFontSet font_set);

   display

   Specifies the connection to the X server.

   font_set

   Specifies the font set.

   The XFreeFontSet function frees the specified font set. The
   associated base font name list, font name list, XFontStruct
   list, and XFontSetExtents, if any, are freed.

Obtaining Font Set Metrics

   Metrics for the internationalized text drawing functions are
   defined in terms of a primary draw direction, which is the
   default direction in which the character origin advances for
   each succeeding character in the string. The Xlib interface is
   currently defined to support only a left-to-right primary draw
   direction. The drawing origin is the position passed to the
   drawing function when the text is drawn. The baseline is a line
   drawn through the drawing origin parallel to the primary draw
   direction. Character ink is the pixels painted in the
   foreground color and does not include interline or
   intercharacter spacing or image text background pixels.

   The drawing functions are allowed to implement implicit text
   directionality control, reversing the order in which characters
   are rendered along the primary draw direction in response to
   locale-specific lexical analysis of the string.

   Regardless of the character rendering order, the origins of all
   characters are on the primary draw direction side of the
   drawing origin. The screen location of a particular character
   image may be determined with XmbTextPerCharExtents or
   XwcTextPerCharExtents.

   The drawing functions are allowed to implement
   context-dependent rendering, where the glyphs drawn for a
   string are not simply a concatenation of the glyphs that
   represent each individual character. A string of two characters
   drawn with XmbDrawString may render differently than if the two
   characters were drawn with separate calls to XmbDrawString. If
   the client appends or inserts a character in a previously drawn
   string, the client may need to redraw some adjacent characters
   to obtain proper rendering.

   To find out about direction-dependent rendering, use
   XDirectionalDependentDrawing.

   Bool XDirectionalDependentDrawing(XFontSet font_set);

   font_set

   Specifies the font set.

   The XDirectionalDependentDrawing function returns True if the
   drawing functions implement implicit text directionality;
   otherwise, it returns False.

   To find out about context-dependent rendering, use
   XContextualDrawing.

   Bool XContextualDrawing(XFontSet font_set);

   font_set

   Specifies the font set.

   The XContextualDrawing function returns True if text drawn with
   the font set might include context-dependent drawing;
   otherwise, it returns False.

   To find out about context-dependent or direction-dependent
   rendering, use XContextDependentDrawing.

   Bool XContextDependentDrawing(XFontSet font_set);

   font_set

   Specifies the font set.

   The XContextDependentDrawing function returns True if the
   drawing functions implement implicit text directionality or if
   text drawn with the font_set might include context-dependent
   drawing; otherwise, it returns False.

   The drawing functions do not interpret newline, tab, or other
   control characters. The behavior when nonprinting characters
   other than space are drawn is implementation-dependent. It is
   the client's responsibility to interpret control characters in
   a text stream.

   The maximum character extents for the fonts that are used by
   the text drawing layers can be accessed by the XFontSetExtents
   structure:



typedef struct {
     XRectangle max_ink_extent;     /* over all drawable characters */
     XRectangle max_logical_extent; /* over all drawable characters */
} XFontSetExtents;

   The XRectangle structures used to return font set metrics are
   the usual Xlib screen-oriented rectangles with x, y giving the
   upper left corner, and width and height always positive.

   The max_ink_extent member gives the maximum extent, over all
   drawable characters, of the rectangles that bound the character
   glyph image drawn in the foreground color, relative to a
   constant origin. See XmbTextExtents and XwcTextExtents for
   detailed semantics.

   The max_logical_extent member gives the maximum extent, over
   all drawable characters, of the rectangles that specify minimum
   spacing to other graphical features, relative to a constant
   origin. Other graphical features drawn by the client, for
   example, a border surrounding the text, should not intersect
   this rectangle. The max_logical_extent member should be used to
   compute minimum interline spacing and the minimum area that
   must be allowed in a text field to draw a given number of
   arbitrary characters.

   Due to context-dependent rendering, appending a given character
   to a string may change the string's extent by an amount other
   than that character's individual extent.

   The rectangles for a given character in a string can be
   obtained from XmbTextPerCharExtents or XwcTextPerCharExtents.

   To obtain the maximum extents structure given an XFontSet, use
   XExtentsOfFontSet.

   XFontSetExtents *XExtentsOfFontSet(XFontSet font_set);

   font_set

   Specifies the font set.

   The XExtentsOfFontSet function returns an XFontSetExtents
   structure for the fonts used by the Xmb and Xwc layers for the
   given font set.

   The XFontSetExtents structure is owned by Xlib and should not
   be modified or freed by the client. It will be freed by a call
   to XFreeFontSet with the associated XFontSet. Until freed, its
   contents will not be modified by Xlib.

   To obtain the escapement in pixels of the specified text as a
   value, use XmbTextEscapement or XwcTextEscapement.

   int XmbTextEscapement(XFontSet font_set, char *string, int
   num_bytes);

   int XwcTextEscapement(XFontSet font_set, wchar_t *string, int
   num_wchars);

   font_set

   Specifies the font set.

   string

   Specifies the character string.

   num_bytes

   Specifies the number of bytes in the string argument.

   num_wchars

   Specifies the number of characters in the string argument.

   The XmbTextEscapement and XwcTextEscapement functions return
   the escapement in pixels of the specified string as a value,
   using the fonts loaded for the specified font set. The
   escapement is the distance in pixels in the primary draw
   direction from the drawing origin to the origin of the next
   character to be drawn, assuming that the rendering of the next
   character is not dependent on the supplied string.

   Regardless of the character rendering order, the escapement is
   always positive.

   To obtain the overall_ink_return and overall_logical_return
   arguments, the overall bounding box of the string's image, and
   a logical bounding box, use XmbTextExtents or XwcTextExtents.

   int XmbTextExtents(XFontSet font_set, char *string, int
   num_bytes, XRectangle *overall_ink_return, XRectangle
   *overall_logical_return);

   int XwcTextExtents(XFontSet font_set, wchar_t *string, int
   num_wchars, XRectangle *overall_ink_return, XRectangle
   *overall_logical_return);

   font_set

   Specifies the font set.

   string

   Specifies the character string.

   num_bytes

   Specifies the number of bytes in the string argument.

   num_wchars

   Specifies the number of characters in the string argument.

   overall_ink_return

   Returns the overall ink dimensions.

   overall_logical_return

   Returns the overall logical dimensions.

   The XmbTextExtents and XwcTextExtents functions set the
   components of the specified overall_ink_return and
   overall_logical_return arguments to the overall bounding box of
   the string's image and a logical bounding box for spacing
   purposes, respectively. They return the value returned by
   XmbTextEscapement or XwcTextEscapement. These metrics are
   relative to the drawing origin of the string, using the fonts
   loaded for the specified font set.

   If the overall_ink_return argument is non-NULL, it is set to
   the bounding box of the string's character ink. The
   overall_ink_return for a nondescending, horizontally drawn
   Latin character is conventionally entirely above the baseline;
   that is, overall_ink_return.height <= -overall_ink_return.y.
   The overall_ink_return for a nonkerned character is entirely
   at, and to the right of, the origin; that is,
   overall_ink_return.x >= 0. A character consisting of a single
   pixel at the origin would set overall_ink_return fields y = 0,
   x = 0, width = 1, and height = 1.

   If the overall_logical_return argument is non-NULL, it is set
   to the bounding box that provides minimum spacing to other
   graphical features for the string. Other graphical features,
   for example, a border surrounding the text, should not
   intersect this rectangle.

   When the XFontSet has missing charsets, metrics for each
   unavailable character are taken from the default string
   returned by XCreateFontSet so that the metrics represent the
   text as it will actually be drawn. The behavior for an invalid
   codepoint is undefined.

   To determine the effective drawing origin for a character in a
   drawn string, the client should call XmbTextPerCharExtents on
   the entire string, then on the character, and subtract the x
   values of the returned rectangles for the character. This is
   useful to redraw portions of a line of text or to justify
   words, but for context-dependent rendering, the client should
   not assume that it can redraw the character by itself and get
   the same rendering.

   To obtain per-character information for a text string, use
   XmbTextPerCharExtents or XwcTextPerCharExtents.

   Status XmbTextPerCharExtents(XFontSet font_set, char *string,
   int num_bytes, XRectangle *ink_array_return, XRectangle
   *logical_array_return, int array_size, int *num_chars_return,
   XRectangle *overall_ink_return, XRectangle
   *overall_logical_return);

   Status XwcTextPerCharExtents(XFontSet font_set, wchar_t
   *string, int num_wchars, XRectangle *ink_array_return,
   XRectangle *logical_array_return, int array_size, int
   *num_chars_return, XRectangle *overall_ink_return, XRectangle
   *overall_logical_return);

   font_set

   Specifies the font set.

   string

   Specifies the character string.

   num_bytes

   Specifies the number of bytes in the string argument.

   num_wchars

   Specifies the number of characters in the string argument.

   ink_array_return

   Returns the ink dimensions for each character.

   logical_array_return

   Returns the logical dimensions for each character.

   array_size

   Specifies the size of ink_array_return and
   logical_array_return. The caller must pass in arrays of this
   size.

   num_chars_return

   Returns the number of characters in the string argument.

   overall_ink_return

   Returns the overall ink dimensions.

   overall_logical_return

   Returns the overall logical dimensions.

   The XmbTextPerCharExtents and XwcTextPerCharExtents functions
   return the text dimensions of each character of the specified
   text, using the fonts loaded for the specified font set. Each
   successive element of ink_array_return and logical_array_return
   is set to the successive character's drawn metrics, relative to
   the drawing origin of the string and one rectangle for each
   character in the supplied text string. The number of elements
   of ink_array_return and logical_array_return that have been set
   is returned to num_chars_return.

   Each element of ink_array_return is set to the bounding box of
   the corresponding character's drawn foreground color. Each
   element of logical_array_return is set to the bounding box that
   provides minimum spacing to other graphical features for the
   corresponding character. Other graphical features should not
   intersect any of the logical_array_return rectangles.

   Note that an XRectangle represents the effective drawing
   dimensions of the character, regardless of the number of font
   glyphs that are used to draw the character or the direction in
   which the character is drawn. If multiple characters map to a
   single character glyph, the dimensions of all the XRectangles
   of those characters are the same.

   When the XFontSet has missing charsets, metrics for each
   unavailable character are taken from the default string
   returned by XCreateFontSet so that the metrics represent the
   text as it will actually be drawn. The behavior for an invalid
   codepoint is undefined.

   If the array_size is too small for the number of characters in
   the supplied text, the functions return zero and
   num_chars_return is set to the number of rectangles required.
   Otherwise, the functions return a nonzero value.

   If the overall_ink_return or overall_logical_return argument is
   non-NULL, XmbTextPerCharExtents and XwcTextPerCharExtents
   return the maximum extent of the string's metrics to
   overall_ink_return or overall_logical_return, as returned by
   XmbTextExtents or XwcTextExtents.

Drawing Text Using Font Sets

   The functions defined in this section draw text at a specified
   location in a drawable. They are similar to the functions
   XDrawText, XDrawString, and XDrawImageString except that they
   work with font sets instead of single fonts and interpret the
   text based on the locale of the font set instead of treating
   the bytes of the string as direct font indexes. See section 8.6
   for details of the use of Graphics Contexts (GCs) and possible
   protocol errors. If a BadFont error is generated, characters
   prior to the offending character may have been drawn.

   The text is drawn using the fonts loaded for the specified font
   set; the font in the GC is ignored and may be modified by the
   functions. No validation that all fonts conform to some width
   rule is performed.

   The text functions XmbDrawText and XwcDrawText use the
   following structures:



typedef struct {
     char     *chars;    /* pointer to string */
     int      nchars;    /* number of bytes */
     int      delta;     /* pixel delta between strings */
     XFontSet font_set;  /* fonts, None means don't change */
} XmbTextItem;



typedef struct {
     wchar_t *chars;     /* pointer to wide char string */
     int nchars;     /* number of wide characters */
     int delta;     /* pixel delta between strings */
     XFontSet font_set;     /* fonts, None means don't change */
} XwcTextItem;

   To draw text using multiple font sets in a given drawable, use
   XmbDrawText or XwcDrawText.

   void XmbDrawText(Display *display, Drawable d, GC gc, int x,
   int y, XmbTextItem *items, int nitems);

   void XwcDrawText(Display *display, Drawable d, GC gc, int x,
   int y, XwcTextItem *items, int nitems);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates of the position in the new
   parent window.

   items

   Specifies an array of text items.

   nitems

   Specifies the number of text items in the array.

   The XmbDrawText and XwcDrawText functions allow complex spacing
   and font set shifts between text strings. Each text item is
   processed in turn, with the origin of a text element advanced
   in the primary draw direction by the escapement of the previous
   text item. A text item delta specifies an additional escapement
   of the text item drawing origin in the primary draw direction.
   A font_set member other than None in an item causes the font
   set to be used for this and subsequent text items in the
   text_items list. Leading text items with a font_set member set
   to None will not be drawn.

   XmbDrawText and XwcDrawText do not perform any
   context-dependent rendering between text segments. Clients may
   compute the drawing metrics by passing each text segment to
   XmbTextExtents and XwcTextExtents or XmbTextPerCharExtents and
   XwcTextPerCharExtents. When the XFontSet has missing charsets,
   each unavailable character is drawn with the default string
   returned by XCreateFontSet. The behavior for an invalid
   codepoint is undefined.

   To draw text using a single font set in a given drawable, use
   XmbDrawString or XwcDrawString.

   void XmbDrawString(Display *display, Drawable d, XFontSet
   font_set, GC gc, int x, int y, char *string, int num_bytes);

   void XwcDrawString(Display *display, Drawable d, XFontSet
   font_set, GC gc, int x, int y, wchar_t *string, int
   num_wchars);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   font_set

   Specifies the font set.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates of the position in the new
   parent window.

   string

   Specifies the character string.

   num_bytes

   Specifies the number of bytes in the string argument.

   num_wchars

   Specifies the number of characters in the string argument.

   The XmbDrawString and XwcDrawString functions draw the
   specified text with the foreground pixel. When the XFontSet has
   missing charsets, each unavailable character is drawn with the
   default string returned by XCreateFontSet. The behavior for an
   invalid codepoint is undefined.

   To draw image text using a single font set in a given drawable,
   use XmbDrawImageString or XwcDrawImageString.

   void XmbDrawImageString(Display *display, Drawable d, XFontSet
   font_set, GC gc, int x, int y, char *string, int num_bytes);

   void XwcDrawImageString(Display *display, Drawable d, XFontSet
   font_set, GC gc, int x, int y, wchar_t *string, int
   num_wchars);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   font_set

   Specifies the font set.

   gc

   Specifies the GC.

   x

   y

   Specify the x and y coordinates of the position in the new
   parent window.

   string

   Specifies the character string.

   num_bytes

   Specifies the number of bytes in the string argument.

   num_wchars

   Specifies the number of characters in the string argument.

   The XmbDrawImageString and XwcDrawImageString functions fill a
   destination rectangle with the background pixel defined in the
   GC and then paint the text with the foreground pixel. The
   filled rectangle is the rectangle returned to
   overall_logical_return by XmbTextExtents or XwcTextExtents for
   the same text and XFontSet.

   When the XFontSet has missing charsets, each unavailable
   character is drawn with the default string returned by
   XCreateFontSet. The behavior for an invalid codepoint is
   undefined.

Input Methods

   This section provides discussions of the following X Input
   Method (XIM) topics:
     * Input method overview
     * Input method management
     * Input method functions
     * Input method values
     * Input context functions
     * Input context values
     * Input method callback semantics
     * Event filtering
     * Getting keyboard input
     * Input method conventions

Input Method Overview

   This section provides definitions for terms and concepts used
   for internationalized text input and a brief overview of the
   intended use of the mechanisms provided by Xlib.

   A large number of languages in the world use alphabets
   consisting of a small set of symbols (letters) to form words.
   To enter text into a computer in an alphabetic language, a user
   usually has a keyboard on which there exist key symbols
   corresponding to the alphabet. Sometimes, a few characters of
   an alphabetic language are missing on the keyboard. Many
   computer users who speak a Latin-alphabet-based language only
   have an English-based keyboard. They need to hit a combination
   of keystrokes to enter a character that does not exist directly
   on the keyboard. A number of algorithms have been developed for
   entering such characters. These are known as European input
   methods, compose input methods, or dead-key input methods.

   Japanese is an example of a language with a phonetic symbol
   set, where each symbol represents a specific sound. There are
   two phonetic symbol sets in Japanese: Katakana and Hiragana. In
   general, Katakana is used for words that are of foreign origin,
   and Hiragana is used for writing native Japanese words.
   Collectively, the two systems are called Kana. Each set
   consists of 48 characters.

   Korean also has a phonetic symbol set, called Hangul. Each of
   the 24 basic phonetic symbols (14 consonants and 10 vowels)
   represents a specific sound. A syllable is composed of two or
   three parts: the initial consonants, the vowels, and the
   optional last consonants. With Hangul, syllables can be treated
   as the basic units on which text processing is done. For
   example, a delete operation may work on a phonetic symbol or a
   syllable. Korean code sets include several thousands of these
   syllables. A user types the phonetic symbols that make up the
   syllables of the words to be entered. The display may change as
   each phonetic symbol is entered. For example, when the second
   phonetic symbol of a syllable is entered, the first phonetic
   symbol may change its shape and size. Likewise, when the third
   phonetic symbol is entered, the first two phonetic symbols may
   change their shape and size.

   Not all languages rely solely on alphabetic or phonetic
   systems. Some languages, including Japanese and Korean, employ
   an ideographic writing system. In an ideographic system, rather
   than taking a small set of symbols and combining them in
   different ways to create words, each word consists of one
   unique symbol (or, occasionally, several symbols). The number
   of symbols can be very large: approximately 50,000 have been
   identified in Hanzi, the Chinese ideographic system.

   Two major aspects of ideographic systems impact their use with
   computers. First, the standard computer character sets in
   Japan, China, and Korea include roughly 8,000 characters, while
   sets in Taiwan have between 15,000 and 30,000 characters. This
   makes it necessary to use more than one byte to represent a
   character. Second, it obviously is impractical to have a
   keyboard that includes all of a given language's ideographic
   symbols. Therefore, a mechanism is required for entering
   characters so that a keyboard with a reasonable number of keys
   can be used. Those input methods are usually based on
   phonetics, but there also exist methods based on the graphical
   properties of characters.

   In Japan, both Kana and the ideographic system Kanji are used.
   In Korea, Hangul and sometimes the ideographic system Hanja are
   used. Now consider entering ideographs in Japan, Korea, China,
   and Taiwan.

   In Japan, either Kana or English characters are typed and then
   a region is selected (sometimes automatically) for conversion
   to Kanji. Several Kanji characters may have the same phonetic
   representation. If that is the case with the string entered, a
   menu of characters is presented and the user must choose the
   appropriate one. If no choice is necessary or a preference has
   been established, the input method does the substitution
   directly. When Latin characters are converted to Kana or Kanji,
   it is called a romaji conversion.

   In Korea, it is usually acceptable to keep Korean text in
   Hangul form, but some people may choose to write
   Hanja-originated words in Hanja rather than in Hangul. To
   change Hangul to Hanja, the user selects a region for
   conversion and then follows the same basic method as that
   described for Japanese.

   Probably because there are well-accepted phonetic writing
   systems for Japanese and Korean, computer input methods in
   these countries for entering ideographs are fairly standard.
   Keyboard keys have both English characters and phonetic symbols
   engraved on them, and the user can switch between the two sets.

   The situation is different for Chinese. While there is a
   phonetic system called Pinyin promoted by authorities, there is
   no consensus for entering Chinese text. Some vendors use a
   phonetic decomposition (Pinyin or another), others use
   ideographic decomposition of Chinese words, with various
   implementations and keyboard layouts. There are about 16 known
   methods, none of which is a clear standard.

   Also, there are actually two ideographic sets used: Traditional
   Chinese (the original written Chinese) and Simplified Chinese.
   Several years ago, the People's Republic of China launched a
   campaign to simplify some ideographic characters and eliminate
   redundancies altogether. Under the plan, characters would be
   streamlined every five years. Characters have been revised
   several times now, resulting in the smaller, simpler set that
   makes up Simplified Chinese.

Input Method Architecture

   As shown in the previous section, there are many different
   input methods in use today, each varying with language,
   culture, and history. A common feature of many input methods is
   that the user may type multiple keystrokes to compose a single
   character (or set of characters). The process of composing
   characters from keystrokes is called preediting. It may require
   complex algorithms and large dictionaries involving substantial
   computer resources.

   Input methods may require one or more areas in which to show
   the feedback of the actual keystrokes, to propose
   disambiguation to the user, to list dictionaries, and so on.
   The input method areas of concern are as follows:
     * The status area is a logical extension of the LEDs that
       exist on the physical keyboard. It is a window that is
       intended to present the internal state of the input method
       that is critical to the user. The status area may consist
       of text data and bitmaps or some combination.
     * The preedit area displays the intermediate text for those
       languages that are composing prior to the client handling
       the data.
     * The auxiliary area is used for pop-up menus and customizing
       dialogs that may be required for an input method. There may
       be multiple auxiliary areas for an input method. Auxiliary
       areas are managed by the input method independent of the
       client. Auxiliary areas are assumed to be separate dialogs,
       which are maintained by the input method.

   There are various user interaction styles used for preediting.
   The ones supported by Xlib are as follows:
     * For on-the-spot input methods, preediting data will be
       displayed directly in the application window. Application
       data is moved to allow preedit data to appear at the point
       of insertion.
     * Over-the-spot preediting means that the data is displayed
       in a preedit window that is placed over the point of
       insertion.
     * Off-the-spot preediting means that the preedit window is
       inside the application window but not at the point of
       insertion. Often, this type of window is placed at the
       bottom of the application window.
     * Root-window preediting refers to input methods that use a
       preedit window that is the child of RootWindow.

   It would require a lot of computing resources if portable
   applications had to include input methods for all the languages
   in the world. To avoid this, a goal of the Xlib design is to
   allow an application to communicate with an input method placed
   in a separate process. Such a process is called an input
   server. The server to which the application should connect is
   dependent on the environment when the application is started
   up, that is, the user language and the actual encoding to be
   used for it. The input method connection is said to be
   locale-dependent. It is also user-dependent. For a given
   language, the user can choose, to some extent, the user
   interface style of input method (if choice is possible among
   several).

   Using an input server implies communication overhead, but
   applications can be migrated without relinking. Input methods
   can be implemented either as a stub communicating to an input
   server or as a local library.

   An input method may be based on a front-end or a back-end
   architecture. In a front-end architecture, there are two
   separate connections to the X server: keystrokes go directly
   from the X server to the input method on one connection and
   other events to the regular client connection. The input method
   is then acting as a filter and sends composed strings to the
   client. A front-end architecture requires synchronization
   between the two connections to avoid lost key events or locking
   issues.

   In a back-end architecture, a single X server connection is
   used. A dispatching mechanism must decide on this channel to
   delegate appropriate keystrokes to the input method. For
   instance, it may retain a Help keystroke for its own purpose.
   In the case where the input method is a separate process (that
   is, a server), there must be a special communication protocol
   between the back-end client and the input server.

   A front-end architecture introduces synchronization issues and
   a filtering mechanism for noncharacter keystrokes (Function
   keys, Help, and so on). A back-end architecture sometimes
   implies more communication overhead and more process switching.
   If all three processes (X server, input server, client) are
   running on a single workstation, there are two process switches
   for each keystroke in a back-end architecture, but there is
   only one in a front-end architecture.

   The abstraction used by a client to communicate with an input
   method is an opaque data structure represented by the XIM data
   type. This data structure is returned by the XOpenIM function,
   which opens an input method on a given display. Subsequent
   operations on this data structure encapsulate all communication
   between client and input method. There is no need for an X
   client to use any networking library or natural language
   package to use an input method.

   A single input server may be used for one or more languages,
   supporting one or more encoding schemes. But the strings
   returned from an input method will always be encoded in the
   (single) locale associated with the XIM object.

Input Contexts

   Xlib provides the ability to manage a multi-threaded state for
   text input. A client may be using multiple windows, each window
   with multiple text entry areas, and the user possibly switching
   among them at any time. The abstraction for representing the
   state of a particular input thread is called an input context.
   The Xlib representation of an input context is an XIC.

   An input context is the abstraction retaining the state,
   properties, and semantics of communication between a client and
   an input method. An input context is a combination of an input
   method, a locale specifying the encoding of the character
   strings to be returned, a client window, internal state
   information, and various layout or appearance characteristics.
   The input context concept somewhat matches for input the
   graphics context abstraction defined for graphics output.

   One input context belongs to exactly one input method.
   Different input contexts may be associated with the same input
   method, possibly with the same client window. An XIC is created
   with the XCreateIC function, providing an XIM argument and
   affiliating the input context to the input method for its
   lifetime. When an input method is closed with XCloseIM, all of
   its affiliated input contexts should not be used any more (and
   should preferably be destroyed before closing the input
   method).

   Considering the example of a client window with multiple text
   entry areas, the application programmer could, for example,
   choose to implement as follows:
     * As many input contexts are created as text entry areas, and
       the client will get the input accumulated on each context
       each time it looks up in that context.
     * A single context is created for a top-level window in the
       application. If such a window contains several text entry
       areas, each time the user moves to another text entry area,
       the client has to indicate changes in the context.

   A range of choices can be made by application designers to use
   either a single or multiple input contexts, according to the
   needs of their application.

Getting Keyboard Input

   To obtain characters from an input method, a client must call
   the function XmbLookupString or XwcLookupString with an input
   context created from that input method. Both a locale and
   display are bound to an input method when it is opened, and an
   input context inherits this locale and display. Any strings
   returned by XmbLookupString or XwcLookupString will be encoded
   in that locale.

Focus Management

   For each text entry area in which the XmbLookupString or
   XwcLookupString functions are used, there will be an associated
   input context.

   When the application focus moves to a text entry area, the
   application must set the input context focus to the input
   context associated with that area. The input context focus is
   set by calling XSetICFocus with the appropriate input context.

   Also, when the application focus moves out of a text entry
   area, the application should unset the focus for the associated
   input context by calling XUnsetICFocus. As an optimization, if
   XSetICFocus is called successively on two different input
   contexts, setting the focus on the second will automatically
   unset the focus on the first.

   To set and unset the input context focus correctly, it is
   necessary to track application-level focus changes. Such focus
   changes do not necessarily correspond to X server focus
   changes.

   If a single input context is being used to do input for
   multiple text entry areas, it will also be necessary to set the
   focus window of the input context whenever the focus window
   changes (see section 13.5.6.3).

Geometry Management

   In most input method architectures (on-the-spot being the
   notable exception), the input method will perform the display
   of its own data. To provide better visual locality, it is often
   desirable to have the input method areas embedded within a
   client. To do this, the client may need to allocate space for
   an input method. Xlib provides support that allows the size and
   position of input method areas to be provided by a client. The
   input method areas that are supported for geometry management
   are the status area and the preedit area.

   The fundamental concept on which geometry management for input
   method windows is based is the proper division of
   responsibilities between the client (or toolkit) and the input
   method. The division of responsibilities is as follows:
     * The client is responsible for the geometry of the input
       method window.
     * The input method is responsible for the contents of the
       input method window.

   An input method is able to suggest a size to the client, but it
   cannot suggest a placement. Also the input method can only
   suggest a size. It does not determine the size, and it must
   accept the size it is given.

   Before a client provides geometry management for an input
   method, it must determine if geometry management is needed. The
   input method indicates the need for geometry management by
   setting XIMPreeditArea or XIMStatusArea in its XIMStyles value
   returned by XGetIMValues. When a client has decided that it
   will provide geometry management for an input method, it
   indicates that decision by setting the XNInputStyle value in
   the XIC.

   After a client has established with the input method that it
   will do geometry management, the client must negotiate the
   geometry with the input method. The geometry is negotiated by
   the following steps:
     * The client suggests an area to the input method by setting
       the XNAreaNeeded value for that area. If the client has no
       constraints for the input method, it either will not
       suggest an area or will set the width and height to zero.
       Otherwise, it will set one of the values.
     * The client will get the XIC value XNAreaNeeded. The input
       method will return its suggested size in this value. The
       input method should pay attention to any constraints
       suggested by the client.
     * The client sets the XIC value XNArea to inform the input
       method of the geometry of its window. The client should try
       to honor the geometry requested by the input method. The
       input method must accept this geometry.

   Clients doing geometry management must be aware that setting
   other XIC values may affect the geometry desired by an input
   method. For example, XNFontSet and XNLineSpace may change the
   geometry desired by the input method.

   The table of XIC values (see section 13.5.6) indicates the
   values that can cause the desired geometry to change when they
   are set. It is the responsibility of the client to renegotiate
   the geometry of the input method window when it is needed.

   In addition, a geometry management callback is provided by
   which an input method can initiate a geometry change.

Event Filtering

   A filtering mechanism is provided to allow input methods to
   capture X events transparently to clients. It is expected that
   toolkits (or clients) using XmbLookupString or XwcLookupString
   will call this filter at some point in the event processing
   mechanism to make sure that events needed by an input method
   can be filtered by that input method.

   If there were no filter, a client could receive and discard
   events that are necessary for the proper functioning of an
   input method. The following provides a few examples of such
   events:
     * Expose events on preedit window in local mode.
     * Events may be used by an input method to communicate with
       an input server. Such input server protocol-related events
       have to be intercepted if one does not want to disturb
       client code.
     * Key events can be sent to a filter before they are bound to
       translations such as those the X Toolkit Intrinsics library
       provides.

   Clients are expected to get the XIC value XNFilterEvents and
   augment the event mask for the client window with that event
   mask. This mask may be zero.

Callbacks

   When an on-the-spot input method is implemented, only the
   client can insert or delete preedit data in place and possibly
   scroll existing text. This means that the echo of the
   keystrokes has to be achieved by the client itself, tightly
   coupled with the input method logic.

   When the user enters a keystroke, the client calls
   XmbLookupString or XwcLookupString. At this point, in the
   on-the-spot case, the echo of the keystroke in the preedit has
   not yet been done. Before returning to the client logic that
   handles the input characters, the look-up function must call
   the echoing logic to insert the new keystroke. If the
   keystrokes entered so far make up a character, the keystrokes
   entered need to be deleted, and the composed character will be
   returned. Hence, what happens is that, while being called by
   client code, the input method logic has to call back to the
   client before it returns. The client code, that is, a callback
   procedure, is called from the input method logic.

   There are a number of cases where the input method logic has to
   call back the client. Each of those cases is associated with a
   well-defined callback action. It is possible for the client to
   specify, for each input context, what callback is to be called
   for each action.

   There are also callbacks provided for feedback of status
   information and a callback to initiate a geometry request for
   an input method.

Visible Position Feedback Masks

   In the on-the-spot input style, there is a problem when
   attempting to draw preedit strings that are longer than the
   available space. Once the display area is exceeded, it is not
   clear how best to display the preedit string. The visible
   position feedback masks of XIMText help resolve this problem by
   allowing the input method to specify hints that indicate the
   essential portions of the preedit string. For example, such
   hints can help developers implement scrolling of a long preedit
   string within a short preedit display area.

Preedit String Management

   As highlighted before, the input method architecture provides
   preediting, which supports a type of preprocessor input
   composition. In this case, composition consists of interpreting
   a sequence of key events and returning a committed string via
   XmbLookupString or XwcLookupString. This provides the basics
   for input methods.

   In addition to preediting based on key events, a general
   framework is provided to give a client that desires it more
   advanced preediting based on the text within the client. This
   framework is called string conversion and is provided using XIC
   values. The fundamental concept of string conversion is to
   allow the input method to manipulate the client's text
   independent of any user preediting operation.

   The need for string conversion is based on language needs and
   input method capabilities. The following are some examples of
   string conversion:
     * Transliteration conversion provides language-specific
       conversions within the input method. In the case of Korean
       input, users wish to convert a Hangul string into a Hanja
       string while in preediting, after preediting, or in other
       situations (for example, on a selected string). The
       conversion is triggered when the user presses a
       Hangul-to-Hanja key sequence (which may be input method
       specific). Sometimes the user may want to invoke the
       conversion after finishing preediting or on a user-selected
       string. Thus, the string to be converted is in an
       application buffer, not in the preedit area of the input
       method. The string conversion services allow the client to
       request this transliteration conversion from the input
       method. There are many other transliteration conversions
       defined for various languages, for example, Kana-to-Kanji
       conversion in Japanese. The key to remember is that
       transliteration conversions are triggered at the request of
       the user and returned to the client immediately without
       affecting the preedit area of the input method.
     * Reconversion of a previously committed string or a selected
       string is supported by many input methods as a convenience
       to the user. For example, a user tends to mistype the
       commit key while preediting. In that case, some input
       methods provide a special key sequence to request a
       ``reconvert'' operation on the committed string, similar to
       the undo facility provided by most text editors. Another
       example is where the user is proofreading a document that
       has some misconversions from preediting and wants to
       correct the misconverted text. Such reconversion is again
       triggered by the user invoking some special action, but
       reconversions should not affect the state of the preedit
       area.
     * Context-sensitive conversion is required for some languages
       and input methods that need to retrieve text that surrounds
       the current spot location (cursor position) of the client's
       buffer. Such text is needed when the preediting operation
       depends on some surrounding characters (usually preceding
       the spot location). For example, in Thai language input,
       certain character sequences may be invalid and the input
       method may want to check whether characters constitute a
       valid word. Input methods that do such context-dependent
       checking need to retrieve the characters surrounding the
       current cursor position to obtain complete words. Unlike
       other conversions, this conversion is not explicitly
       requested by the user. Input methods that provide such
       context-sensitive conversion continuously need to request
       context from the client, and any change in the context of
       the spot location may affect such conversions. The client's
       context would be needed if the user moves the cursor and
       starts editing again. For this reason, an input method
       supporting this type of conversion should take notice of
       when the client calls XmbResetIC or XwcResetIC, which is
       usually an indication of a context change.

   Context-sensitive conversions just need a copy of the client's
   text, while other conversions replace the client's text with
   new text to achieve the reconversion or transliteration. Yet in
   all cases the result of a conversion, either immediately or via
   preediting, is returned by the XmbLookupString and
   XwcLookupString functions.

   String conversion support is dependent on the availability of
   the XNStringConversion or XNStringConversionCallback XIC
   values. Because the input method may not support string
   conversions, clients have to query the availability of string
   conversion operations by checking the supported XIC values list
   by calling XGetIMValues with the XNQueryICValuesList IM value.

   The difference between these two values is whether the
   conversion is invoked by the client or the input method. The
   XNStringConversion XIC value is used by clients to request a
   string conversion from the input method. The client is
   responsible for determining which events are used to trigger
   the string conversion and whether the string to be converted
   should be copied or deleted. The type of conversion is
   determined by the input method; the client can only pass the
   string to be converted. The client is guaranteed that no
   XNStringConversionCallback will be issued when this value is
   set; thus, the client need only set one of these values.

   The XNStringConversionCallback XIC value is used by the client
   to notify the input method that it will accept requests from
   the input method for string conversion. If this value is set,
   it is the input method's responsibility to determine which
   events are used to trigger the string conversion. When such
   events occur, the input method issues a call to the
   client-supplied procedure to retrieve the string to be
   converted. The client's callback procedure is notified whether
   to copy or delete the string and is provided with hints as to
   the amount of text needed. The
   XIMStringConversionCallbackStruct specifies which text should
   be passed back to the input method.

   Finally, the input method may call the client's
   XNStringConversionCallback procedure multiple times if the
   string returned from the callback is not sufficient to perform
   a successful conversion. The arguments to the client's
   procedure allow the input method to define a position (in
   character units) relative to the client's cursor position and
   the size of the text needed. By varying the position and size
   of the desired text in subsequent callbacks, the input method
   can retrieve additional text.

Input Method Management

   The interface to input methods might appear to be simply
   creating an input method (XOpenIM) and freeing an input method
   (XCloseIM). However, input methods may require complex
   communication with input method servers (IM servers), for
   example:
     * If the X server, IM server, and X clients are started
       asynchronously, some clients may attempt to connect to the
       IM server before it is fully operational, and fail.
       Therefore, some mechanism is needed to allow clients to
       detect when an IM server has started.

   It is up to clients to decide what should be done when an IM
   server is not available (for example, wait, or use some other
   IM server).

     * Some input methods may allow the underlying IM server to be
       switched. Such customization may be desired without
       restarting the entire client.

   To support management of input methods in these cases, the
   following functions are provided:
   XRegisterIMInstantiateCallback This function allows clients to
   register a callback procedure to be called when Xlib detects
   that an IM server is up and available.
   XOpenIM A client calls this function as a result of the
   callback procedure being called.
   XSetIMValues, XSetICValues These functions use the XIM and XIC
   values, XNDestroyCallback, to allow a client to register a
   callback procedure to be called when Xlib detects that an IM
   server that was associated with an opened input method is no
   longer available. In addition, this function can be used to
   switch IM servers for those input methods that support such
   functionality. The IM value for switching IM servers is
   implementation-dependent; see the description below about
   switching IM servers.
   XUnregisterIMInstantiateCallback This function removes a
   callback procedure registered by the client.

   Input methods that support switching of IM servers may exhibit
   some side-effects:
     * The input method will ensure that any new IM server
       supports any of the input styles being used by input
       contexts already associated with the input method. However,
       the list of supported input styles may be different.

     * Geometry management requests on previously created input
       contexts may be initiated by the new IM server.

Hot Keys

   Some clients need to guarantee which keys can be used to escape
   from the input method, regardless of the input method state;
   for example, the client-specific Help key or the keys to move
   the input focus. The HotKey mechanism allows clients to specify
   a set of keys for this purpose. However, the input method might
   not allow clients to specify hot keys. Therefore, clients have
   to query support of hot keys by checking the supported XIC
   values list by calling XGetIMValues with the
   XNQueryICValuesList IM value. When the hot keys specified
   conflict with the key bindings of the input method, hot keys
   take precedence over the key bindings of the input method.

Preedit State Operation

   An input method may have several internal states, depending on
   its implementation and the locale. However, one state that is
   independent of locale and implementation is whether the input
   method is currently performing a preediting operation. Xlib
   provides the ability for an application to manage the preedit
   state programmatically. Two methods are provided for retrieving
   the preedit state of an input context. One method is to query
   the state by calling XGetICValues with the XNPreeditState XIC
   value. Another method is to receive notification whenever the
   preedit state is changed. To receive such notification, an
   application needs to register a callback by calling
   XSetICValues with the XNPreeditStateNotifyCallback XIC value.
   In order to change the preedit state programmatically, an
   application needs to call XSetICValues with XNPreeditState.

   Availability of the preedit state is input method dependent.
   The input method may not provide the ability to set the state
   or to retrieve the state programmatically. Therefore, clients
   have to query availability of preedit state operations by
   checking the supported XIC values list by calling XGetIMValues
   with the XNQueryICValuesList IM value.

Input Method Functions

   To open a connection, use XOpenIM.

   XIM XOpenIM(Display *display, XrmDatabase db, char *res_name,
   char *res_class);

   display

   Specifies the connection to the X server.

   db

   Specifies a pointer to the resource database.

   res_name

   Specifies the full resource name of the application.

   res_class

   Specifies the full class name of the application.

   The XOpenIM function opens an input method, matching the
   current locale and modifiers specification. Current locale and
   modifiers are bound to the input method at opening time. The
   locale associated with an input method cannot be changed
   dynamically. This implies that the strings returned by
   XmbLookupString or XwcLookupString, for any input context
   affiliated with a given input method, will be encoded in the
   locale current at the time the input method is opened.

   The specific input method to which this call will be routed is
   identified on the basis of the current locale. XOpenIM will
   identify a default input method corresponding to the current
   locale. That default can be modified using XSetLocaleModifiers
   for the input method modifier.

   The db argument is the resource database to be used by the
   input method for looking up resources that are private to the
   input method. It is not intended that this database be used to
   look up values that can be set as IC values in an input
   context. If db is NULL, no database is passed to the input
   method.

   The res_name and res_class arguments specify the resource name
   and class of the application. They are intended to be used as
   prefixes by the input method when looking up resources that are
   common to all input contexts that may be created for this input
   method. The characters used for resource names and classes must
   be in the X Portable Character Set. The resources looked up are
   not fully specified if res_name or res_class is NULL.

   The res_name and res_class arguments are not assumed to exist
   beyond the call to XOpenIM. The specified resource database is
   assumed to exist for the lifetime of the input method.

   XOpenIM returns NULL if no input method could be opened.

   To close a connection, use XCloseIM.

   Status XCloseIM(XIM im);

   im

   Specifies the input method.

   The XCloseIM function closes the specified input method.

   To set input method attributes, use XSetIMValues.

   char *XSetIMValues(XIM im);

   im

   Specifies the input method.

   ...

   Specifies the variable-length argument list to set XIM values.

   The XSetIMValues function presents a variable argument list
   programming interface for setting attributes of the specified
   input method. It returns NULL if it succeeds; otherwise, it
   returns the name of the first argument that could not be set.
   Xlib does not attempt to set arguments from the supplied list
   that follow the failed argument; all arguments in the list
   preceding the failed argument have been set correctly.

   To query an input method, use XGetIMValues.

   char *XGetIMValues(XIM im);

   im

   Specifies the input method.

   ...

   Specifies the variable length argument list to get XIM values.

   The XGetIMValues function presents a variable argument list
   programming interface for querying properties or features of
   the specified input method. This function returns NULL if it
   succeeds; otherwise, it returns the name of the first argument
   that could not be obtained.

   Each XIM value argument (following a name) must point to a
   location where the XIM value is to be stored. That is, if the
   XIM value is of type T, the argument must be of type T*. If T
   itself is a pointer type, then XGetIMValues allocates memory to
   store the actual data, and the client is responsible for
   freeing this data by calling XFree with the returned pointer.

   To obtain the display associated with an input method, use
   XDisplayOfIM.

   Display *XDisplayOfIM(XIM im);

   im

   Specifies the input method.

   The XDisplayOfIM function returns the display associated with
   the specified input method.

   To get the locale associated with an input method, use
   XLocaleOfIM.

   char *XLocaleOfIM(XIM im);

   im

   Specifies the input method.

   The XLocaleOfIM function returns the locale associated with the
   specified input method.

   To register an input method instantiate callback, use
   XRegisterIMInstantiateCallback.

   Bool XRegisterIMInstantiateCallback(Display *display,
   XrmDatabase db, char *res_name, char *res_class, XIMProc
   callback, XPointer *client_data);

   display

   Specifies the connection to the X server.

   db

   Specifies a pointer to the resource database.

   res_name

   Specifies the full resource name of the application.

   res_class

   Specifies the full class name of the application.

   callback

   Specifies a pointer to the input method instantiate callback.

   client_data

   Specifies the additional client data.

   The XRegisterIMInstantiateCallback function registers a
   callback to be invoked whenever a new input method becomes
   available for the specified display that matches the current
   locale and modifiers.

   The function returns True if it succeeds; otherwise, it returns
   False.

   The generic prototype is as follows:

   void IMInstantiateCallback(Display *display, XPointer
   client_data, XPointer call_data);

   display

   Specifies the connection to the X server.

   client_data

   Specifies the additional client data.

   call_data

   Not used for this callback and always passed as NULL.

   To unregister an input method instantiation callback, use
   XUnregisterIMInstantiateCallback.

   Bool XUnregisterIMInstantiateCallback(Display *display,
   XrmDatabase db, char *res_name, char *res_class, XIMProc
   callback, XPointer *client_data);

   display

   Specifies the connection to the X server.

   db

   Specifies a pointer to the resource database.

   res_name

   Specifies the full resource name of the application.

   res_class

   Specifies the full class name of the application.

   callback

   Specifies a pointer to the input method instantiate callback.

   client_data

   Specifies the additional client data.

   The XUnregisterIMInstantiateCallback function removes an input
   method instantiation callback previously registered. The
   function returns True if it succeeds; otherwise, it returns
   False.

Input Method Values

   The following table describes how XIM values are interpreted by
   an input method. The first column lists the XIM values. The
   second column indicates how each of the XIM values are treated
   by that input style.

   The following keys apply to this table.
   Key Explanation
   D This value may be set using XSetIMValues. If it is not set, a
   default is provided.
   S This value may be set using XSetIMValues.
   G This value may be read using XGetIMValues.

   XIM Value           Key
   XNQueryInputStyle   G
   XNResourceName      D-S-G
   XNResourceClass     D-S-G
   XNDestroyCallback   D-S-G
   XNQueryIMValuesList G
   XNQueryICValuesList G
   XNVisiblePosition   G
   XNR6PreeditCallback D-S-G

   XNR6PreeditCallback is obsolete and its use is not recommended
   (see section 13.5.4.6).

Query Input Style

   A client should always query the input method to determine
   which input styles are supported. The client should then find
   an input style it is capable of supporting.

   If the client cannot find an input style that it can support,
   it should negotiate with the user the continuation of the
   program (exit, choose another input method, and so on).

   The argument value must be a pointer to a location where the
   returned value will be stored. The returned value is a pointer
   to a structure of type XIMStyles. Clients are responsible for
   freeing the XIMStyles structure. To do so, use XFree.

   The XIMStyles structure is defined as follows:
typedef unsigned long XIMStyle;


#define     XIMPreeditArea             0x0001L
#define     XIMPreeditCallbacks        0x0002L
#define     XIMPreeditPosition         0x0004L
#define     XIMPreeditNothing          0x0008L
#define     XIMPreeditNone             0x0010L

#define     XIMStatusArea              0x0100L
#define     XIMStatusCallbacks         0x0200L
#define     XIMStatusNothing           0x0400L
#define     XIMStatusNone              0x0800L

typedef struct {
      unsigned short count_styles;
      XIMStyle * supported_styles;
} XIMStyles;


   An XIMStyles structure contains the number of input styles
   supported in its count_styles field. This is also the size of
   the supported_styles array.

   The supported styles is a list of bitmask combinations, which
   indicate the combination of styles for each of the areas
   supported. These areas are described later. Each element in the
   list should select one of the bitmask values for each area. The
   list describes the complete set of combinations supported. Only
   these combinations are supported by the input method.

   The preedit category defines what type of support is provided
   by the input method for preedit information.
   XIMPreeditArea If chosen, the input method would require the
   client to provide some area values for it to do its preediting.
   Refer to XIC values XNArea and XNAreaNeeded.
   XIMPreeditPosition If chosen, the input method would require
   the client to provide positional values. Refer to XIC values
   XNSpotLocation and XNFocusWindow.
   XIMPreeditCallbacks If chosen, the input method would require
   the client to define the set of preedit callbacks. Refer to XIC
   values XNPreeditStartCallback, XNPreeditDoneCallback,
   XNPreeditDrawCallback, and XNPreeditCaretCallback.
   XIMPreeditNothing If chosen, the input method can function
   without any preedit values.
   XIMPreeditNone The input method does not provide any preedit
   feedback. Any preedit value is ignored. This style is mutually
   exclusive with the other preedit styles.

   The status category defines what type of support is provided by
   the input method for status information.
   XIMStatusArea The input method requires the client to provide
   some area values for it to do its status feedback. See XNArea
   and XNAreaNeeded.
   XIMStatusCallbacks The input method requires the client to
   define the set of status callbacks, XNStatusStartCallback,
   XNStatusDoneCallback, and XNStatusDrawCallback.
   XIMStatusNothing The input method can function without any
   status values.
   XIMStatusNone The input method does not provide any status
   feedback. If chosen, any status value is ignored. This style is
   mutually exclusive with the other status styles.

Resource Name and Class

   The XNResourceName and XNResourceClass arguments are strings
   that specify the full name and class used by the input method.
   These values should be used as prefixes for the name and class
   when looking up resources that may vary according to the input
   method. If these values are not set, the resources will not be
   fully specified.

   It is not intended that values that can be set as XIM values be
   set as resources.

Destroy Callback

   The XNDestroyCallback argument is a pointer to a structure of
   type XIMCallback. XNDestroyCallback is triggered when an input
   method stops its service for any reason. After the callback is
   invoked, the input method is closed and the associated input
   context(s) are destroyed by Xlib. Therefore, the client should
   not call XCloseIM or XDestroyIC.

   The generic prototype of this callback function is as follows:

   void DestroyCallback(XIM im, XPointer client_data, XPointer
   call_data);

   im

   Specifies the input method.

   client_data

   Specifies the additional client data.

   call_data

   Not used for this callback and always passed as NULL.

   A DestroyCallback is always called with a NULL call_data
   argument.

Query IM/IC Values List

   XNQueryIMValuesList and XNQueryICValuesList are used to query
   about XIM and XIC values supported by the input method.

   The argument value must be a pointer to a location where the
   returned value will be stored. The returned value is a pointer
   to a structure of type XIMValuesList. Clients are responsible
   for freeing the XIMValuesList structure. To do so, use XFree.

   The XIMValuesList structure is defined as follows:


typedef struct {
     unsigned short count_values;
     char **supported_values;
} XIMValuesList;

Visible Position

   The XNVisiblePosition argument indicates whether the visible
   position masks of XIMFeedback in XIMText are available.

   The argument value must be a pointer to a location where the
   returned value will be stored. The returned value is of type
   Bool. If the returned value is True, the input method uses the
   visible position masks of XIMFeedback in XIMText; otherwise,
   the input method does not use the masks.

   Because this XIM value is optional, a client should call
   XGetIMValues with argument XNQueryIMValuesList before using
   this argument. If the XNVisiblePosition does not exist in the
   IM values list returned from XNQueryIMValuesList, the visible
   position masks of XIMFeedback in XIMText are not used to
   indicate the visible position.

Preedit Callback Behavior

   The XNR6PreeditCallback argument originally included in the
   X11R6 specification has been deprecated.\(dg During formulation
   of the X11R6 specification, the behavior of the R6
   PreeditDrawCallbacks was going to differ significantly from
   that of the R5 callbacks. Late changes to the specification
   converged the R5 and R6 behaviors, eliminating the need for
   XNR6PreeditCallback. Unfortunately, this argument was not
   removed from the R6 specification before it was published.

   The XNR6PreeditCallback argument indicates whether the behavior
   of preedit callbacks regarding XIMPreeditDrawCallbackStruct
   values follows Release 5 or Release 6 semantics.

   The value is of type Bool. When querying for
   XNR6PreeditCallback, if the returned value is True, the input
   method uses the Release 6 behavior; otherwise, it uses the
   Release 5 behavior. The default value is False. In order to use
   Release 6 semantics, the value of XNR6PreeditCallback must be
   set to True.

   Because this XIM value is optional, a client should call
   XGetIMValues with argument XNQueryIMValuesList before using
   this argument. If the XNR6PreeditCallback does not exist in the
   IM values list returned from XNQueryIMValuesList, the
   PreeditCallback behavior is Release 5 semantics.

Input Context Functions

   An input context is an abstraction that is used to contain both
   the data required (if any) by an input method and the
   information required to display that data. There may be
   multiple input contexts for one input method. The programming
   interfaces for creating, reading, or modifying an input context
   use a variable argument list. The name elements of the argument
   lists are referred to as XIC values. It is intended that input
   methods be controlled by these XIC values. As new XIC values
   are created, they should be registered with the X Consortium.

   To create an input context, use XCreateIC.

   XIC XCreateIC(XIM im);

   im

   Specifies the input method.

   ...

   Specifies the variable length argument list to set XIC values.

   The XCreateIC function creates a context within the specified
   input method.

   Some of the arguments are mandatory at creation time, and the
   input context will not be created if those arguments are not
   provided. The mandatory arguments are the input style and the
   set of text callbacks (if the input style selected requires
   callbacks). All other input context values can be set later.

   XCreateIC returns a NULL value if no input context could be
   created. A NULL value could be returned for any of the
   following reasons:
     * A required argument was not set.
     * A read-only argument was set (for example, XNFilterEvents).
     * The argument name is not recognized.
     * The input method encountered an input method
       implementation-dependent error.

   XCreateIC can generate BadAtom, BadColor, BadPixmap, and
   BadWindow errors.

   To destroy an input context, use XDestroyIC.

   void XDestroyIC(XIC ic);

   ic

   Specifies the input context.

   XDestroyIC destroys the specified input context.

   To communicate to and synchronize with input method for any
   changes in keyboard focus from the client side, use XSetICFocus
   and XUnsetICFocus.

   void XSetICFocus(XIC ic);

   ic

   Specifies the input context.

   The XSetICFocus function allows a client to notify an input
   method that the focus window attached to the specified input
   context has received keyboard focus. The input method should
   take action to provide appropriate feedback. Complete feedback
   specification is a matter of user interface policy.

   Calling XSetICFocus does not affect the focus window value.

   void XUnsetICFocus(XIC ic);

   ic

   Specifies the input context.

   The XUnsetICFocus function allows a client to notify an input
   method that the specified input context has lost the keyboard
   focus and that no more input is expected on the focus window
   attached to that input context. The input method should take
   action to provide appropriate feedback. Complete feedback
   specification is a matter of user interface policy.

   Calling XUnsetICFocus does not affect the focus window value;
   the client may still receive events from the input method that
   are directed to the focus window.

   To reset the state of an input context to its initial state,
   use XmbResetIC or XwcResetIC.

   char *XmbResetIC(XIC ic);

   wchar_t *XwcResetIC(XIC ic);

   ic

   Specifies the input context.

   When XNResetState is set to XIMInitialState, XmbResetIC and
   XwcResetIC reset an input context to its initial state; when
   XNResetState is set to XIMPreserveState, the current input
   context state is preserved. In both cases, any input pending on
   that context is deleted. The input method is required to clear
   the preedit area, if any, and update the status accordingly.
   Calling XmbResetIC or XwcResetIC does not change the focus.

   The return value of XmbResetIC is its current preedit string as
   a multibyte string. If there is any preedit text drawn or
   visible to the user, then these procedures must return a
   non-NULL string. If there is no visible preedit text, then it
   is input method implementation-dependent whether these
   procedures return a non-NULL string or NULL.

   The client should free the returned string by calling XFree.

   To get the input method associated with an input context, use
   XIMOfIC.

   XIM XIMOfIC(XIC ic);

   ic

   Specifies the input context.

   The XIMOfIC function returns the input method associated with
   the specified input context.

   Xlib provides two functions for setting and reading XIC values,
   respectively, XSetICValues and XGetICValues. Both functions
   have a variable-length argument list. In that argument list,
   any XIC value's name must be denoted with a character string
   using the X Portable Character Set.

   To set XIC values, use XSetICValues.

   char *XSetICValues(XIC ic);

   ic

   Specifies the input context.

   ...

   Specifies the variable length argument list to set XIC values.

   The XSetICValues function returns NULL if no error occurred;
   otherwise, it returns the name of the first argument that could
   not be set. An argument might not be set for any of the
   following reasons:
     * The argument is read-only (for example, XNFilterEvents).
     * The argument name is not recognized.
     * An implementation-dependent error occurs.

   Each value to be set must be an appropriate datum, matching the
   data type imposed by the semantics of the argument.

   XSetICValues can generate BadAtom, BadColor, BadCursor,
   BadPixmap, and BadWindow errors.

   To obtain XIC values, use XGetICValues.

   char *XGetICValues(XIC ic);

   ic

   Specifies the input context.

   ...

   Specifies the variable length argument list to get XIC values.

   The XGetICValues function returns NULL if no error occurred;
   otherwise, it returns the name of the first argument that could
   not be obtained. An argument could not be obtained for any of
   the following reasons:
     * The argument name is not recognized.
     * The input method encountered an implementation-dependent
       error.

   Each IC attribute value argument (following a name) must point
   to a location where the IC value is to be stored. That is, if
   the IC value is of type T, the argument must be of type T*. If
   T itself is a pointer type, then XGetICValues allocates memory
   to store the actual data, and the client is responsible for
   freeing this data by calling XFree with the returned pointer.
   The exception to this rule is for an IC value of type
   XVaNestedList (for preedit and status attributes). In this
   case, the argument must also be of type XVaNestedList. Then,
   the rule of changing type T to T* and freeing the allocated
   data applies to each element of the nested list.

Input Context Values

   The following tables describe how XIC values are interpreted by
   an input method depending on the input style chosen by the
   user.

   The first column lists the XIC values. The second column
   indicates which values are involved in affecting, negotiating,
   and setting the geometry of the input method windows. The
   subentries under the third column indicate the different input
   styles that are supported. Each of these columns indicates how
   each of the XIC values are treated by that input style.

   The following keys apply to these tables.
   Key Explanation
   C This value must be set with XCreateIC.
   D This value may be set using XCreateIC.> If it is not set,> a
   default is provided.
   G This value may be read using XGetICValues.
   GN This value may cause geometry negotiation when its value is
   set by means of XCreateIC or XSetICValues.
   GR This value will be the response of the input method when any
   GN value is changed.
   GS This value will cause the geometry of the input method
   window to be set.
   O This value must be set once and only once. It need not be set
   at create time.
   S This value may be set with XSetICValues.
   Ignored This value is ignored by the input method for the given
   input style.

   XIC Value Geometry Management Preedit Callback Preedit Position
   Input Style Preedit Area Preedit Nothing Preedit None
   Input Style   C-G C-G C-G C-G C-G
   Client Window   O-G O-G O-G O-G Ignored
   Focus Window GN D-S-G D-S-G D-S-G D-S-G Ignored
   Resource Name   Ignored D-S-G D-S-G D-S-G Ignored
   Resource Class   Ignored D-S-G D-S-G D-S-G Ignored
   Geometry Callback   Ignored Ignored D-S-G Ignored Ignored
   Filter Events   G G G G Ignored
   Destroy Callback   D-S-G D-S-G D-S-G D-S-G D-S-G
   String Conversion Callback   S-G S-G S-G S-G S-G
   String Conversion   D-S-G D-S-G D-S-G D-S-G D-S-G
   Reset State   D-S-G D-S-G D-S-G D-S-G Ignored
   HotKey   S-G S-G S-G S-G Ignored
   HotKeyState   D-S-G D-S-G D-S-G D-S-G Ignored
   Preedit
   Area GS Ignored D-S-G D-S-G Ignored Ignored
   Area Needed GN-GR Ignored Ignored S-G Ignored Ignored
   Spot Location   Ignored D-S-G Ignored Ignored Ignored
   Colormap   Ignored D-S-G D-S-G D-S-G Ignored
   Foreground   Ignored D-S-G D-S-G D-S-G Ignored
   Background   Ignored D-S-G D-S-G D-S-G Ignored
   Background Pixmap   Ignored D-S-G D-S-G D-S-G Ignored
   Font Set GN Ignored D-S-G D-S-G D-S-G Ignored
   Line Spacing GN Ignored D-S-G D-S-G D-S-G Ignored
   Cursor   Ignored D-S-G D-S-G D-S-G Ignored
   Preedit State   D-S-G D-S-G D-S-G D-S-G Ignored
   Preedit State Notify Callback   S-G S-G S-G S-G Ignored
   Preedit Callbacks   C-S-G Ignored Ignored Ignored Ignored

   XIC Value Geomentry Management Status Callback Status Area
   Status Nothing Status None
   Input Style   C-G C-G C-G C-G
   Client Window   O-G O-G O-G Ignored
   Focus Window GN D-S-G D-S-G D-S-G Ignored
   Resource Name   Ignored D-S-G D-S-G Ignored
   Resource Class   Ignored D-S-G D-S-G Ignored
   Geometry Callback   Ignored D-S-G Ignored Ignored
   Filter Events   G G G G
   Status
   Area GS Ignored D-S-G Ignored Ignored
   Area Needed GN-GR Ignored S-G Ignored Ignored
   Colormap   Ignored D-S-G D-S-G Ignored
   Foreground   Ignored D-S-G D-S-G Ignored
   Background   Ignored D-S-G D-S-G Ignored
   Background Pixmap   Ignored D-S-G D-S-G Ignored
   Font Set GN Ignored D-S-G D-S-G Ignored
   Line Spacing GN Ignored D-S-G D-S-G Ignored
   Cursor   Ignored D-S-G D-S-G Ignored
   Status Callbacks   C-S-G Ignored Ignored Ignored

Input Style

   The XNInputStyle argument specifies the input style to be used.
   The value of this argument must be one of the values returned
   by the XGetIMValues function with the XNQueryInputStyle
   argument specified in the supported_styles list.

   Note that this argument must be set at creation time and cannot
   be changed.

Client Window

   The XNClientWindow argument specifies to the input method the
   client window in which the input method can display data or
   create subwindows. Geometry values for input method areas are
   given with respect to the client window. Dynamic change of
   client window is not supported. This argument may be set only
   once and should be set before any input is done using this
   input context. If it is not set, the input method may not
   operate correctly.

   If an attempt is made to set this value a second time with
   XSetICValues, the string XNClientWindow will be returned by
   XSetICValues, and the client window will not be changed.

   If the client window is not a valid window ID on the display
   attached to the input method, a BadWindow error can be
   generated when this value is used by the input method.

Focus Window

   The XNFocusWindow argument specifies the focus window. The
   primary purpose of the XNFocusWindow is to identify the window
   that will receive the key event when input is composed. In
   addition, the input method may possibly affect the focus window
   as follows:
     * Select events on it
     * Send events to it
     * Modify its properties
     * Grab the keyboard within that window

   The associated value must be of type Window. If the focus
   window is not a valid window ID on the display attached to the
   input method, a BadWindow error can be generated when this
   value is used by the input method.

   When this XIC value is left unspecified, the input method will
   use the client window as the default focus window.

Resource Name and Class

   The XNResourceName and XNResourceClass arguments are strings
   that specify the full name and class used by the client to
   obtain resources for the client window. These values should be
   used as prefixes for name and class when looking up resources
   that may vary according to the input context. If these values
   are not set, the resources will not be fully specified.

   It is not intended that values that can be set as XIC values be
   set as resources.

Geometry Callback

   The XNGeometryCallback argument is a structure of type
   XIMCallback (see section 13.5.6.13.12).

   The XNGeometryCallback argument specifies the geometry callback
   that a client can set. This callback is not required for
   correct operation of either an input method or a client. It can
   be set for a client whose user interface policy permits an
   input method to request the dynamic change of that input
   method's window. An input method that does dynamic change will
   need to filter any events that it uses to initiate the change.

Filter Events

   The XNFilterEvents argument returns the event mask that an
   input method needs to have selected for. The client is expected
   to augment its own event mask for the client window with this
   one.

   This argument is read-only, is set by the input method at
   create time, and is never changed.

   The type of this argument is unsigned long. Setting this value
   will cause an error.

Destroy Callback

   The XNDestroyCallback argument is a pointer to a structure of
   type XIMCallback (see section 13.5.6.13.12). This callback is
   triggered when the input method stops its service for any
   reason; for example, when a connection to an IM server is
   broken. After the destroy callback is called, the input context
   is destroyed and the input method is closed. Therefore, the
   client should not call XDestroyIC and XCloseIM.

String Conversion Callback

   The XNStringConversionCallback argument is a structure of type
   XIMCallback (see section 13.5.6.13.12).

   The XNStringConversionCallback argument specifies a string
   conversion callback. This callback is not required for correct
   operation of either the input method or the client. It can be
   set by a client to support string conversions that may be
   requested by the input method. An input method that does string
   conversions will filter any events that it uses to initiate the
   conversion.

   Because this XIC value is optional, a client should call
   XGetIMValues with argument XNQueryICValuesList before using
   this argument.

String Conversion

   The XNStringConversion argument is a structure of type
   XIMStringConversionText.

   The XNStringConversion argument specifies the string to be
   converted by an input method. This argument is not required for
   correct operation of either the input method or the client.

   String conversion facilitates the manipulation of text
   independent of preediting. It is essential for some input
   methods and clients to manipulate text by performing
   context-sensitive conversion, reconversion, or transliteration
   conversion on it.

   Because this XIC value is optional, a client should call
   XGetIMValues with argument XNQueryICValuesList before using
   this argument.

   The XIMStringConversionText structure is defined as follows:


typedef struct _XIMStringConversionText {
     unsigned short              length;
     XIMStringConversionFeedback *feedback;
     Bool                        encoding_is_wchar;
     union {
          char     *mbs;
          wchar_t  *wcs;
     } string;
} XIMStringConversionText;

typedef unsigned long XIMStringConversionFeedback;

   The feedback member is reserved for future use. The text to be
   converted is defined by the string and length members. The
   length is indicated in characters. To prevent the library from
   freeing memory pointed to by an uninitialized pointer, the
   client should set the feedback element to NULL.

Reset State

   The XNResetState argument specifies the state the input context
   will return to after calling XmbResetIC or XwcResetIC.

   The XIC state may be set to its initial state, as specified by
   the XNPreeditState value when XCreateIC was called, or it may
   be set to preserve the current state.

   The valid masks for XIMResetState are as follows:

typedef unsigned long XIMResetState;

#define XIMInitialState  (1L)
#define XIMPreserveState (1L<<1)


   If XIMInitialState is set, then XmbResetIC and XwcResetIC will
   return to the initial XNPreeditState state of the XIC.

   If XIMPreserveState is set, then XmbResetIC and XwcResetIC will
   preserve the current state of the XIC.

   If XNResetState is left unspecified, the default is
   XIMInitialState.

   XIMResetState values other than those specified above will
   default to XIMInitialState.

   Because this XIC value is optional, a client should call
   XGetIMValues with argument XNQueryICValuesList before using
   this argument.

Hot Keys

   The XNHotKey argument specifies the hot key list to the XIC.
   The hot key list is a pointer to the structure of type
   XIMHotKeyTriggers, which specifies the key events that must be
   received without any interruption of the input method. For the
   hot key list set with this argument to be utilized, the client
   must also set XNHotKeyState to XIMHotKeyStateON.

   Because this XIC value is optional, a client should call
   XGetIMValues with argument XNQueryICValuesList before using
   this functionality.

   The value of the argument is a pointer to a structure of type
   XIMHotKeyTriggers.

   If an event for a key in the hot key list is found, then the
   process will receive the event and it will be processed inside
   the client.



typedef struct {
     KeySym keysym;
     unsigned int modifier;
     unsigned int modifier_mask;
} XIMHotKeyTrigger;

typedef struct {
     int num_hot_key;
     XIMHotKeyTrigger *key;
} XIMHotKeyTriggers;

   The combination of modifier and modifier_mask are used to
   represent one of three states for each modifier: either the
   modifier must be on, or the modifier must be off, or the
   modifier is a ``don't care'' - it may be on or off. When a
   modifier_mask bit is set to 0, the state of the associated
   modifier is ignored when evaluating whether the key is hot or
   not.
   Modifier Bit Mask Bit Meaning
   0            1        The modifier must be off.
   1            1        The modifier must be on.
   n/a          0        Do not care if the modifier is on or off.

Hot Key State

   The XNHotKeyState argument specifies the hot key state of the
   input method. This is usually used to switch the input method
   between hot key operation and normal input processing.

   The value of the argument is a pointer to a structure of type
   XIMHotKeyState .
typedef unsigned long XIMHotKeyState;

#define XIMHotKeyStateON            (0x0001L)
#define XIMHotKeyStateOFF           (0x0002L)


   If not specified, the default is XIMHotKeyStateOFF.

Preedit and Status Attributes

   The XNPreeditAttributes and XNStatusAttributes arguments
   specify to an input method the attributes to be used for the
   preedit and status areas, if any. Those attributes are passed
   to XSetICValues or XGetICValues as a nested variable-length
   list. The names to be used in these lists are described in the
   following sections.

Area

   The value of the XNArea argument must be a pointer to a
   structure of type XRectangle. The interpretation of the XNArea
   argument is dependent on the input method style that has been
   set.

   If the input method style is XIMPreeditPosition, XNArea
   specifies the clipping region within which preediting will take
   place. If the focus window has been set, the coordinates are
   assumed to be relative to the focus window. Otherwise, the
   coordinates are assumed to be relative to the client window. If
   neither has been set, the results are undefined.

   If XNArea is not specified, is set to NULL, or is invalid, the
   input method will default the clipping region to the geometry
   of the XNFocusWindow. If the area specified is NULL or invalid,
   the results are undefined.

   If the input style is XIMPreeditArea or XIMStatusArea, XNArea
   specifies the geometry provided by the client to the input
   method. The input method may use this area to display its data,
   either preedit or status depending on the area designated. The
   input method may create a window as a child of the client
   window with dimensions that fit the XNArea. The coordinates are
   relative to the client window. If the client window has not
   been set yet, the input method should save these values and
   apply them when the client window is set. If XNArea is not
   specified, is set to NULL, or is invalid, the results are
   undefined.

Area Needed

   When set, the XNAreaNeeded argument specifies the geometry
   suggested by the client for this area (preedit or status). The
   value associated with the argument must be a pointer to a
   structure of type XRectangle. Note that the x, y values are not
   used and that nonzero values for width or height are the
   constraints that the client wishes the input method to respect.

   When read, the XNAreaNeeded argument specifies the preferred
   geometry desired by the input method for the area.

   This argument is only valid if the input style is
   XIMPreeditArea or XIMStatusArea. It is used for geometry
   negotiation between the client and the input method and has no
   other effect on the input method (see section 13.5.1.5).

Spot Location

   The XNSpotLocation argument specifies to the input method the
   coordinates of the spot to be used by an input method executing
   with XNInputStyle set to XIMPreeditPosition. When specified to
   any input method other than XIMPreeditPosition, this XIC value
   is ignored. Some Xlib implementations will allow this to be set
   when XNInputStyle is set to XIMPreeditCallbacks. Behavior in
   that case is implementation defined.

   The x coordinate specifies the position where the next
   character would be inserted. The y coordinate is the position
   of the baseline used by the current text line in the focus
   window. The x and y coordinates are relative to the focus
   window, if it has been set; otherwise, they are relative to the
   client window. If neither the focus window nor the client
   window has been set, the results are undefined.

   The value of the argument is a pointer to a structure of type
   XPoint.

Colormap

   Two different arguments can be used to indicate what colormap
   the input method should use to allocate colors, a colormap ID,
   or a standard colormap name.

   The XNColormap argument is used to specify a colormap ID. The
   argument value is of type Colormap. An invalid argument may
   generate a BadColor error when it is used by the input method.

   The XNStdColormap argument is used to indicate the name of the
   standard colormap in which the input method should allocate
   colors. The argument value is an Atom that should be a valid
   atom for calling XGetRGBColormaps. An invalid argument may
   generate a BadAtom error when it is used by the input method.

   If the colormap is left unspecified, the client window colormap
   becomes the default.

Foreground and Background

   The XNForeground and XNBackground arguments specify the
   foreground and background pixel, respectively. The argument
   value is of type unsigned long. It must be a valid pixel in the
   input method colormap.

   If these values are left unspecified, the default is determined
   by the input method.

Background Pixmap

   The XNBackgroundPixmap argument specifies a background pixmap
   to be used as the background of the window. The value must be
   of type Pixmap. An invalid argument may generate a BadPixmap
   error when it is used by the input method.

   If this value is left unspecified, the default is determined by
   the input method.

Font Set

   The XNFontSet argument specifies to the input method what font
   set is to be used. The argument value is of type XFontSet.

   If this value is left unspecified, the default is determined by
   the input method.

Line Spacing

   The XNLineSpace argument specifies to the input method what
   line spacing is to be used in the preedit window if more than
   one line is to be used. This argument is of type int.

   If this value is left unspecified, the default is determined by
   the input method.

Cursor

   The XNCursor argument specifies to the input method what cursor
   is to be used in the specified window. This argument is of type
   Cursor.

   An invalid argument may generate a BadCursor error when it is
   used by the input method. If this value is left unspecified,
   the default is determined by the input method.

Preedit State

   The XNPreeditState argument specifies the state of input
   preediting for the input method. Input preediting can be on or
   off.

   The valid mask names for XNPreeditState are as follows:

typedef unsigned long XIMPreeditState;

#define XIMPreeditUnknown    0L
#define XIMPreeditEnable     1L
#define XIMPreeditDisable    (1L<<1)


   If a value of XIMPreeditEnable is set, then input preediting is
   turned on by the input method.

   If a value of XIMPreeditDisable is set, then input preediting
   is turned off by the input method.

   If XNPreeditState is left unspecified, then the state will be
   implementation-dependent.

   When XNResetState is set to XIMInitialState, the XNPreeditState
   value specified at the creation time will be reflected as the
   initial state for XmbResetIC and XwcResetIC.

   Because this XIC value is optional, a client should call
   XGetIMValues with argument XNQueryICValuesList before using
   this argument.

Preedit State Notify Callback

   The preedit state notify callback is triggered by the input
   method when the preediting state has changed. The value of the
   XNPreeditStateNotifyCallback argument is a pointer to a
   structure of type XIMCallback. The generic prototype is as
   follows:

   void PreeditStateNotifyCallback(XIC ic, XPointer client_data,
   XIMPreeditStateNotifyCallbackStruct *call_data);

   ic

   Specifies the input context.

   client_data

   Specifies the additional client data.

   call_data

   Specifies the current preedit state.

   The XIMPreeditStateNotifyCallbackStruct structure is defined as
   follows:



typedef struct _XIMPreeditStateNotifyCallbackStruct {
     XIMPreeditState state;
} XIMPreeditStateNotifyCallbackStruct;

   Because this XIC value is optional, a client should call
   XGetIMValues with argument XNQueryICValuesList before using
   this argument.

Preedit and Status Callbacks

   A client that wants to support the input style
   XIMPreeditCallbacks must provide a set of preedit callbacks to
   the input method. The set of preedit callbacks is as follows:
   XNPreeditStartCallback This is called when the input method
   starts preedit.
   XNPreeditDoneCallback This is called when the input method
   stops preedit.
   XNPreeditDrawCallback This is called when a number of preedit
   keystrokes should be echoed.
   XNPreeditCaretCallback This is called to move the text
   insertion point within the preedit string.

   A client that wants to support the input style
   XIMStatusCallbacks must provide a set of status callbacks to
   the input method. The set of status callbacks is as follows:
   XNStatusStartCallback This is called when the input method
   initializes the status area.
   XNStatusDoneCallback This is called when the input method no
   longer needs the status area.
   XNStatusDrawCallback This is called when updating of the status
   area is required.

   The value of any status or preedit argument is a pointer to a
   structure of type XIMCallback.



typedef void (*XIMProc)();

typedef struct {
     XPointer client_data;
     XIMProc callback;
} XIMCallback;

   Each callback has some particular semantics and will carry the
   data that expresses the environment necessary to the client
   into a specific data structure. This paragraph only describes
   the arguments to be used to set the callback.

   Setting any of these values while doing preedit may cause
   unexpected results.

Input Method Callback Semantics

   XIM callbacks are procedures defined by clients or text drawing
   packages that are to be called from the input method when
   selected events occur. Most clients will use a text editing
   package or a toolkit and, hence, will not need to define such
   callbacks. This section defines the callback semantics, when
   they are triggered, and what their arguments are. This
   information is mostly useful for X toolkit implementors.

   Callbacks are mostly provided so that clients (or text editing
   packages) can implement on-the-spot preediting in their own
   window. In that case, the input method needs to communicate and
   synchronize with the client. The input method needs to
   communicate changes in the preedit window when it is under
   control of the client. Those callbacks allow the client to
   initialize the preedit area, display a new preedit string, move
   the text insertion point during preedit, terminate preedit, or
   update the status area.

   All callback procedures follow the generic prototype:

   void CallbackPrototype(XIC ic, XPointer client_data, SomeType
   call_data);

   ic

   Specifies the input context.

   client_data

   Specifies the additional client data.

   call_data

   Specifies data specific to the callback.

   The call_data argument is a structure that expresses the
   arguments needed to achieve the semantics; that is, it is a
   specific data structure appropriate to the callback. In cases
   where no data is needed in the callback, this call_data
   argument is NULL. The client_data argument is a closure that
   has been initially specified by the client when specifying the
   callback and passed back. It may serve, for example, to inherit
   application context in the callback.

   The following paragraphs describe the programming semantics and
   specific data structure associated with the different reasons.

Geometry Callback

   The geometry callback is triggered by the input method to
   indicate that it wants the client to negotiate geometry. The
   generic prototype is as follows:

   void GeometryCallback(XIC ic, XPointer client_data, XPointer
   call_data);

   ic

   Specifies the input context.

   client_data

   Specifies the additional client data.

   call_data

   Not used for this callback and always passed as NULL.

   The callback is called with a NULL call_data argument.

Destroy Callback

   The destroy callback is triggered by the input method when it
   stops service for any reason. After the callback is invoked,
   the input context will be freed by Xlib. The generic prototype
   is as follows:

   void DestroyCallback(XIC ic, XPointer client_data, XPointer
   call_data);

   ic

   Specifies the input context.

   client_data

   Specifies the additional client data.

   call_data

   Not used for this callback and always passed as NULL.

   The callback is called with a NULL call_data argument.

String Conversion Callback

   The string conversion callback is triggered by the input method
   to request the client to return the string to be converted. The
   returned string may be either a multibyte or wide character
   string, with an encoding matching the locale bound to the input
   context. The callback prototype is as follows:

   void StringConversionCallback(XIC ic, XPointer client_data,
   XIMStringConversionCallbackStruct *call_data);

   ic

   Specifies the input method.

   client_data

   Specifies the additional client data.

   call_data

   Specifies the amount of the string to be converted.

   The callback is passed an XIMStringConversionCallbackStruct
   structure in the call_data argument. The text member is an
   XIMStringConversionText structure (see section 13.5.6.9) to be
   filled in by the client and describes the text to be sent to
   the input method. The data pointed to by the string and
   feedback elements of the XIMStringConversionText structure will
   be freed using XFree by the input method after the callback
   returns. So the client should not point to internal buffers
   that are critical to the client. Similarly, because the
   feedback element is currently reserved for future use, the
   client should set feedback to NULL to prevent the library from
   freeing memory at some random location due to an uninitialized
   pointer.

   The XIMStringConversionCallbackStruct structure is defined as
   follows:

typedef struct _XIMStringConversionCallbackStruct {
     XIMStringConversionPosition position;
     XIMCaretDirection direction;
     short factor;
     XIMStringConversionOperation operation;
     XIMStringConversionText *text;
} XIMStringConversionCallbackStruct;

typedef short XIMStringConversionPosition;

typedef unsigned short XIMStringConversionOperation;

#define XIMStringConversionSubstitution       (0x0001)
#define XIMStringConversionRetrieval          (0x0001)


   XIMStringConversionPosition specifies the starting position of
   the string to be returned in the XIMStringConversionText
   structure. The value identifies a position, in units of
   characters, relative to the client's cursor position in the
   client's buffer.

   The ending position of the text buffer is determined by the
   direction and factor members. Specifically, it is the character
   position relative to the starting point as defined by the
   XIMCaretDirection. The factor member of
   XIMStringConversionCallbackStruct specifies the number of
   XIMCaretDirection positions to be applied. For example, if the
   direction specifies XIMLineEnd and factor is 1, then all
   characters from the starting position to the end of the current
   display line are returned. If the direction specifies
   XIMForwardChar or XIMBackwardChar, then the factor specifies a
   relative position, indicated in characters, from the starting
   position.

   XIMStringConversionOperation specifies whether the string to be
   converted should be deleted (substitution) or copied
   (retrieval) from the client's buffer. When the
   XIMStringConversionOperation is
   XIMStringConversionSubstitution, the client must delete the
   string to be converted from its own buffer. When the
   XIMStringConversionOperation is XIMStringConversionRetrieval,
   the client must not delete the string to be converted from its
   buffer. The substitute operation is typically used for
   reconversion and transliteration conversion, while the
   retrieval operation is typically used for context-sensitive
   conversion.

Preedit State Callbacks

   When the input method turns preediting on or off, a
   PreeditStartCallback or PreeditDoneCallback callback is
   triggered to let the toolkit do the setup or the cleanup for
   the preedit region.

   int PreeditStartCallback(XIC ic, XPointer client_data, XPointer
   call_data);

   ic

   Specifies the input context.

   client_data

   Specifies the additional client data.

   call_data

   Not used for this callback and always passed as NULL.

   When preedit starts on the specified input context, the
   callback is called with a NULL call_data argument.
   PreeditStartCallback will return the maximum size of the
   preedit string. A positive number indicates the maximum number
   of bytes allowed in the preedit string, and a value of -1
   indicates there is no limit.

   void PreeditDoneCallback(XIC ic, XPointer client_data, XPointer
   call_data);

   ic

   Specifies the input context.

   client_data

   Specifies the additional client data.

   call_data

   Not used for this callback and always passed as NULL.

   When preedit stops on the specified input context, the callback
   is called with a NULL call_data argument. The client can
   release the data allocated by PreeditStartCallback.

   PreeditStartCallback should initialize appropriate data needed
   for displaying preedit information and for handling further
   PreeditDrawCallback calls. Once PreeditStartCallback is called,
   it will not be called again before PreeditDoneCallback has been
   called.

Preedit Draw Callback

   This callback is triggered to draw and insert, delete or
   replace, preedit text in the preedit region. The preedit text
   may include unconverted input text such as Japanese Kana,
   converted text such as Japanese Kanji characters, or characters
   of both kinds. That string is either a multibyte or wide
   character string, whose encoding matches the locale bound to
   the input context. The callback prototype is as follows:

   void PreeditDrawCallback(XIC ic, XPointer client_data,
   XIMPreeditDrawCallbackStruct *call_data);

   ic

   Specifies the input context.

   client_data

   Specifies the additional client data.

   call_data

   Specifies the preedit drawing information.

   The callback is passed an XIMPreeditDrawCallbackStruct
   structure in the call_data argument. The text member of this
   structure contains the text to be drawn. After the string has
   been drawn, the caret should be moved to the specified
   location.

   The XIMPreeditDrawCallbackStruct structure is defined as
   follows:



typedef struct _XIMPreeditDrawCallbackStruct {
     int caret;     /* Cursor offset within preedit string */
     int chg_first;     /* Starting change position */
     int chg_length;     /* Length of the change in character count */
     XIMText *text;
} XIMPreeditDrawCallbackStruct;

   The client must keep updating a buffer of the preedit text and
   the callback arguments referring to indexes in that buffer. The
   call_data fields have specific meanings according to the
   operation, as follows:
     * To indicate text deletion, the call_data member specifies a
       NULL text field. The text to be deleted is then the current
       text in the buffer from position chg_first (starting at
       zero) on a character length of chg_length.
     * When text is non-NULL, it indicates insertion or
       replacement of text in the buffer.
     * The chg_length member identifies the number of characters
       in the current preedit buffer that are affected by this
       call. A positive chg_length indicates that chg_length
       number of characters, starting at chg_first, must be
       deleted or must be replaced by text, whose length is
       specified in the XIMText structure.
     * A chg_length value of zero indicates that text must be
       inserted right at the position specified by chg_first. A
       value of zero for chg_first specifies the first character
       in the buffer.
     * chg_length and chg_first combine to identify the
       modification required to the preedit buffer; beginning at
       chg_first, replace chg_length number of characters with the
       text in the supplied XIMText structure. For example,
       suppose the preedit buffer contains the string "ABCDE".
     *

Text:      A B C D E
          ^ ^ ^ ^ ^ ^
CharPos:  0 1 2 3 4 5



       The CharPos in the diagram shows the location of the
       character position relative to the character.
     * If the value of chg_first is 1 and the value of chg_length
       is 3, this says to replace 3 characters beginning at
       character position 1 with the string in the XIMText
       structure. Hence, BCD would be replaced by the value in the
       structure.
     * Though chg_length and chg_first are both signed integers
       they will never have a negative value.
     * The caret member identifies the character position before
       which the cursor should be placed - after modification to
       the preedit buffer has been completed. For example, if
       caret is zero, the cursor is at the beginning of the
       buffer. If the caret is one, the cursor is between the
       first and second character.


typedef struct _XIMText {
     unsigned short length;
     XIMFeedback * feedback;
     Bool encoding_is_wchar;
     union {
          char * multi_byte;
          wchar_t * wide_char;
     } string;
} XIMText;

   The text string passed is actually a structure specifying as
   follows:
     * The length member is the text length in characters.
     * The encoding_is_wchar member is a value that indicates if
       the text string is encoded in wide character or multibyte
       format. The text string may be passed either as multibyte
       or as wide character; the input method controls in which
       form data is passed. The client's callback routine must be
       able to handle data passed in either form.
     * The string member is the text string.
     * The feedback member indicates rendering type for each
       character in the string member. If string is NULL
       (indicating that only highlighting of the existing preedit
       buffer should be updated), feedback points to length
       highlight elements that should be applied to the existing
       preedit buffer, beginning at chg_first.

   The feedback member expresses the types of rendering feedback
   the callback should apply when drawing text. Rendering of the
   text to be drawn is specified either in generic ways (for
   example, primary, secondary) or in specific ways (reverse,
   underline). When generic indications are given, the client is
   free to choose the rendering style. It is necessary, however,
   that primary and secondary be mapped to two distinct rendering
   styles.

   If an input method wants to control display of the preedit
   string, an input method can indicate the visibility hints using
   feedbacks in a specific way. The XIMVisibleToForward,
   XIMVisibleToBackword, and XIMVisibleToCenter masks are
   exclusively used for these visibility hints. The
   XIMVisibleToForward mask indicates that the preedit text is
   preferably displayed in the primary draw direction from the
   caret position in the preedit area forward. The
   XIMVisibleToBackword mask indicates that the preedit text is
   preferably displayed from the caret position in the preedit
   area backward, relative to the primary draw direction. The
   XIMVisibleToCenter mask indicates that the preedit text is
   preferably displayed with the caret position in the preedit
   area centered.

   The insertion point of the preedit string could exist outside
   of the visible area when visibility hints are used. Only one of
   the masks is valid for the entire preedit string, and only one
   character can hold one of these feedbacks for a given input
   context at one time. This feedback may be OR'ed together with
   another highlight (such as XIMReverse). Only the most recently
   set feedback is valid, and any previous feedback is
   automatically canceled. This is a hint to the client, and the
   client is free to choose how to display the preedit string.

   The feedback member also specifies how rendering of the text
   argument should be performed. If the feedback is NULL, the
   callback should apply the same feedback as is used for the
   surrounding characters in the preedit buffer; if chg_first is
   at a highlight boundary, the client can choose which of the two
   highlights to use. If feedback is not NULL, feedback specifies
   an array defining the rendering for each character of the
   string, and the length of the array is thus length.

   If an input method wants to indicate that it is only updating
   the feedback of the preedit text without changing the content
   of it, the XIMText structure will contain a NULL value for the
   string field, the number of characters affected (relative to
   chg_first) will be in the length field, and the feedback field
   will point to an array of XIMFeedback.

   Each element in the feedback array is a bitmask represented by
   a value of type XIMFeedback. The valid mask names are as
   follows:

typedef unsigned long XIMFeedback;

#define     XIMReverse                     1L
#define     XIMUnderline                   (1L<<1)
#define     XIMHighlight                   (1L<<2)
#define     XIMPrimary                     (1L<<5)*
#define     XIMSecondary                   (1L<<6)*
#define     XIMTertiary                    (1L<<7)*
#define     XIMVisibleToForward            (1L<<8)
#define     XIMVisibleToBackward           (1L<<9)
#define     XIMVisibleToCenter               (1L<<10)

*/- The values for XIMPrimary, XIMSecondary, and XIMTertiary were incorr
ectly defined in
the R5 specification. The X Consortium's X11R5 implementation correctly
implemented the values for these highlights. The value of these highligh
ts has
been corrected in this specification to agree with the values in the
Consortium's X11R5 and X11R6 implementations.


   Characters drawn with the XIMReverse highlight should be drawn
   by swapping the foreground and background colors used to draw
   normal, unhighlighted characters. Characters drawn with the
   XIMUnderline highlight should be underlined. Characters drawn
   with the XIMHighlight, XIMPrimary, XIMSecondary, and
   XIMTertiary highlights should be drawn in some unique manner
   that must be different from XIMReverse and XIMUnderline. The
   values for XIMPrimary, XIMSecondary, and XIMTertiary were
   incorrectly defined in the R5 specification. The X Consortium's
   X11R5 implementation correctly implemented the values for these
   highlights. The value of these highlights has been corrected in
   this specification to agree with the values in the Consortium's
   X11R5 and X11R6 implementations.

Preedit Caret Callback

   An input method may have its own navigation keys to allow the
   user to move the text insertion point in the preedit area (for
   example, to move backward or forward). Consequently, input
   method needs to indicate to the client that it should move the
   text insertion point. It then calls the PreeditCaretCallback.

   void PreeditCaretCallback(XIC ic, XPointer client_data,
   XIMPreeditCaretCallbackStruct *call_data);

   ic

   Specifies the input context.

   client_data

   Specifies the additional client data.

   call_data

   Specifies the preedit caret information.

   The input method will trigger PreeditCaretCallback to move the
   text insertion point during preedit. The call_data argument
   contains a pointer to an XIMPreeditCaretCallbackStruct
   structure, which indicates where the caret should be moved. The
   callback must move the insertion point to its new location and
   return, in field position, the new offset value from the
   initial position.

   The XIMPreeditCaretCallbackStruct structure is defined as
   follows:



typedef struct _XIMPreeditCaretCallbackStruct {
     int position;     /* Caret offset within preedit string */
     XIMCaretDirection direction;     /* Caret moves direction */
     XIMCaretStyle style;     /* Feedback of the caret */
} XIMPreeditCaretCallbackStruct;

   The XIMCaretStyle structure is defined as follows:



typedef enum {
     XIMIsInvisible,     /* Disable caret feedback */
     XIMIsPrimary,     /* UI defined caret feedback */
     XIMIsSecondary,     /* UI defined caret feedback */
} XIMCaretStyle;

   The XIMCaretDirection structure is defined as follows:



typedef enum {
     XIMForwardChar, XIMBackwardChar,
     XIMForwardWord, XIMBackwardWord,
     XIMCaretUp, XIMCaretDown,
     XIMNextLine, XIMPreviousLine,
     XIMLineStart, XIMLineEnd,
     XIMAbsolutePosition,
     XIMDontChange,
 } XIMCaretDirection;

   These values are defined as follows:
   XIMForwardChar Move the caret forward one character position.
   XIMBackwardChar Move the caret backward one character position.
   XIMForwardWord Move the caret forward one word.
   XIMBackwardWord Move the caret backward one word.
   XIMCaretUp Move the caret up one line keeping the current
   horizontal offset.
   XIMCaretDown Move the caret down one line keeping the current
   horizontal offset.
   XIMPreviousLine Move the caret to the beginning of the previous
   line.
   XIMNextLine Move the caret to the beginning of the next line.
   XIMLineStart Move the caret to the beginning of the current
   display line that contains the caret.
   XIMLineEnd Move the caret to the end of the current display
   line that contains the caret.
   XIMAbsolutePosition The callback must move to the location
   specified by the position field of the callback data, indicated
   in characters, starting from the beginning of the preedit text.
   Hence, a value of zero means move back to the beginning of the
   preedit text.
   XIMDontChange The caret position does not change.

Status Callbacks

   An input method may communicate changes in the status of an
   input context (for example, created, destroyed, or focus
   changes) with three status callbacks: StatusStartCallback,
   StatusDoneCallback, and StatusDrawCallback.

   When the input context is created or gains focus, the input
   method calls the StatusStartCallback callback.

   void StatusStartCallback(XIC ic, XPointer client_data, XPointer
   call_data);

   ic

   Specifies the input context.

   client_data

   Specifies the additional client data.

   call_data

   Not used for this callback and always passed as NULL.

   The callback should initialize appropriate data for displaying
   status and for responding to StatusDrawCallback calls. Once
   StatusStartCallback is called, it will not be called again
   before StatusDoneCallback has been called.

   When an input context is destroyed or when it loses focus, the
   input method calls StatusDoneCallback.

   void StatusDoneCallback(XIC ic, XPointer client_data, XPointer
   call_data);

   ic

   Specifies the input context.

   client_data

   Specifies the additional client data.

   call_data

   Not used for this callback and always passed as NULL.

   The callback may release any data allocated on StatusStart.

   When an input context status has to be updated, the input
   method calls StatusDrawCallback.

   void StatusDrawCallback(XIC ic, XPointer client_data,
   XIMStatusDrawCallbackStruct *call_data);

   ic

   Specifies the input context.

   client_data

   Specifies the additional client data.

   call_data

   Specifies the status drawing information.

   The callback should update the status area by either drawing a
   string or imaging a bitmap in the status area.

   The XIMStatusDataType and XIMStatusDrawCallbackStruct
   structures are defined as follows:



typedef enum {
     XIMTextType,
     XIMBitmapType,
} XIMStatusDataType;

typedef struct _XIMStatusDrawCallbackStruct {
     XIMStatusDataType type;
     union {
          XIMText *text;
          Pixmap  bitmap;
     } data;
} XIMStatusDrawCallbackStruct;

   The feedback styles XIMVisibleToForward, XIMVisibleToBackword,
   and XIMVisibleToCenter are not relevant and will not appear in
   the XIMFeedback element of the XIMText structure.

Event Filtering

   Xlib provides the ability for an input method to register a
   filter internal to Xlib. This filter is called by a client (or
   toolkit) by calling XFilterEvent after calling XNextEvent. Any
   client that uses the XIM interface should call XFilterEvent to
   allow input methods to process their events without knowledge
   of the client's dispatching mechanism. A client's user
   interface policy may determine the priority of event filters
   with respect to other event-handling mechanisms (for example,
   modal grabs).

   Clients may not know how many filters there are, if any, and
   what they do. They may only know if an event has been filtered
   on return of XFilterEvent. Clients should discard filtered
   events.

   To filter an event, use XFilterEvent.

   Bool XFilterEvent(XEvent *event, Window w);

   event

   Specifies the event to filter.

   w

   Specifies the window for which the filter is to be applied.

   If the window argument is None, XFilterEvent applies the filter
   to the window specified in the XEvent structure. The window
   argument is provided so that layers above Xlib that do event
   redirection can indicate to which window an event has been
   redirected.

   If XFilterEvent returns True, then some input method has
   filtered the event, and the client should discard the event. If
   XFilterEvent returns False, then the client should continue
   processing the event.

   If a grab has occurred in the client and XFilterEvent returns
   True, the client should ungrab the keyboard.

Getting Keyboard Input

   To get composed input from an input method, use XmbLookupString
   or XwcLookupString.

   int XmbLookupString(XIC ic, XKeyPressedEvent *event, char
   *buffer_return, int bytes_buffer, KeySym *keysym_return, Status
   *status_return);

   int XwcLookupString(XIC ic, XKeyPressedEvent *event, wchar_t
   *buffer_return, int wchars_buffer, KeySym *keysym_return,
   Status *status_return);

   ic

   Specifies the input context.

   event

   Specifies the key event to be used.

   buffer_return

   Returns a multibyte string or wide character string (if any)
   from the input method.

   bytes_buffer

   wchars_buffer

   Specifies space available in the return buffer.

   keysym_return

   Returns the KeySym computed from the event if this argument is
   not NULL.

   status_return

   Returns a value indicating what kind of data is returned.

   The XmbLookupString and XwcLookupString functions return the
   string from the input method specified in the buffer_return
   argument. If no string is returned, the buffer_return argument
   is unchanged.

   The KeySym into which the KeyCode from the event was mapped is
   returned in the keysym_return argument if it is non-NULL and
   the status_return argument indicates that a KeySym was
   returned. If both a string and a KeySym are returned, the
   KeySym value does not necessarily correspond to the string
   returned.

   XmbLookupString returns the length of the string in bytes, and
   XwcLookupString returns the length of the string in characters.
   Both XmbLookupString and XwcLookupString return text in the
   encoding of the locale bound to the input method of the
   specified input context.

   Each string returned by XmbLookupString and XwcLookupString
   begins in the initial state of the encoding of the locale (if
   the encoding of the locale is state-dependent).

Note

   To insure proper input processing, it is essential that the
   client pass only KeyPress events to XmbLookupString and
   XwcLookupString. Their behavior when a client passes a
   KeyRelease event is undefined.

   Clients should check the status_return argument before using
   the other returned values. These two functions both return a
   value to status_return that indicates what has been returned in
   the other arguments. The possible values returned are:
   XBufferOverflow The input string to be returned is too large
   for the supplied buffer_return. The required size
   (XmbLookupString in bytes; XwcLookupString in characters) is
   returned as the value of the function, and the contents of
   buffer_return and keysym_return are not modified. The client
   should recall the function with the same event and a buffer of
   adequate size to obtain the string.
   XLookupNone No consistent input has been composed so far. The
   contents of buffer_return and keysym_return are not modified,
   and the function returns zero.
   XLookupChars Some input characters have been composed. They are
   placed in the buffer_return argument, and the string length is
   returned as the value of the function. The string is encoded in
   the locale bound to the input context. The content of the
   keysym_return argument is not modified.
   XLookupKeySym A KeySym has been returned instead of a string
   and is returned in keysym_return. The content of the
   buffer_return argument is not modified, and the function
   returns zero.
   XLookupBoth Both a KeySym and a string are returned;
   XLookupChars and XLookupKeySym occur simultaneously.

   It does not make any difference if the input context passed as
   an argument to XmbLookupString and XwcLookupString is the one
   currently in possession of the focus or not. Input may have
   been composed within an input context before it lost the focus,
   and that input may be returned on subsequent calls to
   XmbLookupString or XwcLookupString even though it does not have
   any more keyboard focus.

Input Method Conventions

   The input method architecture is transparent to the client.
   However, clients should respect a number of conventions in
   order to work properly. Clients must also be aware of possible
   effects of synchronization between input method and library in
   the case of a remote input server.

Client Conventions

   A well-behaved client (or toolkit) should first query the input
   method style. If the client cannot satisfy the requirements of
   the supported styles (in terms of geometry management or
   callbacks), it should negotiate with the user continuation of
   the program or raise an exception or error of some sort.

Synchronization Conventions

   A KeyPress event with a KeyCode of zero is used exclusively as
   a signal that an input method has composed input that can be
   returned by XmbLookupString or XwcLookupString. No other use is
   made of a KeyPress event with KeyCode of zero.

   Such an event may be generated by either a front-end or a
   back-end input method in an implementation-dependent manner.
   Some possible ways to generate this event include:
     * A synthetic event sent by an input method server
     * An artificial event created by a input method filter and
       pushed onto a client's event queue
     * A KeyPress event whose KeyCode value is modified by an
       input method filter

   When callback support is specified by the client, input methods
   will not take action unless they explicitly called back the
   client and obtained no response (the callback is not specified
   or returned invalid data).

String Constants

   The following symbols for string constants are defined in
   <X11/Xlib.h>. Although they are shown here with particular
   macro definitions, they may be implemented as macros, as global
   symbols, or as a mixture of the two. The string pointer value
   itself is not significant; clients must not assume that
   inequality of two values implies inequality of the actual
   string data.
#define XNVaNestedList                       "XNVaNestedList"
#define XNSeparatorofNestedList              "separatorofNestedList"
#define XNQueryInputStyle                    "queryInputStyle"
#define XNClientWindow                       "clientWindow"
#define XNInputStyle                         "inputStyle"
#define XNFocusWindow                        "focusWindow"
#define XNResourceName                       "resourceName"
#define XNResourceClass                      "resourceClass"
#define XNGeometryCallback                   "geometryCallback"
#define XNDestroyCallback                    "destroyCallback"
#define XNFilterEvents                       "filterEvents"
#define XNPreeditStartCallback               "preeditStartCallback"
#define XNPreeditDoneCallback                "preeditDoneCallback"
#define XNPreeditDrawCallback                "preeditDrawCallback"
#define XNPreeditCaretCallback               "preeditCaretCallback"
#define XNPreeditStateNotifyCallback         "preeditStateNotifyCallback
"
#define XNPreeditAttributes                  "preeditAttributes"
#define XNStatusStartCallback                "statusStartCallback"
#define XNStatusDoneCallback                 "statusDoneCallback"
#define XNStatusDrawCallback                 "statusDrawCallback"
#define XNStatusAttributes                   "statusAttributes"
#define XNArea                               "area"
#define XNAreaNeeded                         "areaNeeded"
#define XNSpotLocation                       "spotLocation"
#define XNColormap                           "colorMap"
#define XNStdColormap                        "stdColorMap"
#define XNForeground                         "foreground"
#define XNBackground                         "background"
#define XNBackgroundPixmap                   "backgroundPixmap"
#define XNFontSet                            "fontSet"
#define XNLineSpace                          "lineSpace"
#define XNCursor                             "cursor"
#define XNQueryIMValuesList                  "queryIMValuesList"
#define XNQueryICValuesList                  "queryICValuesList"
#define XNStringConversionCallback           "stringConversionCallback"
#define XNStringConversion                   "stringConversion"
#define XNResetState                         "resetState"
#define XNHotKey                             "hotkey"
#define XNHotKeyState                        "hotkeyState"
#define XNPreeditState                       "preeditState"
#define XNVisiblePosition                    "visiblePosition"
#define XNR6PreeditCallbackBehavior          "r6PreeditCallback"
#define XNRequiredCharSet                    "requiredCharSet"
#define XNQueryOrientation                   "queryOrientation"
#define XNDirectionalDependentDrawing        "directionalDependentDrawin
g"
#define XNContextualDrawing                  "contextualDrawing"
#define XNBaseFontName                       "baseFontName"
#define XNMissingCharSet                     "missingCharSet"
#define XNDefaultString                      "defaultString"
#define XNOrientation                        "orientation"
#define XNFontInfo                           "fontInfo"
#define XNOMAutomatic                        "omAutomatic"


Chapter 14. Inter-Client Communication Functions

   Table of Contents

   Client to Window Manager Communication

        Manipulating Top-Level Windows
        Converting String Lists
        Setting and Reading Text Properties
        Setting and Reading the WM_NAME Property
        Setting and Reading the WM_ICON_NAME Property
        Setting and Reading the WM_HINTS Property
        Setting and Reading the WM_NORMAL_HINTS Property
        Setting and Reading the WM_CLASS Property
        Setting and Reading the WM_TRANSIENT_FOR Property
        Setting and Reading the WM_PROTOCOLS Property
        Setting and Reading the WM_COLORMAP_WINDOWS Property
        Setting and Reading the WM_ICON_SIZE Property
        Using Window Manager Convenience Functions

   Client to Session Manager Communication

        Setting and Reading the WM_COMMAND Property
        Setting and Reading the WM_CLIENT_MACHINE Property

   Standard Colormaps

        Standard Colormap Properties and Atoms
        Setting and Obtaining Standard Colormaps

   The Inter-Client Communication Conventions Manual, hereafter
   referred to as the ICCCM, details the X Consortium approved
   conventions that govern inter-client communications. These
   conventions ensure peer-to-peer client cooperation in the use
   of selections, cut buffers, and shared resources as well as
   client cooperation with window and session managers. For
   further information, see the Inter-Client Communication
   Conventions Manual.

   Xlib provides a number of standard properties and programming
   interfaces that are ICCCM compliant. The predefined atoms for
   some of these properties are defined in the <X11/Xatom.h>
   header file, where to avoid name conflicts with user symbols
   their #define name has an XA_ prefix. For further information
   about atoms and properties, see section 4.3.

   Xlib's selection and cut buffer mechanisms provide the primary
   programming interfaces by which peer client applications
   communicate with each other (see sections 4.5 and 16.6). The
   functions discussed in this chapter provide the primary
   programming interfaces by which client applications communicate
   with their window and session managers as well as share
   standard colormaps.

   The standard properties that are of special interest for
   communicating with window and session managers are:
   Name Type Format Description
   WM_CLASS STRING 8 Set by application programs to allow window
   and session managers to obtain the application's resources from
   the resource database.
   WM_CLIENT_MACHINE TEXT   The string name of the machine on
   which the client application is running.
   WM_COLORMAP_WINDOWS WINDOWS 32 The list of window IDs that may
   need a different colormap from that of their top-level window.
   WM_COMMAND TEXT   The command and arguments, null separated,
   used to invoke the application.
   WM_HINTS WM_HINTS 32 Additional hints set by the client for use
   by the window manager. The C type of this property is XWMHints.
   WM_ICON_NAME TEXT   The name to be used in an icon.
   WM_ICON_SIZE WM_ICON_SIZE 32 The window manager may set this
   property on the root window to specify the icon sizes it
   supports. The C type of this property is XIconSize.
   WM_NAME TEXT   The name of the application.
   WM_NORMAL_HINTS WM_NORMAL_HINTS 32 Size hints for a window in
   its normal state. The C type of this property is XSizeHints.
   WM_PROTOCOLS ATOM 32 List of atoms that identify the
   communications protocols between the client and window manager
   in which the client is willing to participate.
   WM_STATE WM_STATE 32 Intended for communication between window
   and session managers only.
   WM_TRANSIENT_FOR WINDOW 32 Set by application programs to
   indicate to the window manager that a transient top-level
   window, such as a dialog box.

   The remainder of this chapter discusses:
     * Client to window manager communication
     * Client to session manager communication
     * Standard colormaps

Client to Window Manager Communication

   This section discusses how to:
     * Manipulate top-level windows
     * Convert string lists
     * Set and read text properties
     * Set and read the WM_NAME property
     * Set and read the WM_ICON_NAME property
     * Set and read the WM_HINTS property
     * Set and read the WM_NORMAL_HINTS property
     * Set and read the WM_CLASS property
     * Set and read the WM_TRANSIENT_FOR property
     * Set and read the WM_PROTOCOLS property
     * Set and read the WM_COLORMAP_WINDOWS property
     * Set and read the WM_ICON_SIZE property
     * Use window manager convenience functions

Manipulating Top-Level Windows

   Xlib provides functions that you can use to change the
   visibility or size of top-level windows (that is, those that
   were created as children of the root window). Note that the
   subwindows that you create are ignored by window managers.
   Therefore, you should use the basic window functions described
   in chapter 3 to manipulate your application's subwindows.

   To request that a top-level window be iconified, use
   XIconifyWindow.

   Status XIconifyWindow(Display *display, Window w, int
   screen_number);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   screen_number

   Specifies the appropriate screen number on the host server.

   The XIconifyWindow function sends a WM_CHANGE_STATE
   ClientMessage event with a format of 32 and a first data
   element of IconicState (as described in section 4.1.4 of the
   Inter-Client Communication Conventions Manual) and a window of
   w to the root window of the specified screen with an event mask
   set to SubstructureNotifyMask | SubstructureRedirectMask.
   Window managers may elect to receive this message and if the
   window is in its normal state, may treat it as a request to
   change the window's state from normal to iconic. If the
   WM_CHANGE_STATE property cannot be interned, XIconifyWindow
   does not send a message and returns a zero status. It returns a
   nonzero status if the client message is sent successfully;
   otherwise, it returns a zero status.

   To request that a top-level window be withdrawn, use
   XWithdrawWindow.

   Status XWithdrawWindow(Display *display, Window w, int
   screen_number);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   screen_number

   Specifies the appropriate screen number on the host server.

   The XWithdrawWindow function unmaps the specified window and
   sends a synthetic UnmapNotify event to the root window of the
   specified screen. Window managers may elect to receive this
   message and may treat it as a request to change the window's
   state to withdrawn. When a window is in the withdrawn state,
   neither its normal nor its iconic representations is visible.
   It returns a nonzero status if the UnmapNotify event is
   successfully sent; otherwise, it returns a zero status.

   XWithdrawWindow can generate a BadWindow error.

   To request that a top-level window be reconfigured, use
   XReconfigureWMWindow.

   Status XReconfigureWMWindow(Display *display, Window w, int
   screen_number, unsigned int value_mask, XWindowChanges
   *values);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   screen_number

   Specifies the appropriate screen number on the host server.

   value_mask

   Specifies which values are to be set using information in the
   values structure. This mask is the bitwise inclusive OR of the
   valid configure window values bits.

   values

   Specifies the XWindowChanges structure.

   The XReconfigureWMWindow function issues a ConfigureWindow
   request on the specified top-level window. If the stacking mode
   is changed and the request fails with a BadMatch error, the
   error is trapped by Xlib and a synthetic ConfigureRequestEvent
   containing the same configuration parameters is sent to the
   root of the specified window. Window managers may elect to
   receive this event and treat it as a request to reconfigure the
   indicated window. It returns a nonzero status if the request or
   event is successfully sent; otherwise, it returns a zero
   status.

   XReconfigureWMWindow can generate BadValue and BadWindow
   errors.

Converting String Lists

   Many of the text properties allow a variety of types and
   formats. Because the data stored in these properties are not
   simple null-terminated strings, an XTextProperty structure is
   used to describe the encoding, type, and length of the text as
   well as its value. The XTextProperty structure contains:


typedef struct {
        unsigned char *value;   /* property data */
        Atom encoding;  /* type of property */
        int format;     /* 8, 16, or 32 */
        unsigned long nitems;   /* number of items in value */
} XTextProperty;

   Xlib provides functions to convert localized text to or from
   encodings that support the inter-client communication
   conventions for text. In addition, functions are provided for
   converting between lists of pointers to character strings and
   text properties in the STRING encoding.

   The functions for localized text return a signed integer error
   status that encodes Success as zero, specific error conditions
   as negative numbers, and partial conversion as a count of
   unconvertible characters.

#define #XNoMemory           -1
#define #XLocaleNotSupported -2
#define #XConverterNotFound  -3

typedef enum {
        XStringStyle,           /* STRING */
        XCompoundTextStyle,     /* COMPOUND_TEXT */
        XTextStyle,             /* text in owner's encoding (current loc
ale) */
        XStdICCTextStyle        /* STRING, else COMPOUND_TEXT */
} XICCEncodingStyle;

   To convert a list of text strings to an XTextProperty
   structure, use XmbTextListToTextProperty or
   XwcTextListToTextProperty.

   int XmbTextListToTextProperty(Display *display, char **list,
   int count, XICCEncodingStyle style, XTextProperty
   *text_prop_return);

   int XwcTextListToTextProperty(Display *display, wchar_t **list,
   int count, XICCEncodingStyle style, XTextProperty
   *text_prop_return);

   display

   Specifies the connection to the X server.

   list

   Specifies a list of null-terminated character strings.

   count

   Specifies the number of strings specified.

   style

   Specifies the manner in which the property is encoded.

   text_prop_return

   Returns the XTextProperty structure.

   The XmbTextListToTextProperty and XwcTextListToTextProperty
   functions set the specified XTextProperty value to a set of
   null-separated elements representing the concatenation of the
   specified list of null-terminated text strings. A final
   terminating null is stored at the end of the value field of
   text_prop_return but is not included in the nitems member.

   The functions set the encoding field of text_prop_return to an
   Atom for the specified display naming the encoding determined
   by the specified style and convert the specified text list to
   this encoding for storage in the text_prop_return value field.
   If the style XStringStyle or XCompoundTextStyle is specified,
   this encoding is ``STRING'' or ``COMPOUND_TEXT'', respectively.
   If the style XTextStyle is specified, this encoding is the
   encoding of the current locale. If the style XStdICCTextStyle
   is specified, this encoding is ``STRING'' if the text is fully
   convertible to STRING, else ``COMPOUND_TEXT''.

   If insufficient memory is available for the new value string,
   the functions return XNoMemory. If the current locale is not
   supported, the functions return XLocaleNotSupported. In both of
   these error cases, the functions do not set text_prop_return.

   To determine if the functions are guaranteed not to return
   XLocaleNotSupported, use XSupportsLocale.

   If the supplied text is not fully convertible to the specified
   encoding, the functions return the number of unconvertible
   characters. Each unconvertible character is converted to an
   implementation-defined and encoding-specific default string.
   Otherwise, the functions return Success. Note that full
   convertibility to all styles except XStringStyle is guaranteed.

   To free the storage for the value field, use XFree.

   To obtain a list of text strings from an XTextProperty
   structure, use XmbTextPropertyToTextList or
   XwcTextPropertyToTextList.

   int XmbTextPropertyToTextList(Display *display, XTextProperty
   *text_prop, char ***list_return, int *count_return);

   int XwcTextPropertyToTextList(Display *display, XTextProperty
   *text_prop, wchar_t ***list_return, int *count_return);

   display

   Specifies the connection to the X server.

   text_prop

   Specifies the XTextProperty structure to be used.

   list_return

   Returns a list of null-terminated character strings.

   count_return

   Returns the number of strings.

   The XmbTextPropertyToTextList and XwcTextPropertyToTextList
   functions return a list of text strings in the current locale
   representing the null-separated elements of the specified
   XTextProperty structure. The data in text_prop must be format
   8.

   Multiple elements of the property (for example, the strings in
   a disjoint text selection) are separated by a null byte. The
   contents of the property are not required to be
   null-terminated; any terminating null should not be included in
   text_prop.nitems.

   If insufficient memory is available for the list and its
   elements, XmbTextPropertyToTextList and
   XwcTextPropertyToTextList return XNoMemory. If the current
   locale is not supported, the functions return
   XLocaleNotSupported. Otherwise, if the encoding field of
   text_prop is not convertible to the encoding of the current
   locale, the functions return XConverterNotFound. For supported
   locales, existence of a converter from COMPOUND_TEXT, STRING or
   the encoding of the current locale is guaranteed if
   XSupportsLocale returns True for the current locale (but the
   actual text may contain unconvertible characters). Conversion
   of other encodings is implementation-dependent. In all of these
   error cases, the functions do not set any return values.

   Otherwise, XmbTextPropertyToTextList and
   XwcTextPropertyToTextList return the list of null-terminated
   text strings to list_return and the number of text strings to
   count_return.

   If the value field of text_prop is not fully convertible to the
   encoding of the current locale, the functions return the number
   of unconvertible characters. Each unconvertible character is
   converted to a string in the current locale that is specific to
   the current locale. To obtain the value of this string, use
   XDefaultString. Otherwise, XmbTextPropertyToTextList and
   XwcTextPropertyToTextList return Success.

   To free the storage for the list and its contents returned by
   XmbTextPropertyToTextList, use XFreeStringList. To free the
   storage for the list and its contents returned by
   XwcTextPropertyToTextList, use XwcFreeStringList.

   To free the in-memory data associated with the specified wide
   character string list, use XwcFreeStringList.

   void XwcFreeStringList(wchar_t **list);

   list

   Specifies the list of strings to be freed.

   The XwcFreeStringList function frees memory allocated by
   XwcTextPropertyToTextList.

   To obtain the default string for text conversion in the current
   locale, use

   char *XDefaultString(void);

   The XDefaultString function returns the default string used by
   Xlib for text conversion (for example, in
   XmbTextPropertyToTextList). The default string is the string in
   the current locale that is output when an unconvertible
   character is found during text conversion. If the string
   returned by XDefaultString is the empty string (""), no
   character is output in the converted text. XDefaultString does
   not return NULL.

   The string returned by XDefaultString is independent of the
   default string for text drawing; see XCreateFontSet to obtain
   the default string for an XFontSet.

   The behavior when an invalid codepoint is supplied to any Xlib
   function is undefined.

   The returned string is null-terminated. It is owned by Xlib and
   should not be modified or freed by the client. It may be freed
   after the current locale is changed. Until freed, it will not
   be modified by Xlib.

   To set the specified list of strings in the STRING encoding to
   a XTextProperty structure, use XStringListToTextProperty.

   Status XStringListToTextProperty(char **list, int count,
   XTextProperty *text_prop_return);

   list

   Specifies a list of null-terminated character strings.

   count

   Specifies the number of strings.

   text_prop_return

   Returns the XTextProperty structure.

   The XStringListToTextProperty function sets the specified
   XTextProperty to be of type STRING (format 8) with a value
   representing the concatenation of the specified list of
   null-separated character strings. An extra null byte (which is
   not included in the nitems member) is stored at the end of the
   value field of text_prop_return. The strings are assumed
   (without verification) to be in the STRING encoding. If
   insufficient memory is available for the new value string,
   XStringListToTextProperty does not set any fields in the
   XTextProperty structure and returns a zero status. Otherwise,
   it returns a nonzero status. To free the storage for the value
   field, use XFree.

   To obtain a list of strings from a specified XTextProperty
   structure in the STRING encoding, use
   XTextPropertyToStringList.

   Status XTextPropertyToStringList(XTextProperty *text_prop, char
   ***list_return, int *count_return);

   text_prop

   Specifies the XTextProperty structure to be used.

   list_return

   Returns a list of null-terminated character strings.

   count_return

   Returns the number of strings.

   The XTextPropertyToStringList function returns a list of
   strings representing the null-separated elements of the
   specified XTextProperty structure. The data in text_prop must
   be of type STRING and format 8. Multiple elements of the
   property (for example, the strings in a disjoint text
   selection) are separated by NULL (encoding 0). The contents of
   the property are not null-terminated. If insufficient memory is
   available for the list and its elements,
   XTextPropertyToStringList sets no return values and returns a
   zero status. Otherwise, it returns a nonzero status. To free
   the storage for the list and its contents, use XFreeStringList.

   To free the in-memory data associated with the specified string
   list, use XFreeStringList.

   void XFreeStringList(char **list);

   list

   Specifies the list of strings to be freed.

   The XFreeStringList function releases memory allocated by
   XmbTextPropertyToTextList and XTextPropertyToStringList and the
   missing charset list allocated by XCreateFontSet.

Setting and Reading Text Properties

   Xlib provides two functions that you can use to set and read
   the text properties for a given window. You can use these
   functions to set and read those properties of type TEXT
   (WM_NAME, WM_ICON_NAME, WM_COMMAND, and WM_CLIENT_MACHINE). In
   addition, Xlib provides separate convenience functions that you
   can use to set each of these properties. For further
   information about these convenience functions, see sections
   14.1.4, 14.1.5, 14.2.1, and 14.2.2, respectively.

   To set one of a window's text properties, use XSetTextProperty.

   void XSetTextProperty(Display *display, Window w, XTextProperty
   *text_prop, Atom property);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   text_prop

   Specifies the XTextProperty structure to be used.

   property

   Specifies the property name.

   The XSetTextProperty function replaces the existing specified
   property for the named window with the data, type, format, and
   number of items determined by the value field, the encoding
   field, the format field, and the nitems field, respectively, of
   the specified XTextProperty structure. If the property does not
   already exist, XSetTextProperty sets it for the specified
   window.

   XSetTextProperty can generate BadAlloc, BadAtom, BadValue, and
   BadWindow errors.

   To read one of a window's text properties, use
   XGetTextProperty.

   Status XGetTextProperty(Display *display, Window w,
   XTextProperty *text_prop_return, Atom property);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   text_prop_return

   Returns the XTextProperty structure.

   property

   Specifies the property name.

   The XGetTextProperty function reads the specified property from
   the window and stores the data in the returned XTextProperty
   structure. It stores the data in the value field, the type of
   the data in the encoding field, the format of the data in the
   format field, and the number of items of data in the nitems
   field. An extra byte containing null (which is not included in
   the nitems member) is stored at the end of the value field of
   text_prop_return. The particular interpretation of the
   property's encoding and data as text is left to the calling
   application. If the specified property does not exist on the
   window, XGetTextProperty sets the value field to NULL, the
   encoding field to None, the format field to zero, and the
   nitems field to zero.

   If it was able to read and store the data in the XTextProperty
   structure, XGetTextProperty returns a nonzero status;
   otherwise, it returns a zero status.

   XGetTextProperty can generate BadAtom and BadWindow errors.

Setting and Reading the WM_NAME Property

   Xlib provides convenience functions that you can use to set and
   read the WM_NAME property for a given window.

   To set a window's WM_NAME property with the supplied
   convenience function, use XSetWMName.

   void XSetWMName(Display *display, Window w, XTextProperty
   *text_prop);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   text_prop

   Specifies the XTextProperty structure to be used.

   The XSetWMName convenience function calls XSetTextProperty to
   set the WM_NAME property.

   To read a window's WM_NAME property with the supplied
   convenience function, use XGetWMName.

   Status XGetWMName(Display *display, Window w, XTextProperty
   *text_prop_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   text_prop_return

   Returns the XTextProperty structure.

   The XGetWMName convenience function calls XGetTextProperty to
   obtain the WM_NAME property. It returns a nonzero status on
   success; otherwise, it returns a zero status.

   The following two functions have been superseded by XSetWMName
   and XGetWMName, respectively. You can use these additional
   convenience functions for window names that are encoded as
   STRING properties.

   To assign a name to a window, use XStoreName.

   XStoreName(Display *display, Window w, char *window_name);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   window_name

   Specifies the window name, which should be a null-terminated
   string.

   The XStoreName function assigns the name passed to window_name
   to the specified window. A window manager can display the
   window name in some prominent place, such as the title bar, to
   allow users to identify windows easily. Some window managers
   may display a window's name in the window's icon, although they
   are encouraged to use the window's icon name if one is provided
   by the application. If the string is not in the Host Portable
   Character Encoding, the result is implementation-dependent.

   XStoreName can generate BadAlloc and BadWindow errors.

   To get the name of a window, use XFetchName.

   Status XFetchName(Display *display, Window w, char
   **window_name_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   window_name_return

   Returns the window name, which is a null-terminated string.

   The XFetchName function returns the name of the specified
   window. If it succeeds, it returns a nonzero status; otherwise,
   no name has been set for the window, and it returns zero. If
   the WM_NAME property has not been set for this window,
   XFetchName sets window_name_return to NULL. If the data
   returned by the server is in the Latin Portable Character
   Encoding, then the returned string is in the Host Portable
   Character Encoding. Otherwise, the result is
   implementation-dependent. When finished with it, a client must
   free the window name string using XFree.

   XFetchName can generate a BadWindow error.

Setting and Reading the WM_ICON_NAME Property

   Xlib provides convenience functions that you can use to set and
   read the WM_ICON_NAME property for a given window.

   To set a window's WM_ICON_NAME property, use XSetWMIconName.

   void XSetWMIconName(Display *display, Window w, XTextProperty
   *text_prop);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   text_prop

   Specifies the XTextProperty structure to be used.

   The XSetWMIconName convenience function calls XSetTextProperty
   to set the WM_ICON_NAME property.

   To read a window's WM_ICON_NAME property, use XGetWMIconName.

   Status XGetWMIconName(Display *display, Window w, XTextProperty
   *text_prop_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   text_prop_return

   Returns the XTextProperty structure.

   The XGetWMIconName convenience function calls XGetTextProperty
   to obtain the WM_ICON_NAME property. It returns a nonzero
   status on success; otherwise, it returns a zero status.

   The next two functions have been superseded by XSetWMIconName
   and XGetWMIconName, respectively. You can use these additional
   convenience functions for window names that are encoded as
   STRING properties.

   To set the name to be displayed in a window's icon, use
   XSetIconName.

   XSetIconName(Display *display, Window w, char *icon_name);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   icon_name

   Specifies the icon name, which should be a null-terminated
   string.

   If the string is not in the Host Portable Character Encoding,
   the result is implementation-dependent. XSetIconName can
   generate BadAlloc and BadWindow errors.

   To get the name a window wants displayed in its icon, use
   XGetIconName.

   Status XGetIconName(Display *display, Window w, char
   **icon_name_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   icon_name_return

   Returns the window's icon name, which is a null-terminated
   string.

   The XGetIconName function returns the name to be displayed in
   the specified window's icon. If it succeeds, it returns a
   nonzero status; otherwise, if no icon name has been set for the
   window, it returns zero. If you never assigned a name to the
   window, XGetIconName sets icon_name_return to NULL. If the data
   returned by the server is in the Latin Portable Character
   Encoding, then the returned string is in the Host Portable
   Character Encoding. Otherwise, the result is
   implementation-dependent. When finished with it, a client must
   free the icon name string using XFree.

   XGetIconName can generate a BadWindow error.

Setting and Reading the WM_HINTS Property

   Xlib provides functions that you can use to set and read the
   WM_HINTS property for a given window. These functions use the
   flags and the XWMHints structure, as defined in the
   <X11/Xutil.h> header file.

   To allocate an XWMHints structure, use XAllocWMHints.

   XWMHints *XAllocWMHints(void);

   The XAllocWMHints function allocates and returns a pointer to
   an XWMHints structure. Note that all fields in the XWMHints
   structure are initially set to zero. If insufficient memory is
   available, XAllocWMHints returns NULL. To free the memory
   allocated to this structure, use XFree.

   The XWMHints structure contains:
/* Window manager hints mask bits */

#define         InputHint             (1L<<0)
#define         StateHint             (1L<<1)
#define         IconPixmapHint        (1L<<2)
#define         IconWindowHint        (1L<<3)
#define         IconPositionHint      (1L<<4)
#define         IconMaskHint          (1L<<5)
#define         WindowGroupHint       (1L<<6)
#define         UrgencyHint           (1L<<8)
#define         AllHints              (InputHint|StateHint|IconPixmapHin
t|
                                       IconWIndowHint|IconPositionHint|
                                       IconMaskHint|WindowGroupHint)


/* Values */

typedef struct {
        long flags;             /* marks which fields in this structure
are defined */
        Bool input;             /* does this application rely on the win
dow manager to
                                   get keyboard input? */
        int initial_state;      /* see below */
        Pixmap icon_pixmap;     /* pixmap to be used as icon */
        Window icon_window;     /* window to be used as icon */
        int icon_x, icon_y;     /* initial position of icon */
        Pixmap icon_mask;       /* pixmap to be used as mask for icon_pi
xmap */
        XID window_group;       /* id of related window group */
        /* this structure may be extended in the future */
} XWMHints;

   The input member is used to communicate to the window manager
   the input focus model used by the application. Applications
   that expect input but never explicitly set focus to any of
   their subwindows (that is, use the push model of focus
   management), such as X Version 10 style applications that use
   real-estate driven focus, should set this member to True.
   Similarly, applications that set input focus to their
   subwindows only when it is given to their top-level window by a
   window manager should also set this member to True.
   Applications that manage their own input focus by explicitly
   setting focus to one of their subwindows whenever they want
   keyboard input (that is, use the pull model of focus
   management) should set this member to False. Applications that
   never expect any keyboard input also should set this member to
   False.

   Pull model window managers should make it possible for push
   model applications to get input by setting input focus to the
   top-level windows of applications whose input member is True.
   Push model window managers should make sure that pull model
   applications do not break them by resetting input focus to
   PointerRoot when it is appropriate (for example, whenever an
   application whose input member is False sets input focus to one
   of its subwindows).

   The definitions for the initial_state flag are:
#define      WithdrawnState 0
#define      NormalState    1   /* most applications start this way */
#define      IconicState    3   /* application wants to start as an icon
 */


   The icon_mask specifies which pixels of the icon_pixmap should
   be used as the icon. This allows for nonrectangular icons. Both
   icon_pixmap and icon_mask must be bitmaps. The icon_window lets
   an application provide a window for use as an icon for window
   managers that support such use. The window_group lets you
   specify that this window belongs to a group of other windows.
   For example, if a single application manipulates multiple
   top-level windows, this allows you to provide enough
   information that a window manager can iconify all of the
   windows rather than just the one window.

   The UrgencyHint flag, if set in the flags field, indicates that
   the client deems the window contents to be urgent, requiring
   the timely response of the user. The window manager will make
   some effort to draw the user's attention to this window while
   this flag is set. The client must provide some means by which
   the user can cause the urgency flag to be cleared (either
   mitigating the condition that made the window urgent or merely
   shutting off the alarm) or the window to be withdrawn.

   To set a window's WM_HINTS property, use XSetWMHints.

   XSetWMHints(Display *display, Window w, XWMHints *wmhints);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   wmhints

   Specifies the XWMHints structure to be used.

   The XSetWMHints function sets the window manager hints that
   include icon information and location, the initial state of the
   window, and whether the application relies on the window
   manager to get keyboard input.

   XSetWMHints can generate BadAlloc and BadWindow errors.

   To read a window's WM_HINTS property, use XGetWMHints.

   XWMHints *XGetWMHints(Display *display, Window w);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   The XGetWMHints function reads the window manager hints and
   returns NULL if no WM_HINTS property was set on the window or
   returns a pointer to an XWMHints structure if it succeeds. When
   finished with the data, free the space used for it by calling
   XFree.

   XGetWMHints can generate a BadWindow error.

Setting and Reading the WM_NORMAL_HINTS Property

   Xlib provides functions that you can use to set or read the
   WM_NORMAL_HINTS property for a given window. The functions use
   the flags and the XSizeHints structure, as defined in the
   <X11/Xutil.h> header file.

   The size of the XSizeHints structure may grow in future
   releases, as new components are added to support new ICCCM
   features. Passing statically allocated instances of this
   structure into Xlib may result in memory corruption when
   running against a future release of the library. As such, it is
   recommended that only dynamically allocated instances of the
   structure be used.

   To allocate an XSizeHints structure, use XAllocSizeHints.

   XSizeHints *XAllocSizeHints(void);

   The XAllocSizeHints function allocates and returns a pointer to
   an XSizeHints structure. Note that all fields in the XSizeHints
   structure are initially set to zero. If insufficient memory is
   available, XAllocSizeHints returns NULL. To free the memory
   allocated to this structure, use XFree.

   The XSizeHints structure contains:
/* Size hints mask bits */

#define           USPosition         (1L<<0)  /* user specified x,y */
#define           USSize             (1L<<1)  /* user specified width,he
ight */
#define           PPosition          (1L<<2)  /* program specified posit
ion */
#define           PSize              (1L<<3)  /* program specified size
*/
#define           PMinSize           (1L<<4)  /* program specified minim
um size */
#define           PMaxSize           (1L<<5)  /* program specified maxim
um size */
#define           PResizeInc         (1L<<5)  /* program specified resiz
e increments */
#define           PAspect            (1L<<6)  /* program specified min a
nd max aspect ratios */
#define           PBaseSize          (1L<<8)
#define           PWinGravity        (1L<<9)
#define           PAllHints          (PPosition|Psize|
                                      PMinSize|PMaxSize|
                                      PResizeInc|PAspect)


/* Values */

typedef struct {
        long flags;             /* marks which fields in this structure
are defined */
        int x, y;               /* Obsolete */
        int width, height;      /* Obsolete */
        int min_width, min_height;
        int max_width, max_height;
        int width_inc, height_inc;
        struct {
               int x;           /* numerator */
               int y;           /* denominator */
        } min_aspect, max_aspect;
        int base_width, base_height;
        int win_gravity;
        /* this structure may be extended in the future */
} XSizeHints;

   The x, y, width, and height members are now obsolete and are
   left solely for compatibility reasons. The min_width and
   min_height members specify the minimum window size that still
   allows the application to be useful. The max_width and
   max_height members specify the maximum window size. The
   width_inc and height_inc members define an arithmetic
   progression of sizes (minimum to maximum) into which the window
   prefers to be resized. The min_aspect and max_aspect members
   are expressed as ratios of x and y, and they allow an
   application to specify the range of aspect ratios it prefers.
   The base_width and base_height members define the desired size
   of the window. The window manager will interpret the position
   of the window and its border width to position the point of the
   outer rectangle of the overall window specified by the
   win_gravity member. The outer rectangle of the window includes
   any borders or decorations supplied by the window manager. In
   other words, if the window manager decides to place the window
   where the client asked, the position on the parent window's
   border named by the win_gravity will be placed where the client
   window would have been placed in the absence of a window
   manager.

   Note that use of the PAllHints macro is highly discouraged.

   To set a window's WM_NORMAL_HINTS property, use
   XSetWMNormalHints.

   void XSetWMNormalHints(Display *display, Window w, XSizeHints
   *hints);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   hints

   Specifies the size hints for the window in its normal state.

   The XSetWMNormalHints function replaces the size hints for the
   WM_NORMAL_HINTS property on the specified window. If the
   property does not already exist, XSetWMNormalHints sets the
   size hints for the WM_NORMAL_HINTS property on the specified
   window. The property is stored with a type of WM_SIZE_HINTS and
   a format of 32.

   XSetWMNormalHints can generate BadAlloc and BadWindow errors.

   To read a window's WM_NORMAL_HINTS property, use
   XGetWMNormalHints.

   Status XGetWMNormalHints(Display *display, Window w, XSizeHints
   *hints_return, long *supplied_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   hints_return

   Returns the size hints for the window in its normal state.

   supplied_return

   Returns the hints that were supplied by the user.

   The XGetWMNormalHints function returns the size hints stored in
   the WM_NORMAL_HINTS property on the specified window. If the
   property is of type WM_SIZE_HINTS, is of format 32, and is long
   enough to contain either an old (pre-ICCCM) or new size hints
   structure, XGetWMNormalHints sets the various fields of the
   XSizeHints structure, sets the supplied_return argument to the
   list of fields that were supplied by the user (whether or not
   they contained defined values), and returns a nonzero status.
   Otherwise, it returns a zero status.

   If XGetWMNormalHints returns successfully and a pre-ICCCM size
   hints property is read, the supplied_return argument will
   contain the following bits:

(USPosition|USSize|PPosition|PSize|PMinSize|
 PMaxSize|PResizeInc|PAspect)

   If the property is large enough to contain the base size and
   window gravity fields as well, the supplied_return argument
   will also contain the following bits:

PBaseSize|PWinGravity

   XGetWMNormalHints can generate a BadWindow error.

   To set a window's WM_SIZE_HINTS property, use XSetWMSizeHints.

   void XSetWMSizeHints(Display *display, Window w, XSizeHints
   *hints, Atom property);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   hints

   Specifies the XSizeHints structure to be used.

   property

   Specifies the property name.

   The XSetWMSizeHints function replaces the size hints for the
   specified property on the named window. If the specified
   property does not already exist, XSetWMSizeHints sets the size
   hints for the specified property on the named window. The
   property is stored with a type of WM_SIZE_HINTS and a format of
   32. To set a window's normal size hints, you can use the
   XSetWMNormalHints function.

   XSetWMSizeHints can generate BadAlloc, BadAtom, and BadWindow
   errors.

   To read a window's WM_SIZE_HINTS property, use XGetWMSizeHints.

   Status XGetWMSizeHints(Display *display, Window w, XSizeHints
   *hints_return, long *supplied_return, Atom property);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   hints_return

   Returns the XSizeHints structure.

   supplied_return

   Returns the hints that were supplied by the user.

   property

   Specifies the property name.

   The XGetWMSizeHints function returns the size hints stored in
   the specified property on the named window. If the property is
   of type WM_SIZE_HINTS, is of format 32, and is long enough to
   contain either an old (pre-ICCCM) or new size hints structure,
   XGetWMSizeHints sets the various fields of the XSizeHints
   structure, sets the supplied_return argument to the list of
   fields that were supplied by the user (whether or not they
   contained defined values), and returns a nonzero status.
   Otherwise, it returns a zero status. To get a window's normal
   size hints, you can use the XGetWMNormalHints function.

   If XGetWMSizeHints returns successfully and a pre-ICCCM size
   hints property is read, the supplied_return argument will
   contain the following bits:

(USPosition|USSize|PPosition|PSize|PMinSize|
 PMaxSize|PResizeInc|PAspect)

   If the property is large enough to contain the base size and
   window gravity fields as well, the supplied_return argument
   will also contain the following bits:

PBaseSize|PWinGravity

   XGetWMSizeHints can generate BadAtom and BadWindow errors.

Setting and Reading the WM_CLASS Property

   Xlib provides functions that you can use to set and get the
   WM_CLASS property for a given window. These functions use the
   XClassHint structure, which is defined in the <X11/Xutil.h>
   header file.

   To allocate an XClassHint structure, use XAllocClassHint.

   XClassHint *XAllocClassHint(void);

   The XAllocClassHint function allocates and returns a pointer to
   an XClassHint structure. Note that the pointer fields in the
   XClassHint structure are initially set to NULL. If insufficient
   memory is available, XAllocClassHint returns NULL. To free the
   memory allocated to this structure, use XFree.

   The XClassHint contains:



typedef struct {
        char *res_name;
        char *res_class;
} XClassHint;

   The res_name member contains the application name, and the
   res_class member contains the application class. Note that the
   name set in this property may differ from the name set as
   WM_NAME. That is, WM_NAME specifies what should be displayed in
   the title bar and, therefore, can contain temporal information
   (for example, the name of a file currently in an editor's
   buffer). On the other hand, the name specified as part of
   WM_CLASS is the formal name of the application that should be
   used when retrieving the application's resources from the
   resource database.

   To set a window's WM_CLASS property, use XSetClassHint.

   XSetClassHint(Display *display, Window w, XClassHint
   *class_hints);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   class_hints

   Specifies the XClassHint structure that is to be used.

   The XSetClassHint function sets the class hint for the
   specified window. If the strings are not in the Host Portable
   Character Encoding, the result is implementation-dependent.

   XSetClassHint can generate BadAlloc and BadWindow errors.

   To read a window's WM_CLASS property, use XGetClassHint.

   Status XGetClassHint(Display *display, Window w, XClassHint
   *class_hints_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   class_hints_return

   Returns the XClassHint structure.

   The XGetClassHint function returns the class hint of the
   specified window to the members of the supplied structure. If
   the data returned by the server is in the Latin Portable
   Character Encoding, then the returned strings are in the Host
   Portable Character Encoding. Otherwise, the result is
   implementation-dependent. It returns a nonzero status on
   success; otherwise, it returns a zero status. To free res_name
   and res_class when finished with the strings, use XFree on each
   individually.

   XGetClassHint can generate a BadWindow error.

Setting and Reading the WM_TRANSIENT_FOR Property

   Xlib provides functions that you can use to set and read the
   WM_TRANSIENT_FOR property for a given window.

   To set a window's WM_TRANSIENT_FOR property, use
   XSetTransientForHint.

   XSetTransientForHint(Display *display, Window w, Window
   prop_window);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   prop_window

   Specifies the window that the WM_TRANSIENT_FOR property is to
   be set to.

   The XSetTransientForHint function sets the WM_TRANSIENT_FOR
   property of the specified window to the specified prop_window.

   XSetTransientForHint can generate BadAlloc and BadWindow
   errors.

   To read a window's WM_TRANSIENT_FOR property, use
   XGetTransientForHint.

   Status XGetTransientForHint(Display *display, Window w, Window
   *prop_window_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   prop_window_return

   Returns the WM_TRANSIENT_FOR property of the specified window.

   The XGetTransientForHint function returns the WM_TRANSIENT_FOR
   property for the specified window. It returns a nonzero status
   on success; otherwise, it returns a zero status.

   XGetTransientForHint can generate a BadWindow error.

Setting and Reading the WM_PROTOCOLS Property

   Xlib provides functions that you can use to set and read the
   WM_PROTOCOLS property for a given window.

   To set a window's WM_PROTOCOLS property, use XSetWMProtocols.

   Status XSetWMProtocols(Display *display, Window w, Atom
   *protocols, int count);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   protocols

   Specifies the list of protocols.

   count

   Specifies the number of protocols in the list.

   The XSetWMProtocols function replaces the WM_PROTOCOLS property
   on the specified window with the list of atoms specified by the
   protocols argument. If the property does not already exist,
   XSetWMProtocols sets the WM_PROTOCOLS property on the specified
   window to the list of atoms specified by the protocols
   argument. The property is stored with a type of ATOM and a
   format of 32. If it cannot intern the WM_PROTOCOLS atom,
   XSetWMProtocols returns a zero status. Otherwise, it returns a
   nonzero status.

   XSetWMProtocols can generate BadAlloc and BadWindow errors.

   To read a window's WM_PROTOCOLS property, use XGetWMProtocols.

   Status XGetWMProtocols(Display *display, Window w, Atom
   **protocols_return, int *count_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   protocols_return

   Returns the list of protocols.

   count_return

   Returns the number of protocols in the list.

   The XGetWMProtocols function returns the list of atoms stored
   in the WM_PROTOCOLS property on the specified window. These
   atoms describe window manager protocols in which the owner of
   this window is willing to participate. If the property exists,
   is of type ATOM, is of format 32, and the atom WM_PROTOCOLS can
   be interned, XGetWMProtocols sets the protocols_return argument
   to a list of atoms, sets the count_return argument to the
   number of elements in the list, and returns a nonzero status.
   Otherwise, it sets neither of the return arguments and returns
   a zero status. To release the list of atoms, use XFree.

   XGetWMProtocols can generate a BadWindow error.

Setting and Reading the WM_COLORMAP_WINDOWS Property

   Xlib provides functions that you can use to set and read the
   WM_COLORMAP_WINDOWS property for a given window.

   To set a window's WM_COLORMAP_WINDOWS property, use
   XSetWMColormapWindows.

   Status XSetWMColormapWindows(Display *display, Window w, Window
   *colormap_windows, int count);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   colormap_windows

   Specifies the list of windows.

   count

   Specifies the number of windows in the list.

   The XSetWMColormapWindows function replaces the
   WM_COLORMAP_WINDOWS property on the specified window with the
   list of windows specified by the colormap_windows argument. If
   the property does not already exist, XSetWMColormapWindows sets
   the WM_COLORMAP_WINDOWS property on the specified window to the
   list of windows specified by the colormap_windows argument. The
   property is stored with a type of WINDOW and a format of 32. If
   it cannot intern the WM_COLORMAP_WINDOWS atom,
   XSetWMColormapWindows returns a zero status. Otherwise, it
   returns a nonzero status.

   XSetWMColormapWindows can generate BadAlloc and BadWindow
   errors.

   To read a window's WM_COLORMAP_WINDOWS property, use
   XGetWMColormapWindows.

   Status XGetWMColormapWindows(Display *display, Window w, Window
   **colormap_windows_return, int *count_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   colormap_windows_return

   Returns the list of windows.

   count_return

   Returns the number of windows in the list.

   The XGetWMColormapWindows function returns the list of window
   identifiers stored in the WM_COLORMAP_WINDOWS property on the
   specified window. These identifiers indicate the colormaps that
   the window manager may need to install for this window. If the
   property exists, is of type WINDOW, is of format 32, and the
   atom WM_COLORMAP_WINDOWS can be interned, XGetWMColormapWindows
   sets the windows_return argument to a list of window
   identifiers, sets the count_return argument to the number of
   elements in the list, and returns a nonzero status. Otherwise,
   it sets neither of the return arguments and returns a zero
   status. To release the list of window identifiers, use XFree.

   XGetWMColormapWindows can generate a BadWindow error.

Setting and Reading the WM_ICON_SIZE Property

   Xlib provides functions that you can use to set and read the
   WM_ICON_SIZE property for a given window. These functions use
   the XIconSize structure, which is defined in the <X11/Xutil.h>
   header file.

   To allocate an XIconSize structure, use XAllocIconSize.

   XIconSize *XAllocIconSize(void);

   The XAllocIconSize function allocates and returns a pointer to
   an XIconSize structure. Note that all fields in the XIconSize
   structure are initially set to zero. If insufficient memory is
   available, XAllocIconSize returns NULL. To free the memory
   allocated to this structure, use XFree.

   The XIconSize structure contains:



typedef struct {
        int min_width, min_height;
        int max_width, max_height;
        int width_inc, height_inc;
} XIconSize;

   The width_inc and height_inc members define an arithmetic
   progression of sizes (minimum to maximum) that represent the
   supported icon sizes.

   To set a window's WM_ICON_SIZE property, use XSetIconSizes.

   XSetIconSizes(Display *display, Window w, XIconSize *size_list,
   int count);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   size_list

   Specifies the size list.

   count

   Specifies the number of items in the size list.

   The XSetIconSizes function is used only by window managers to
   set the supported icon sizes.

   XSetIconSizes can generate BadAlloc and BadWindow errors.

   To read a window's WM_ICON_SIZE property, use XGetIconSizes.

   Status XGetIconSizes(Display *display, Window w, XIconSize
   **size_list_return, int *count_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   size_list_return

   Returns the size list.

   count_return

   Returns the number of items in the size list.

   The XGetIconSizes function returns zero if a window manager has
   not set icon sizes; otherwise, it returns nonzero.
   XGetIconSizes should be called by an application that wants to
   find out what icon sizes would be most appreciated by the
   window manager under which the application is running. The
   application should then use XSetWMHints to supply the window
   manager with an icon pixmap or window in one of the supported
   sizes. To free the data allocated in size_list_return, use
   XFree.

   XGetIconSizes can generate a BadWindow error.

Using Window Manager Convenience Functions

   The XmbSetWMProperties function stores the standard set of
   window manager properties, with text properties in standard
   encodings for internationalized text communication. The
   standard window manager properties for a given window are
   WM_NAME, WM_ICON_NAME, WM_HINTS, WM_NORMAL_HINTS, WM_CLASS,
   WM_COMMAND, WM_CLIENT_MACHINE, and WM_LOCALE_NAME.

   void XmbSetWMProperties(Display *display, Window w, char
   *window_name, char *icon_name, char *argv[], int argc,
   XSizeHints *normal_hints, XWMHints *wm_hints, XClassHint
   *class_hints);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   window_name

   Specifies the window name, which should be a null-terminated
   string.

   icon_name

   Specifies the icon name, which should be a null-terminated
   string.

   argv

   Specifies the application's argument list.

   argc

   Specifies the number of arguments.

   hints

   Specifies the size hints for the window in its normal state.

   wm_hints

   Specifies the XWMHints structure to be used.

   class_hints

   Specifies the XClassHint structure to be used.

   The XmbSetWMProperties convenience function provides a simple
   programming interface for setting those essential window
   properties that are used for communicating with other clients
   (particularly window and session managers).

   If the window_name argument is non-NULL, XmbSetWMProperties
   sets the WM_NAME property. If the icon_name argument is
   non-NULL, XmbSetWMProperties sets the WM_ICON_NAME property.
   The window_name and icon_name arguments are null-terminated
   strings in the encoding of the current locale. If the arguments
   can be fully converted to the STRING encoding, the properties
   are created with type ``STRING''; otherwise, the arguments are
   converted to Compound Text, and the properties are created with
   type ``COMPOUND_TEXT''.

   If the normal_hints argument is non-NULL, XmbSetWMProperties
   calls XSetWMNormalHints, which sets the WM_NORMAL_HINTS
   property (see section 14.1.7). If the wm_hints argument is
   non-NULL, XmbSetWMProperties calls XSetWMHints, which sets the
   WM_HINTS property (see section 14.1.6).

   If the argv argument is non-NULL, XmbSetWMProperties sets the
   WM_COMMAND property from argv and argc. An argc of zero
   indicates a zero-length command.

   The hostname of the machine is stored using XSetWMClientMachine
   (see section 14.2.2).

   If the class_hints argument is non-NULL, XmbSetWMProperties
   sets the WM_CLASS property. If the res_name member in the
   XClassHint structure is set to the NULL pointer and the
   RESOURCE_NAME environment variable is set, the value of the
   environment variable is substituted for res_name. If the
   res_name member is NULL, the environment variable is not set,
   and argv and argv[0] are set, then the value of argv[0],
   stripped of any directory prefixes, is substituted for
   res_name.

   It is assumed that the supplied class_hints.res_name and argv,
   the RESOURCE_NAME environment variable, and the hostname of the
   machine are in the encoding of the locale announced for the
   LC_CTYPE category (on POSIX-compliant systems, the LC_CTYPE,
   else LANG environment variable). The corresponding WM_CLASS,
   WM_COMMAND, and WM_CLIENT_MACHINE properties are typed
   according to the local host locale announcer. No encoding
   conversion is performed prior to storage in the properties.

   For clients that need to process the property text in a locale,
   XmbSetWMProperties sets the WM_LOCALE_NAME property to be the
   name of the current locale. The name is assumed to be in the
   Host Portable Character Encoding and is converted to STRING for
   storage in the property.

   XmbSetWMProperties can generate BadAlloc and BadWindow errors.

   To set a window's standard window manager properties with
   strings in client-specified encodings, use XSetWMProperties.
   The standard window manager properties for a given window are
   WM_NAME, WM_ICON_NAME, WM_HINTS, WM_NORMAL_HINTS, WM_CLASS,
   WM_COMMAND, and WM_CLIENT_MACHINE.

   void XSetWMProperties(Display *display, Window w, XTextProperty
   *window_name, XTextProperty *icon_name, char **argv, int argc,
   XSizeHints *normal_hints, XWMHints *wm_hints, XClassHint
   *class_hints);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   window_name

   Specifies the window name, which should be a null-terminated
   string.

   icon_name

   Specifies the icon name, which should be a null-terminated
   string.

   argv

   Specifies the application's argument list.

   argc

   Specifies the number of arguments.

   normal_hints

   Specifies the size hints for the window in its normal state.

   wm_hints

   Specifies the XWMHints structure to be used.

   class_hints

   Specifies the XClassHint structure to be used.

   The XSetWMProperties convenience function provides a single
   programming interface for setting those essential window
   properties that are used for communicating with other clients
   (particularly window and session managers).

   If the window_name argument is non-NULL, XSetWMProperties calls
   XSetWMName, which, in turn, sets the WM_NAME property (see
   section 14.1.4). If the icon_name argument is non-NULL,
   XSetWMProperties calls XSetWMIconName, which sets the
   WM_ICON_NAME property (see section 14.1.5). If the argv
   argument is non-NULL, XSetWMProperties calls XSetCommand, which
   sets the WM_COMMAND property (see section 14.2.1). Note that an
   argc of zero is allowed to indicate a zero-length command. Note
   also that the hostname of this machine is stored using
   XSetWMClientMachine (see section 14.2.2).

   If the normal_hints argument is non-NULL, XSetWMProperties
   calls XSetWMNormalHints, which sets the WM_NORMAL_HINTS
   property (see section 14.1.7). If the wm_hints argument is
   non-NULL, XSetWMProperties calls XSetWMHints, which sets the
   WM_HINTS property (see section 14.1.6).

   If the class_hints argument is non-NULL, XSetWMProperties calls
   XSetClassHint, which sets the WM_CLASS property (see section
   14.1.8). If the res_name member in the XClassHint structure is
   set to the NULL pointer and the RESOURCE_NAME environment
   variable is set, then the value of the environment variable is
   substituted for res_name. If the res_name member is NULL, the
   environment variable is not set, and argv and argv[0] are set,
   then the value of argv[0], stripped of any directory prefixes,
   is substituted for res_name.

   XSetWMProperties can generate BadAlloc and BadWindow errors.

Client to Session Manager Communication

   This section discusses how to:
     * Set and read the WM_COMMAND property
     * Set and read the WM_CLIENT_MACHINE property

Setting and Reading the WM_COMMAND Property

   Xlib provides functions that you can use to set and read the
   WM_COMMAND property for a given window.

   To set a window's WM_COMMAND property, use XSetCommand.

   XSetCommand(Display *display, Window w, char **argv, int argc);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   argv

   Specifies the application's argument list.

   argc

   Specifies the number of arguments.

   The XSetCommand function sets the command and arguments used to
   invoke the application. (Typically, argv is the argv array of
   your main program.) If the strings are not in the Host Portable
   Character Encoding, the result is implementation-dependent.

   XSetCommand can generate BadAlloc and BadWindow errors.

   To read a window's WM_COMMAND property, use XGetCommand.

   Status XGetCommand(Display *display, Window w, char
   ***argv_return, int *argc_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   argv_return

   Returns the application's argument list.

   argc_return

   Returns the number of arguments returned.

   The XGetCommand function reads the WM_COMMAND property from the
   specified window and returns a string list. If the WM_COMMAND
   property exists, it is of type STRING and format 8. If
   sufficient memory can be allocated to contain the string list,
   XGetCommand fills in the argv_return and argc_return arguments
   and returns a nonzero status. Otherwise, it returns a zero
   status. If the data returned by the server is in the Latin
   Portable Character Encoding, then the returned strings are in
   the Host Portable Character Encoding. Otherwise, the result is
   implementation-dependent. To free the memory allocated to the
   string list, use XFreeStringList.

Setting and Reading the WM_CLIENT_MACHINE Property

   Xlib provides functions that you can use to set and read the
   WM_CLIENT_MACHINE property for a given window.

   To set a window's WM_CLIENT_MACHINE property, use
   XSetWMClientMachine.

   void XSetWMClientMachine(Display *display, Window w,
   XTextProperty *text_prop);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   text_prop

   Specifies the XTextProperty structure to be used.

   The XSetWMClientMachine convenience function calls
   XSetTextProperty to set the WM_CLIENT_MACHINE property.

   To read a window's WM_CLIENT_MACHINE property, use
   XGetWMClientMachine.

   Status XGetWMClientMachine(Display *display, Window w,
   XTextProperty *text_prop_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   text_prop_return

   Returns the XTextProperty structure.

   The XGetWMClientMachine convenience function performs an
   XGetTextProperty on the WM_CLIENT_MACHINE property. It returns
   a nonzero status on success; otherwise, it returns a zero
   status.

Standard Colormaps

   Applications with color palettes, smooth-shaded drawings, or
   digitized images demand large numbers of colors. In addition,
   these applications often require an efficient mapping from
   color triples to pixel values that display the appropriate
   colors.

   As an example, consider a three-dimensional display program
   that wants to draw a smoothly shaded sphere. At each pixel in
   the image of the sphere, the program computes the intensity and
   color of light reflected back to the viewer. The result of each
   computation is a triple of red, green, and blue (RGB)
   coefficients in the range 0.0 to 1.0. To draw the sphere, the
   program needs a colormap that provides a large range of
   uniformly distributed colors. The colormap should be arranged
   so that the program can convert its RGB triples into pixel
   values very quickly, because drawing the entire sphere requires
   many such conversions.

   On many current workstations, the display is limited to 256 or
   fewer colors. Applications must allocate colors carefully, not
   only to make sure they cover the entire range they need but
   also to make use of as many of the available colors as
   possible. On a typical X display, many applications are active
   at once. Most workstations have only one hardware look-up table
   for colors, so only one application colormap can be installed
   at a given time. The application using the installed colormap
   is displayed correctly, and the other applications go
   technicolor and are displayed with false colors.

   As another example, consider a user who is running an image
   processing program to display earth-resources data. The image
   processing program needs a colormap set up with 8 reds, 8
   greens, and 4 blues, for a total of 256 colors. Because some
   colors are already in use in the default colormap, the image
   processing program allocates and installs a new colormap.

   The user decides to alter some of the colors in the image by
   invoking a color palette program to mix and choose colors. The
   color palette program also needs a colormap with eight reds,
   eight greens, and four blues, so just like the image processing
   program, it must allocate and install a new colormap.

   Because only one colormap can be installed at a time, the color
   palette may be displayed incorrectly whenever the image
   processing program is active. Conversely, whenever the palette
   program is active, the image may be displayed incorrectly. The
   user can never match or compare colors in the palette and
   image. Contention for colormap resources can be reduced if
   applications with similar color needs share colormaps.

   The image processing program and the color palette program
   could share the same colormap if there existed a convention
   that described how the colormap was set up. Whenever either
   program was active, both would be displayed correctly.

   The standard colormap properties define a set of commonly used
   colormaps. Applications that share these colormaps and
   conventions display true colors more often and provide a better
   interface to the user.

   Standard colormaps allow applications to share commonly used
   color resources. This allows many applications to be displayed
   in true colors simultaneously, even when each application needs
   an entirely filled colormap.

   Several standard colormaps are described in this section.
   Usually, a window manager creates these colormaps. Applications
   should use the standard colormaps if they already exist.

   To allocate an XStandardColormap structure, use
   XAllocStandardColormap.

   XStandardColormap *XAllocStandardColormap(void);

   The XAllocStandardColormap function allocates and returns a
   pointer to an XStandardColormap structure. Note that all fields
   in the XStandardColormap structure are initially set to zero.
   If insufficient memory is available, XAllocStandardColormap
   returns NULL. To free the memory allocated to this structure,
   use XFree.

   The XStandardColormap structure contains:
/* Hints */

#define       ReeaseByFreeingColormap  ((XID)1L)

/* Values */

typedef struct {
        Colormap colormap;
        unsigned long red_max;
        unsigned long red_mult;
        unsigned long green_max;
        unsigned long green_mult;
        unsigned long blue_max;
        unsigned long blue_mult;
        unsigned long base_pixel;
        VisualID visualid;
        XID killid;
} XStandardColormap;

   The colormap member is the colormap created by the
   XCreateColormap function. The red_max, green_max, and blue_max
   members give the maximum red, green, and blue values,
   respectively. Each color coefficient ranges from zero to its
   max, inclusive. For example, a common colormap allocation is
   3/3/2 (3 planes for red, 3 planes for green, and 2 planes for
   blue). This colormap would have red_max = 7, green_max = 7, and
   blue_max = 3. An alternate allocation that uses only 216 colors
   is red_max = 5, green_max = 5, and blue_max = 5.

   The red_mult, green_mult, and blue_mult members give the scale
   factors used to compose a full pixel value. (See the discussion
   of the base_pixel members for further information.) For a 3/3/2
   allocation, red_mult might be 32, green_mult might be 4, and
   blue_mult might be 1. For a 6-colors-each allocation, red_mult
   might be 36, green_mult might be 6, and blue_mult might be 1.

   The base_pixel member gives the base pixel value used to
   compose a full pixel value. Usually, the base_pixel is obtained
   from a call to the XAllocColorPlanes function. Given integer
   red, green, and blue coefficients in their appropriate ranges,
   one then can compute a corresponding pixel value by using the
   following expression:



(r * red_mult + g * green_mult + b * blue_mult + base_pixel) & 0xFFFFFFF
F

   For GrayScale colormaps, only the colormap, red_max, red_mult,
   and base_pixel members are defined. The other members are
   ignored. To compute a GrayScale pixel value, use the following
   expression:



(gray * red_mult + base_pixel) & 0xFFFFFFFF

   Negative multipliers can be represented by converting the 2's
   complement representation of the multiplier into an unsigned
   long and storing the result in the appropriate _mult field. The
   step of masking by 0xFFFFFFFF effectively converts the
   resulting positive multiplier into a negative one. The masking
   step will take place automatically on many machine
   architectures, depending on the size of the integer type used
   to do the computation.

   The visualid member gives the ID number of the visual from
   which the colormap was created. The killid member gives a
   resource ID that indicates whether the cells held by this
   standard colormap are to be released by freeing the colormap ID
   or by calling the XKillClient function on the indicated
   resource. (Note that this method is necessary for allocating
   out of an existing colormap.)

   The properties containing the XStandardColormap information
   have the type RGB_COLOR_MAP.

   The remainder of this section discusses standard colormap
   properties and atoms as well as how to manipulate standard
   colormaps.

Standard Colormap Properties and Atoms

   Several standard colormaps are available. Each standard
   colormap is defined by a property, and each such property is
   identified by an atom. The following list names the atoms and
   describes the colormap associated with each one. The
   <X11/Xatom.h> header file contains the definitions for each of
   the following atoms, which are prefixed with XA_.

   RGB_DEFAULT_MAP

   This atom names a property. The value of the property is an
   array of XStandardColormap structures. Each entry in the array
   describes an RGB subset of the default color map for the Visual
   specified by visual_id.

   Some applications only need a few RGB colors and may be able to
   allocate them from the system default colormap. This is the
   ideal situation because the fewer colormaps that are active in
   the system the more applications are displayed with correct
   colors at all times.

   A typical allocation for the RGB_DEFAULT_MAP on 8-plane
   displays is 6 reds, 6 greens, and 6 blues. This gives 216
   uniformly distributed colors (6 intensities of 36 different
   hues) and still leaves 40 elements of a 256-element colormap
   available for special-purpose colors for text, borders, and so
   on.

   RGB_BEST_MAP

   This atom names a property. The value of the property is an
   XStandardColormap.

   The property defines the best RGB colormap available on the
   screen. (Of course, this is a subjective evaluation.) Many
   image processing and three-dimensional applications need to use
   all available colormap cells and to distribute as many
   perceptually distinct colors as possible over those cells. This
   implies that there may be more green values available than red,
   as well as more green or red than blue.

   For an 8-plane PseudoColor visual, RGB_BEST_MAP is likely to be
   a 3/3/2 allocation. For a 24-plane DirectColor visual,
   RGB_BEST_MAP is normally an 8/8/8 allocation.

   RGB_RED_MAP,RGB_GREEN_MAP,RGB_BLUE_MAP

   These atoms name properties. The value of each property is an
   XStandardColormap.

   The properties define all-red, all-green, and all-blue
   colormaps, respectively. These maps are used by applications
   that want to make color-separated images. For example, a user
   might generate a full-color image on an 8-plane display both by
   rendering an image three times (once with high color resolution
   in red, once with green, and once with blue) and by multiply
   exposing a single frame in a camera.

   RGB_GRAY_MAP

   This atom names a property. The value of the property is an
   XStandardColormap.

   The property describes the best GrayScale colormap available on
   the screen. As previously mentioned, only the colormap,
   red_max, red_mult, and base_pixel members of the
   XStandardColormap structure are used for GrayScale colormaps.

Setting and Obtaining Standard Colormaps

   Xlib provides functions that you can use to set and obtain an
   XStandardColormap structure.

   To set an XStandardColormap structure, use XSetRGBColormaps.

   void XSetRGBColormaps(Display *display, Window w,
   XStandardColormap *std_colormap, int count, Atom property);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   std_colormap

   Specifies the XStandardColormap structure to be used.

   count

   Specifies the number of colormaps.

   property

   Specifies the property name.

   The XSetRGBColormaps function replaces the RGB colormap
   definition in the specified property on the named window. If
   the property does not already exist, XSetRGBColormaps sets the
   RGB colormap definition in the specified property on the named
   window. The property is stored with a type of RGB_COLOR_MAP and
   a format of 32. Note that it is the caller's responsibility to
   honor the ICCCM restriction that only RGB_DEFAULT_MAP contain
   more than one definition.

   The XSetRGBColormaps function usually is only used by window or
   session managers. To create a standard colormap, follow this
   procedure:
     * Open a new connection to the same server.
     * Grab the server.
     * See if the property is on the property list of the root
       window for the screen.
     * If the desired property is not present:
     * Create a colormap (unless you are using the default
       colormap of the screen).
     * Determine the color characteristics of the visual.
     * Allocate cells in the colormap (or create it with
       AllocAll).
     * Call XStoreColors to store appropriate color values in the
       colormap.
     * Fill in the descriptive members in the XStandardColormap
       structure.
     * Attach the property to the root window.
     * Use XSetCloseDownMode to make the resource permanent.
     * Ungrab the server.

   XSetRGBColormaps can generate BadAlloc, BadAtom, and BadWindow
   errors.

   To obtain the XStandardColormap structure associated with the
   specified property, use XGetRGBColormaps.

   Status XGetRGBColormaps(Display *display, Window w,
   XStandardColormap **std_colormap_return, int *count_return,
   Atom property);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   std_colormap_return

   Returns the XStandardColormap structure.

   count_return

   Returns the number of colormaps.

   property

   Specifies the property name.

   The XGetRGBColormaps function returns the RGB colormap
   definitions stored in the specified property on the named
   window. If the property exists, is of type RGB_COLOR_MAP, is of
   format 32, and is long enough to contain a colormap definition,
   XGetRGBColormaps allocates and fills in space for the returned
   colormaps and returns a nonzero status. If the visualid is not
   present, XGetRGBColormaps assumes the default visual for the
   screen on which the window is located; if the killid is not
   present, None is assumed, which indicates that the resources
   cannot be released. Otherwise, none of the fields are set, and
   XGetRGBColormaps returns a zero status. Note that it is the
   caller's responsibility to honor the ICCCM restriction that
   only RGB_DEFAULT_MAP contain more than one definition.

   XGetRGBColormaps can generate BadAtom and BadWindow errors.

Chapter 15. Resource Manager Functions

   Table of Contents

   Resource File Syntax
   Resource Manager Matching Rules
   Quarks
   Creating and Storing Databases
   Merging Resource Databases
   Looking Up Resources
   Storing into a Resource Database
   Enumerating Database Entries
   Parsing Command Line Options

   A program often needs a variety of options in the X environment
   (for example, fonts, colors, icons, and cursors). Specifying
   all of these options on the command line is awkward because
   users may want to customize many aspects of the program and
   need a convenient way to establish these customizations as the
   default settings. The resource manager is provided for this
   purpose. Resource specifications are usually stored in
   human-readable files and in server properties.

   The resource manager is a database manager with a twist. In
   most database systems, you perform a query using an imprecise
   specification, and you get back a set of records. The resource
   manager, however, allows you to specify a large set of values
   with an imprecise specification, to query the database with a
   precise specification, and to get back only a single value.
   This should be used by applications that need to know what the
   user prefers for colors, fonts, and other resources. It is this
   use as a database for dealing with X resources that inspired
   the name "Resource Manager," although the resource manager can
   be and is used in other ways.

   For example, a user of your application may want to specify
   that all windows should have a blue background but that all
   mail-reading windows should have a red background. With
   well-engineered and coordinated applications, a user can define
   this information using only two lines of specifications.

   As an example of how the resource manager works, consider a
   mail-reading application called xmh. Assume that it is designed
   so that it uses a complex window hierarchy all the way down to
   individual command buttons, which may be actual small
   subwindows in some toolkits. These are often called objects or
   widgets. In such toolkit systems, each user interface object
   can be composed of other objects and can be assigned a name and
   a class. Fully qualified names or classes can have arbitrary
   numbers of component names, but a fully qualified name always
   has the same number of component names as a fully qualified
   class. This generally reflects the structure of the application
   as composed of these objects, starting with the application
   itself.

   For example, the xmh mail program has a name "xmh" and is one
   of a class of "Mail" programs. By convention, the first
   character of class components is capitalized, and the first
   letter of name components is in lowercase. Each name and class
   finally has an attribute (for example, "foreground" or "font").
   If each window is properly assigned a name and class, it is
   easy for the user to specify attributes of any portion of the
   application.

   At the top level, the application might consist of a paned
   window (that is, a window divided into several sections) named
   "toc". One pane of the paned window is a button box window
   named "buttons" and is filled with command buttons. One of
   these command buttons is used to incorporate new mail and has
   the name "incorporate". This window has a fully qualified name,
   "xmh.toc.buttons.incorporate", and a fully qualified class,
   "Xmh.Paned.Box.Command". Its fully qualified name is the name
   of its parent, "xmh.toc.buttons", followed by its name,
   "incorporate". Its class is the class of its parent,
   "Xmh.Paned.Box", followed by its particular class, "Command".
   The fully qualified name of a resource is the attribute's name
   appended to the object's fully qualified name, and the fully
   qualified class is its class appended to the object's class.

   The incorporate button might need the following resources:
   Title string, Font, Foreground color for its inactive state,
   Background color for its inactive state, Foreground color for
   its active state, and Background color for its active state.
   Each resource is considered to be an attribute of the button
   and, as such, has a name and a class. For example, the
   foreground color for the button in its active state might be
   named "activeForeground", and its class might be "Foreground".

   When an application looks up a resource (for example, a color),
   it passes the complete name and complete class of the resource
   to a look-up routine. The resource manager compares this
   complete specification against the incomplete specifications of
   entries in the resource database, finds the best match, and
   returns the corresponding value for that entry.

   The definitions for the resource manager are contained in
   <X11/Xresource.h>.

Resource File Syntax

   The syntax of a resource file is a sequence of resource lines
   terminated by newline characters or the end of the file. The
   syntax of an individual resource line is:



ResourceLine     =     Comment | IncludeFile | ResourceSpec | <empty lin
e>
Comment     =     "!" {<any character except null or newline>}
IncludeFile     =     "#" WhiteSpace "include" WhiteSpace FileName White
Space
FileName     =     <valid filename for operating system>
ResourceSpec     =     WhiteSpace ResourceName WhiteSpace ":" WhiteSpace
 Value
ResourceName     =     [Binding] {Component Binding} ComponentName
Binding     =     "." | "*"
WhiteSpace     =     {<space> | <horizontal tab>}
Component     =     "?" | ComponentName
ComponentName     =     NameChar {NameChar}
NameChar     =     "a"-"z" | "A"-"Z" | "0"-"9" | "_" | "-"
Value     =     {<any character except null or unescaped newline>}

   Elements separated by vertical bar (|) are alternatives. Curly
   braces ({......}) indicate zero or more repetitions of the
   enclosed elements. Square brackets ([......]) indicate that the
   enclosed element is optional. Quotes ("......") are used around
   literal characters.

   IncludeFile lines are interpreted by replacing the line with
   the contents of the specified file. The word "include" must be
   in lowercase. The file name is interpreted relative to the
   directory of the file in which the line occurs (for example, if
   the file name contains no directory or contains a relative
   directory specification).

   If a ResourceName contains a contiguous sequence of two or more
   Binding characters, the sequence will be replaced with a single
   ".." character if the sequence contains only ".." characters;
   otherwise, the sequence will be replaced with a single "*"
   character.

   A resource database never contains more than one entry for a
   given ResourceName. If a resource file contains multiple lines
   with the same ResourceName, the last line in the file is used.

   Any white space characters before or after the name or colon in
   a ResourceSpec are ignored. To allow a Value to begin with
   white space, the two-character sequence "\\space" (backslash
   followed by space) is recognized and replaced by a space
   character, and the two-character sequence "\\tab" (backslash
   followed by horizontal tab) is recognized and replaced by a
   horizontal tab character. To allow a Value to contain embedded
   newline characters, the two-character sequence "\\n" is
   recognized and replaced by a newline character. To allow a
   Value to be broken across multiple lines in a text file, the
   two-character sequence "\\newline" (backslash followed by
   newline) is recognized and removed from the value. To allow a
   Value to contain arbitrary character codes, the four-character
   sequence "\\nnn", where each n is a digit character in the
   range of "0"-"7", is recognized and replaced with a single byte
   that contains the octal value specified by the sequence.
   Finally, the two-character sequence "\newline" is recognized
   and replaced with a single backslash.

   As an example of these sequences, the following resource line
   contains a value consisting of four characters: a backslash, a
   null, a "z", and a newline:
magic.values: \\000\
z\n

Resource Manager Matching Rules

   The algorithm for determining which resource database entry
   matches a given query is the heart of the resource manager. All
   queries must fully specify the name and class of the desired
   resource (use of the characters "*" and "?" is not permitted).
   The library supports up to 100 components in a full name or
   class. Resources are stored in the database with only partially
   specified names and classes, using pattern matching constructs.
   An asterisk (*) is a loose binding and is used to represent any
   number of intervening components, including none. A period (.)
   is a tight binding and is used to separate immediately adjacent
   components. A question mark (?) is used to match any single
   component name or class. A database entry cannot end in a loose
   binding; the final component (which cannot be the character
   "?") must be specified. The lookup algorithm searches the
   database for the entry that most closely matches (is most
   specific for) the full name and class being queried. When more
   than one database entry matches the full name and class,
   precedence rules are used to select just one.

   The full name and class are scanned from left to right (from
   highest level in the hierarchy to lowest), one component at a
   time. At each level, the corresponding component and/or binding
   of each matching entry is determined, and these matching
   components and bindings are compared according to precedence
   rules. Each of the rules is applied at each level before moving
   to the next level, until a rule selects a single entry over all
   others. The rules, in order of precedence, are:
     * An entry that contains a matching component (whether name,
       class, or the character "?") takes precedence over entries
       that elide the level (that is, entries that match the level
       in a loose binding).
     * An entry with a matching name takes precedence over both
       entries with a matching class and entries that match using
       the character "?". An entry with a matching class takes
       precedence over entries that match using the character "?".
     * An entry preceded by a tight binding takes precedence over
       entries preceded by a loose binding.

   To illustrate these rules, consider the following resource
   database entries:


xmh*Paned*activeForeground:     red     (entry A)
*incorporate.Foreground:     blue     (entry B)
xmh.toc*Command*activeForeground:     green     (entry C)
xmh.toc*?.Foreground:     white     (entry D)
xmh.toc*Command.activeForeground:     black     (entry E)

   Consider a query for the resource:



xmh.toc.messagefunctions.incorporate.activeForeground     (name)
Xmh.Paned.Box.Command.Foreground     (class)

   At the first level (xmh, Xmh), rule 1 eliminates entry B. At
   the second level (toc, Paned), rule 2 eliminates entry A. At
   the third level (messagefunctions, Box), no entries are
   eliminated. At the fourth level (incorporate, Command), rule 2
   eliminates entry D. At the fifth level (activeForeground,
   Foreground), rule 3 eliminates entry C.

Quarks

   Most uses of the resource manager involve defining names,
   classes, and representation types as string constants. However,
   always referring to strings in the resource manager can be
   slow, because it is so heavily used in some toolkits. To solve
   this problem, a shorthand for a string is used in place of the
   string in many of the resource manager functions. Simple
   comparisons can be performed rather than string comparisons.
   The shorthand name for a string is called a quark and is the
   type XrmQuark. On some occasions, you may want to allocate a
   quark that has no string equivalent.

   A quark is to a string what an atom is to a string in the
   server, but its use is entirely local to your application.

   To allocate a new quark, use XrmUniqueQuark.

   XrmQuark XrmUniqueQuark(void);

   The XrmUniqueQuark function allocates a quark that is
   guaranteed not to represent any string that is known to the
   resource manager.

   Each name, class, and representation type is typedef'd as an
   XrmQuark.

typedef int XrmQuark, *XrmQuarkList;
typedef XrmQuark XrmName;
typedef XrmQuark XrmClass;
typedef XrmQuark XrmRepresentation;
#define NULLQUARK ((XrmQuark) 0)

   Lists are represented as null-terminated arrays of quarks. The
   size of the array must be large enough for the number of
   components used.

typedef XrmQuarkList XrmNameList;
typedef XrmQuarkList XrmClassList;

   To convert a string to a quark, use XrmStringToQuark or
   XrmPermStringToQuark.
#define XrmStringToName(string) XrmStringToQuark(string)
#define XrmStringToClass(string) XrmStringToQuark(string)
#define XrmStringToRepresentation(string) XrmStringToQuark(string)

   XrmQuark XrmStringToQuark(char *string);

   string

   Specifies the string for which a quark(Ql is to be allocated.

   These functions can be used to convert from string to quark
   representation. If the string is not in the Host Portable
   Character Encoding, the conversion is implementation-dependent.
   The string argument to XrmStringToQuark need not be permanently
   allocated storage. XrmPermStringToQuark is just like
   XrmStringToQuark, except that Xlib is permitted to assume the
   string argument is permanently allocated, and, hence, that it
   can be used as the value to be returned by XrmQuarkToString.

   For any given quark, if XrmStringToQuark returns a non-NULL
   value, all future calls will return the same value (identical
   address).

   To convert a quark to a string, use XrmQuarkToString.
#define XrmNameToString(name)  XrmQuarkToString(name)
#define XrmClassToString(class)  XrmQuarkToString(name)
#define XrmRepresentationToString(type)  XrmQuarkToString(type)

   char *XrmQuarkToString(XrmQuark quark);

   quark

   Specifies the quark for which the equivalent string is desired.

   These functions can be used to convert from quark
   representation to string. The string pointed to by the return
   value must not be modified or freed. The returned string is
   byte-for-byte equal to the original string passed to one of the
   string-to-quark routines. If no string exists for that quark,
   XrmQuarkToString returns NULL. For any given quark, if
   XrmQuarkToString returns a non-NULL value, all future calls
   will return the same value (identical address).

   To convert a string with one or more components to a quark
   list, use XrmStringToQuarkList.
#define XrmStringToNameList(str,name)  XrmStringToQuarkList((str), (name
))
#define XrmStringToClassList(str,class)  XrmStringToQuarkList((str), (cl
ass))

   void XrmStringToQuarkList(char *string, XrmQuarkList
   quarks_return);

   string

   Specifies the string for which a quark list is to be allocated.

   quarks_return

   Returns the list of quarks. The caller must allocate sufficient
   space for the quarks list before calling XrmStringToQuarkList.

   The XrmStringToQuarkList function converts the null-terminated
   string (generally a fully qualified name) to a list of quarks.
   Note that the string must be in the valid ResourceName format
   (see section 15.1). If the string is not in the Host Portable
   Character Encoding, the conversion is implementation-dependent.

   A binding list is a list of type XrmBindingList and indicates
   if components of name or class lists are bound tightly or
   loosely (that is, if wildcarding of intermediate components is
   specified).

typedef enum {XrmBindTightly, XrmBindLoosely} XrmBinding, *XrmBindingLis
t;

   XrmBindTightly indicates that a period separates the
   components, and XrmBindLoosely indicates that an asterisk
   separates the components.

   To convert a string with one or more components to a binding
   list and a quark list, use XrmStringToBindingQuarkList.

   XrmStringToBindingQuarkList(char *string, XrmBindingList
   bindings_return, XrmQuarkList quarks_return);

   string

   Specifies the string for which a quark list is to be allocated.

   bindings_return

   Returns the binding list. The caller must allocate sufficient
   space for the binding list before calling
   XrmStringToBindingQuarkList.

   quarks_return

   Returns the list of quarks. The caller must allocate sufficient
   space for the quarks list before calling
   XrmStringToBindingQuarkList.

   Component names in the list are separated by a period or an
   asterisk character. The string must be in the format of a valid
   ResourceName (see section 15.1). If the string does not start
   with a period or an asterisk, a tight binding is assumed. For
   example, the string ``*a.b*c'' becomes:



quarks:       a         b         c
bindings:     loose     tight     loose

Creating and Storing Databases

   A resource database is an opaque type, XrmDatabase. Each
   database value is stored in an XrmValue structure. This
   structure consists of a size, an address, and a representation
   type. The size is specified in bytes. The representation type
   is a way for you to store data tagged by some
   application-defined type (for example, the strings ``font'' or
   ``color''). It has nothing to do with the C data type or with
   its class. The XrmValue structure is defined as:



typedef struct {
     unsigned int size;
     XPointer addr;
} XrmValue, *XrmValuePtr;

   To initialize the resource manager, use XrmInitialize.

   void XrmInitialize(void XrmInitialize(\|));

   To retrieve a database from disk, use XrmGetFileDatabase.

   XrmDatabase XrmGetFileDatabase(char *filename);

   filename

   Specifies the resource database file name.

   The XrmGetFileDatabase function opens the specified file,
   creates a new resource database, and loads it with the
   specifications read in from the specified file. The specified
   file should contain a sequence of entries in valid ResourceLine
   format (see section 15.1); the database that results from
   reading a file with incorrect syntax is
   implementation-dependent. The file is parsed in the current
   locale, and the database is created in the current locale. If
   it cannot open the specified file, XrmGetFileDatabase returns
   NULL.

   To store a copy of a database to disk, use XrmPutFileDatabase.

   void XrmPutFileDatabase(XrmDatabase database, char *stored_db);

   database

   Specifies the database that is to be used.

   stored_db

   Specifies the file name for the stored database.

   The XrmPutFileDatabase function stores a copy of the specified
   database in the specified file. Text is written to the file as
   a sequence of entries in valid ResourceLine format (see section
   15.1). The file is written in the locale of the database.
   Entries containing resource names that are not in the Host
   Portable Character Encoding or containing values that are not
   in the encoding of the database locale, are written in an
   implementation-dependent manner. The order in which entries are
   written is implementation-dependent. Entries with
   representation types other than ``String'' are ignored.

   To obtain a pointer to the screen-independent resources of a
   display, use XResourceManagerString.

   char *XResourceManagerString(Display *display);

   display

   Specifies the connection to the X server.

   The XResourceManagerString function returns the
   RESOURCE_MANAGER property from the server's root window of
   screen zero, which was returned when the connection was opened
   using XOpenDisplay. The property is converted from type STRING
   to the current locale. The conversion is identical to that
   produced by XmbTextPropertyToTextList for a single element
   STRING property. The returned string is owned by Xlib and
   should not be freed by the client. The property value must be
   in a format that is acceptable to XrmGetStringDatabase. If no
   property exists, NULL is returned.

   To obtain a pointer to the screen-specific resources of a
   screen, use XScreenResourceString.

   char *XScreenResourceString(Screen *screen);

   screen

   Specifies the screen.

   The XScreenResourceString function returns the SCREEN_RESOURCES
   property from the root window of the specified screen. The
   property is converted from type STRING to the current locale.
   The conversion is identical to that produced by
   XmbTextPropertyToTextList for a single element STRING property.
   The property value must be in a format that is acceptable to
   XrmGetStringDatabase. If no property exists, NULL is returned.
   The caller is responsible for freeing the returned string by
   using XFree.

   To create a database from a string, use XrmGetStringDatabase.

   XrmDatabase XrmGetStringDatabase(char *data);

   data

   Specifies the database contents using a string.

   The XrmGetStringDatabase function creates a new database and
   stores the resources specified in the specified null-terminated
   string. XrmGetStringDatabase is similar to XrmGetFileDatabase
   except that it reads the information out of a string instead of
   out of a file. The string should contain a sequence of entries
   in valid ResourceLine format (see section 15.1) terminated by a
   null character; the database that results from using a string
   with incorrect syntax is implementation-dependent. The string
   is parsed in the current locale, and the database is created in
   the current locale.

   To obtain the locale name of a database, use
   XrmLocaleOfDatabase.

   char *XrmLocaleOfDatabase(XrmDatabase database);

   database

   Specifies the resource database.

   The XrmLocaleOfDatabase function returns the name of the locale
   bound to the specified database, as a null-terminated string.
   The returned locale name string is owned by Xlib and should not
   be modified or freed by the client. Xlib is not permitted to
   free the string until the database is destroyed. Until the
   string is freed, it will not be modified by Xlib.

   To destroy a resource database and free its allocated memory,
   use XrmDestroyDatabase.

   void XrmDestroyDatabase(XrmDatabase database);

   database

   Specifies the resource database.

   If database is NULL, XrmDestroyDatabase returns immediately.

   To associate a resource database with a display, use
   XrmSetDatabase.

   void XrmSetDatabase(Display *display, XrmDatabase database);

   display

   Specifies the connection to the X server.

   database

   Specifies the resource database.

   The XrmSetDatabase function associates the specified resource
   database (or NULL) with the specified display. The database
   previously associated with the display (if any) is not
   destroyed. A client or toolkit may find this function
   convenient for retaining a database once it is constructed.

   To get the resource database associated with a display, use
   XrmGetDatabase.

   XrmDatabase XrmGetDatabase(Display *display);

   display

   Specifies the connection to the X server.

   The XrmGetDatabase function returns the database associated
   with the specified display. It returns NULL if a database has
   not yet been set.

Merging Resource Databases

   To merge the contents of a resource file into a database, use
   XrmCombineFileDatabase.

   Status XrmCombineFileDatabase(char *filename, XrmDatabase
   *target_db, Bool override);

   filename

   Specifies the resource database file name.

   target_db

   Specifies the resource database into which the source database
   is to be merged.

   override

   Specifies whether source entries override target ones.

   The XrmCombineFileDatabase function merges the contents of a
   resource file into a database. If the same specifier is used
   for an entry in both the file and the database, the entry in
   the file will replace the entry in the database if override is
   True; otherwise, the entry in the file is discarded. The file
   is parsed in the current locale. If the file cannot be read, a
   zero status is returned; otherwise, a nonzero status is
   returned. If target_db contains NULL, XrmCombineFileDatabase
   creates and returns a new database to it. Otherwise, the
   database pointed to by target_db is not destroyed by the merge.
   The database entries are merged without changing values or
   types, regardless of the locale of the database. The locale of
   the target database is not modified.

   To merge the contents of one database into another database,
   use XrmCombineDatabase.

   void XrmCombineDatabase(XrmDatabase source_db, XrmDatabase
   *target_db, Bool override);

   source_db

   Specifies the resource database that is to be merged into the
   target database.

   target_db

   Specifies the resource database into which the source database
   is to be merged.

   override

   Specifies whether source entries override target ones.

   The XrmCombineDatabase function merges the contents of one
   database into another. If the same specifier is used for an
   entry in both databases, the entry in the source_db will
   replace the entry in the target_db if override is True;
   otherwise, the entry in source_db is discarded. If target_db
   contains NULL, XrmCombineDatabase simply stores source_db in
   it. Otherwise, source_db is destroyed by the merge, but the
   database pointed to by target_db is not destroyed. The database
   entries are merged without changing values or types, regardless
   of the locales of the databases. The locale of the target
   database is not modified.

   To merge the contents of one database into another database
   with override semantics, use XrmMergeDatabases.

   void XrmMergeDatabases(XrmDatabase source_db, XrmDatabase
   *target_db);

   source_db

   Specifies the resource database that is to be merged into the
   target database.

   target_db

   Specifies the resource database into which the source database
   is to be merged.

   Calling the XrmMergeDatabases function is equivalent to calling
   the XrmCombineDatabase function with an override argument of
   True.

Looking Up Resources

   To retrieve a resource from a resource database, use
   XrmGetResource, XrmQGetResource, or XrmQGetSearchResource.

   Bool XrmGetResource(XrmDatabase database, char *str_name, char
   *str_class, char **str_type_return, XrmValue *value_return);

   database

   Specifies the database that is to be used.

   str_name

   Specifies the fully qualified name of the value being retrieved
   (as a string).

   str_class

   Specifies the fully qualified class of the value being
   retrieved (as a string).

   str_type_return

   Returns the representation type of the destination (as a
   string).

   value_return

   Returns the value in the database.

   Bool XrmQGetResource(XrmDatabase database, XrmNameList
   quark_name, XrmClassList quark_class, XrmRepresentation
   *quark_type_return, XrmValue *value_return);

   database

   Specifies the database that is to be used.

   quark_name

   Specifies the fully qualified name of the value being retrieved
   (as a quark).

   quark_class

   Specifies the fully qualified class of the value being
   retrieved (as a quark).

   quark_type_return

   Returns the representation type of the destination (as a
   quark).

   value_return

   Returns the value in the database.

   The XrmGetResource and XrmQGetResource functions retrieve a
   resource from the specified database. Both take a fully
   qualified name/class pair, a destination resource
   representation, and the address of a value (size/address pair).
   The value and returned type point into database memory;
   therefore, you must not modify the data.

   The database only frees or overwrites entries on
   XrmPutResource, XrmQPutResource, or XrmMergeDatabases. A client
   that is not storing new values into the database or is not
   merging the database should be safe using the address passed
   back at any time until it exits. If a resource was found, both
   XrmGetResource and XrmQGetResource return True; otherwise, they
   return False.

   Most applications and toolkits do not make random probes into a
   resource database to fetch resources. The X toolkit access
   pattern for a resource database is quite stylized. A series of
   from 1 to 20 probes is made with only the last name/class
   differing in each probe. The XrmGetResource function is at
   worst a 2^n algorithm, where n is the length of the name/class
   list. This can be improved upon by the application programmer
   by prefetching a list of database levels that might match the
   first part of a name/class list.

   To obtain a list of database levels, use XrmQGetSearchList.

   Bool XrmQGetSearchResource(XrmDatabase database, XrmNameList
   names, XrmClassList classes, XrmSearchList list_return, int
   list_length);

   database

   Specifies the database that is to be used.

   names

   Specifies a list of resource names.

   classes

   Specifies a list of resource classes.

   list_return

   Returns a search list for further use. The caller must allocate
   sufficient space for the list before calling XrmQGetSearchList.

   list_length

   Specifies the number of entries (not the byte size) allocated
   for list_return.

   The XrmQGetSearchList function takes a list of names and
   classes and returns a list of database levels where a match
   might occur. The returned list is in best-to-worst order and
   uses the same algorithm as XrmGetResource for determining
   precedence. If list_return was large enough for the search
   list, XrmQGetSearchList returns True; otherwise, it returns
   False.

   The size of the search list that the caller must allocate is
   dependent upon the number of levels and wildcards in the
   resource specifiers that are stored in the database. The worst
   case length is 3^n, where n is the number of name or class
   components in names or classes.

   When using XrmQGetSearchList followed by multiple probes for
   resources with a common name and class prefix, only the common
   prefix should be specified in the name and class list to
   XrmQGetSearchList.

   To search resource database levels for a given resource, use
   XrmQGetSearchResource.

   Bool XrmQGetSearchResource(XrmSearchList list, XrmName name,
   XrmClass class, XrmRepresentation *type_return, XrmValue
   *value_return);

   list

   Specifies the search list returned by XrmQGetSearchList.

   name

   Specifies the resource name.

   class

   Specifies the resource class.

   type_return

   Returns data representation type.

   value_return

   Returns the value in the database.

   The XrmQGetSearchResource function searches the specified
   database levels for the resource that is fully identified by
   the specified name and class. The search stops with the first
   match. XrmQGetSearchResource returns True if the resource was
   found; otherwise, it returns False.

   A call to XrmQGetSearchList with a name and class list
   containing all but the last component of a resource name
   followed by a call to XrmQGetSearchResource with the last
   component name and class returns the same database entry as
   XrmGetResource and XrmQGetResource with the fully qualified
   name and class.

Storing into a Resource Database

   To store resources into the database, use XrmPutResource or
   XrmQPutResource. Both functions take a partial resource
   specification, a representation type, and a value. This value
   is copied into the specified database.

   void XrmPutResource(XrmDatabase *database, char *specifier,
   char *type, XrmValue *value);

   database

   Specifies the resource database.

   specifier

   Specifies a complete or partial specification of the resource.

   type

   Specifies the type of the resource.

   value

   Specifies the value of the resource, which is specified as a
   string.

   If database contains NULL, XrmPutResource creates a new
   database and returns a pointer to it. XrmPutResource is a
   convenience function that calls XrmStringToBindingQuarkList
   followed by:

XrmQPutResource(database, bindings, quarks, XrmStringToQuark(type), valu
e)

   If the specifier and type are not in the Host Portable
   Character Encoding, the result is implementation-dependent. The
   value is stored in the database without modification.

   void XrmQPutResource(XrmDatabase *database, XrmBindingList
   bindings, XrmQuarkList quarks, XrmRepresentation type, XrmValue
   *value);

   database

   Specifies the resource database.

   bindings

   Specifies a list of bindings.

   quarks

   Specifies the complete or partial name or the class list of the
   resource.

   type

   Specifies the type of the resource.

   value

   Specifies the value of the resource, which is specified as a
   string.

   If database contains NULL, XrmQPutResource creates a new
   database and returns a pointer to it. If a resource entry with
   the identical bindings and quarks already exists in the
   database, the previous type and value are replaced by the new
   specified type and value. The value is stored in the database
   without modification.

   To add a resource that is specified as a string, use
   XrmPutStringResource.

   void XrmPutStringResource(XrmDatabase *database, char
   *specifier, char *value);

   database

   Specifies the resource database.

   specifier

   Specifies a complete or partial specification of the resource.

   value

   Specifies the value of the resource, which is specified as a
   string.

   If database contains NULL, XrmPutStringResource creates a new
   database and returns a pointer to it. XrmPutStringResource adds
   a resource with the specified value to the specified database.
   XrmPutStringResource is a convenience function that first calls
   XrmStringToBindingQuarkList on the specifier and then calls
   XrmQPutResource, using a ``String'' representation type. If the
   specifier is not in the Host Portable Character Encoding, the
   result is implementation-dependent. The value is stored in the
   database without modification.

   To add a string resource using quarks as a specification, use
   XrmQPutStringResource.

   void XrmQPutStringResource(XrmDatabase *database,
   XrmBindingList bindings, XrmQuarkList quarks, char *value);

   database

   Specifies the resource database.

   bindings

   Specifies a list of bindings.

   quarks

   Specifies the complete or partial name or the class list of the
   resource.

   value

   Specifies the value of the resource, which is specified as a
   string.

   If database contains NULL, XrmQPutStringResource creates a new
   database and returns a pointer to it. XrmQPutStringResource is
   a convenience routine that constructs an XrmValue for the value
   string (by calling strlen to compute the size) and then calls
   XrmQPutResource, using a ``String'' representation type. The
   value is stored in the database without modification.

   To add a single resource entry that is specified as a string
   that contains both a name and a value, use XrmPutLineResource.

   void XrmPutLineResource(XrmDatabase *database, char *line);

   database

   Specifies the resource database.

   line

   Specifies the resource name and value pair as a single string.

   If database contains NULL, XrmPutLineResource creates a new
   database and returns a pointer to it. XrmPutLineResource adds a
   single resource entry to the specified database. The line
   should be in valid ResourceLine format (see section 15.1)
   terminated by a newline or null character; the database that
   results from using a string with incorrect syntax is
   implementation-dependent. The string is parsed in the locale of
   the database. If the ResourceName is not in the Host Portable
   Character Encoding, the result is implementation-dependent.
   Note that comment lines are not stored.

Enumerating Database Entries

   To enumerate the entries of a database, use
   XrmEnumerateDatabase.
#define       XrmEnumAllLevels       0
#define       XrmEnumOneLevel        0

   Bool XrmEnumerateDatabase(XrmDatabase database, XrmNameList
   name_prefix, XrmClassList class_prefix, int mode, Bool
   (*proc)(), XPointer arg);

   database

   Specifies the resource database.

   name_prefix

   Specifies the resource name prefix.

   class_prefix

   Specifies the resource class prefix.

   mode

   Specifies the number of levels to enumerate.

   proc

   Specifies the procedure that is to be called for each matching
   entry.

   arg

   Specifies the user-supplied argument that will be passed to the
   procedure.

   The XrmEnumerateDatabase function calls the specified procedure
   for each resource in the database that would match some
   completion of the given name/class resource prefix. The order
   in which resources are found is implementation-dependent. If
   mode is XrmEnumOneLevel, a resource must match the given
   name/class prefix with just a single name and class appended.
   If mode is XrmEnumAllLevels, the resource must match the given
   name/class prefix with one or more names and classes appended.
   If the procedure returns True, the enumeration terminates and
   the function returns True. If the procedure always returns
   False, all matching resources are enumerated and the function
   returns False.

   The procedure is called with the following arguments:



(*proc)(database, bindings, quarks, type, value, arg)
     XrmDatabase *database;
     XrmBindingList bindings;
     XrmQuarkList quarks;
     XrmRepresentation *type;
     XrmValue *value;
     XPointer arg;

   The bindings and quarks lists are terminated by NULLQUARK. Note
   that pointers to the database and type are passed, but these
   values should not be modified.

   The procedure must not modify the database. If Xlib has been
   initialized for threads, the procedure is called with the
   database locked and the result of a call by the procedure to
   any Xlib function using the same database is not defined.

Parsing Command Line Options

   The XrmParseCommand function can be used to parse the command
   line arguments to a program and modify a resource database with
   selected entries from the command line.



typedef enum {
     XrmoptionNoArg,     /* Value is specified in XrmOptionDescRec.value
 */
     XrmoptionIsArg,     /* Value is the option string itself */
     XrmoptionStickyArg,     /* Value is characters immediately followin
g option */
     XrmoptionSepArg,     /* Value is next argument in argv */
     XrmoptionResArg,     /* Resource and value in next argument in argv
 */
     XrmoptionSkipArg,     /* Ignore this option and the next argument i
n argv */
     XrmoptionSkipLine,     /* Ignore this option and the rest of argv *
/
     XrmoptionSkipNArgs     /* Ignore this option and the next
          \ \ \ XrmOptionDescRec.value arguments in argv */
} XrmOptionKind;

   Note that XrmoptionSkipArg is equivalent to XrmoptionSkipNArgs
   with the XrmOptionDescRec.value field containing the value one.
   Note also that the value zero for XrmoptionSkipNArgs indicates
   that only the option itself is to be skipped.



typedef struct {
     char *option;     /* Option specification string in argv
   */
     char *specifier;     /* Binding and resource name (sans application
 name)    */
     XrmOptionKind argKind;     /* Which style of option it is         *
/
     XPointer value;     /* Value to provide if XrmoptionNoArg or
          \ \ \ XrmoptionSkipNArgs   */
} XrmOptionDescRec, *XrmOptionDescList;

   To load a resource database from a C command line, use
   XrmParseCommand.

   void XrmParseCommand(XrmDatabase *database, XrmOptionDescList
   table, int table_count, char *name, int *argc_in_out, char
   **argv_in_out);

   database

   Specifies the resource database.

   table

   Specifies the table of command line arguments to be parsed.

   table_count

   Specifies the number of entries in the table.

   name

   Specifies the application name.

   argc_in_out

   Specifies the number of arguments and returns the number of
   remaining arguments.

   argv_in_out

   Specifies the command line arguments and returns the remaining
   arguments.

   The XrmParseCommand function parses an (argc, argv) pair
   according to the specified option table, loads recognized
   options into the specified database with type ``String,'' and
   modifies the (argc, argv) pair to remove all recognized
   options. If database contains NULL, XrmParseCommand creates a
   new database and returns a pointer to it. Otherwise, entries
   are added to the database specified. If a database is created,
   it is created in the current locale.

   The specified table is used to parse the command line.
   Recognized options in the table are removed from argv, and
   entries are added to the specified resource database in the
   order they occur in argv. The table entries contain information
   on the option string, the option name, the style of option, and
   a value to provide if the option kind is XrmoptionNoArg. The
   option names are compared byte-for-byte to arguments in argv,
   independent of any locale. The resource values given in the
   table are stored in the resource database without modification.
   All resource database entries are created using a ``String''
   representation type. The argc argument specifies the number of
   arguments in argv and is set on return to the remaining number
   of arguments that were not parsed. The name argument should be
   the name of your application for use in building the database
   entry. The name argument is prefixed to the resourceName in the
   option table before storing a database entry. The name argument
   is treated as a single component, even if it has embedded
   periods. No separating (binding) character is inserted, so the
   table must contain either a period (.) or an asterisk (*) as
   the first character in each resourceName entry. To specify a
   more completely qualified resource name, the resourceName entry
   can contain multiple components. If the name argument and the
   resourceNames are not in the Host Portable Character Encoding,
   the result is implementation-dependent.

   The following provides a sample option table:



static XrmOptionDescRec opTable[] = {
{"-background",     "*background",                 XrmoptionSepArg,    (
XPointer) NULL},
{"-bd",             "*borderColor",                XrmoptionSepArg,    (
XPointer) NULL},
{"-bg",             "*background",                 XrmoptionSepArg,    (
XPointer) NULL},
{"-borderwidth",    "*TopLevelShell.borderWidth",  XrmoptionSepArg,    (
XPointer) NULL},
{"-bordercolor",    "*borderColor",                XrmoptionSepArg,    (
XPointer) NULL},
{"-bw",             "*TopLevelShell.borderWidth",  XrmoptionSepArg,    (
XPointer) NULL},
{"-display",        ".display",                    XrmoptionSepArg,    (
XPointer) NULL},
{"-fg",             "*foreground",                 XrmoptionSepArg,    (
XPointer) NULL},
{"-fn",             "*font",                       XrmoptionSepArg,    (
XPointer) NULL},
{"-font",           "*font",                       XrmoptionSepArg,    (
XPointer) NULL},
{"-foreground",     "*foreground",                 XrmoptionSepArg,    (
XPointer) NULL},
{"-geometry",       ".TopLevelShell.geometry",     XrmoptionSepArg,    (
XPointer) NULL},
{"-iconic",         ".TopLevelShell.iconic",       XrmoptionNoArg,     (
XPointer) "on"},
{"-name",           ".name",                       XrmoptionSepArg,    (
XPointer) NULL},
{"-reverse",        "*reverseVideo",               XrmoptionNoArg,     (
XPointer) "on"},
{"-rv",             "*reverseVideo",               XrmoptionNoArg,     (
XPointer) "on"},
{"-synchronous",    "*synchronous",                XrmoptionNoArg,     (
XPointer) "on"},
{"-title",          ".TopLevelShell.title",        XrmoptionSepArg,    (
XPointer) NULL},
{"-xrm",            NULL,                          XrmoptionResArg,    (
XPointer) NULL},
};

   In this table, if the -background (or -bg) option is used to
   set background colors, the stored resource specifier matches
   all resources of attribute background. If the -borderwidth
   option is used, the stored resource specifier applies only to
   border width attributes of class TopLevelShell (that is,
   outer-most windows, including pop-up windows). If the -title
   option is used to set a window name, only the topmost
   application windows receive the resource.

   When parsing the command line, any unique unambiguous
   abbreviation for an option name in the table is considered a
   match for the option. Note that uppercase and lowercase matter.

Chapter 16. Application Utility Functions

   Table of Contents

   Using Keyboard Utility Functions

        KeySym Classification Macros

   Using Latin-1 Keyboard Event Functions
   Allocating Permanent Storage
   Parsing the Window Geometry
   Manipulating Regions

        Creating, Copying, or Destroying Regions
        Moving or Shrinking Regions
        Computing with Regions
        Determining if Regions Are Empty or Equal
        Locating a Point or a Rectangle in a Region

   Using Cut Buffers
   Determining the Appropriate Visual Type
   Manipulating Images
   Manipulating Bitmaps
   Using the Context Manager

   Once you have initialized the X system, you can use the Xlib
   utility functions to:
     * Use keyboard utility functions
     * Use Latin-1 keyboard event functions
     * Allocate permanent storage
     * Parse the window geometry
     * Manipulate regions
     * Use cut buffers
     * Determine the appropriate visual type
     * Manipulate images
     * Manipulate bitmaps
     * Use the context manager

   As a group, the functions discussed in this chapter provide the
   functionality that is frequently needed and that spans
   toolkits. Many of these functions do not generate actual
   protocol requests to the server.

Using Keyboard Utility Functions

   This section discusses mapping between KeyCodes and KeySyms,
   classifying KeySyms, and mapping between KeySyms and string
   names. The first three functions in this section operate on a
   cached copy of the server keyboard mapping. The first four
   KeySyms for each KeyCode are modified according to the rules
   given in section 12.7. To obtain the untransformed KeySyms
   defined for a key, use the functions described in section 12.7.

   To obtain a KeySym for the KeyCode of an event, use
   XLookupKeysym.

   KeySym XLookupKeysym(XKeyEvent *key_event, int index);

   key_event

   Specifies the KeyPress or KeyRelease event.

   index

   Specifies the index into the KeySyms list for the event's
   KeyCode.

   The XLookupKeysym function uses a given keyboard event and the
   index you specified to return the KeySym from the list that
   corresponds to the KeyCode member in the XKeyPressedEvent or
   XKeyReleasedEvent structure. If no KeySym is defined for the
   KeyCode of the event, XLookupKeysym returns NoSymbol.

   To obtain a KeySym for a specific KeyCode, use
   XKeycodeToKeysym.

   KeySym XKeycodeToKeysym(Display *display, KeyCode keycode, int
   index);

   display

   Specifies the connection to the X server.

   keycode

   Specifies the KeyCode.

   index

   Specifies the element of KeyCode vector.

   The XKeycodeToKeysym function uses internal Xlib tables and
   returns the KeySym defined for the specified KeyCode and the
   element of the KeyCode vector. If no symbol is defined,
   XKeycodeToKeysym returns NoSymbol.

   To obtain a KeyCode for a key having a specific KeySym, use
   XKeysymToKeycode.

   KeyCode XKeysymToKeycode(Display *display, KeySym keysym);

   display

   Specifies the connection to the X server.

   keysym

   Specifies the KeySym that is to be searched for.

   If the specified KeySym is not defined for any KeyCode,
   XKeysymToKeycode returns zero.

   The mapping between KeyCodes and KeySyms is cached internal to
   Xlib. When this information is changed at the server, an Xlib
   function must be called to refresh the cache. To refresh the
   stored modifier and keymap information, use
   XRefreshKeyboardMapping.

   XRefreshKeyboardMapping(XMappingEvent *event_map);

   event_map

   Specifies the mapping event that is to be used.

   The XRefreshKeyboardMapping function refreshes the stored
   modifier and keymap information. You usually call this function
   when a MappingNotify event with a request member of
   MappingKeyboard or MappingModifier occurs. The result is to
   update Xlib's knowledge of the keyboard.

   To obtain the uppercase and lowercase forms of a KeySym, use
   XConvertCase.

   void XConvertCase(KeySym keysym, KeySym *lower_return, KeySym
   *upper_return);

   keysym

   Specifies the KeySym that is to be converted.

   lower_return

   Returns the lowercase form of keysym, or keysym.

   upper_return

   Returns the uppercase form of keysym, or keysym.

   The XConvertCase function returns the uppercase and lowercase
   forms of the specified Keysym, if the KeySym is subject to case
   conversion; otherwise, the specified KeySym is returned to both
   lower_return and upper_return. Support for conversion of other
   than Latin and Cyrillic KeySyms is implementation-dependent.

   KeySyms have string names as well as numeric codes. To convert
   the name of the KeySym to the KeySym code, use XStringToKeysym.

   KeySym XStringToKeysym(char *string);

   string

   Specifies the name of the KeySym that is to be converted.

   Standard KeySym names are obtained from <X11/keysymdef.h> by
   removing the XK_ prefix from each name. KeySyms that are not
   part of the Xlib standard also may be obtained with this
   function. The set of KeySyms that are available in this manner
   and the mechanisms by which Xlib obtains them is
   implementation-dependent.

   If the KeySym name is not in the Host Portable Character
   Encoding, the result is implementation-dependent. If the
   specified string does not match a valid KeySym, XStringToKeysym
   returns NoSymbol.

   To convert a KeySym code to the name of the KeySym, use
   XKeysymToString.

   char *XKeysymToString(KeySym keysym);

   keysym

   Specifies the KeySym that is to be converted.

   The returned string is in a static area and must not be
   modified. The returned string is in the Host Portable Character
   Encoding. If the specified KeySym is not defined,
   XKeysymToString returns a NULL.

KeySym Classification Macros

   You may want to test if a KeySym is, for example, on the keypad
   or on one of the function keys. You can use KeySym macros to
   perform the following tests.

   IsCursorKey(keysym)

   keysym

   Specifies the KeySym that is to be tested.

   Returns True if the specified KeySym is a cursor key.

   IsFunctionKey(keysym)

   keysym

   Specifies the KeySym that is to be tested.

   Returns True if the specified KeySym is a function key.

   IsKeypadKey(keysym)

   keysym

   Specifies the KeySym that is to be tested.

   Returns True if the specified KeySym is a standard keypad key.

   IsPrivateKeypadKey(keysym)

   keysym

   Specifies the KeySym that is to be tested.

   Returns True if the specified KeySym is a vendor-private keypad
   key.

   IsMiscFunctionKey(keysym)

   keysym

   Specifies the KeySym that is to be tested.

   Returns True if the specified KeySym is a miscellaneous
   function key.

   IsModifierKey(keysym)

   keysym

   Specifies the KeySym that is to be tested.

   Returns True if the specified KeySym is a modifier key.

   IsPFKey(keysym)

   keysym

   Specifies the KeySym that is to be tested.

   Returns True if the specified KeySym is a PF key.

Using Latin-1 Keyboard Event Functions

   Chapter 13 describes internationalized text input facilities,
   but sometimes it is expedient to write an application that only
   deals with Latin-1 characters and ASCII controls, so Xlib
   provides a simple function for that purpose. XLookupString
   handles the standard modifier semantics described in section
   12.7. This function does not use any of the input method
   facilities described in chapter 13 and does not depend on the
   current locale.

   To map a key event to an ISO Latin-1 string, use XLookupString.

   int XLookupString(XKeyEvent *event_struct, char *buffer_return,
   int bytes_buffer, KeySym *keysym_return, XComposeStatus
   *status_in_out);

   event_struct

   Specifies the key event structure to be used. You can pass
   XKeyPressedEvent or XKeyReleasedEvent.

   buffer_return

   Returns the translated characters.

   bytes_buffer

   Specifies the length of the buffer. No more than bytes_buffer
   of translation are returned.

   keysym_return

   Returns the KeySym computed from the event if this argument is
   not NULL.

   status_in_out

   Specifies or returns the XComposeStatus structure or NULL.

   The XLookupString function translates a key event to a KeySym
   and a string. The KeySym is obtained by using the standard
   interpretation of the Shift, Lock, group, and numlock modifiers
   as defined in the X Protocol specification. If the KeySym has
   been rebound (see XRebindKeysym), the bound string will be
   stored in the buffer. Otherwise, the KeySym is mapped, if
   possible, to an ISO Latin-1 character or (if the Control
   modifier is on) to an ASCII control character, and that
   character is stored in the buffer. XLookupString returns the
   number of characters that are stored in the buffer.

   If present (non-NULL), the XComposeStatus structure records the
   state, which is private to Xlib, that needs preservation across
   calls to XLookupString to implement compose processing. The
   creation of XComposeStatus structures is
   implementation-dependent; a portable program must pass NULL for
   this argument.

   XLookupString depends on the cached keyboard information
   mentioned in the previous section, so it is necessary to use
   XRefreshKeyboardMapping to keep this information up-to-date.

   To rebind the meaning of a KeySym for XLookupString, use
   XRebindKeysym.

   XRebindKeysym(Display *display, KeySym keysym, KeySym list[ ],
   int mod_count, unsignedchar *string, int num_bytes);

   display

   Specifies the connection to the X server.

   keysym

   Specifies the KeySym that is to be rebound.

   list

   Specifies the KeySyms to be used as modifiers.

   mod_count

   Specifies the number of modifiers in the modifier list.

   string

   Specifies the string that is copied and will be returned by
   XLookupString.

   num_bytes

   Specifies the number of bytes in the string argument.

   The XRebindKeysym function can be used to rebind the meaning of
   a KeySym for the client. It does not redefine any key in the X
   server but merely provides an easy way for long strings to be
   attached to keys. XLookupString returns this string when the
   appropriate set of modifier keys are pressed and when the
   KeySym would have been used for the translation. No text
   conversions are performed; the client is responsible for
   supplying appropriately encoded strings. Note that you can
   rebind a KeySym that may not exist.

Allocating Permanent Storage

   To allocate some memory you will never give back, use
   Xpermalloc.

   char *Xpermalloc(unsigned int size);

   The Xpermalloc function allocates storage that can never be
   freed for the life of the program. The memory is allocated with
   alignment for the C type double. This function may provide some
   performance and space savings over the standard operating
   system memory allocator.

Parsing the Window Geometry

   To parse standard window geometry strings, use XParseGeometry.

   int XParseGeometry(char *parsestring, int *x_return, int
   *y_return, unsigned int *width_return, unsigned int
   *height_return);

   parsestring

   Specifies the string you want to parse.

   x_return

   y_return

   Return the x and y offsets.

   width_return

   height_return

   Return the width and height determined.

   By convention, X applications use a standard string to indicate
   window size and placement. XParseGeometry makes it easier to
   conform to this standard because it allows you to parse the
   standard window geometry. Specifically, this function lets you
   parse strings of the form:

[=][<width>{xX}<height>][{+-}<xoffset>{+-}<yoffset>]

   The fields map into the arguments associated with this
   function. (Items enclosed in < > are integers, items in [ ] are
   optional, and items enclosed in { } indicate ``choose one of.''
   Note that the brackets should not appear in the actual string.)
   If the string is not in the Host Portable Character Encoding,
   the result is implementation-dependent.

   The XParseGeometry function returns a bitmask that indicates
   which of the four values (width, height, xoffset, and yoffset)
   were actually found in the string and whether the x and y
   values are negative. By convention, -0 is not equal to +0,
   because the user needs to be able to say ``position the window
   relative to the right or bottom edge.'' For each value found,
   the corresponding argument is updated. For each value not
   found, the argument is left unchanged. The bits are represented
   by XValue, YValue, WidthValue, HeightValue, XNegative, or
   YNegative and are defined in <X11/Xutil.h>. They will be set
   whenever one of the values is defined or one of the signs is
   set.

   If the function returns either the XValue or YValue flag, you
   should place the window at the requested position.

   To construct a window's geometry information, use XWMGeometry.

   int XWMGeometry(Display *display, int screen, char *user_geom,
   char *def_geom, unsigned int bwidth, XSizeHints *hints, int
   *x_return, int *y_return, int *width_return, int
   *height_return, int *gravity_return);

   display

   Specifies the connection to the X server.

   screen

   Specifies the screen.

   user_geom

   Specifies the user-specified geometry or NULL.

   def_geom

   Specifies the application's default geometry or NULL.

   bwidth

   Specifies the border width.

   hints

   Specifies the size hints for the window in its normal state.

   x_return

   y_return

   Return the x and y offsets.

   width_return

   height_return

   Return the width and height determined.

   gravity_return

   Returns the window gravity.

   The XWMGeometry function combines any geometry information
   (given in the format used by XParseGeometry) specified by the
   user and by the calling program with size hints (usually the
   ones to be stored in WM_NORMAL_HINTS) and returns the position,
   size, and gravity (NorthWestGravity, NorthEastGravity,
   SouthEastGravity, or SouthWestGravity) that describe the
   window. If the base size is not set in the XSizeHints
   structure, the minimum size is used if set. Otherwise, a base
   size of zero is assumed. If no minimum size is set in the hints
   structure, the base size is used. A mask (in the form returned
   by XParseGeometry) that describes which values came from the
   user specification and whether or not the position coordinates
   are relative to the right and bottom edges is returned. Note
   that these coordinates will have already been accounted for in
   the x_return and y_return values.

   Note that invalid geometry specifications can cause a width or
   height of zero to be returned. The caller may pass the address
   of the hints win_gravity field as gravity_return to update the
   hints directly.

Manipulating Regions

   Regions are arbitrary sets of pixel locations. Xlib provides
   functions for manipulating regions. The opaque type Region is
   defined in <X11/Xutil.h>. Xlib provides functions that you can
   use to manipulate regions. This section discusses how to:
     * Create, copy, or destroy regions
     * Move or shrink regions
     * Compute with regions
     * Determine if regions are empty or equal
     * Locate a point or rectangle in a region

Creating, Copying, or Destroying Regions

   To create a new empty region, use XCreateRegion.

   Region XCreateRegion(void);

   To generate a region from a polygon, use XPolygonRegion.

   Region XPolygonRegion(XPoint points[], int n, int fill_rule);

   points

   Specifies an array of points.

   n

   Specifies the number of points in the polygon.

   fill_rule

   Specifies the fill-rule you want to set for the specified GC.
   You can pass EvenOddRule or WindingRule.

   The XPolygonRegion function returns a region for the polygon
   defined by the points array. For an explanation of fill_rule,
   see XCreateGC.

   To set the clip-mask of a GC to a region, use XSetRegion.

   XSetRegion(Display *display, GC gc, Region r);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   r

   Specifies the region.

   The XSetRegion function sets the clip-mask in the GC to the
   specified region. The region is specified relative to the
   drawable's origin. The resulting GC clip origin is
   implementation-dependent. Once it is set in the GC, the region
   can be destroyed.

   To deallocate the storage associated with a specified region,
   use XDestroyRegion.

   XDestroyRegion(Region r);

   r

   Specifies the region.

Moving or Shrinking Regions

   To move a region by a specified amount, use XOffsetRegion.

   XOffsetRegion(Region r, int dx, int dy);

   r

   Specifies the region.

   dx

   dy

   Specify the x and y coordinates, which define the amount you
   want to move the specified region.

   To reduce a region by a specified amount, use XShrinkRegion.

   XShrinkRegion(Region r, int dx, int dy);

   r

   Specifies the region.

   dx

   dy

   Specify the x and y coordinates, which define the amount you
   want to shrink the specified region.

   Positive values shrink the size of the region, and negative
   values expand the region.

Computing with Regions

   To generate the smallest rectangle enclosing a region, use
   XClipBox.

   XClipBox(Region r, XRectangle *rect_return);

   r

   Specifies the region.

   rect_return

   Returns the smallest enclosing rectangle.

   The XClipBox function returns the smallest rectangle enclosing
   the specified region.

   To compute the intersection of two regions, use
   XIntersectRegion.

   XIntersectRegion(Region sra, Region srb, Region dr_return);

   sra

   srb

   Specify the two regions with which you want to perform the
   computation.

   dr_return

   Returns the result of the computation.

   To compute the union of two regions, use XUnionRegion.

   XUnionRegion(Region sra, Region srb, Region dr_return);

   sra

   srb

   Specify the two regions with which you want to perform the
   computation.

   dr_return

   Returns the result of the computation.

   To create a union of a source region and a rectangle, use
   XUnionRectWithRegion.

   XUnionRectWithRegion(XRectangle *rectangle, Region src_region,
   Region dest_region_return);

   rectangle

   Specifies the rectangle.

   src_region

   Specifies the source region to be used.

   dest_region_return

   Returns the destination region.

   The XUnionRectWithRegion function updates the destination
   region from a union of the specified rectangle and the
   specified source region.

   To subtract two regions, use XSubtractRegion.

   XSubtractRegion(Region sra, Region srb, Region dr_return);

   sra

   srb

   Specify the two regions with which you want to perform the
   computation.

   dr_return

   Returns the result of the computation.

   The XSubtractRegion function subtracts srb from sra and stores
   the results in dr_return.

   To calculate the difference between the union and intersection
   of two regions, use XXorRegion.

   XXorRegion(Region sra, Region srb, Region dr_return);

   sra

   srb

   Specify the two regions with which you want to perform the
   computation.

   dr_return

   Returns the result of the computation.

Determining if Regions Are Empty or Equal

   To determine if the specified region is empty, use
   XEmptyRegion.

   Bool XEmptyRegion(Region r);

   r

   Specifies the region.

   The XEmptyRegion function returns True if the region is empty.

   To determine if two regions have the same offset, size, and
   shape, use XEqualRegion.

   Bool XEqualRegion(Region r1, Region r2);

   r1

   r2

   Specify the two regions.

   The XEqualRegion function returns True if the two regions have
   the same offset, size, and shape.

Locating a Point or a Rectangle in a Region

   To determine if a specified point resides in a specified
   region, use XPointInRegion.

   Bool XPointInRegion(Region r, int x, int y);

   r

   Specifies the region.

   x

   y

   Specify the x and y coordinates, which define the point.

   The XPointInRegion function returns True if the point (x, y) is
   contained in the region r.

   To determine if a specified rectangle is inside a region, use
   XRectInRegion.

   int XRectInRegion(Region r, int x, int y, unsigned int width,
   unsigned int height);

   r

   Specifies the region.

   x

   y

   Specify the x and y coordinates, which define the coordinates
   of the upper-left corner of the rectangle.

   width

   height

   Specify the width and height, which define the rectangle.

   The XRectInRegion function returns RectangleIn if the rectangle
   is entirely in the specified region, RectangleOut if the
   rectangle is entirely out of the specified region, and
   RectanglePart if the rectangle is partially in the specified
   region.

Using Cut Buffers

   Xlib provides functions to manipulate cut buffers, a very
   simple form of cut-and-paste inter-client communication.
   Selections are a much more powerful and useful mechanism for
   interchanging data between client (see section 4.5) and
   generally should be used instead of cut buffers.

   Cut buffers are implemented as properties on the first root
   window of the display. The buffers can only contain text, in
   the STRING encoding. The text encoding is not changed by Xlib
   when fetching or storing. Eight buffers are provided and can be
   accessed as a ring or as explicit buffers (numbered 0 through
   7).

   To store data in cut buffer 0, use XStoreBytes.

   XStoreBytes(Display *display, char *bytes, int nbytes);

   display

   Specifies the connection to the X server.

   bytes

   Specifies the bytes, which are not necessarily ASCII or
   null-terminated.

   nbytes

   Specifies the number of bytes to be stored.

   The data can have embedded null characters and need not be
   null-terminated. The cut buffer's contents can be retrieved
   later by any client calling XFetchBytes.

   XStoreBytes can generate a BadAlloc error.

   To store data in a specified cut buffer, use XStoreBuffer.

   XStoreBuffer(Display *display, char *bytes, int nbytes, int
   buffer);

   display

   Specifies the connection to the X server.

   bytes

   Specifies the bytes, which are not necessarily ASCII or
   null-terminated.

   nbytes

   Specifies the number of bytes to be stored.

   buffer

   Specifies the buffer in which you want to store the bytes.

   If an invalid buffer is specified, the call has no effect. The
   data can have embedded null characters and need not be
   null-terminated.

   XStoreBuffer can generate a BadAlloc error.

   To return data from cut buffer 0, use XFetchBytes.

   char *XFetchBytes(Display *display, int *nbytes_return);

   display

   Specifies the connection to the X server.

   nbytes_return

   Returns the number of bytes in the buffer.

   The XFetchBytes function returns the number of bytes in the
   nbytes_return argument, if the buffer contains data. Otherwise,
   the function returns NULL and sets nbytes to 0. The appropriate
   amount of storage is allocated and the pointer returned. The
   client must free this storage when finished with it by calling
   XFree.

   To return data from a specified cut buffer, use XFetchBuffer.

   char *XFetchBuffer(Display *display, int *nbytes_return, int
   buffer);

   display

   Specifies the connection to the X server.

   nbytes_return

   Returns the number of bytes in the buffer.

   buffer

   Specifies the buffer from which you want the stored data
   returned.

   The XFetchBuffer function returns zero to the nbytes_return
   argument if there is no data in the buffer or if an invalid
   buffer is specified.

   To rotate the cut buffers, use XRotateBuffers.

   XRotateBuffers(Display *display, int rotate);

   display

   Specifies the connection to the X server.

   rotate

   Specifies how much to rotate the cut buffers.

   The XRotateBuffers function rotates the cut buffers, such that
   buffer 0 becomes buffer n, buffer 1 becomes n + 1 mod 8, and so
   on. This cut buffer numbering is global to the display. Note
   that XRotateBuffers generates BadMatch errors if any of the
   eight buffers have not been created.

Determining the Appropriate Visual Type

   A single display can support multiple screens. Each screen can
   have several different visual types supported at different
   depths. You can use the functions described in this section to
   determine which visual to use for your application.

   The functions in this section use the visual information masks
   and the XVisualInfo structure, which is defined in
   <X11/Xutil.h> and contains:

/* Visual information mask bits */


#define   VisualNoMask                 0x0
#define   VisualIDMask                 0x1
#define   VisualScreenMask             0x2
#define   VisualDepthMask              0x4
#define   VisualClassMask              0x8
#define   VisualRedMaskMask            0x10
#define   VisualGreenMaskMask          0x20
#define   VisualBlueMaskMask           0x40
#define   VisualColormapSizeMask       0x80
#define   VisualBitsPerRGBMask         0x100
#define   VisualAllMask                0x1FF




/* Values */

typedef struct {
     Visual *visual;
     VisualID visualid;
     int screen;
     unsigned int depth;
     int class;
     unsigned long red_mask;
     unsigned long green_mask;
     unsigned long blue_mask;
     int colormap_size;
     int bits_per_rgb;
} XVisualInfo;

   To obtain a list of visual information structures that match a
   specified template, use XGetVisualInfo.

   XVisualInfo *XGetVisualInfo(Display *display, long vinfo_mask,
   XVisualInfo *vinfo_template, int *nitems_return);

   display

   Specifies the connection to the X server.

   vinfo_mask

   Specifies the visual mask value.

   vinfo_template

   Specifies the visual attributes that are to be used in matching
   the visual structures.

   nitems_return

   Returns the number of matching visual structures.

   The XGetVisualInfo function returns a list of visual structures
   that have attributes equal to the attributes specified by
   vinfo_template. If no visual structures match the template
   using the specified vinfo_mask, XGetVisualInfo returns a NULL.
   To free the data returned by this function, use XFree.

   To obtain the visual information that matches the specified
   depth and class of the screen, use XMatchVisualInfo.

   Status XMatchVisualInfo(Display *display, int screen, int
   depth, int class, XVisualInfo *vinfo_return);

   display

   Specifies the connection to the X server.

   screen

   Specifies the screen.

   depth

   Specifies the depth of the screen.

   class

   Specifies the class of the screen.

   vinfo_return

   Returns the matched visual information.

   The XMatchVisualInfo function returns the visual information
   for a visual that matches the specified depth and class for a
   screen. Because multiple visuals that match the specified depth
   and class can exist, the exact visual chosen is undefined. If a
   visual is found, XMatchVisualInfo returns nonzero and the
   information on the visual to vinfo_return. Otherwise, when a
   visual is not found, XMatchVisualInfo returns zero.

Manipulating Images

   Xlib provides several functions that perform basic operations
   on images. All operations on images are defined using an XImage
   structure, as defined in <X11/Xlib.h>. Because the number of
   different types of image formats can be very large, this hides
   details of image storage properly from applications.

   This section describes the functions for generic operations on
   images. Manufacturers can provide very fast implementations of
   these for the formats frequently encountered on their hardware.
   These functions are neither sufficient nor desirable to use for
   general image processing. Rather, they are here to provide
   minimal functions on screen format images. The basic operations
   for getting and putting images are XGetImage and XPutImage.

   Note that no functions have been defined, as yet, to read and
   write images to and from disk files.

   The XImage structure describes an image as it exists in the
   client's memory. The user can request that some of the members
   such as height, width, and xoffset be changed when the image is
   sent to the server. Note that bytes_per_line in concert with
   offset can be used to extract a subset of the image. Other
   members (for example, byte order, bitmap_unit, and so forth)
   are characteristics of both the image and the server. If these
   members differ between the image and the server, XPutImage
   makes the appropriate conversions. The first byte of the first
   line of plane n must be located at the address (data + (n *
   height * bytes_per_line)). For a description of the XImage
   structure, see section 8.7.

   To allocate an XImage structure and initialize it with image
   format values from a display, use XCreateImage.

   XImage *XCreateImage(Display *display, Visual *visual, unsigned
   int depth, int format, int offset, char *data, unsigned int
   width, unsigned int height, int bitmap_pad, int
   bytes_per_line);

   display

   Specifies the connection to the X server.

   visual

   Specifies the Visual structure.

   depth

   Specifies the depth of the image.

   format

   Specifies the format for the image. You can pass XYBitmap,
   XYPixmap, or ZPixmap.

   offset

   Specifies the number of pixels to ignore at the beginning of
   the scanline.

   data

   Specifies the image data.

   width

   Specifies the width of the image, in pixels.

   height

   Specifies the height of the image, in pixels.

   bitmap_pad

   Specifies the quantum of a scanline (8, 16, or 32). In other
   words, the start of one scanline is separated in client memory
   from the start of the next scanline by an integer multiple of
   this many bits.

   bytes_per_line

   Specifies the number of bytes in the client image between the
   start of one scanline and the start of the next.

   The XCreateImage function allocates the memory needed for an
   XImage structure for the specified display but does not
   allocate space for the image itself. Rather, it initializes the
   structure byte-order, bit-order, and bitmap-unit values from
   the display and returns a pointer to the XImage structure. The
   red, green, and blue mask values are defined for Z format
   images only and are derived from the Visual structure passed
   in. Other values also are passed in. The offset permits the
   rapid displaying of the image without requiring each scanline
   to be shifted into position. If you pass a zero value in
   bytes_per_line, Xlib assumes that the scanlines are contiguous
   in memory and calculates the value of bytes_per_line itself.

   Note that when the image is created using XCreateImage,
   XGetImage, or XSubImage, the destroy procedure that the
   XDestroyImage function calls frees both the image structure and
   the data pointed to by the image structure.

   The basic functions used to get a pixel, set a pixel, create a
   subimage, and add a constant value to an image are defined in
   the image object. The functions in this section are really
   macro invocations of the functions in the image object and are
   defined in <X11/Xutil.h>.

   To obtain a pixel value in an image, use XGetPixel.

   unsigned long XGetPixel(XImage *ximage, int x, int y);

   ximage

   Specifies the image.

   x

   y

   Specify the x and y coordinates.

   The XGetPixel function returns the specified pixel from the
   named image. The pixel value is returned in normalized format
   (that is, the least significant byte of the long is the least
   significant byte of the pixel). The image must contain the x
   and y coordinates.

   To set a pixel value in an image, use XPutPixel.

   XPutPixel(XImage *ximage, int x, int y, unsigned long pixel);

   ximage

   Specifies the image.

   x

   y

   Specify the x and y coordinates.

   pixel

   Specifies the new pixel value.

   The XPutPixel function overwrites the pixel in the named image
   with the specified pixel value. The input pixel value must be
   in normalized format (that is, the least significant byte of
   the long is the least significant byte of the pixel). The image
   must contain the x and y coordinates.

   To create a subimage, use XSubImage.

   XImage *XSubImage(XImage *ximage, int x, int y, unsigned int
   subimage_width, unsigned int subimage_height);

   ximage

   Specifies the image.

   x

   y

   Specify the x and y coordinates.

   subimage_width

   Specifies the width of the new subimage, in pixels.

   subimage_height

   Specifies the height of the new subimage, in pixels.

   The XSubImage function creates a new image that is a subsection
   of an existing one. It allocates the memory necessary for the
   new XImage structure and returns a pointer to the new image.
   The data is copied from the source image, and the image must
   contain the rectangle defined by x, y, subimage_width, and
   subimage_height.

   To increment each pixel in an image by a constant value, use
   XAddPixel.

   XAddPixel(XImage *ximage, long value);

   ximage

   Specifies the image.

   value

   Specifies the constant value that is to be added.

   The XAddPixel function adds a constant value to every pixel in
   an image. It is useful when you have a base pixel value from
   allocating color resources and need to manipulate the image to
   that form.

   To deallocate the memory allocated in a previous call to
   XCreateImage, use XDestroyImage.

   XDestroyImage(XImage *ximage);

   ximage

   Specifies the image.

   The XDestroyImage function deallocates the memory associated
   with the XImage structure.

   Note that when the image is created using XCreateImage,
   XGetImage, or XSubImage, the destroy procedure that this macro
   calls frees both the image structure and the data pointed to by
   the image structure.

Manipulating Bitmaps

   Xlib provides functions that you can use to read a bitmap from
   a file, save a bitmap to a file, or create a bitmap. This
   section describes those functions that transfer bitmaps to and
   from the client's file system, thus allowing their reuse in a
   later connection (for example, from an entirely different
   client or to a different display or server).

   The X version 11 bitmap file format is:

#define name_width width
#define name_height height
#define name_x_hot x
#define name_y_hot y
static unsigned char name_bits[] = { 0xNN,... }

   The lines for the variables ending with _x_hot and _y_hot
   suffixes are optional because they are present only if a
   hotspot has been defined for this bitmap. The lines for the
   other variables are required. The word ``unsigned'' is
   optional; that is, the type of the _bits array can be ``char''
   or ``unsigned char''. The _bits array must be large enough to
   contain the size bitmap. The bitmap unit is 8.

   To read a bitmap from a file and store it in a pixmap, use
   XReadBitmapFile.

   int XReadBitmapFile(Display *display, Drawable d, char
   *filename, unsigned int *width_return, unsigned int
   *height_return, Pixmap *bitmap_return, int *x_hot_return, int
   *y_hot_return);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable that indicates the screen.

   filename

   Specifies the file name to use. The format of the file name is
   operating-system dependent.

   width_return

   height_return

   Return the width and height values of the read in bitmap file.

   bitmap_return

   Returns the bitmap that is created.

   x_hot_return

   y_hot_return

   Return the hotspot coordinates.

   The XReadBitmapFile function reads in a file containing a
   bitmap. The file is parsed in the encoding of the current
   locale. The ability to read other than the standard format is
   implementation-dependent. If the file cannot be opened,
   XReadBitmapFile returns BitmapOpenFailed. If the file can be
   opened but does not contain valid bitmap data, it returns
   BitmapFileInvalid. If insufficient working storage is
   allocated, it returns BitmapNoMemory. If the file is readable
   and valid, it returns BitmapSuccess.

   XReadBitmapFile returns the bitmap's height and width, as read
   from the file, to width_return and height_return. It then
   creates a pixmap of the appropriate size, reads the bitmap data
   from the file into the pixmap, and assigns the pixmap to the
   caller's variable bitmap. The caller must free the bitmap using
   XFreePixmap when finished. If name_x_hot and name_y_hot exist,
   XReadBitmapFile returns them to x_hot_return and y_hot_return;
   otherwise, it returns -1,-1.

   XReadBitmapFile can generate BadAlloc, BadDrawable, and BadGC
   errors.

   To read a bitmap from a file and return it as data, use
   XReadBitmapFileData.

   int XReadBitmapFileData(char *filename, unsigned int
   *width_return, unsigned int *height_return, unsignedchar
   *data_return, int *x_hot_return, int *y_hot_return);

   filename

   Specifies the file name to use. The format of the file name is
   operating-system dependent.

   width_return

   height_return

   Return the width and height values of the read in bitmap file.

   data_return

   Returns the bitmap data.

   x_hot_return

   y_hot_return

   Return the hotspot coordinates.

   The XReadBitmapFileData function reads in a file containing a
   bitmap, in the same manner as XReadBitmapFile, but returns the
   data directly rather than creating a pixmap in the server. The
   bitmap data is returned in data_return; the client must free
   this storage when finished with it by calling XFree. The status
   and other return values are the same as for XReadBitmapFile.

   To write out a bitmap from a pixmap to a file, use
   XWriteBitmapFile.

   int XWriteBitmapFile(Display *display, char *filename, Pixmap
   bitmap, unsigned int width, unsigned int height, int x_hot, int
   y_hot);

   display

   Specifies the connection to the X server.

   filename

   Specifies the file name to use. The format of the file name is
   operating-system dependent.

   bitmap

   Specifies the bitmap.

   width

   height

   Specify the width and height.

   x_hot

   y_hot

   Specify where to place the hotspot coordinates (or -1,-1 if
   none are present) in the file.

   The XWriteBitmapFile function writes a bitmap out to a file in
   the X Version 11 format. The name used in the output file is
   derived from the file name by deleting the directory prefix.
   The file is written in the encoding of the current locale. If
   the file cannot be opened for writing, it returns
   BitmapOpenFailed. If insufficient memory is allocated,
   XWriteBitmapFile returns BitmapNoMemory; otherwise, on no
   error, it returns BitmapSuccess. If x_hot and y_hot are not -1,
   -1, XWriteBitmapFile writes them out as the hotspot coordinates
   for the bitmap.

   XWriteBitmapFile can generate BadDrawable and BadMatch errors.

   To create a pixmap and then store bitmap-format data into it,
   use XCreatePixmapFromBitmapData.

   Pixmap XCreatePixmapFromBitmapData(Display *display, Drawable
   d, char *data, unsigned int width, unsigned int height,
   unsigned long fg, unsigned long bg, unsigned int depth);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable that indicates the screen.

   data

   Specifies the data in bitmap format.

   width

   height

   Specify the width and height.

   fg

   bg

   Specify the foreground and background pixel values to use.

   depth

   Specifies the depth of the pixmap.

   The XCreatePixmapFromBitmapData function creates a pixmap of
   the given depth and then does a bitmap-format XPutImage of the
   data into it. The depth must be supported by the screen of the
   specified drawable, or a BadMatch error results.

   XCreatePixmapFromBitmapData can generate BadAlloc, BadDrawable,
   BadGC, and BadValue errors.

   To include a bitmap written out by XWriteBitmapFile in a
   program directly, as opposed to reading it in every time at run
   time, use XCreateBitmapFromData.

   Pixmap XCreateBitmapFromData(Display *display, Drawable d, char
   *data, unsigned int width, unsigned int height);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable that indicates the screen.

   data

   Specifies the location of the bitmap data.

   width

   height

   Specify the width and height.

   The XCreateBitmapFromData function allows you to include in
   your C program (using #include) a bitmap file that was written
   out by XWriteBitmapFile (X version 11 format only) without
   reading in the bitmap file. The following example creates a
   gray bitmap:

#include "gray.bitmap"

Pixmap bitmap;
bitmap = XCreateBitmapFromData(display, window, gray_bits, gray_width, g
ray_height);

   If insufficient working storage was allocated,
   XCreateBitmapFromData returns None. It is your responsibility
   to free the bitmap using XFreePixmap when finished.

   XCreateBitmapFromData can generate BadAlloc and BadGC errors.

Using the Context Manager

   The context manager provides a way of associating data with an
   X resource ID (mostly typically a window) in your program. Note
   that this is local to your program; the data is not stored in
   the server on a property list. Any amount of data in any number
   of pieces can be associated with a resource ID, and each piece
   of data has a type associated with it. The context manager
   requires knowledge of the resource ID and type to store or
   retrieve data.

   Essentially, the context manager can be viewed as a
   two-dimensional, sparse array: one dimension is subscripted by
   the X resource ID and the other by a context type field. Each
   entry in the array contains a pointer to the data. Xlib
   provides context management functions with which you can save
   data values, get data values, delete entries, and create a
   unique context type. The symbols used are in <X11/Xutil.h>.

   To save a data value that corresponds to a resource ID and
   context type, use XSaveContext.

   int XSaveContext(Display *display, XID rid, XContext context,
   XPointer data);

   display

   Specifies the connection to the X server.

   rid

   Specifies the resource ID with which the data is associated.

   context

   Specifies the context type to which the data belongs.

   data

   Specifies the data to be associated with the window and type.

   If an entry with the specified resource ID and type already
   exists, XSaveContext overrides it with the specified context.
   The XSaveContext function returns a nonzero error code if an
   error has occurred and zero otherwise. Possible errors are
   XCNOMEM (out of memory).

   To get the data associated with a resource ID and type, use
   XFindContext.

   int XFindContext(Display *display, XID rid, XContext context,
   XPointer *data_return);

   display

   Specifies the connection to the X server.

   rid

   Specifies the resource ID with which the data is associated.

   context

   Specifies the context type to which the data belongs.

   data_return

   Returns the data.

   Because it is a return value, the data is a pointer. The
   XFindContext function returns a nonzero error code if an error
   has occurred and zero otherwise. Possible errors are XCNOENT
   (context-not-found).

   To delete an entry for a given resource ID and type, use
   XDeleteContext.

   int XDeleteContext(Display *display, XID rid, XContext
   context);

   display

   Specifies the connection to the X server.

   rid

   Specifies the resource ID with which the data is associated.

   context

   Specifies the context type to which the data belongs.

   The XDeleteContext function deletes the entry for the given
   resource ID and type from the data structure. This function
   returns the same error codes that XFindContext returns if
   called with the same arguments. XDeleteContext does not free
   the data whose address was saved.

   To create a unique context type that may be used in subsequent
   calls to XSaveContext and XFindContext, use XUniqueContext.

   XContext XUniqueContext(void);

Appendix A. Xlib Functions and Protocol Requests

   This appendix provides two tables that relate to Xlib functions
   and the X protocol. The following table lists each Xlib
   function (in alphabetical order) and the corresponding protocol
   request that it generates.

   Table A.1. Protocol requests made by each Xlib function
   Xlib Function              Protocol Request
   XActivateScreenSaver       ForceScreenSaver
   XAddHost                   ChangeHosts
   XAddHosts                  ChangeHosts
   XAddToSaveSet              ChangeSaveSet
   XAllocColor                AllocColor
   XAllocColorCells           AllocColorCells
   XAllocColorPlanes          AllocColorPlanes
   XAllocNamedColor           AllocNamedColor
   XAllowEvents               AllowEvents
   XAutoRepeatOff             ChangeKeyboardControl
   XAutoRepeatOn              ChangeKeyboardControl
   XBell                      Bell
   XChangeActivePointerGrab   ChangeActivePointerGrab
   XChangeGC                  ChangeGC
   XChangeKeyboardControl     ChangeKeyboardControl
   XChangeKeyboardMapping     ChangeKeyboardMapping
   XChangePointerControl      ChangePointerControl
   XChangeProperty            ChangeProperty
   XChangeSaveSet             ChangeSaveSet
   XChangeWindowAttributes    ChangeWindowAttributes
   XCirculateSubwindows       CirculateWindow
   XCirculateSubwindowsDown   CirculateWindow
   XCirculateSubwindowsUp     CirculateWindow
   XClearArea                 ClearArea
   XClearWindow               ClearArea
   XConfigureWindow           ConfigureWindow
   XConvertSelection          ConvertSelection
   XCopyArea                  CopyArea
   XCopyColormapAndFree       CopyColormapAndFree
   XCopyGC                    CopyGC
   XCopyPlane                 CopyPlane
   XCreateBitmapFromData      CreateGC
                              CreatePixmap
                              FreeGC
                              PutImage
   XCreateColormap            CreateColormap
   XCreateFontCursor          CreateGlyphCursor
   XCreateGC                  CreateGC
   XCreateGlyphCursor         CreateGlyphCursor
   XCreatePixmap              CreatePixmap
   XCreatePixmapCursor        CreateCursor
   XCreatePixmapFromData      CreateGC
                              CreatePixmap
                              FreeGC
                              PutImage
   XCreateSimpleWindow        CreateWindow
   XCreateWindow              CreateWindow
   XDefineCursor              ChangeWindowAttributes
   XDeleteProperty            DeleteProperty
   XDestroySubwindows         DestroySubwindows
   XDestroyWindow             DestroyWindow
   XDisableAccessControl      SetAccessControl
   XDrawArc                   PolyArc
   XDrawArcs                  PolyArc
   XDrawImageString           ImageText8
   XDrawImageString16         ImageText16
   XDrawLine                  PolySegment
   XDrawLines                 PolyLine
   XDrawPoint                 PolyPoint
   XDrawPoints                PolyPoint
   XDrawRectangle             PolyRectangle
   XDrawRectangles            PolyRectangle
   XDrawSegments              PolySegment
   XDrawString                PolyText8
   XDrawString16              PolyText16
   XDrawText                  PolyText8
   XDrawText16                PolyText16
   XEnableAccessControl       SetAccessControl
   XFetchBytes                GetProperty
   XFetchName                 GetProperty
   XFillArc                   PolyFillArc
   XFillArcs                  PolyFillArc
   XFillPolygon               FillPoly
   XFillRectangle             PolyFillRectangle
   XFillRectangles            PolyFillRectangle
   XForceScreenSaver          ForceScreenSaver
   XFreeColormap              FreeColormap
   XFreeColors                FreeColors
   XFreeCursor                FreeCursor
   XFreeFont                  CloseFont
   XFreeGC                    FreeGC
   XFreePixmap                FreePixmap
   XGetAtomName               GetAtomName
   XGetClassHint              GetProperty
   XGetFontPath               GetFontPath
   XGetGeometry               GetGeometry
   XGetIconName               GetProperty
   XGetIconSizes              GetProperty
   XGetImage                  GetImage
   XGetInputFocus             GetInputFocus
   XGetKeyboardControl        GetKeyboardControl
   XGetKeyboardMapping        GetKeyboardMapping
   XGetModifierMapping        GetModifierMapping
                              GetMotionEvents
   XGetNormalHints            GetProperty
   XGetPointerControl         GetPointerControl
   XGetPointerMapping         GetPointerMapping
   XGetRGBColormaps           GetProperty
   XGetScreenSaver            GetScreenSaver
   XGetSelectionOwner         GetSelectionOwner
   XGetSizeHints              GetProperty
   XGetTextProperty           GetProperty
   XGetTransientForHint       GetProperty
   XGetWMClientMachine        GetProperty
   XGetWMColormapWindows      GetProperty
                              InternAtom
   XGetWMHints                GetProperty
   XGetWMIconName             GetProperty
   XGetWMName                 GetProperty
   XGetWMNormalHints          GetProperty
   XGetWMProtocols            GetProperty
                              InternAtom
   XGetWMSizeHints            GetProperty
   XGetWindowAttributes       GetWindowAttributes
                              GetGeometry
   XGetWindowProperty         GetProperty
   XGetZoomHints              GetProperty
   XGrabButton                GrabButton
   XGrabKey                   GrabKey
   XGrabKeyboard              GrabKeyboard
   XGrabPointer               GrabPointer
   XGrabServer                GrabServer
   XIconifyWindow             InternAtom
                              SendEvent
   XInitExtension             QueryExtension
   XInstallColormap           InstallColormap
   XInternAtom                InternAtom
   XKillClient                KillClient
   XListExtensions            ListExtensions
   XListFonts                 ListFonts
   XListFontsWithInfo         ListFontsWithInfo
   XListHosts                 ListHosts
   XListInstalledColormaps    ListInstalledColormaps
   XListProperties            ListProperties
   XLoadFont                  OpenFont
   XLoadQueryFont             OpenFont
                              QueryFont
   XLookupColor               LookupColor
   XLowerWindow               ConfigureWindow
   XMapRaised                 ConfigureWindow
                              MapWindow
   XMapSubwindows             MapSubwindows
   XMapWindow                 MapWindow
   XMoveResizeWindow          ConfigureWindow
   XMoveWindow                ConfigureWindow
   XNoOp                      NoOperation
   XOpenDisplay               CreateGC
   XParseColor                LookupColor
   XPutImage                  PutImage
   XQueryBestCursor           QueryBestSize
   XQueryBestSize             QueryBestSize
   XQueryBestStipple          QueryBestSize
   XQueryBestTile             QueryBestSize
   XQueryColor                QueryColors
   XQueryColors               QueryColors
   XQueryExtension            QueryExtension
   XQueryFont                 QueryFont
   XQueryKeymap               QueryKeymap
   XQueryPointer              QueryPointer
   XQueryTextExtents          QueryTextExtents
   XQueryTextExtents16        QueryTextExtents
   XQueryTree                 QueryTree
   XRaiseWindow               ConfigureWindow
   XReadBitmapFile            CreateGC
                              CreatePixmap
                              FreeGC
                              PutImage
   XRecolorCursor             RecolorCursor
   XReconfigureWMWindow       ConfigureWindow
                              SendEvent
   XRemoveFromSaveSet         ChangeSaveSet
   XRemoveHost                ChangeHosts
   XRemoveHosts               ChangeHosts
   XReparentWindow            ReparentWindow
   XResetScreenSaver          ForceScreenSaver
   XResizeWindow              ConfigureWindow
   XRestackWindows            ConfigureWindow
   XRotateBuffers             RotateProperties
   XRotateWindowProperties    RotateProperties
   XSelectInput               ChangeWindowAttributes
   XSendEvent                 SendEvent
   XSetAccessControl          SetAccessControl
   XSetArcMode                ChangeGC
   XSetBackground             ChangeGC
   XSetClassHint              ChangeProperty
   XSetClipMask               ChangeGC
   XSetClipOrigin             ChangeGC
   XSetClipRectangles         SetClipRectangles
   XSetCloseDownMode          SetCloseDownMode
   XSetCommand                ChangeProperty
   XSetDashes                 SetDashes
   XSetFillRule               ChangeGC
   XSetFillStyle              ChangeGC
   XSetFont                   ChangeGC
   XSetFontPath               SetFontPath
   XSetForeground             ChangeGC
   XSetFunction               ChangeGC
   XSetGraphicsExposures      ChangeGC
   XSetIconName               ChangeProperty
   XSetIconSizes              ChangeProperty
   XSetInputFocus             SetInputFocus
   XSetLineAttributes         ChangeGC
   XSetModifierMapping        SetModifierMapping
   XSetNormalHints            ChangeProperty
   XSetPlaneMask              ChangeGC
   XSetPointerMapping         SetPointerMapping
   XSetRGBColormaps           ChangeProperty
   XSetScreenSaver            SetScreenSaver
   XSetSelectionOwner         SetSelectionOwner
   XSetSizeHints              ChangeProperty
   XSetStandardProperties     ChangeProperty
   XSetState                  ChangeGC
   XSetStipple                ChangeGC
   XSetSubwindowMode          ChangeGC
   XSetTextProperty           ChangeProperty
   XSetTile                   ChangeGC
   XSetTransientForHint       ChangeProperty
   XSetTSOrigin               ChangeGC
   XSetWMClientMachine        ChangeProperty
   XSetWMColormapWindows      ChangeProperty
                              InternAtom
   XSetWMHints                ChangeProperty
   XSetWMIconName             ChangeProperty
   XSetWMName                 ChangeProperty
   XSetWMNormalHints          ChangeProperty
   XSetWMProperties           ChangeProperty
   XSetWMProtocols            ChangeProperty
                              InternAtom
   XSetWMSizeHints            ChangeProperty
   XSetWindowBackground       ChangeWindowAttributes
   XSetWindowBackgroundPixmap ChangeWindowAttributes
   XSetWindowBorder           ChangeWindowAttributes
   XSetWindowBorderPixmap     ChangeWindowAttributes
   XSetWindowBorderWidth      ConfigureWindow
   XSetWindowColormap         ChangeWindowAttributes
   XSetZoomHints              ChangeProperty
   XStoreBuffer               ChangeProperty
   XStoreBytes                ChangeProperty
   XStoreColor                StoreColors
   XStoreColors               StoreColors
   XStoreName                 ChangeProperty
   XStoreNamedColor           StoreNamedColor
   XSync                      GetInputFocus
   XSynchronize               GetInputFocus
   XTranslateCoordinates      TranslateCoordinates
   XUndefineCursor            ChangeWindowAttributes
   XUngrabButton              UngrabButton
   XUngrabKey                 UngrabKey
   XUngrabKeyboard            UngrabKeyboard
   XUngrabPointer             UngrabPointer
   XUngrabServer              UngrabServer
   XUninstallColormap         UninstallColormap
   XUnloadFont                CloseFont
   XUnmapSubwindows           UnmapSubwindows
   XUnmapWindow               UnmapWindow
   XWarpPointer               WarpPointer
   XWithdrawWindow            SendEvent
                              UnmapWindow

   The following table lists each X protocol request (in
   alphabetical order) and the Xlib functions that reference it.

   Table A.2. Xlib functions which use each Protocol Request
   Protocol Request        Xlib Function
   AllocColor              XAllocColor
   AllocColorCells         XAllocColorCells
   AllocColorPlanes        XAllocColorPlanes
   AllocNamedColor         XAllocNamedColor
   AllowEvents             XAllowEvents
   Bell                    XBell
   ChangeActivePointerGrab XChangeActivePointerGrab
   ChangeGC                XChangeGC
                           XSetArcMode
                           XSetBackground
                           XSetClipMask
                           XSetClipOrigin
                           XSetFillRule
                           XSetFillStyle
                           XSetFont
                           XSetForeground
                           XSetFunction
                           XSetGraphicsExposures
                           XSetLineAttributes
                           XSetPlaneMask
                           XSetState
                           XSetStipple
                           XSetSubwindowMode
                           XSetTile
                           XSetTSOrigin
   ChangeHosts             XAddHost
                           XAddHosts
                           XRemoveHost
                           XRemoveHosts
   ChangeKeyboardControl   XAutoRepeatOff
                           XAutoRepeatOn
                           XChangeKeyboardControl
   ChangeKeyboardMapping   XChangeKeyboardMapping
   ChangePointerControl    XChangePointerControl
   ChangeProperty          XChangeProperty
                           XSetClassHint
                           XSetCommand
                           XSetIconName
                           XSetIconSizes
                           XSetNormalHints
                           XSetRGBColormaps
                           XSetSizeHints
                           XSetStandardProperties
                           XSetTextProperty
                           XSetTransientForHint
                           XSetWMClientMachine
                           XSetWMColormapWindows
                           XSetWMHints
                           XSetWMIconName
                           XSetWMName
                           XSetWMNormalHints
                           XSetWMProperties
                           XSetWMProtocols
                           XSetWMSizeHints
                           XSetZoomHints
                           XStoreBuffer
                           XStoreBytes
                           XStoreName
   ChangeSaveSet           XAddToSaveSet
                           XChangeSaveSet
                           XRemoveFromSaveSet
   ChangeWindowAttributes  XChangeWindowAttributes
                           XDefineCursor
                           XSelectInput
                           XSetWindowBackground
                           XSetWindowBackgroundPixmap
                           XSetWindowBorder
                           XSetWindowBorderPixmap
                           XSetWindowColormap
                           XUndefineCursor
   CirculateWindow         XCirculateSubwindowsDown
                           XCirculateSubwindowsUp
                           XCirculateSubwindows
   ClearArea               XClearArea
                           XClearWindow
   CloseFont               XFreeFont
                           XUnloadFont
   ConfigureWindow         XConfigureWindow
                           XLowerWindow
                           XMapRaised
                           XMoveResizeWindow
                           XMoveWindow
                           XRaiseWindow
                           XReconfigureWMWindow
                           XResizeWindow
                           XRestackWindows
                           XSetWindowBorderWidth
   ConvertSelection        XConvertSelection
   CopyArea                XCopyArea
   CopyColormapAndFree     XCopyColormapAndFree
   CopyGC                  XCopyGC
   CopyPlane               XCopyPlane
   CreateColormap          XCreateColormap
   CreateCursor            XCreatePixmapCursor
   CreateGC                XCreateGC
                           XCreateBitmapFromData
                           XCreatePixmapFromData
                           XOpenDisplay
                           XReadBitmapFile
   CreateGlyphCursor       XCreateFontCursor
                           XCreateGlyphCursor
   CreatePixmap            XCreatePixmap
                           XCreateBitmapFromData
                           XCreatePixmapFromData
                           XReadBitmapFile
   CreateWindow            XCreateSimpleWindow
                           XCreateWindow
   DeleteProperty          XDeleteProperty
   DestroySubwindows       XDestroySubwindows
   DestroyWindow           XDestroyWindow
   FillPoly                XFillPolygon
   ForceScreenSaver        XActivateScreenSaver
                           XForceScreenSaver
                           XResetScreenSaver
   FreeColormap            XFreeColormap
   FreeColors              XFreeColors
   FreeCursor              XFreeCursor
   FreeGC                  XFreeGC
                           XCreateBitmapFromData
                           XCreatePixmapFromData
                           XReadBitmapFile
   FreePixmap              XFreePixmap
   GetAtomName             XGetAtomName
   GetFontPath             XGetFontPath
   GetGeometry             XGetGeometry
                           XGetWindowAttributes
   GetImage                XGetImage
   GetInputFocus           XGetInputFocus
                           XSync
                           XSynchronize
   GetKeyboardControl      XGetKeyboardControl
   GetKeyboardMapping      XGetKeyboardMapping
   GetModifierMapping      XGetModifierMapping
   GetMotionEvents
   GetPointerControl       XGetPointerControl
   GetPointerMapping       XGetPointerMapping
   GetProperty             XFetchBytes
                           XFetchName
                           XGetClassHint
                           XGetIconName
                           XGetIconSizes
                           XGetNormalHints
                           XGetRGBColormaps
                           XGetSizeHints
                           XGetTextProperty
                           XGetTransientForHint
                           XGetWMClientMachine
                           XGetWMColormapWindows
                           XGetWMHints
                           XGetWMIconName
                           XGetWMName
                           XGetWMNormalHints
                           XGetWMProtocols
                           XGetWMSizeHints
                           XGetWindowProperty
                           XGetZoomHints
   GetSelectionOwner       XGetSelectionOwner
   GetWindowAttributes     XGetWindowAttributes
   GrabButton              XGrabButton
   GrabKey                 XGrabKey
   GrabKeyboard            XGrabKeyboard
   GrabPointer             XGrabPointer
   GrabServer              XGrabServer
   ImageText8              XDrawImageString
   ImageText16             XDrawImageString16
   InstallColormap         XInstallColormap
   InternAtom              XGetWMColormapWindows
                           XGetWMProtocols
                           XIconifyWindow
                           XInternAtom
                           XSetWMColormapWindows
                           XSetWMProtocols
   KillClient              XKillClient
   ListExtensions          XListExtensions
   ListFonts               XListFonts
   ListFontsWithInfo       XListFontsWithInfo
   ListHosts               XListHosts
   ListInstalledColormaps  XListInstalledColormaps
   ListProperties          XListProperties
   LookupColor             XLookupColor
                           XParseColor
   MapSubwindows           XMapSubwindows
   MapWindow               XMapRaised
                           XMapWindow
   NoOperation             XNoOp
   OpenFont                XLoadFont
                           XLoadQueryFont
   PolyArc                 XDrawArc
                           XDrawArcs
   PolyFillArc             XFillArc
                           XFillArcs
   PolyFillRectangle       XFillRectangle
                           XFillRectangles
   PolyLine                XDrawLines
   PolyPoint               XDrawPoint
                           XDrawPoints
   PolyRectangle           XDrawRectangle
                           XDrawRectangles
   PolySegment             XDrawLine
                           XDrawSegments
   PolyText8               XDrawString
                           XDrawText
   PolyText16              XDrawString16
                           XDrawText16
   PutImage                XPutImage
                           XCreateBitmapFromData
                           XCreatePixmapFromData
                           XReadBitmapFile
   QueryBestSize           XQueryBestCursor
                           XQueryBestSize
                           XQueryBestStipple
                           XQueryBestTile
   QueryColors             XQueryColor
                           XQueryColors
   QueryExtension          XInitExtension
                           XQueryExtension
   QueryFont               XLoadQueryFont
                           XQueryFont
   QueryKeymap             XQueryKeymap
   QueryPointer            XQueryPointer
   QueryTextExtents        XQueryTextExtents
                           XQueryTextExtents16
   QueryTree               XQueryTree
   RecolorCursor           XRecolorCursor
   ReparentWindow          XReparentWindow
   RotateProperties        XRotateBuffers
                           XRotateWindowProperties
   SendEvent               XIconifyWindow
                           XReconfigureWMWindow
                           XSendEvent
                           XWithdrawWindow
   SetAccessControl        XDisableAccessControl
                           XEnableAccessControl
                           XSetAccessControl
   SetClipRectangles       XSetClipRectangles
   SetCloseDownMode        XSetCloseDownMode
   SetDashes               XSetDashes
   SetFontPath             XSetFontPath
   SetInputFocus           XSetInputFocus
   SetModifierMapping      XSetModifierMapping
   SetPointerMapping       XSetPointerMapping
   SetScreenSaver          XGetScreenSaver
                           XSetScreenSaver
   SetSelectionOwner       XSetSelectionOwner
   StoreColors             XStoreColor
                           XStoreColors
   StoreNamedColor         XStoreNamedColor
   TranslateCoordinates    XTranslateCoordinates
   UngrabButton            XUngrabButton
   UngrabKey               XUngrabKey
   UngrabKeyboard          XUngrabKeyboard
   UngrabPointer           XUngrabPointer
   UngrabServer            XUngrabServer
   UninstallColormap       XUninstallColormap
   UnmapSubwindows         XUnmapSubWindows
   UnmapWindow             XUnmapWindow
                           XWithdrawWindow
   WarpPointer             XWarpPointer

Appendix B. X Font Cursors

   The following are the available cursors that can be used with
   XCreateFontCursor.
#define XC_X_cursor 0                     #define XC_ll_angle 76
#define XC_arrow 2                        #define XC_lr_angle 78
#define XC_based_arrow_down 4             #define XC_man 80
#define XC_based_arrow_up 6               #define XC_middlebutton 82
#define XC_boat 8                         #define XC_mouse 84
#define XC_bogosity 10                    #define XC_pencil 86
#define XC_bottom_left_corner 12          #define XC_pirate 88
#define XC_bottom_right_corner 14         #define XC_plus 90
#define XC_bottom_side 16                 #define XC_question_arrow 92
#define XC_bottom_tee 18                  #define XC_right_ptr 94
#define XC_box_spiral 20                  #define XC_right_side 96
#define XC_center_ptr 22                  #define XC_right_tee 98
#define XC_circle 24                      #define XC_rightbutton 100
#define XC_clock 26                       #define XC_rtl_logo 102
#define XC_coffee_mug 28                  #define XC_sailboat 104
#define XC_cross 30                       #define XC_sb_down_arrow 106
#define XC_cross_reverse 32               #define XC_sb_h_double_arrow 1
08
#define XC_crosshair 34                   #define XC_sb_left_arrow 110
#define XC_diamond_cross 36               #define XC_sb_right_arrow 112
#define XC_dot 38                         #define XC_sb_up_arrow 114
#define XC_dot_box_mask 40                #define XC_sb_v_double_arrow 1
16
#define XC_double_arrow 42                #define XC_shuttle 118
#define XC_draft_large 44                 #define XC_sizing 120
#define XC_draft_small 46                 #define XC_spider 122
#define XC_draped_box 48                  #define XC_spraycan 124
#define XC_exchange 50                    #define XC_star 126
#define XC_fleur 52                       #define XC_target 128
#define XC_gobbler 54                     #define XC_tcross 130
#define XC_gumby 56                       #define XC_top_left_arrow 132
#define XC_hand1 58                       #define XC_top_left_corner 134
#define XC_hand2 60                       #define XC_top_right_corner 13
6
#define XC_heart 62                       #define XC_top_side 138
#define XC_icon 64                        #define XC_top_tee 140
#define XC_iron_cross 66                  #define XC_trek 142
#define XC_left_ptr 68                    #define XC_ul_angle 144
#define XC_left_side 70                   #define XC_umbrella 146
#define XC_left_tee 72                    #define XC_ur_angle 148
#define XC_leftbutton 74                  #define XC_watch 150
                                          #define XC_xterm 152

Appendix C. Extensions

   Table of Contents

   Basic Protocol Support Routines
   Hooking into Xlib

        Hooks into the Library
        Hooks onto Xlib Data Structures

   GC Caching
   Graphics Batching
   Writing Extension Stubs

        Requests, Replies, and Xproto.h
        Request Format
        Starting to Write a Stub Procedure
        Locking Data Structures
        Sending the Protocol Request and Arguments
        Variable Length Arguments
        Replies
        Synchronous Calling
        Allocating and Deallocating Memory
        Portability Considerations
        Deriving the Correct Extension Opcode

   Because X can evolve by extensions to the core protocol, it is
   important that extensions not be perceived as second-class
   citizens. At some point, your favorite extensions may be
   adopted as additional parts of the X Standard.

   Therefore, there should be little to distinguish the use of an
   extension from that of the core protocol. To avoid having to
   initialize extensions explicitly in application programs, it is
   also important that extensions perform lazy evaluations,
   automatically initializing themselves when called for the first
   time.

   This appendix describes techniques for writing extensions to
   Xlib that will run at essentially the same performance as the
   core protocol requests.

Note

   It is expected that a given extension to X consists of multiple
   requests. Defining 10 new features as 10 separate extensions is
   a bad practice. Rather, they should be packaged into a single
   extension and should use minor opcodes to distinguish the
   requests.

   The symbols and macros used for writing stubs to Xlib are
   listed in <X11/Xlibint.h>.

Basic Protocol Support Routines

   The basic protocol requests for extensions are XQueryExtension
   and XListExtensions.

   Bool XQueryExtension(Display *display, char *name, int
   *major_opcode_return, int *first_event_return, int
   *first_error_return);

   display

   Specifies the connection to the X server.

   name

   Specifies the extension name.

   major_opcode_return

   Returns the major opcode.

   first_event_return

   Returns the first event code, if any.

   first_error_return

   Returns the first error code, if any.

   The XQueryExtension function determines if the named extension
   is present. If the extension is not present, XQueryExtension
   returns False; otherwise, it returns True. If the extension is
   present, XQueryExtension returns the major opcode for the
   extension to major_opcode_return; otherwise, it returns zero.
   Any minor opcode and the request formats are specific to the
   extension. If the extension involves additional event types,
   XQueryExtension returns the base event type code to
   first_event_return; otherwise, it returns zero. The format of
   the events is specific to the extension. If the extension
   involves additional error codes, XQueryExtension returns the
   base error code to first_error_return; otherwise, it returns
   zero. The format of additional data in the errors is specific
   to the extension.

   If the extension name is not in the Host Portable Character
   Encoding the result is implementation-dependent. Uppercase and
   lowercase matter; the strings ``thing'', ``Thing'', and
   ``thinG'' are all considered different names.

   char **XListExtensions(Display *display, int
   *nextensions_return);

   display

   Specifies the connection to the X server.

   nextensions_return

   Returns the number of extensions listed.

   The XListExtensions function returns a list of all extensions
   supported by the server. If the data returned by the server is
   in the Latin Portable Character Encoding, then the returned
   strings are in the Host Portable Character Encoding. Otherwise,
   the result is implementation-dependent.

   XFreeExtensionList(char **list);

   list

   Specifies the list of extension names.

   The XFreeExtensionList function frees the memory allocated by
   XListExtensions.

Hooking into Xlib

   These functions allow you to hook into the library. They are
   not normally used by application programmers but are used by
   people who need to extend the core X protocol and the X library
   interface. The functions, which generate protocol requests for
   X, are typically called stubs.

   In extensions, stubs first should check to see if they have
   initialized themselves on a connection. If they have not, they
   then should call XInitExtension to attempt to initialize
   themselves on the connection.

   If the extension needs to be informed of GC/font allocation or
   deallocation or if the extension defines new event types, the
   functions described here allow the extension to be called when
   these events occur.

   The XExtCodes structure returns the information from
   XInitExtension and is defined in <X11/Xlib.h>:

typedef struct _XExtCodes {     /* public to extension, cannot be change
d */
        int extension;          /* extension number */
        int major_opcode;       /* major op-code assigned by server */
        int first_event;        /* first event number for the extension
*/
        int first_error;        /* first error number for the extension
*/
} XExtCodes;

   XExtCodes *XInitExtension(Display *display, char *name);

   display

   Specifies the connection to the X server.

   name

   Specifies the extension name.

   The XInitExtension function determines if the named extension
   exists. Then, it allocates storage for maintaining the
   information about the extension on the connection, chains this
   onto the extension list for the connection, and returns the
   information the stub implementor will need to access the
   extension. If the extension does not exist, XInitExtension
   returns NULL.

   If the extension name is not in the Host Portable Character
   Encoding, the result is implementation-dependent. Uppercase and
   lowercase matter; the strings ``thing'', ``Thing'', and
   ``thinG'' are all considered different names.

   The extension number in the XExtCodes structure is needed in
   the other calls that follow. This extension number is unique
   only to a single connection.

   XExtCodes *XAddExtension(Display *display);

   display

   Specifies the connection to the X server.

   For local Xlib extensions, the XAddExtension function allocates
   the XExtCodes structure, bumps the extension number count, and
   chains the extension onto the extension list. (This permits
   extensions to Xlib without requiring server extensions.)

Hooks into the Library

   These functions allow you to define procedures that are to be
   called when various circumstances occur. The procedures include
   the creation of a new GC for a connection, the copying of a GC,
   the freeing of a GC, the creating and freeing of fonts, the
   conversion of events defined by extensions to and from wire
   format, and the handling of errors.

   All of these functions return the previous procedure defined
   for this extension.

   int XESetCloseDisplay(Display *display, int extension, int
   (*proc)());

   display

   Specifies the connection to the X server.

   extension

   Specifies the extension number.

   proc

   Specifies the procedure to call when the display is closed.

   The XESetCloseDisplay function defines a procedure to be called
   whenever XCloseDisplay is called. It returns any previously
   defined procedure, usually NULL.

   When XCloseDisplay is called, your procedure is called with
   these arguments:

   int (*proc)(Display *display, XExtCodes *codes);

   int *XESetCreateGC(Display *display, int extension, int
   (*proc)());

   display

   Specifies the connection to the X server.

   extension

   Specifies the extension number.

   proc

   Specifies the procedure to call when a GC is closed.

   The XESetCreateGC function defines a procedure to be called
   whenever a new GC is created. It returns any previously defined
   procedure, usually NULL.

   When a GC is created, your procedure is called with these
   arguments:

   int (*proc)(Display *display, GC gc, XExtCodes *codes);

   int *XESetCopyGC(Display *display, int extension, int
   (*proc)());

   display

   Specifies the connection to the X server.

   extension

   Specifies the extension number.

   proc

   Specifies the procedure to call when GC components are copied.

   The XESetCopyGC function defines a procedure to be called
   whenever a GC is copied. It returns any previously defined
   procedure, usually NULL.

   When a GC is copied, your procedure is called with these
   arguments:

   int (*proc)(Display *display, GC gc, XExtCodes *codes);

   int *XESetFreeGC(Display *display, int extension, int
   (*proc)());

   display

   Specifies the connection to the X server.

   extension

   Specifies the extension number.

   proc

   Specifies the procedure to call when a GC is freed.

   The XESetFreeGC function defines a procedure to be called
   whenever a GC is freed. It returns any previously defined
   procedure, usually NULL.

   When a GC is freed, your procedure is called with these
   arguments:

   int (*proc)(Display *display, GC gc, XExtCodes *codes);

   int *XESetCreateFont(Display *display, int extension, int
   (*proc)());

   display

   Specifies the connection to the X server.

   extension

   Specifies the extension number.

   proc

   Specifies the procedure to call when a font is created.

   The XESetCreateFont function defines a procedure to be called
   whenever XLoadQueryFont and XQueryFont are called. It returns
   any previously defined procedure, usually NULL.

   When XLoadQueryFont or XQueryFont is called, your procedure is
   called with these arguments:

   int (*proc)(Display *display, XFontStruct *fs, XExtCodes
   *codes);

   int *XESetFreeFont(Display *display, int extension, int
   (*proc)());

   display

   Specifies the connection to the X server.

   extension

   Specifies the extension number.

   proc

   Specifies the procedure to call when a font is freed.

   The XESetFreeFont function defines a procedure to be called
   whenever XFreeFont is called. It returns any previously defined
   procedure, usually NULL.

   When XFreeFont is called, your procedure is called with these
   arguments:

   int (*proc)(Display *display, XFontStruct *fs, XExtCodes
   *codes);

   The XESetWireToEvent and XESetEventToWire functions allow you
   to define new events to the library. An XEvent structure always
   has a type code (type int) as the first component. This
   uniquely identifies what kind of event it is. The second
   component is always the serial number (type unsigned long) of
   the last request processed by the server. The third component
   is always a Boolean (type Bool) indicating whether the event
   came from a SendEvent protocol request. The fourth component is
   always a pointer to the display the event was read from. The
   fifth component is always a resource ID of one kind or another,
   usually a window, carefully selected to be useful to toolkit
   dispatchers. The fifth component should always exist, even if
   the event does not have a natural destination; if there is no
   value from the protocol to put in this component, initialize it
   to zero. There is an implementation limit such that your host
   event structure size cannot be bigger than the size of the
   XEvent union of structures. There also is no way to guarantee
   that more than 24 elements or 96 characters in the structure
   will be fully portable between machines.

   int *XESetWireToEvent(Display *display, int event_number,
   Status (*proc)());

   display

   Specifies the connection to the X server.

   event_number

   Specifies the event code.

   proc

   Specifies the procedure to call when converting an event.

   The XESetWireToEvent function defines a procedure to be called
   when an event needs to be converted from wire format (xEvent)
   to host format (XEvent). The event number defines which
   protocol event number to install a conversion procedure for.
   XESetWireToEvent returns any previously defined procedure. You
   can replace a core event conversion function with one of your
   own, although this is not encouraged. It would, however, allow
   you to intercept a core event and modify it before being placed
   in the queue or otherwise examined. When Xlib needs to convert
   an event from wire format to host format, your procedure is
   called with these arguments:

   int (*proc)(Display *display, XEvent *re, xEvent *event);

   Your procedure must return status to indicate if the conversion
   succeeded. The re argument is a pointer to where the host
   format event should be stored, and the event argument is the
   32-byte wire event structure. In the XEvent structure you are
   creating, you must fill in the five required members of the
   event structure. You should fill in the type member with the
   type specified for the xEvent structure. You should copy all
   other members from the xEvent structure (wire format) to the
   XEvent structure (host format). Your conversion procedure
   should return True if the event should be placed in the queue
   or False if it should not be placed in the queue.

   To initialize the serial number component of the event, call
   _XSetLastRequestRead with the event and use the return value.

   unsigned long_XSetLastRequestRead(Display *display,
   xGenericReply *rep);

   display

   Specifies the connection to the X server.

   rep

   Specifies the wire event structure.

   The _XSetLastRequestRead function computes and returns a
   complete serial number from the partial serial number in the
   event.

   Status *XESetEventToWire(Display *display, int event_number,
   int (*proc)());

   display

   Specifies the connection to the X server.

   event_number

   Specifies the event code.

   proc

   Specifies the procedure to call when converting an event.

   The XESetEventToWire function defines a procedure to be called
   when an event needs to be converted from host format (XEvent)
   to wire format (xEvent) form. The event number defines which
   protocol event number to install a conversion procedure for.
   XESetEventToWire returns any previously defined procedure. It
   returns zero if the conversion fails or nonzero otherwise. You
   can replace a core event conversion function with one of your
   own, although this is not encouraged. It would, however, allow
   you to intercept a core event and modify it before being sent
   to another client. When Xlib needs to convert an event from
   host format to wire format, your procedure is called with these
   arguments:

   int (*proc)(Display *display, XEvent *re, xEvent *event);

   The re argument is a pointer to the host format event, and the
   event argument is a pointer to where the 32-byte wire event
   structure should be stored. You should fill in the type with
   the type from the XEvent structure. All other members then
   should be copied from the host format to the xEvent structure.

   Bool *XESetWireToError(Display *display, int error_number, Bool
   (*proc)());

   display

   Specifies the connection to the X server.

   error_number

   Specifies the error code.

   proc

   Specifies the procedure to call when an error is received.

   The XESetWireToError function defines a procedure to be called
   when an extension error needs to be converted from wire format
   to host format. The error number defines which protocol error
   code to install the conversion procedure for. XESetWireToError
   returns any previously defined procedure.

   Use this function for extension errors that contain additional
   error values beyond those in a core X error, when multiple wire
   errors must be combined into a single Xlib error, or when it is
   necessary to intercept an X error before it is otherwise
   examined.

   When Xlib needs to convert an error from wire format to host
   format, the procedure is called with these arguments:

   int (*proc)(Display *display, XErrorEvent *he, xError *we);

   The he argument is a pointer to where the host format error
   should be stored. The structure pointed at by he is guaranteed
   to be as large as an XEvent structure and so can be cast to a
   type larger than an XErrorEvent to store additional values. If
   the error is to be completely ignored by Xlib (for example,
   several protocol error structures will be combined into one
   Xlib error), then the function should return False; otherwise,
   it should return True.

   int *XESetError(Display *display, int extension, int
   (*proc)());

   display

   Specifies the connection to the X server.

   extension

   Specifies the extension number.

   proc

   Specifies the procedure to call when an error is received.

   Inside Xlib, there are times that you may want to suppress the
   calling of the external error handling when an error occurs.
   This allows status to be returned on a call at the cost of the
   call being synchronous (though most such functions are query
   operations, in any case, and are typically programmed to be
   synchronous).

   When Xlib detects a protocol error in _XReply, it calls your
   procedure with these arguments:

   int (*proc)(Display *display, xError *err, XExtCodes *codes,
   int *ret_code);

   The err argument is a pointer to the 32-byte wire format error.
   The codes argument is a pointer to the extension codes
   structure. The ret_code argument is the return code you may
   want _XReply returned to.

   If your procedure returns a zero value, the error is not
   suppressed, and the client's error handler is called. (For
   further information, see section 11.8.2.) If your procedure
   returns nonzero, the error is suppressed, and _XReply returns
   the value of ret_code.

   char *XESetErrorString(Display *display, int extension, char
   *(*proc)());

   display

   Specifies the connection to the X server.

   extension

   Specifies the extension number.

   proc

   Specifies the procedure to call to obtain an error string.

   The XGetErrorText function returns a string to the user for an
   error. XESetErrorString allows you to define a procedure to be
   called that should return a pointer to the error message. The
   following is an example.

   int (*proc)(Display *display, int code, XExtCodes *codes, char
   *buffer, int nbytes);

   Your procedure is called with the error code for every error
   detected. You should copy nbytes of a null-terminated string
   containing the error message into buffer.

   void *XESetPrintErrorValues(Display *display, int extension,
   void (*proc)());

   display

   Specifies the connection to the X server.

   extension

   Specifies the extension number.

   proc

   Specifies the procedure to call when an error is printed.

   The XESetPrintErrorValues function defines a procedure to be
   called when an extension error is printed, to print the error
   values. Use this function for extension errors that contain
   additional error values beyond those in a core X error. It
   returns any previously defined procedure.

   When Xlib needs to print an error, the procedure is called with
   these arguments:

   void (*proc)(Display *display, XErrorEvent *ev, void *fp);

   The structure pointed at by ev is guaranteed to be as large as
   an XEvent structure and so can be cast to a type larger than an
   XErrorEvent to obtain additional values set by using
   XESetWireToError. The underlying type of the fp argument is
   system dependent; on a POSIX-compliant system, fp should be
   cast to type FILE*.

   int *XESetFlushGC(Display *display, int extension, int
   *(*proc)());

   display

   Specifies the connection to the X server.

   extension

   Specifies the extension number.

   proc

   Specifies the procedure to call when a GC is flushed.

   The procedure set by the XESetFlushGC function has the same
   interface as the procedure set by the XESetCopyGC function, but
   is called when a GC cache needs to be updated in the server.

   int *XESetCopyGC(Display *display, int extension, int
   *(*proc)());

   display

   Specifies the connection to the X server.

   extension

   Specifies the extension number.

   proc

   Specifies the procedure to call when a buffer is flushed.

   The XESetBeforeFlush function defines a procedure to be called
   when data is about to be sent to the server. When data is about
   to be sent, your procedure is called one or more times with
   these arguments:

   void (*proc)(Display *display, XExtCodes *codes, char *data,
   long len);

   The data argument specifies a portion of the outgoing data
   buffer, and its length in bytes is specified by the len
   argument. Your procedure must not alter the contents of the
   data and must not do additional protocol requests to the same
   display.

Hooks onto Xlib Data Structures

   Various Xlib data structures have provisions for extension
   procedures to chain extension supplied data onto a list. These
   structures are GC, Visual, Screen, ScreenFormat, Display, and
   XFontStruct. Because the list pointer is always the first
   member in the structure, a single set of procedures can be used
   to manipulate the data on these lists.

   The following structure is used in the functions in this
   section and is defined in <X11/Xlib.h>

typedef struct _XExtData {
        int number;     /* number returned by XInitExtension */
        struct _XExtData *next; /* next item on list of data for structu
re */
        int (*free_private)();  /* if defined,  called to free private *
/
        XPointer private_data;  /* data private to this extension. */
} XExtData;

   When any of the data structures listed above are freed, the
   list is walked, and the structure's free procedure (if any) is
   called. If free is NULL, then the library frees both the data
   pointed to by the private_data member and the structure itself.

union { Display *display;
        GC gc;
        Visual *visual;
        Screen *screen;
        ScreenFormat *pixmap_format;
        XFontStruct *font } XEDataObject;

   XExtData **XEHeadOfExtensionList(XEDataObject object);

   object

   Specifies the object.

   The XEHeadOfExtensionList function returns a pointer to the
   list of extension structures attached to the specified object.
   In concert with XAddToExtensionList, XEHeadOfExtensionList
   allows an extension to attach arbitrary data to any of the
   structures of types contained in XEDataObject.

   XAddToExtensionList(XExtData **structure, XExtData *ext_data);

   structure

   Specifies the extension list.

   ext_data

   Specifies the extension data structure to add.

   The structure argument is a pointer to one of the data
   structures enumerated above. You must initialize
   ext_data->number with the extension number before calling this
   function.

   XExtData *XFindOnExtensionList(struct_XExtData **structure, int
   number);

   structure

   Specifies the extension list.

   number

   Specifies the extension number from XInitExtension.

   The XFindOnExtensionList function returns the first extension
   data structure for the extension numbered number. It is
   expected that an extension will add at most one extension data
   structure to any single data structure's extension data list.
   There is no way to find additional structures.

   The XAllocID macro, which allocates and returns a resource ID,
   is defined in <X11/Xlib.h>.

   XAllocID(Display *display);

   display

   Specifies the connection to the X server.

   This macro is a call through the Display structure to an
   internal resource ID allocator. It returns a resource ID that
   you can use when creating new resources.

   The XAllocIDs macro allocates and returns an array of resource
   ID.

   XAllocIDs(Display *display, XID *ids_return, int count);

   display

   Specifies the connection to the X server.

   ids_return

   Returns the resource IDs.

   rep

   Specifies the number of resource IDs requested.

   This macro is a call through the Display structure to an
   internal resource ID allocator. It returns resource IDs to the
   array supplied by the caller. To correctly handle automatic
   reuse of resource IDs, you must call XAllocIDs when requesting
   multiple resource IDs. This call might generate protocol
   requests.

GC Caching

   GCs are cached by the library to allow merging of independent
   change requests to the same GC into single protocol requests.
   This is typically called a write-back cache. Any extension
   procedure whose behavior depends on the contents of a GC must
   flush the GC cache to make sure the server has up-to-date
   contents in its GC.

   The FlushGC macro checks the dirty bits in the library's GC
   structure and calls _XFlushGCCache if any elements have
   changed. The FlushGC macro is defined as follows:

   FlushGC(Display *display, GC gc);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

   Note that if you extend the GC to add additional resource ID
   components, you should ensure that the library stub sends the
   change request immediately. This is because a client can free a
   resource immediately after using it, so if you only stored the
   value in the cache without forcing a protocol request, the
   resource might be destroyed before being set into the GC. You
   can use the _XFlushGCCache procedure to force the cache to be
   flushed. The _XFlushGCCache procedure is defined as follows:

   _XFlushGCCache(Display *display, GC gc);

   display

   Specifies the connection to the X server.

   gc

   Specifies the GC.

Graphics Batching

   If you extend X to add more poly graphics primitives, you may
   be able to take advantage of facilities in the library to allow
   back-to-back single calls to be transformed into poly requests.
   This may dramatically improve performance of programs that are
   not written using poly requests. A pointer to an xReq, called
   last_req in the display structure, is the last request being
   processed. By checking that the last request type, drawable,
   gc, and other options are the same as the new one and that
   there is enough space left in the buffer, you may be able to
   just extend the previous graphics request by extending the
   length field of the request and appending the data to the
   buffer. This can improve performance by five times or more in
   naive programs. For example, here is the source for the
   XDrawPoint stub. (Writing extension stubs is discussed in the
   next section.)
#include <X11/Xlibint.h>

/* precompute the maximum size of batching request allowed */

static int size = sizeof(xPolyPointReq) + EPERBATCH * sizeof(xPoint);

XDrawPoint(dpy, d, gc, x, y)
    register Display *dpy;
    Drawable d;
    GC gc;
    int x, y; /* INT16 */
{
    xPoint *point;
    LockDisplay(dpy);
    FlushGC(dpy, gc);
    {
    register xPolyPointReq *req = (xPolyPointReq *) dpy->last_req;
    /* if same as previous request, with same drawable, batch requests *
/
    if (
          (req->reqType == X_PolyPoint)
       && (req->drawable == d)
       && (req->gc == gc->gid)
       && (req->coordMode == CoordModeOrigin)
       && ((dpy->bufptr + sizeof (xPoint)) <= dpy->bufmax)
       && (((char *)dpy->bufptr - (char *)req) < size) ) {
         point = (xPoint *) dpy->bufptr;
         req->length += sizeof (xPoint) >> 2;
         dpy->bufptr += sizeof (xPoint);
         }

    else {
        GetReqExtra(PolyPoint, 4, req); /* 1 point = 4 bytes */
        req->drawable = d;
        req->gc = gc->gid;
        req->coordMode = CoordModeOrigin;
        point = (xPoint *) (req + 1);
        }
    point->x = x;
    point->y = y;
    }
    UnlockDisplay(dpy);
    SyncHandle();
}

   To keep clients from generating very long requests that may
   monopolize the server, there is a symbol defined in
   <X11/Xlibint.h> of EPERBATCH on the number of requests batched.
   Most of the performance benefit occurs in the first few merged
   requests. Note that FlushGC is called before picking up the
   value of last_req, because it may modify this field.

Writing Extension Stubs

   All X requests always contain the length of the request,
   expressed as a 16-bit quantity of 32 bit words. This means that
   a single request can be no more than 256K bytes in length. Some
   servers may not support single requests of such a length. The
   value of dpy->max_request_size contains the maximum length as
   defined by the server implementation. For further information,
   see X Window System Protocol.

Requests, Replies, and Xproto.h

   The <X11/Xproto.h> file contains three sets of definitions that
   are of interest to the stub implementor: request names, request
   structures, and reply structures.

   You need to generate a file equivalent to <X11/Xproto.h> for
   your extension and need to include it in your stub procedure.
   Each stub procedure also must include <X11/Xlibint.h>.

   The identifiers are deliberately chosen in such a way that, if
   the request is called X_DoSomething, then its request structure
   is xDoSomethingReq, and its reply is xDoSomethingReply. The
   GetReq family of macros, defined in <X11/Xlibint.h>, takes
   advantage of this naming scheme.

   For each X request, there is a definition in <X11/Xproto.h>
   that looks similar to this:

#define X_DoSomething   42

   In your extension header file, this will be a minor opcode,
   instead of a major opcode.

Request Format

   Every request contains an 8-bit major opcode and a 16-bit
   length field expressed in units of 4 bytes. Every request
   consists of 4 bytes of header (containing the major opcode, the
   length field, and a data byte) followed by zero or more
   additional bytes of data. The length field defines the total
   length of the request, including the header. The length field
   in a request must equal the minimum length required to contain
   the request. If the specified length is smaller or larger than
   the required length, the server should generate a BadLength
   error. Unused bytes in a request are not required to be zero.
   Extensions should be designed in such a way that long protocol
   requests can be split up into smaller requests, if it is
   possible to exceed the maximum request size of the server. The
   protocol guarantees the maximum request size to be no smaller
   than 4096 units (16384 bytes).

   Major opcodes 128 through 255 are reserved for extensions.
   Extensions are intended to contain multiple requests, so
   extension requests typically have an additional minor opcode
   encoded in the second data byte in the request header, but the
   placement and interpretation of this minor opcode as well as
   all other fields in extension requests are not defined by the
   core protocol. Every request is implicitly assigned a sequence
   number (starting with one) used in replies, errors, and events.

   Most protocol requests have a corresponding structure typedef
   in <X11/Xproto.h>, which looks like:

typedef struct _DoSomethingReq {
        CARD8 reqType;          /* X_DoSomething */
        CARD8 someDatum;        /* used differently in different request
s */
        CARD16 length;          /* total # of bytes in request, divided
by 4 */
        ...
        /* request-specific data */
        ...
} xDoSomethingReq;

   If a core protocol request has a single 32-bit argument, you
   need not declare a request structure in your extension header
   file. Instead, such requests use the xResourceReq structure in
   <X11/Xproto.h>. This structure is used for any request whose
   single argument is a Window, Pixmap, Drawable, GContext, Font,
   Cursor, Colormap, Atom, or VisualID.

typedef struct _ResourceReq {
        CARD8 reqType;  /* the request type, e.g. X_DoSomething */
        BYTE pad;       /* not used */
        CARD16 length;  /* 2 (= total # of bytes in request, divided by
4) */
        CARD32 id;      /* the Window, Drawable, Font, GContext, etc. */
} xResourceReq;

   If convenient, you can do something similar in your extension
   header file.

   In both of these structures, the reqType field identifies the
   type of the request (for example, X_MapWindow or
   X_CreatePixmap). The length field tells how long the request is
   in units of 4-byte longwords. This length includes both the
   request structure itself and any variable-length data, such as
   strings or lists, that follow the request structure. Request
   structures come in different sizes, but all requests are padded
   to be multiples of four bytes long.

   A few protocol requests take no arguments at all. Instead, they
   use the xReq structure in <X11/Xproto.h>, which contains only a
   reqType and a length (and a pad byte).

   If the protocol request requires a reply, then <X11/Xproto.h>
   also contains a reply structure typedef:

typedef struct _DoSomethingReply {
        BYTE type;      /* always X_Reply */
        BYTE someDatum; /* used differently in different requests */
        CARD16 sequenceNumber;  /* # of requests sent so far */
        CARD32 length;  /* # of additional bytes, divided by 4 */
        ...
        /* request-specific data */
        ...
} xDoSomethingReply;

   Most of these reply structures are 32 bytes long. If there are
   not that many reply values, then they contain a sufficient
   number of pad fields to bring them up to 32 bytes. The length
   field is the total number of bytes in the request minus 32,
   divided by 4. This length will be nonzero only if:
     * The reply structure is followed by variable-length data,
       such as a list or string.
     * The reply structure is longer than 32 bytes.

   Only GetWindowAttributesl, QueryFont, QueryKeymap, and
   GetKeyboardControl have reply structures longer than 32 bytes
   in the core protocol.

   A few protocol requests return replies that contain no data.
   <X11/Xproto.h> does not define reply structures for these.
   Instead, they use the xGenericReply structure, which contains
   only a type, length, and sequence number (and sufficient
   padding to make it 32 bytes long).

Starting to Write a Stub Procedure

   An Xlib stub procedure should start like this:

#include "<X11/Xlibint.h>

XDoSomething (arguments, ... )
/* argument declarations */
{

register XDoSomethingReq *req;
...

   If the protocol request has a reply, then the variable
   declarations should include the reply structure for the
   request. The following is an example:

xDoSomethingReply rep;

Locking Data Structures

   To lock the display structure for systems that want to support
   multithreaded access to a single display connection, each stub
   will need to lock its critical section. Generally, this section
   is the point from just before the appropriate GetReq call until
   all arguments to the call have been stored into the buffer. The
   precise instructions needed for this locking depend upon the
   machine architecture. Two calls, which are generally
   implemented as macros, have been provided.

   LockDisplay(Display *display);

   UnlockDisplay(Display *display);

   display

   Specifies the connection to the X server.

Sending the Protocol Request and Arguments

   After the variable declarations, a stub procedure should call
   one of four macros defined in <X11/Xlibint.h>: GetReq,
   GetReqExtra, GetResReq, or GetEmptyReq. All of these macros
   take, as their first argument, the name of the protocol request
   as declared in <X11/Xproto.h> except with X_ removed. Each one
   declares a Display structure pointer, called dpy, and a pointer
   to a request structure, called req, which is of the appropriate
   type. The macro then appends the request structure to the
   output buffer, fills in its type and length field, and sets req
   to point to it.

   If the protocol request has no arguments (for instance,
   X_GrabServer), then use GetEmptyReq.

GetEmptyReq (DoSomething, req);

   If the protocol request has a single 32-bit argument (such as a
   Pixmap, Window, Drawable, Atom, and so on), then use GetResReq.
   The second argument to the macro is the 32-bit object.
   X_MapWindow is a good example.

GetResReq (DoSomething, rid, req);

   The rid argument is the Pixmap, Window, or other resource ID.

   If the protocol request takes any other argument list, then
   call GetReq. After the GetReq, you need to set all the other
   fields in the request structure, usually from arguments to the
   stub procedure.

GetReq (DoSomething, req);
/* fill in arguments here */
req->arg1 = arg1;
req->arg2 = arg2;
...

   A few stub procedures (such as XCreateGC and XCreatePixmap)
   return a resource ID to the caller but pass a resource ID as an
   argument to the protocol request. Such procedures use the macro
   XAllocID to allocate a resource ID from the range of IDs that
   were assigned to this client when it opened the connection.

rid = req->rid = XAllocID();
...
return (rid);

   Finally, some stub procedures transmit a fixed amount of
   variable-length data after the request. Typically, these
   procedures (such as XMoveWindow and XSetBackground) are special
   cases of more general functions like XMoveResizeWindow and
   XChangeGC. These procedures use GetReqExtra, which is the same
   as GetReq except that it takes an additional argument (the
   number of extra bytes to allocate in the output buffer after
   the request structure). This number should always be a multiple
   of four. Note that it is possible for req to be set to NULL as
   a defensive measure if the requested length exceeds the Xlib's
   buffer size (normally 16K).

Variable Length Arguments

   Some protocol requests take additional variable-length data
   that follow the xDoSomethingReq structure. The format of this
   data varies from request to request. Some requests require a
   sequence of 8-bit bytes, others a sequence of 16-bit or 32-bit
   entities, and still others a sequence of structures.

   It is necessary to add the length of any variable-length data
   to the length field of the request structure. That length field
   is in units of 32-bit longwords. If the data is a string or
   other sequence of 8-bit bytes, then you must round the length
   up and shift it before adding:

req->length += (nbytes+3)>>2;

   To transmit variable-length data, use the Data macros. If the
   data fits into the output buffer, then this macro copies it to
   the buffer. If it does not fit, however, the Data macro calls
   _XSend, which transmits first the contents of the buffer and
   then your data. The Data macros take three arguments: the
   display, a pointer to the beginning of the data, and the number
   of bytes to be sent.

   Data(display, (char *) data, nbytes);

   Data16(display, (short *) data, nbytes);

   Data32(display, (long *) data, nbytes);

   Data, Data16, and Data32 are macros that may use their last
   argument more than once, so that argument should be a variable
   rather than an expression such as ``nitems*sizeof(item)''. You
   should do that kind of computation in a separate statement
   before calling them. Use the appropriate macro when sending
   byte, short, or long data.

   If the protocol request requires a reply, then call the
   procedure _XSend instead of the Data macro. _XSend takes the
   same arguments, but because it sends your data immediately
   instead of copying it into the output buffer (which would later
   be flushed anyway by the following call on _XReply), it is
   faster.

Replies

   If the protocol request has a reply, then call _XReply after
   you have finished dealing with all the fixed-length and
   variable-length arguments. _XReply flushes the output buffer
   and waits for an xReply packet to arrive. If any events arrive
   in the meantime, _XReply places them in the queue for later
   use.

   Status _XReply(Display *display, xReply *rep, int extra, Bool
   discard);

   display

   Specifies the connection to the X server.

   rep

   Specifies the reply structure.

   extra

   Specifies the number of 32-bit words expected after the replay.

   discard

   Specifies if any data beyond that specified in the extra
   argument should be discarded.

   The _XReply function waits for a reply packet and copies its
   contents into the specified rep. _XReply handles error and
   event packets that occur before the reply is received. _XReply
   takes four arguments:
     * A Display * structure
     * A pointer to a reply structure (which must be cast to an
       xReply *)
     * The number of additional 32-bit words (beyond sizeof(
       xReply) = 32 bytes) in the reply structure
     * A Boolean that indicates whether _XReply is to discard any
       additional bytes beyond those it was told to read

   Because most reply structures are 32 bytes long, the third
   argument is usually 0. The only core protocol exceptions are
   the replies to GetWindowAttributesl, QueryFont, QueryKeymap,
   and GetKeyboardControl, which have longer replies.

   The last argument should be False if the reply structure is
   followed by additional variable-length data (such as a list or
   string). It should be True if there is not any variable-length
   data. This last argument is provided for upward-compatibility
   reasons to allow a client to communicate properly with a
   hypothetical later version of the server that sends more data
   than the client expected. For example, some later version of
   GetWindowAttributesl might use a larger, but compatible,
   xGetWindowAttributesReply that contains additional attribute
   data at the end. _XReply returns True if it received a reply
   successfully or False if it received any sort of error.

   For a request with a reply that is not followed by
   variable-length data, you write something like:

_XReply(display, (xReply *)&rep, 0, True);
*ret1 = rep.ret1;
*ret2 = rep.ret2;
*ret3 = rep.ret3;
...
UnlockDisplay(dpy);
SyncHandle();
return (rep.ret4);
}

   If there is variable-length data after the reply, change the
   True to False, and use the appropriate _XRead function to read
   the variable-length data.

   _XRead(Display *display, char *data_return, long nbytes);

   display

   Specifies the connection to the X server.

   data_return

   Specifies the buffer.

   nbytes

   Specifies the number of bytes required.

   The _XRead function reads the specified number of bytes into
   data_return.

   _XRead16(Display *display, short *data_return, long nbytes);

   display

   Specifies the connection to the X server.

   data_return

   Specifies the buffer.

   nbytes

   Specifies the number of bytes required.

   The _XRead16 function reads the specified number of bytes,
   unpacking them as 16-bit quantities, into the specified array
   as shorts.

   _XRead32(Display *display, long *data_return, long nbytes);

   display

   Specifies the connection to the X server.

   data_return

   Specifies the buffer.

   nbytes

   Specifies the number of bytes required.

   The _XRead32 function reads the specified number of bytes,
   unpacking them as 32-bit quantities, into the specified array
   as longs.

   _XRead16Pad(Display *display, short *data_return, long nbytes);

   display

   Specifies the connection to the X server.

   data_return

   Specifies the buffer.

   nbytes

   Specifies the number of bytes required.

   The _XRead16Pad function reads the specified number of bytes,
   unpacking them as 16-bit quantities, into the specified array
   as shorts. If the number of bytes is not a multiple of four,
   _XRead16Pad reads and discards up to two additional pad bytes.

   _XReadPad(Display *display, char *data_return, long nbytes);

   display

   Specifies the connection to the X server.

   data_return

   Specifies the buffer.

   nbytes

   Specifies the number of bytes required.

   The _XReadPad function reads the specified number of bytes into
   data_return. If the number of bytes is not a multiple of four,
   _XReadPad reads and discards up to three additional pad bytes.

   Each protocol request is a little different. For further
   information, see the Xlib sources for examples.

Synchronous Calling

   Each procedure should have a call, just before returning to the
   user, to a macro called SyncHandle. If synchronous mode is
   enabled (see XSynchronize), the request is sent immediately.
   The library, however, waits until any error the procedure could
   generate at the server has been handled.

Allocating and Deallocating Memory

   To support the possible reentry of these procedures, you must
   observe several conventions when allocating and deallocating
   memory, most often done when returning data to the user from
   the window system of a size the caller could not know in
   advance (for example, a list of fonts or a list of extensions).
   The standard C library functions on many systems are not
   protected against signals or other multithreaded uses. The
   following analogies to standard I/O library functions have been
   defined:

   These should be used in place of any calls you would make to
   the normal C library functions.

   If you need a single scratch buffer inside a critical section
   (for example, to pack and unpack data to and from the wire
   protocol), the general memory allocators may be too expensive
   to use (particularly in output functions, which are performance
   critical). The following function returns a scratch buffer for
   use within a critical section:

   char *_XAllocScratch(Display *display, unsigned long nbytes);

   display

   Specifies the connection to the X server.

   nbytes

   Specifies the number of bytes required.

   This storage must only be used inside of a critical section of
   your stub. The returned pointer cannot be assumed valid after
   any call that might permit another thread to execute inside
   Xlib. For example, the pointer cannot be assumed valid after
   any use of the GetReq or Data families of macros, after any use
   of _XReply, or after any use of the _XSend or _XRead families
   of functions.

   The following function returns a scratch buffer for use across
   critical sections:

   char *_XAllocTemp(Display *display, unsigned long nbytes);

   display

   Specifies the connection to the X server.

   nbytes

   Specifies the number of bytes required.

   This storage can be used across calls that might permit another
   thread to execute inside Xlib. The storage must be explicitly
   returned to Xlib. The following function returns the storage:

   void _XFreeTemp(Display *display, char *buf, unsigned long
   nbytes);

   display

   Specifies the connection to the X server.

   buf

   Specifies the buffer to return.

   nbytes

   Specifies the size of the buffer.

   You must pass back the same pointer and size that were returned
   by _XAllocTemp.

Portability Considerations

   Many machine architectures do not correctly or efficiently
   access data at unaligned locations; their compilers pad out
   structures to preserve this characteristic. Many other machines
   capable of unaligned references pad inside of structures as
   well to preserve alignment, because accessing aligned data is
   usually much faster. Because the library and the server use
   structures to access data at arbitrary points in a byte stream,
   all data in request and reply packets must be naturally
   aligned; that is, 16-bit data starts on 16-bit boundaries in
   the request and 32-bit data on 32-bit boundaries. All requests
   must be a multiple of 32 bits in length to preserve the natural
   alignment in the data stream. You must pad structures out to
   32-bit boundaries. Pad information does not have to be zeroed
   unless you want to preserve such fields for future use in your
   protocol requests, but it is recommended to zero it to avoid
   inadvertent data leakage and improve compressability. Floating
   point varies radically between machines and should be avoided
   completely if at all possible.

   This code may run on machines with 16-bit ints. So, if any
   integer argument, variable, or return value either can take
   only nonnegative values or is declared as a CARD16 in the
   protocol, be sure to declare it as unsigned int and not as int.
   (This, of course, does not apply to Booleans or enumerations.)

   Similarly, if any integer argument or return value is declared
   CARD32 in the protocol, declare it as an unsigned long and not
   as int or long. This also goes for any internal variables that
   may take on values larger than the maximum 16-bit unsigned int.

   The library has always assumed that a char is 8 bits, a short
   is 16 bits, an int is 16 or 32 bits, and a long is 32 bits.
   Unfortunately, this assumption remains on machines where a long
   can hold 64-bits, and many functions and structures require
   unnecessarily large fields to avoid breaking compatibility with
   existing code. Special care must be taken with arrays of values
   that are transmitted in the protocol as CARD32 or INT32 but
   have to be converted to arrays of 64-bit long when passed to or
   from client applications.

   The PackData macro is a half-hearted attempt to deal with the
   possibility of 32 bit shorts. However, much more work is needed
   to make this work properly.

Deriving the Correct Extension Opcode

   The remaining problem a writer of an extension stub procedure
   faces that the core protocol does not face is to map from the
   call to the proper major and minor opcodes. While there are a
   number of strategies, the simplest and fastest is outlined
   below.
     * Declare an array of pointers, _NFILE long (this is normally
       found in <stdio.h> and is the number of file descriptors
       supported on the system) of type XExtCodes. Make sure these
       are all initialized to NULL.
     * When your stub is entered, your initialization test is just
       to use the display pointer passed in to access the file
       descriptor and an index into the array. If the entry is
       NULL, then this is the first time you are entering the
       procedure for this display. Call your initialization
       procedure and pass to it the display pointer.
     * Once in your initialization procedure, call XInitExtension;
       if it succeeds, store the pointer returned into this array.
       Make sure to establish a close display handler to allow you
       to zero the entry. Do whatever other initialization your
       extension requires. (For example, install event handlers
       and so on.) Your initialization procedure would normally
       return a pointer to the XExtCodes structure for this
       extension, which is what would normally be found in your
       array of pointers.
     * After returning from your initialization procedure, the
       stub can now continue normally, because it has its major
       opcode safely in its hand in the XExtCodes structure.

Appendix D. Compatibility Functions

   Table of Contents

   X Version 11 Compatibility Functions

        Setting Standard Properties
        Setting and Getting Window Sizing Hints
        Getting and Setting an XStandardColormap Structure
        Parsing Window Geometry
        Getting the X Environment Defaults

   X Version 10 Compatibility Functions

        Drawing and Filling Polygons and Curves
        Associating User Data with a Value

   The X Version 11 and X Version 10 functions discussed in this
   appendix are obsolete, have been superseded by newer X Version
   11 functions, and are maintained for compatibility reasons
   only.

X Version 11 Compatibility Functions

   You can use the X Version 11 compatibility functions to:
     * Set standard properties
     * Set and get window sizing hints
     * Set and get an XStandardColormap structure
     * Parse window geometry
     * Get X environment defaults

Setting Standard Properties

   To specify a minimum set of properties describing the simplest
   application, use XSetStandardProperties. This function has been
   superseded by XSetWMProperties and sets all or portions of the
   WM_NAME, WM_ICON_NAME, WM_HINTS, WM_COMMAND, and
   WM_NORMAL_HINTS properties.

   XSetStandardProperties(Display *display, Window w, char
   *window_name, char *icon_name, Pixmap icon_pixmap, char **argv,
   int argc, XSizeHints *hints);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   window_name

   Specifies the window name, which should be a null-terminated
   string.

   icon_name

   Specifies the icon name, which should be a null-terminated
   string.

   icon_pixmap

   Specifies the bitmap that is to be used for the icon or None.

   argv

   Specifies the application's argument list.

   argc

   Specifies the number of arguments.

   hints

   Specifies a pointer to the size hints for the window in its
   normal state.

   The XSetStandardProperties function provides a means by which
   simple applications set the most essential properties with a
   single call. XSetStandardProperties should be used to give a
   window manager some information about your program's
   preferences. It should not be used by applications that need to
   communicate more information than is possible with
   XSetStandardProperties. (Typically, argv is the argv array of
   your main program.) If the strings are not in the Host Portable
   Character Encoding, the result is implementation-dependent.

   XSetStandardProperties can generate BadAlloc and BadWindow
   errors.

Setting and Getting Window Sizing Hints

   Xlib provides functions that you can use to set or get window
   sizing hints. The functions discussed in this section use the
   flags and the XSizeHints structure, as defined in the
   <X11/Xutil.h> header file and use the WM_NORMAL_HINTS property.

   To set the size hints for a given window in its normal state,
   use XSetNormalHints. This function has been superseded by
   XSetWMNormalHints.

   XSetNormalHints(Display *display, Window w, XSizeHints *hints);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   hints

   Specifies a pointer to the size hints for the window in its
   normal state.

   The XSetNormalHints function sets the size hints structure for
   the specified window. Applications use XSetNormalHints to
   inform the window manager of the size or position desirable for
   that window. In addition, an application that wants to move or
   resize itself should call XSetNormalHints and specify its new
   desired location and size as well as making direct Xlib calls
   to move or resize. This is because window managers may ignore
   redirected configure requests, but they pay attention to
   property changes.

   To set size hints, an application not only must assign values
   to the appropriate members in the hints structure but also must
   set the flags member of the structure to indicate which
   information is present and where it came from. A call to
   XSetNormalHints is meaningless, unless the flags member is set
   to indicate which members of the structure have been assigned
   values.

   XSetNormalHints can generate BadAlloc and BadWindow errors.

   To return the size hints for a window in its normal state, use
   XGetNormalHints. This function has been superseded by
   XGetWMNormalHints.

   Status XGetNormalHints(Display *display, Window w, XSizeHints
   *hints_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   hints_return

   Returns the size hints for the window in its normal state.

   The XGetNormalHints function returns the size hints for a
   window in its normal state. It returns a nonzero status if it
   succeeds or zero if the application specified no normal size
   hints for this window.

   XGetNormalHints can generate a BadWindow error.

   The next two functions set and read the WM_ZOOM_HINTS property.

   To set the zoom hints for a window, use XSetZoomHints. This
   function is no longer supported by the Inter-Client
   Communication Conventions Manual.

   XSetZoomHints(Display *display, Window w, XSizeHints *zhints);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   zhints

   Specifies a pointer to the zoom hints.

   Many window managers think of windows in one of three states:
   iconic, normal, or zoomed. The XSetZoomHints function provides
   the window manager with information for the window in the
   zoomed state.

   XSetZoomHints can generate BadAlloc and BadWindow errors.

   To read the zoom hints for a window, use XGetZoomHints. This
   function is no longer supported by the Inter-Client
   Communication Conventions Manual.

   Status XGetZoomHints(Display *display, Window w, XSizeHints
   *zhints_return);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   zhints_return

   Returns the zoom hints.

   The XGetZoomHints function returns the size hints for a window
   in its zoomed state. It returns a nonzero status if it succeeds
   or zero if the application specified no zoom size hints for
   this window.

   XGetZoomHints can generate a BadWindow error.

   To set the value of any property of type WM_SIZE_HINTS, use
   XSetSizeHints. This function has been superseded by
   XSetWMSizeHints.

   XSetSizeHints(Display *display, Window w, XSizeHints *hints,
   Atom property);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   hints

   Specifies a pointer to the size hints.

   property

   Specifies the property name.

   The XSetSizeHints function sets the XSizeHints structure for
   the named property and the specified window. This is used by
   XSetNormalHints and XSetZoomHints and can be used to set the
   value of any property of type WM_SIZE_HINTS. Thus, it may be
   useful if other properties of that type get defined.

   XSetSizeHints can generate BadAlloc, BadAtom, and BadWindow
   errors.

   To read the value of any property of type WM_SIZE_HINTS, use
   XGetSizeHints. This function has been superseded by
   XGetWMSizeHints.

   Status XGetSizeHints(Display *display, Window w, XSizeHints
   *hints_return, Atom property);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   hints_return

   Returns the size hints.

   property

   Specifies the property name.

   The XGetSizeHints function returns the XSizeHints structure for
   the named property and the specified window. This is used by
   XGetNormalHints and XGetZoomHints. It also can be used to
   retrieve the value of any property of type WM_SIZE_HINTS. Thus,
   it may be useful if other properties of that type get defined.
   XGetSizeHints returns a nonzero status if a size hint was
   defined or zero otherwise.

   XGetSizeHints can generate BadAtom and BadWindow errors.

Getting and Setting an XStandardColormap Structure

   To get the XStandardColormap structure associated with one of
   the described atoms, use XGetStandardColormap. This function
   has been superseded by XGetRGBColormaps.

   Status XGetStandardColormap(Display *display, Window w,
   XStandardColormap *colormap_return, Atom property);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   colormap_return

   Returns the colormap associated with the specified atom.

   property

   Specifies the property name.

   The XGetStandardColormap function returns the colormap
   definition associated with the atom supplied as the property
   argument. XGetStandardColormap returns a nonzero status if
   successful and zero otherwise. For example, to fetch the
   standard GrayScale colormap for a display, you use
   XGetStandardColormap with the following syntax:
XGetStandardColormap(dpy, DefaultRootWindow(dpy), &cmap, XA_RGB_GRAY_MAP
);

   See section 14.3 for the semantics of standard colormaps.

   XGetStandardColormap can generate BadAtom and BadWindow errors.

   To set a standard colormap, use XSetStandardColormap. This
   function has been superseded by XSetRGBColormaps.

   XSetStandardColormap(Display *display, Window w,
   XStandardColormap *colormap, Atom property);

   display

   Specifies the connection to the X server.

   w

   Specifies the window.

   colormap

   Specifies the colormap.

   property

   Specifies the property name.

   The XSetStandardColormap function usually is only used by
   window or session managers.

   XSetStandardColormap can generate BadAlloc, BadAtom,
   BadDrawable, and BadWindow errors.

Parsing Window Geometry

   To parse window geometry given a user-specified position and a
   default position, use XGeometry. This function has been
   superseded by XWMGeometry.

   int XGeometry(Display *display, int screen, char *position,
   char *default_position, unsigned int bwidth, unsigned int
   fwidth, unsigned int fheight, int xadder, int yadder, int
   *x_return, int *y_return, int *width_return, int
   *height_return);

   display

   Specifies the connection to the X server.

   screen

   Specifies the screen.

   position

   default_position

   Specify the geometry specifications.

   bwidth

   Specifies the border width.

   fheight

   fwidth

   Specify the font height and width in pixels (increment size).

   xadder

   yadder

   Specify additional interior padding needed in the window.

   x_return

   y_return

   Return the x and y offsets.

   width_return

   height_return

   Return the width and height determined.

   You pass in the border width (bwidth), size of the increments
   fwidth and fheight (typically font width and height), and any
   additional interior space (xadder and yadder) to make it easy
   to compute the resulting size. The XGeometry function returns
   the position the window should be placed given a position and a
   default position. XGeometry determines the placement of a
   window using a geometry specification as specified by
   XParseGeometry and the additional information about the window.
   Given a fully qualified default geometry specification and an
   incomplete geometry specification, XParseGeometry returns a
   bitmask value as defined above in the XParseGeometry call, by
   using the position argument.

   The returned width and height will be the width and height
   specified by default_position as overridden by any
   user-specified position. They are not affected by fwidth,
   fheight, xadder, or yadder. The x and y coordinates are
   computed by using the border width, the screen width and
   height, padding as specified by xadder and yadder, and the
   fheight and fwidth times the width and height from the geometry
   specifications.

Getting the X Environment Defaults

   The XGetDefault function provides a primitive interface to the
   resource manager facilities discussed in chapter 15. It is only
   useful in very simple applications.

   char *XGetDefault(Display *display, char *program, char
   *option);

   display

   Specifies the connection to the X server.

   program

   Specifies the program name for the Xlib defaults (usually
   argv[0] of the main program).

   option

   Specifies the option name.

   The XGetDefault function returns the value of the resource
   prog.option, where prog is the program argument with the
   directory prefix removed and option must be a single component.
   Note that multilevel resources cannot be used with XGetDefault.
   The class "Program.Name" is always used for the resource
   lookup. If the specified option name does not exist for this
   program, XGetDefault returns NULL. The strings returned by
   XGetDefault are owned by Xlib and should not be modified or
   freed by the client.

   If a database has been set with XrmSetDatabase, that database
   is used for the lookup. Otherwise, a database is created and is
   set in the display (as if by calling XrmSetDatabase). The
   database is created in the current locale. To create a
   database, XGetDefault uses resources from the RESOURCE_MANAGER
   property on the root window of screen zero. If no such property
   exists, a resource file in the user's home directory is used.
   On a POSIX-conformant system, this file is "$HOME/.Xdefaults".
   After loading these defaults, XGetDefault merges additional
   defaults specified by the XENVIRONMENT environment variable. If
   XENVIRONMENT is defined, it contains a full path name for the
   additional resource file. If XENVIRONMENT is not defined,
   XGetDefault looks for "$HOME/.Xdefaults-name" , where name
   specifies the name of the machine on which the application is
   running.

X Version 10 Compatibility Functions

   You can use the X Version 10 compatibility functions to:
     * Draw and fill polygons and curves
     * Associate user data with a value

Drawing and Filling Polygons and Curves

   Xlib provides functions that you can use to draw or fill
   arbitrary polygons or curves. These functions are provided
   mainly for compatibility with X Version 10 and have no server
   support. That is, they call other Xlib functions, not the
   server directly. Thus, if you just have straight lines to draw,
   using XDrawLines or XDrawSegments is much faster.

   The functions discussed here provide all the functionality of
   the X Version 10 functions XDraw, XDrawFilled, XDrawPatterned,
   XDrawDashed, and XDrawTiled. They are as compatible as possible
   given X Version 11's new line-drawing functions. One thing to
   note, however, is that VertexDrawLastPoint is no longer
   supported. Also, the error status returned is the opposite of
   what it was under X Version 10 (this is the X Version 11
   standard error status). XAppendVertex and XClearVertexFlag from
   X Version 10 also are not supported.

   Just how the graphics context you use is set up actually
   determines whether you get dashes or not, and so on. Lines are
   properly joined if they connect and include the closing of a
   closed figure (see XDrawLines). The functions discussed here
   fail (return zero) only if they run out of memory or are passed
   a Vertex list that has a Vertex with VertexStartClosed set that
   is not followed by a Vertex with VertexEndClosed set.

   To achieve the effects of the X Version 10 XDraw, XDrawDashed,
   and XDrawPatterned, use XDraw.

   #include <X11/X10.h>

   Status XDraw(Display *display, Drawable d, GC gc, Vertex
   *vlist, int vcount);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   vlist

   Specifies a pointer to the list of vertices that indicate what
   to draw.

   vcount

   Specifies how many vertices are in vlist.

   The XDraw function draws an arbitrary polygon or curve. The
   figure drawn is defined by the specified list of vertices
   (vlist). The points are connected by lines as specified in the
   flags in the vertex structure.

   Each Vertex, as defined in <X11/X10.h>, is a structure with the
   following members:
typedef struct _Vertex {
        short x,y;
        unsigned short flags;
} Vertex;

   The x and y members are the coordinates of the vertex that are
   relative to either the upper left inside corner of the drawable
   (if VertexRelative is zero) or the previous vertex (if
   VertexRelative is one).

   The flags, as defined in <X11/X10.h>, are as follows:
VertexRelative     0x0001     /* else absolute */
VertexDontDraw     0x0002     /* else draw */
VertexCurved       0x0004     /* else straight */
VertexStartClosed  0x0008     /* else not */
VertexEndClosed    0x0010     /* else not */

     * If VertexRelative is not set, the coordinates are absolute
       (that is, relative to the drawable's origin). The first
       vertex must be an absolute vertex.
     * If VertexDontDraw is one, no line or curve is drawn from
       the previous vertex to this one. This is analogous to
       picking up the pen and moving to another place before
       drawing another line.
     * If VertexCurved is one, a spline algorithm is used to draw
       a smooth curve from the previous vertex through this one to
       the next vertex. Otherwise, a straight line is drawn from
       the previous vertex to this one. It makes sense to set
       VertexCurved to one only if a previous and next vertex are
       both defined (either explicitly in the array or through the
       definition of a closed curve).
     * It is permissible for VertexDontDraw bits and VertexCurved
       bits both to be one. This is useful if you want to define
       the previous point for the smooth curve but do not want an
       actual curve drawing to start until this point.
     * If VertexStartClosed is one, then this point marks the
       beginning of a closed curve. This vertex must be followed
       later in the array by another vertex whose effective
       coordinates are identical and that has a VertexEndClosed
       bit of one. The points in between form a cycle to determine
       predecessor and successor vertices for the spline
       algorithm.

   This function uses these GC components: function, plane-mask,
   line-width, line-style, cap-style, join-style, fill-style,
   subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask. It
   also uses these GC mode-dependent components: foreground,
   background, tile, stipple, tile-stipple-x-origin,
   tile-stipple-y-origin, dash-offset, and dash-list.

   To achieve the effects of the X Version 10 XDrawTiled and
   XDrawFilled, use XDrawFilled.

   #include <X11/X10.h>

   Status XDrawFilled(Display *display, Drawable d, GC gc, Vertex
   *vlist, int vcount);

   display

   Specifies the connection to the X server.

   d

   Specifies the drawable.

   gc

   Specifies the GC.

   vlist

   Specifies a pointer to the list of vertices that indicate what
   to draw.

   vcount

   Specifies how many vertices are in vlist.

   The XDrawFilled function draws arbitrary polygons or curves and
   then fills them.

   This function uses these GC components: function, plane-mask,
   line-width, line-style, cap-style, join-style, fill-style,
   subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask. It
   also uses these GC mode-dependent components: foreground,
   background, tile, stipple, tile-stipple-x-origin,
   tile-stipple-y-origin, dash-offset, dash-list, fill-style, and
   fill-rule.

Associating User Data with a Value

   These functions have been superseded by the context management
   functions (see section 16.10). It is often necessary to
   associate arbitrary information with resource IDs. Xlib
   provides the XAssocTable functions that you can use to make
   such an association. Application programs often need to be able
   to easily refer to their own data structures when an event
   arrives. The XAssocTable system provides users of the X library
   with a method for associating their own data structures with X
   resources (Pixmaps, Fonts, Windows, and so on).

   An XAssocTable can be used to type X resources. For example,
   the user may want to have three or four types of windows, each
   with different properties. This can be accomplished by
   associating each X window ID with a pointer to a window
   property data structure defined by the user. A generic type has
   been defined in the X library for resource IDs. It is called an
   XID.

   There are a few guidelines that should be observed when using
   an XAssocTable :
     * All XIDs are relative to the specified display.
     * Because of the hashing scheme used by the association
       mechanism, the following rules for determining the size of
       a XAssocTable should be followed. Associations will be made
       and looked up more efficiently if the table size (number of
       buckets in the hashing system) is a power of two and if
       there are not more than 8 XIDs per bucket.

   To return a pointer to a new XAssocTable, use
   XCreateAssocTable.

   XAssocTable *XCreateAssocTable(int size);

   size

   Specifies the number of buckets in the hash system of
   XAssocTable.

   The size argument specifies the number of buckets in the hash
   system of XAssocTable. For reasons of efficiency the number of
   buckets should be a power of two. Some size suggestions might
   be: use 32 buckets per 100 objects, and a reasonable maximum
   number of objects per buckets is 8. If an error allocating
   memory for the XAssocTable occurs, a NULL pointer is returned.

   To create an entry in a given XAssocTable, use XMakeAssoc.

   XMakeAssoc(Display *display, XAssocTable *table, XID x_id, char
   *data);

   display

   Specifies the connection to the X server.

   table

   Specifies the assoc table.

   x_id

   Specifies the X resource ID.

   data

   Specifies the data to be associated with the X resource ID.

   The XMakeAssoc function inserts data into an XAssocTable keyed
   on an XID. Data is inserted into the table only once. Redundant
   inserts are ignored. The queue in each association bucket is
   sorted from the lowest XID to the highest XID.

   To obtain data from a given XAssocTable, use XLookUpAssoc.

   char *XLookUpAssoc(Display *display, XAssocTable *table, XID
   x_id);

   display

   Specifies the connection to the X server.

   table

   Specifies the assoc table.

   x_id

   Specifies the X resource ID.

   The XLookUpAssoc function retrieves the data stored in an
   XAssocTable by its XID. If an appropriately matching XID can be
   found in the table, XLookUpAssoc returns the data associated
   with it. If the x_id cannot be found in the table, it returns
   NULL.

   To delete an entry from a given XAssocTable, use XDeleteAssoc.

   XDeleteAssoc(Display *display, XAssocTable *table, XID x_id);

   display

   Specifies the connection to the X server.

   table

   Specifies the assoc table.

   x_id

   Specifies the X resource ID.

   The XDeleteAssoc function deletes an association in an
   XAssocTable keyed on its XID. Redundant deletes (and deletes of
   nonexistent XIDs) are ignored. Deleting associations in no way
   impairs the performance of an XAssocTable.

   To free the memory associated with a given XAssocTable, use
   XDestroyAssocTable.

   XDestroyAssocTable(XAssocTable *table);

   table

   Specifies the assoc table.

Glossary

   Access control list
          X maintains a list of hosts from which client programs
          can be run. By default, only programs on the local host
          and hosts specified in an initial list read by the
          server can use the display. This access control list can
          be changed by clients on the local host. Some server
          implementations can also implement other authorization
          mechanisms in addition to or in place of this mechanism.
          The action of this mechanism can be conditional based on
          the authorization protocol name and data received by the
          server at connection setup.

   Active grab
          A grab is active when the pointer or keyboard is
          actually owned by the single grabbing client.

   Ancestors
          If W is an inferior of A, then A is an ancestor of W.

   Atom
          An atom is a unique ID corresponding to a string name.
          Atoms are used to identify properties, types, and
          selections.

   Background
          An InputOutput window can have a background, which is
          defined as a pixmap. When regions of the window have
          their contents lost or invalidated, the server
          automatically tiles those regions with the background.

   Backing store
          When a server maintains the contents of a window, the
          pixels saved off-screen are known as a backing store.

   Base font name
          A font name used to select a family of fonts whose
          members may be encoded in various charsets. The
          CharSetRegistry and CharSetEncoding fields of an XLFD
          name identify the charset of the font. A base font name
          may be a full XLFD name, with all fourteen '-'
          delimiters, or an abbreviated XLFD name containing only
          the first 12 fields of an XLFD name, up to but not
          including CharSetRegistry, with or without the
          thirteenth '-', or a non-XLFD name. Any XLFD fields may
          contain wild cards.

          When creating an XFontSet, Xlib accepts from the client
          a list of one or more base font names which select one
          or more font families. They are combined with charset
          names obtained from the encoding of the locale to load
          the fonts required to render text.

   Bit gravity
          When a window is resized, the contents of the window are
          not necessarily discarded. It is possible to request
          that the server relocate the previous contents to some
          region of the window (though no guarantees are made).
          This attraction of window contents for some location of
          a window is known as bit gravity.

   Bit plane
          When a pixmap or window is thought of as a stack of
          bitmaps, each bitmap is called a bit plane or plane.

   Bitmap
          A bitmap is a pixmap of depth one.

   Border
          An InputOutput window can have a border of equal
          thickness on all four sides of the window. The contents
          of the border are defined by a pixmap, and the server
          automatically maintains the contents of the border.
          Exposure events are never generated for border regions.

   Button grabbing
          Buttons on the pointer can be passively grabbed by a
          client. When the button is pressed, the pointer is then
          actively grabbed by the client.

   Byte order
          For image (pixmap/bitmap) data, the server defines the
          byte order, and clients with different native byte
          ordering must swap bytes as necessary. For all other
          parts of the protocol, the client defines the byte
          order, and the server swaps bytes as necessary.

   Character
          A member of a set of elements used for the organization,
          control, or representation of text (ISO2022, as adapted
          by XPG3). Note that in ISO2022 terms, a character is not
          bound to a coded value until it is identified as part of
          a coded character set.

   Character glyph
          The abstract graphical symbol for a character. Character
          glyphs may or may not map one-to-one to font glyphs, and
          may be context-dependent, varying with the adjacent
          characters. Multiple characters may map to a single
          character glyph.

   Character set
          A collection of characters.

   Charset
          An encoding with a uniform, state-independent mapping
          from characters to codepoints. A coded character set.

          For display in X, there can be a direct mapping from a
          charset to one font, if the width of all characters in
          the charset is either one or two bytes. A text string
          encoded in an encoding such as Shift-JIS cannot be
          passed directly to the X server, because the text
          imaging requests accept only single-width charsets
          (either 8 or 16 bits). Charsets which meet these
          restrictions can serve as ``font charsets''. Font
          charsets strictly speaking map font indices to font
          glyphs, not characters to character glyphs.

          Note that a single font charset is sometimes used as the
          encoding of a locale, for example, ISO8859-1.

   Children
          The children of a window are its first-level subwindows.

   Class
          Windows can be of different classes or types. See the
          entries for InputOnly and InputOutput windows for
          further information about valid window types.

   Client
          An application program connects to the window system
          server by some interprocess communication (IPC) path,
          such as a TCP connection or a shared memory buffer. This
          program is referred to as a client of the window system
          server. More precisely, the client is the IPC path
          itself. A program with multiple paths open to the server
          is viewed as multiple clients by the protocol. Resource
          lifetimes are controlled by connection lifetimes, not by
          program lifetimes.

   Clipping region
          In a graphics context, a bitmap or list of rectangles
          can be specified to restrict output to a particular
          region of the window. The image defined by the bitmap or
          rectangles is called a clipping region.

   Coded character
          A character bound to a codepoint.

   Coded character set
          A set of unambiguous rules that establishes a character
          set and the one-to-one relationship between each
          character of the set and its bit representation.
          (ISO2022, as adapted by XPG3) A definition of a
          one-to-one mapping of a set of characters to a set of
          codepoints.

   Codepoint
          The coded representation of a single character in a
          coded character set.

   Colormap
          A colormap consists of a set of entries defining color
          values. The colormap associated with a window is used to
          display the contents of the window; each pixel value
          indexes the colormap to produce an RGB value that drives
          the guns of a monitor. Depending on hardware
          limitations, one or more colormaps can be installed at
          one time so that windows associated with those maps
          display with true colors.

   Connection
          The IPC path between the server and client program is
          known as a connection. A client program typically (but
          not necessarily) has one connection to the server over
          which requests and events are sent.

   Containment
          A window contains the pointer if the window is viewable
          and the hotspot of the cursor is within a visible region
          of the window or a visible region of one of its
          inferiors. The border of the window is included as part
          of the window for containment. The pointer is in a
          window if the window contains the pointer but no
          inferior contains the pointer.

   Coordinate system
          The coordinate system has X horizontal and Y vertical,
          with the origin [0, 0] at the upper left. Coordinates
          are integral and coincide with pixel centers. Each
          window and pixmap has its own coordinate system. For a
          window, the origin is inside the border at the inside
          upper-left corner.

   Cursor
          A cursor is the visible shape of the pointer on a
          screen. It consists of a hotspot, a source bitmap, a
          shape bitmap, and a pair of colors. The cursor defined
          for a window controls the visible appearance when the
          pointer is in that window.

   Depth
          The depth of a window or pixmap is the number of bits
          per pixel it has. The depth of a graphics context is the
          depth of the drawables it can be used in conjunction
          with graphics output.

   Device
          Keyboards, mice, tablets, track-balls, button boxes, and
          so on are all collectively known as input devices.
          Pointers can have one or more buttons (the most common
          number is three). The core protocol only deals with two
          devices: the keyboard and the pointer.

   DirectColor
          DirectColor is a class of colormap in which a pixel
          value is decomposed into three separate subfields for
          indexing. The first subfield indexes an array to produce
          red intensity values. The second subfield indexes a
          second array to produce blue intensity values. The third
          subfield indexes a third array to produce green
          intensity values. The RGB (red, green, and blue) values
          in the colormap entry can be changed dynamically.

   Display
          A server, together with its screens and input devices,
          is called a display. The Xlib Display structure contains
          all information about the particular display and its
          screens as well as the state that Xlib needs to
          communicate with the display over a particular
          connection.

   Drawable
          Both windows and pixmaps can be used as sources and
          destinations in graphics operations. These windows and
          pixmaps are collectively known as drawables. However, an
          InputOnly window cannot be used as a source or
          destination in a graphics operation.

   Encoding
          A set of unambiguous rules that establishes a character
          set and a relationship between the characters and their
          representations. The character set does not have to be
          fixed to a finite pre-defined set of characters. The
          representations do not have to be of uniform length.
          Examples are an ISO2022 graphic set, a state-independent
          or state-dependent combination of graphic sets, possibly
          including control sets, and the X Compound Text
          encoding.

          In X, encodings are identified by a string which appears
          as: the CharSetRegistry and CharSetEncoding components
          of an XLFD name; the name of a charset of the locale for
          which a font could not be found; or an atom which
          identifies the encoding of a text property or which
          names an encoding for a text selection target type.
          Encoding names should be composed of characters from the
          X Portable Character Set.

   Escapement
          The escapement of a string is the distance in pixels in
          the primary draw direction from the drawing origin to
          the origin of the next character (that is, the one
          following the given string) to be drawn.

   Event
          Clients are informed of information asynchronously by
          means of events. These events can be either
          asynchronously generated from devices or generated as
          side effects of client requests. Events are grouped into
          types. The server never sends an event to a client
          unless the client has specifically asked to be informed
          of that type of event. However, clients can force events
          to be sent to other clients. Events are typically
          reported relative to a window.

   Event mask
          Events are requested relative to a window. The set of
          event types a client requests relative to a window is
          described by using an event mask.

   Event propagation
          Device-related events propagate from the source window
          to ancestor windows until some client has expressed
          interest in handling that type of event or until the
          event is discarded explicitly.

   Event source
          The deepest viewable window that the pointer is in is
          called the source of a device-related event.

   Event synchronization
          There are certain race conditions possible when
          demultiplexing device events to clients (in particular,
          deciding where pointer and keyboard events should be
          sent when in the middle of window management
          operations). The event synchronization mechanism allows
          synchronous processing of device events.

   Exposure event
          Servers do not guarantee to preserve the contents of
          windows when windows are obscured or reconfigured.
          Exposure events are sent to clients to inform them when
          contents of regions of windows have been lost.

   Extension
          Named extensions to the core protocol can be defined to
          extend the system. Extensions to output requests,
          resources, and event types are all possible and
          expected.

   Font
          A font is an array of glyphs (typically characters). The
          protocol does no translation or interpretation of
          character sets. The client simply indicates values used
          to index the glyph array. A font contains additional
          metric information to determine interglyph and interline
          spacing.

   Font glyph
          The abstract graphical symbol for an index into a font.

   Frozen events
          Clients can freeze event processing during keyboard and
          pointer grabs.

   GC
          GC is an abbreviation for graphics context. See Graphics
          context.

   Glyph
          An identified abstract graphical symbol independent of
          any actual image. (ISO/IEC/DIS 9541-1) An abstract
          visual representation of a graphic character, not bound
          to a codepoint.

   Glyph image
          An image of a glyph, as obtained from a glyph
          representation displayed on a presentation surface.
          (ISO/IEC/DIS 9541-1)

   Grab
          Keyboard keys, the keyboard, pointer buttons, the
          pointer, and the server can be grabbed for exclusive use
          by a client. In general, these facilities are not
          intended to be used by normal applications but are
          intended for various input and window managers to
          implement various styles of user interfaces.

   Graphics context
          Various information for graphics output is stored in a
          graphics context (GC), such as foreground pixel,
          background pixel, line width, clipping region, and so
          on. A graphics context can only be used with drawables
          that have the same root and the same depth as the
          graphics context.

   Gravity
          The contents of windows and windows themselves have a
          gravity, which determines how the contents move when a
          window is resized. See Bit gravity and Window gravity.

   GrayScale
          GrayScale can be viewed as a degenerate case of
          PseudoColor, in which the red, green, and blue values in
          any given colormap entry are equal and thus, produce
          shades of gray. The gray values can be changed
          dynamically.

   Host Portable Character Encoding
          The encoding of the X Portable Character Set on the
          host. The encoding itself is not defined by this
          standard, but the encoding must be the same in all
          locales supported by Xlib on the host. If a string is
          said to be in the Host Portable Character Encoding, then
          it only contains characters from the X Portable
          Character Set, in the host encoding.

   Hotspot
          A cursor has an associated hotspot, which defines the
          point in the cursor corresponding to the coordinates
          reported for the pointer.

   Identifier
          An identifier is a unique value associated with a
          resource that clients use to name that resource. The
          identifier can be used over any connection to name the
          resource.

   Inferiors
          The inferiors of a window are all of the subwindows
          nested below it: the children, the children's children,
          and so on.

   Input focus
          The input focus is usually a window defining the scope
          for processing of keyboard input. If a generated
          keyboard event usually would be reported to this window
          or one of its inferiors, the event is reported as usual.
          Otherwise, the event is reported with respect to the
          focus window. The input focus also can be set such that
          all keyboard events are discarded and such that the
          focus window is dynamically taken to be the root window
          of whatever screen the pointer is on at each keyboard
          event.

   Input manager
          Control over keyboard input is typically provided by an
          input manager client, which usually is part of a window
          manager.

   InputOnly window
          An InputOnly window is a window that cannot be used for
          graphics requests. InputOnly windows are invisible and
          are used to control such things as cursors, input event
          generation, and grabbing. InputOnly windows cannot have
          InputOutput windows as inferiors.

   InputOutput window
          An InputOutput window is the normal kind of window that
          is used for both input and output. InputOutput windows
          can have both InputOutput and InputOnly windows as
          inferiors.

   Internationalization
          The process of making software adaptable to the
          requirements of different native languages, local
          customs, and character string encodings. Making a
          computer program adaptable to different locales without
          program source modifications or recompilation.

   ISO2022
          ISO standard for code extension techniques for 7-bit and
          8-bit coded character sets.

   Key grabbing
          Keys on the keyboard can be passively grabbed by a
          client. When the key is pressed, the keyboard is then
          actively grabbed by the client.

   Keyboard grabbing
          A client can actively grab control of the keyboard, and
          key events will be sent to that client rather than the
          client the events would normally have been sent to.

   Keysym
          An encoding of a symbol on a keycap on a keyboard.

   Latin-1
          The coded character set defined by the ISO8859-1
          standard.

   Latin Portable Character Encoding
          The encoding of the X Portable Character Set using the
          Latin-1 codepoints plus ASCII control characters. If a
          string is said to be in the Latin Portable Character
          Encoding, then it only contains characters from the X
          Portable Character Set, not all of Latin-1.

   Locale
          The international environment of a computer program
          defining the ``localized'' behavior of that program at
          run-time. This information can be established from one
          or more sets of localization data. ANSI C defines
          locale-specific processing by C system library calls.
          See ANSI C and the X/Open Portability Guide
          specifications for more details. In this specification,
          on implementations that conform to the ANSI C library,
          the ``current locale'' is the current setting of the
          LC_CTYPE setlocale category. Associated with each locale
          is a text encoding. When text is processed in the
          context of a locale, the text must be in the encoding of
          the locale. The current locale affects Xlib in its:

          + Encoding and processing of input method text
          + Encoding of resource files and values
          + Encoding and imaging of text strings
          + Encoding and decoding for inter-client text
            communication

   Locale name
          The identifier used to select the desired locale for the
          host C library and X library functions. On ANSI C
          library compliant systems, the locale argument to the
          setlocale function.

   Localization
          The process of establishing information within a
          computer system specific to the operation of particular
          native languages, local customs and coded character
          sets. (XPG3)

   Mapped
          A window is said to be mapped if a map call has been
          performed on it. Unmapped windows and their inferiors
          are never viewable or visible.

   Modifier keys
          Shift, Control, Meta, Super, Hyper, Alt, Compose, Apple,
          CapsLock, ShiftLock, and similar keys are called
          modifier keys.

   Monochrome
          Monochrome is a special case of StaticGray in which
          there are only two colormap entries.

   Multibyte
          A character whose codepoint is stored in more than one
          byte; any encoding which can contain multibyte
          characters; text in a multibyte encoding. The ``char *''
          null-terminated string datatype in ANSI C. Note that
          references in this document to multibyte strings imply
          only that the strings may contain multibyte characters.

   Obscure
          A window is obscured if some other window obscures it. A
          window can be partially obscured and so still have
          visible regions. Window A obscures window B if both are
          viewable InputOutput windows, if A is higher in the
          global stacking order, and if the rectangle defined by
          the outside edges of A intersects the rectangle defined
          by the outside edges of B. Note the distinction between
          obscures and occludes. Also note that window borders are
          included in the calculation.

   Occlude
          A window is occluded if some other window occludes it.
          Window A occludes window B if both are mapped, if A is
          higher in the global stacking order, and if the
          rectangle defined by the outside edges of A intersects
          the rectangle defined by the outside edges of B. Note
          the distinction between occludes and obscures. Also note
          that window borders are included in the calculation and
          that InputOnly windows never obscure other windows but
          can occlude other windows.

   Padding
          Some padding bytes are inserted in the data stream to
          maintain alignment of the protocol requests on natural
          boundaries. This increases ease of portability to some
          machine architectures.

   Parent window
          If C is a child of P, then P is the parent of C.

   Passive grab
          Grabbing a key or button is a passive grab. The grab
          activates when the key or button is actually pressed.

   Pixel value
          A pixel is an N-bit value, where N is the number of bit
          planes used in a particular window or pixmap (that is,
          is the depth of the window or pixmap). A pixel in a
          window indexes a colormap to derive an actual color to
          be displayed.

   Pixmap
          A pixmap is a three-dimensional array of bits. A pixmap
          is normally thought of as a two-dimensional array of
          pixels, where each pixel can be a value from 0 to 2^N-1,
          and where N is the depth (z axis) of the pixmap. A
          pixmap can also be thought of as a stack of N bitmaps. A
          pixmap can only be used on the screen that it was
          created in.

   Plane
          When a pixmap or window is thought of as a stack of
          bitmaps, each bitmap is called a plane or bit plane.

   Plane mask
          Graphics operations can be restricted to only affect a
          subset of bit planes of a destination. A plane mask is a
          bit mask describing which planes are to be modified. The
          plane mask is stored in a graphics context.

   Pointer
          The pointer is the pointing device currently attached to
          the cursor and tracked on the screens.

   Pointer grabbing
          A client can actively grab control of the pointer. Then
          button and motion events will be sent to that client
          rather than the client the events would normally have
          been sent to.

   Pointing device
          A pointing device is typically a mouse, tablet, or some
          other device with effective dimensional motion. The core
          protocol defines only one visible cursor, which tracks
          whatever pointing device is attached as the pointer.

   POSIX
          Portable Operating System Interface, ISO/IEC 9945-1
          (IEEE Std 1003.1).

   POSIX Portable Filename Character Set
          The set of 65 characters which can be used in naming
          files on a POSIX-compliant host that are correctly
          processed in all locales. The set is:

          a..z A..Z 0..9 ._-

   Property
          Windows can have associated properties that consist of a
          name, a type, a data format, and some data. The protocol
          places no interpretation on properties. They are
          intended as a general-purpose naming mechanism for
          clients. For example, clients might use properties to
          share information such as resize hints, program names,
          and icon formats with a window manager.

   Property list
          The property list of a window is the list of properties
          that have been defined for the window.

   PseudoColor
          PseudoColor is a class of colormap in which a pixel
          value indexes the colormap entry to produce an
          independent RGB value; that is, the colormap is viewed
          as an array of triples (RGB values). The RGB values can
          be changed dynamically.

   Rectangle
          A rectangle specified by [x,y,w,h] has an infinitely
          thin outline path with corners at [x,y], [x+w,y],
          [x+w,y+h], and [x, y+h]. When a rectangle is filled, the
          lower-right edges are not drawn. For example, if w=h=0,
          nothing would be drawn. For w=h=1, a single pixel would
          be drawn.

   Redirecting control
          Window managers (or client programs) may enforce window
          layout policy in various ways. When a client attempts to
          change the size or position of a window, the operation
          may be redirected to a specified client rather than the
          operation actually being performed.

   Reply
          Information requested by a client program using the X
          protocol is sent back to the client with a reply. Both
          events and replies are multiplexed on the same
          connection. Most requests do not generate replies, but
          some requests generate multiple replies.

   Request
          A command to the server is called a request. It is a
          single block of data sent over a connection.

   Resource
          Windows, pixmaps, cursors, fonts, graphics contexts, and
          colormaps are known as resources. They all have unique
          identifiers associated with them for naming purposes.
          The lifetime of a resource usually is bounded by the
          lifetime of the connection over which the resource was
          created.

   RGB values
          RGB values are the red, green, and blue intensity values
          that are used to define a color. These values are always
          represented as 16-bit, unsigned numbers, with 0 the
          minimum intensity and 65535 the maximum intensity. The X
          server scales these values to match the display
          hardware.

   Root
          The root of a pixmap or graphics context is the same as
          the root of whatever drawable was used when the pixmap
          or GC was created. The root of a window is the root
          window under which the window was created.

   Root window
          Each screen has a root window covering it. The root
          window cannot be reconfigured or unmapped, but otherwise
          it acts as a full-fledged window. A root window has no
          parent.

   Save set
          The save set of a client is a list of other clients'
          windows that, if they are inferiors of one of the
          client's windows at connection close, should not be
          destroyed and that should be remapped if currently
          unmapped. Save sets are typically used by window
          managers to avoid lost windows if the manager should
          terminate abnormally.

   Scanline
          A scanline is a list of pixel or bit values viewed as a
          horizontal row (all values having the same y coordinate)
          of an image, with the values ordered by increasing the x
          coordinate.

   Scanline order
          An image represented in scanline order contains
          scanlines ordered by increasing the y coordinate.

   Screen
          A server can provide several independent screens, which
          typically have physically independent monitors. This
          would be the expected configuration when there is only a
          single keyboard and pointer shared among the screens. A
          Screen structure contains the information about that
          screen and is linked to the Display structure.

   Selection
          A selection can be thought of as an indirect property
          with dynamic type. That is, rather than having the
          property stored in the X server, it is maintained by
          some client (the owner). A selection is global and is
          thought of as belonging to the user and being maintained
          by clients, rather than being private to a particular
          window subhierarchy or a particular set of clients. When
          a client asks for the contents of a selection, it
          specifies a selection target type, which can be used to
          control the transmitted representation of the contents.
          For example, if the selection is ``the last thing the
          user clicked on,'' and that is currently an image, then
          the target type might specify whether the contents of
          the image should be sent in XY format or Z format.

          The target type can also be used to control the class of
          contents transmitted; for example, asking for the
          ``looks'' (fonts, line spacing, indentation, and so
          forth) of a paragraph selection, rather than the text of
          the paragraph. The target type can also be used for
          other purposes. The protocol does not constrain the
          semantics.

   Server
          The server, which is also referred to as the X server,
          provides the basic windowing mechanism. It handles IPC
          connections from clients, multiplexes graphics requests
          onto the screens, and demultiplexes input back to the
          appropriate clients.

   Server grabbing
          The server can be grabbed by a single client for
          exclusive use. This prevents processing of any requests
          from other client connections until the grab is
          completed. This is typically only a transient state for
          such things as rubber-banding, pop-up menus, or
          executing requests indivisibly.

   Shift sequence
          ISO2022 defines control characters and escape sequences
          which temporarily (single shift) or permanently (locking
          shift) cause a different character set to be in effect
          (``invoking'' a character set).

   Sibling
          Children of the same parent window are known as sibling
          windows.

   Stacking order
          Sibling windows, similar to sheets of paper on a desk,
          can stack on top of each other. Windows above both
          obscure and occlude lower windows. The relationship
          between sibling windows is known as the stacking order.

   State-dependent encoding
          An encoding in which an invocation of a charset can
          apply to multiple characters in sequence. A
          state-dependent encoding begins in an ``initial state''
          and enters other ``shift states'' when specific ``shift
          sequences'' are encountered in the byte sequence. In
          ISO2022 terms, this means use of locking shifts, not
          single shifts.

   State-independent encoding
          Any encoding in which the invocations of the charsets
          are fixed, or span only a single character. In ISO2022
          terms, this means use of at most single shifts, not
          locking shifts.

   StaticColor
          StaticColor can be viewed as a degenerate case of
          PseudoColor in which the RGB values are predefined and
          read-only.

   StaticGray
          StaticGray can be viewed as a degenerate case of
          GrayScale in which the gray values are predefined and
          read-only. The values are typically linear or
          near-linear increasing ramps.

   Status
          Many Xlib functions return a success status. If the
          function does not succeed, however, its arguments are
          not disturbed.

   Stipple
          A stipple pattern is a bitmap that is used to tile a
          region to serve as an additional clip mask for a fill
          operation with the foreground color.

   STRING encoding
          Latin-1, plus tab and newline.

   String Equivalence
          Two ISO Latin-1 STRING8 values are considered equal if
          they are the same length and if corresponding bytes are
          either equal or are equivalent as follows: decimal
          values 65 to 90 inclusive (characters ``A'' to ``Z'')
          are pairwise equivalent to decimal values 97 to 122
          inclusive (characters ``a'' to ``z''), decimal values
          192 to 214 inclusive (characters ``A grave'' to ``O
          diaeresis'') are pairwise equivalent to decimal values
          224 to 246 inclusive (characters ``a grave'' to ``o
          diaeresis''), and decimal values 216 to 222 inclusive
          (characters ``O oblique'' to ``THORN'') are pairwise
          equivalent to decimal values 246 to 254 inclusive
          (characters ``o oblique'' to ``thorn'').

   Tile
          A pixmap can be replicated in two dimensions to tile a
          region. The pixmap itself is also known as a tile.

   Timestamp
          A timestamp is a time value expressed in milliseconds.
          It is typically the time since the last server reset.
          Timestamp values wrap around (after about 49.7 days).
          The server, given its current time is represented by
          timestamp T, always interprets timestamps from clients
          by treating half of the timestamp space as being earlier
          in time than T and half of the timestamp space as being
          later in time than T. One timestamp value, represented
          by the constant CurrentTime, is never generated by the
          server. This value is reserved for use in requests to
          represent the current server time.

   TrueColor
          TrueColor can be viewed as a degenerate case of
          DirectColor in which the subfields in the pixel value
          directly encode the corresponding RGB values. That is,
          the colormap has predefined read-only RGB values. The
          values are typically linear or near-linear increasing
          ramps.

   Type
          A type is an arbitrary atom used to identify the
          interpretation of property data. Types are completely
          uninterpreted by the server. They are solely for the
          benefit of clients. X predefines type atoms for many
          frequently used types, and clients also can define new
          types.

   Viewable
          A window is viewable if it and all of its ancestors are
          mapped. This does not imply that any portion of the
          window is actually visible. Graphics requests can be
          performed on a window when it is not viewable, but
          output will not be retained unless the server is
          maintaining backing store.

   Visible
          A region of a window is visible if someone looking at
          the screen can actually see it; that is, the window is
          viewable and the region is not occluded by any other
          window.

   Whitespace
          Any spacing character. On implementations that conform
          to the ANSI C library, whitespace is any character for
          which isspace returns true.

   Window gravity
          When windows are resized, subwindows may be repositioned
          automatically relative to some position in the window.
          This attraction of a subwindow to some part of its
          parent is known as window gravity.

   Window manager
          Manipulation of windows on the screen and much of the
          user interface (policy) is typically provided by a
          window manager client.

   X Portable Character Set
          A basic set of 97 characters which are assumed to exist
          in all locales supported by Xlib. This set contains the
          following characters:

          a..z A..Z 0..9
          !"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~
          <space>, <tab>, and <newline>


          This is the left/lower half (also called the G0 set) of
          the graphic character set of ISO8859-1 plus <space>,
          <tab>, and <newline>. It is also the set of graphic
          characters in 7-bit ASCII plus the same three control
          characters. The actual encoding of these characters on
          the host is system dependent; see the Host Portable
          Character Encoding.

   XLFD
          The X Logical Font Description Conventions that define a
          standard syntax for structured font names.

   XY format
          The data for a pixmap is said to be in XY format if it
          is organized as a set of bitmaps representing individual
          bit planes with the planes appearing from
          most-significant to least-significant bit order.

   Z format
          The data for a pixmap is said to be in Z format if it is
          organized as a set of pixel values in scanline order.

Index

Symbols

   _XAllocScratch, Allocating and Deallocating Memory
   _XAllocTemp, Allocating and Deallocating Memory
   _Xdebug, Enabling or Disabling Synchronization
   _XFlushGCCache, GC Caching
   _XFreeTemp, Allocating and Deallocating Memory
   _XReply, Replies
   _XSetLastRequestRead, Hooks into the Library

A

   Access control list, Controlling Host Access, Glossary
   Active grab, Pointer Grabbing, Glossary
   Allocation

        colormap, Allocating and Freeing Color Cells
        read-only colormap cells, Allocating and Freeing Color
                Cells, Allocating and Freeing Color Cells,
                Allocating and Freeing Color Cells, Allocating and
                Freeing Color Cells

        read/write colormap cells, Allocating and Freeing Color
                Cells

        read/write colormap planes, Allocating and Freeing Color
                Cells

   AllPlanes, Display Macros
   Ancestors, Glossary
   Arcs

        drawing, Drawing Single and Multiple Arcs
        filling, Filling Single and Multiple Arcs

   Areas

        clearing, Clearing Areas
        copying, Copying Areas

   Atom, Properties and Atoms, Properties and Atoms, Glossary

        getting name, Properties and Atoms, Properties and Atoms
        interning, Properties and Atoms, Properties and Atoms
        predefined, Properties and Atoms

   Authentication, Controlling Host Access

B

   Background, Glossary
   Backing store, Glossary
   BadAccess, Using the Default Error Handlers
   BadAlloc, Using the Default Error Handlers
   BadAtom, Using the Default Error Handlers
   BadColor, Using the Default Error Handlers
   BadCursor, Using the Default Error Handlers
   BadDrawable, Using the Default Error Handlers
   BadFont, Using the Default Error Handlers
   BadGC, Using the Default Error Handlers
   BadIDChoice, Using the Default Error Handlers
   BadImplementation, Using the Default Error Handlers
   BadLength, Using the Default Error Handlers
   BadMatch, Using the Default Error Handlers
   BadName, Using the Default Error Handlers
   BadPixmap, Using the Default Error Handlers
   BadRequest, Using the Default Error Handlers
   BadValue, Using the Default Error Handlers
   BadWindow, Using the Default Error Handlers
   Base font name, Glossary
   Bit

        gravity, Glossary
        plane, Glossary

   Bitmap, Overview of the X Window System, Glossary
   BitmapBitOrder, Image Format Functions and Macros
   BitmapPad, Image Format Functions and Macros
   BitmapUnit, Image Format Functions and Macros
   BlackPixel, Display Macros
   BlackPixelOfScreen, Screen Information Macros
   Bool, Generic Values and Types
   Border, Glossary
   Button

        grabbing, Pointer Grabbing, Glossary
        ungrabbing, Pointer Grabbing

   ButtonPress, Keyboard and Pointer Events
   ButtonRelease, Keyboard and Pointer Events
   Byte

        order, Glossary

C

   CallbackPrototype, Input Method Callback Semantics
   CCC, Color Conversion Contexts and Gamut Mapping

        creation, Creating and Freeing a Color Conversion Context
        default, Color Conversion Contexts and Gamut Mapping,
                Color Conversion Context Functions, Obtaining the
                Default Color Conversion Context, Obtaining the
                Default Color Conversion Context

        freeing, Creating and Freeing a Color Conversion Context
        of colormap, Color Conversion Contexts and Gamut Mapping,
                Color Conversion Context Functions, Getting and
                Setting the Color Conversion Context of a
                Colormap, Getting and Setting the Color Conversion
                Context of a Colormap

   CellsOfScreen, Screen Information Macros
   Changing

        pointer grab, Pointer Grabbing

   Character, Glossary
   Character glyph, Glossary
   Character set, Glossary
   Charset, Glossary
   Child window, Overview of the X Window System
   Child Window, Obtaining Window Information
   Children, Glossary
   Chroma, TekHVC Queries, TekHVC Queries, TekHVC Queries

        maximum, TekHVC Queries, TekHVC Queries, TekHVC Queries

   CIE metric lightness, CIELab Queries, CIELab Queries, CIELab
          Queries, CIELab Queries, CIELuv Queries, CIELuv Queries,
          CIELuv Queries, CIELuv Queries

        maximum, CIELab Queries, CIELab Queries, CIELuv Queries,
                CIELuv Queries

        minimum, CIELab Queries, CIELuv Queries

   CirculateNotify, CirculateNotify Events
   CirculateRequest, CirculateRequest Events
   Class, Glossary
   Clearing

        areas, Clearing Areas
        windows, Clearing Areas

   Client, Glossary
   Client White Point, Color Conversion Contexts and Gamut Mapping

        of Color Conversion Context, Modifying Attributes of a
                Color Conversion Context

   ClientMessage, ClientMessage Events
   ClientWhitePointOfCCC, Color Conversion Context Macros
   Clipping region, Glossary
   Coded character, Glossary
   Coded character set, Glossary
   Codepoint, Glossary
   Color, Color Structures

        allocation, Allocating and Freeing Color Cells, Allocating
                and Freeing Color Cells, Allocating and Freeing
                Color Cells, Allocating and Freeing Color Cells,
                Allocating and Freeing Color Cells, Allocating and
                Freeing Color Cells, Allocating and Freeing Color
                Cells

        conversion, Converting between Color Spaces
        deallocation, Allocating and Freeing Color Cells
        naming, Mapping Color Names to Values, Mapping Color Names
                to Values, Mapping Color Names to Values,
                Allocating and Freeing Color Cells, Allocating and
                Freeing Color Cells, Modifying and Querying
                Colormap Cells

        querying, Modifying and Querying Colormap Cells, Modifying
                and Querying Colormap Cells, Modifying and
                Querying Colormap Cells, Modifying and Querying
                Colormap Cells

        storing, Modifying and Querying Colormap Cells, Modifying
                and Querying Colormap Cells, Modifying and
                Querying Colormap Cells, Modifying and Querying
                Colormap Cells, Modifying and Querying Colormap
                Cells

   Color Characterization Data, Creating Additional Function Sets
   Color conversion, Converting between Color Spaces
   Color Conversion Context, Color Conversion Contexts and Gamut
          Mapping

        creation, Color Conversion Contexts and Gamut Mapping,
                Color Conversion Context Functions, Creating and
                Freeing a Color Conversion Context

        default, Color Conversion Contexts and Gamut Mapping,
                Color Conversion Context Functions, Obtaining the
                Default Color Conversion Context, Obtaining the
                Default Color Conversion Context

        freeing, Creating and Freeing a Color Conversion Context
        of colormap, Color Conversion Contexts and Gamut Mapping,
                Color Conversion Context Functions, Getting and
                Setting the Color Conversion Context of a
                Colormap, Getting and Setting the Color Conversion
                Context of a Colormap

   Color map, Color Management Functions, Allocating and Freeing
          Color Cells

   Colormap, Glossary

        CCC of, Getting and Setting the Color Conversion Context
                of a Colormap, Getting and Setting the Color
                Conversion Context of a Colormap

   ColormapNotify, Colormap State Change Events
   Colormaps

        standard, Standard Colormap Properties and Atoms

   ConfigureNotify, ConfigureNotify Events
   ConfigureRequest, ConfigureRequest Events
   Connection, Glossary
   ConnectionNumber, Display Macros
   Containment, Glossary
   Coordinate system, Glossary
   Copying

        areas, Copying Areas
        planes, Copying Areas

   CreateNotify, CreateNotify Events
   CurrentTime, Event Processing Overview, Pointer Grabbing
   Cursor, Glossary

        Initial State, Creating Windows
        limitations, Creating, Recoloring, and Freeing Cursors

   Cut Buffers, Using Cut Buffers

D

   Debugging

        error event, Using the Default Error Handlers
        error handlers, Using the Default Error Handlers
        error message strings, Using the Default Error Handlers
        error numbers, Using the Default Error Handlers
        synchronous mode, Enabling or Disabling Synchronization

   Default Protection, Controlling Host Access
   DefaultColormap, Display Macros
   DefaultColormapOfScreen, Screen Information Macros
   DefaultDepth, Display Macros
   DefaultDepthOfScreen, Screen Information Macros
   DefaultGC, Display Macros
   DefaultGCOfScreen, Screen Information Macros
   DefaultRootWindow, Display Macros
   DefaultScreen, Display Macros
   DefaultScreenOfDisplay, Display Macros
   DefaultVisual, Display Macros
   DefaultVisualOfScreen, Screen Information Macros
   Depth, Glossary
   Destination, Manipulating Graphics Context/State
   DestroyCallback, Destroy Callback, Destroy Callback
   DestroyNotify, DestroyNotify Events
   Device, Glossary
   Device Color Characterization, Function Sets
   Device profile, Color Conversion Contexts and Gamut Mapping,
          Creating Additional Function Sets

   DirectColor, Glossary
   Display, Opening the Display, Glossary

        data structure, Obtaining Information about the Display,
                Image Formats, or Screens

        structure, Glossary, Glossary

   Display Functions, Manipulating Graphics Context/State
   DisplayCells, Display Macros
   DisplayHeight, Image Format Functions and Macros
   DisplayHeightMM, Image Format Functions and Macros
   DisplayOfCCC, Color Conversion Context Macros
   DisplayOfScreen, Screen Information Macros
   DisplayPlanes, Display Macros
   DisplayString, Display Macros
   DisplayWidth, Image Format Functions and Macros
   DisplayWidthMM, Image Format Functions and Macros
   DoesBackingStore, Screen Information Macros
   DoesSaveUnders, Screen Information Macros
   Drawable, Overview of the X Window System, Glossary
   Drawing

        arcs, Drawing Single and Multiple Arcs
        image text, Drawing Image Text Characters
        lines, Drawing Single and Multiple Lines
        points, Drawing Single and Multiple Points
        polygons, Drawing Single and Multiple Lines
        rectangles, Drawing Single and Multiple Rectangles
        strings, Drawing Text Characters
        text items, Drawing Complex Text

E

   Encoding, Glossary
   EnterNotify, Window Entry/Exit Events
   Environment

        DISPLAY, Opening the Display

   Error

        codes, Using the Default Error Handlers
        handlers, Using the Default Error Handlers
        handling, Errors

   Escapement, Glossary
   Event, Overview of the X Window System, Event Types, Glossary

        categories, Event Types
        Exposure, Glossary
        mask, Glossary
        propagation, Selecting Events, Glossary
        source, Glossary
        synchronization, Glossary
        types, Event Types

   Event mask, Event Masks
   EventMaskOfScreen, Screen Information Macros
   Events

        ButtonPress, Keyboard and Pointer Events
        ButtonRelease, Keyboard and Pointer Events
        CirculateNotify, CirculateNotify Events
        CirculateRequest, CirculateRequest Events
        ClientMessage, ClientMessage Events
        ColormapNotify, Colormap State Change Events
        ConfigureNotify, ConfigureNotify Events
        ConfigureRequest, ConfigureRequest Events
        CreateNotify, CreateNotify Events
        DestroyNotify, DestroyNotify Events
        EnterNotify, Window Entry/Exit Events
        Expose, Expose Events
        FocusIn, Input Focus Events
        FocusOut, Input Focus Events
        GraphicsExpose, GraphicsExpose and NoExpose Events
        GravityNotify, GravityNotify Events
        KeymapNotify, Key Map State Notification Events
        KeyPress, Keyboard and Pointer Events
        KeyRelease, Keyboard and Pointer Events
        LeaveNotify, Window Entry/Exit Events
        MapNotify, MapNotify Events
        MappingNotify, MappingNotify Events
        MapRequest, MapRequest Events
        MotionNotify, Keyboard and Pointer Events
        NoExpose, GraphicsExpose and NoExpose Events
        PropertyNotify, PropertyNotify Events
        ReparentNotify, ReparentNotify Events
        ResizeRequest, ResizeRequest Events
        SelectionClear, SelectionClear Events
        SelectionNotify, SelectionNotify Events
        SelectionRequest, SelectionRequest Events
        UnmapNotify, UnmapNotify Events
        VisibilityNotify, VisibilityNotify Events

   Expose, Expose Events
   Extension, Glossary

F

   False, Generic Values and Types
   Files

        $HOME/.Xdefaults, Getting the X Environment Defaults
        /etc/X?.hosts, Controlling Host Access
        <X11/cursorfont.h>, Standard Header Files
        <X11/keysym.h>, Standard Header Files, Manipulating the
                Keyboard Encoding

        <X11/keysymdef.h>, Standard Header Files, Manipulating the
                Keyboard Encoding, Using Keyboard Utility
                Functions

        <X11/X.h>, Overview of the X Window System, Standard
                Header Files, Manipulating Graphics Context/State,
                Event Types, Event Masks

        <X11/X10.h>, Standard Header Files, Drawing and Filling
                Polygons and Curves, Drawing and Filling Polygons
                and Curves

        <X11/Xatom.h>, Standard Header Files, Properties and
                Atoms, Loading and Freeing Fonts, Standard
                Colormap Properties and Atoms

        <X11/Xcms.h>, Standard Header Files, Color Management
                Functions

        <X11/Xlib.h>, Standard Header Files, Opening the Display,
                Color Management Functions, Event Structures,
                Manipulating Images

        <X11/Xlibint.h>, Standard Header Files
        <X11/Xproto.h>, Standard Header Files, GraphicsExpose and
                NoExpose Events

        <X11/Xprotostr.h>, Standard Header Files
        <X11/Xresource.h>, Standard Header Files, Resource Manager
                Functions

        <X11/Xutil.h>, Standard Header Files, Setting and Reading
                the WM_HINTS Property, Setting and Reading the
                WM_NORMAL_HINTS Property, Setting and Reading the
                WM_CLASS Property, Setting and Reading the
                WM_ICON_SIZE Property, Parsing the Window
                Geometry, Manipulating Regions, Determining the
                Appropriate Visual Type, Manipulating Images,
                Using the Context Manager, Setting and Getting
                Window Sizing Hints

   Filling

        arcs, Filling Single and Multiple Arcs
        polygon, Filling a Single Polygon
        rectangles, Filling Single and Multiple Rectangles

   FlushGC, GC Caching
   FocusIn, Input Focus Events
   FocusOut, Input Focus Events
   Font, Font Metrics, Glossary
   Font glyph, Glossary
   Fonts

        freeing font information, Loading and Freeing Fonts
        getting information, Loading and Freeing Fonts
        unloading, Loading and Freeing Fonts

   Freeing

        colors, Allocating and Freeing Color Cells
        resources, Window Attributes, Changing Window Attributes,
                Changing Window Attributes

   Frozen events, Glossary
   Function set, Function Sets

        LINEAR_RGB, Function Sets

G

   Gamut compression, Color Conversion Contexts and Gamut Mapping

        client data, Modifying Attributes of a Color Conversion
                Context

        procedure, Modifying Attributes of a Color Conversion
                Context

        setting in Color Conversion Context, Modifying Attributes
                of a Color Conversion Context

   Gamut handling, Color Conversion Contexts and Gamut Mapping
   Gamut querying, Gamut Querying Functions
   GC, Glossary
   GeometryCallback, Geometry Callback
   Glyph, Glossary
   Glyph image, Glossary
   Grab, Glossary
   Grabbing

        buttons, Pointer Grabbing
        keyboard, Keyboard Grabbing
        keys, Keyboard Grabbing
        pointer, Pointer Grabbing
        server, Grabbing the Server

   Graphics context, Glossary

        initializing, Manipulating Graphics Context/State

   GraphicsExpose, GraphicsExpose and NoExpose Events
   Gravity, Glossary
   GravityNotify, GravityNotify Events
   GrayScale, Glossary

H

   Hash Lookup, Associating User Data with a Value
   Headers, Standard Header Files

        <X11/cursorfont.h>, Standard Header Files
        <X11/keysym.h>, Standard Header Files, Manipulating the
                Keyboard Encoding

        <X11/keysymdef.h>, Standard Header Files, Manipulating the
                Keyboard Encoding, Using Keyboard Utility
                Functions

        <X11/X.h>, Overview of the X Window System, Standard
                Header Files, Manipulating Graphics Context/State,
                Event Types, Event Masks

        <X11/X10.h>, Standard Header Files, Drawing and Filling
                Polygons and Curves, Drawing and Filling Polygons
                and Curves

        <X11/Xatom.h>, Standard Header Files, Properties and
                Atoms, Loading and Freeing Fonts, Standard
                Colormap Properties and Atoms

        <X11/Xcms.h>, Standard Header Files, Color Management
                Functions

        <X11/Xlib.h>, Standard Header Files, Opening the Display,
                Color Management Functions, Event Structures,
                Manipulating Images

        <X11/Xlibint.h>, Standard Header Files
        <X11/Xproto.h>, Standard Header Files, GraphicsExpose and
                NoExpose Events

        <X11/Xprotostr.h>, Standard Header Files
        <X11/Xresource.h>, Standard Header Files, Resource Manager
                Functions

        <X11/Xutil.h>, Standard Header Files, Setting and Reading
                the WM_HINTS Property, Setting and Reading the
                WM_NORMAL_HINTS Property, Setting and Reading the
                WM_CLASS Property, Setting and Reading the
                WM_ICON_SIZE Property, Parsing the Window
                Geometry, Manipulating Regions, Determining the
                Appropriate Visual Type, Manipulating Images,
                Using the Context Manager, Setting and Getting
                Window Sizing Hints

   HeightMMOfScreen, Screen Information Macros
   HeightOfScreen, Screen Information Macros
   Host Portable Character Encoding, Glossary
   Hotspot, Glossary

I

   Identifier, Glossary
   Image text

        drawing, Drawing Image Text Characters

   ImageByteOrder, Image Format Functions and Macros
   IMInstantiateCallback, Input Method Functions
   Inferiors, Glossary
   Input

        focus, Glossary
        manager, Glossary

   Input Control, Event Types
   Internationalization, Glossary
   IsCursorKey, KeySym Classification Macros
   IsFunctionKey, KeySym Classification Macros
   IsKeypadKey, KeySym Classification Macros
   IsMiscFunctionKey, KeySym Classification Macros
   IsModifierKey, KeySym Classification Macros
   ISO2022, Glossary
   IsPFKey, KeySym Classification Macros
   IsPrivateKeypadKey, KeySym Classification Macros

K

   Key

        grabbing, Keyboard Grabbing, Glossary
        ungrabbing, Keyboard Grabbing

   Keyboard

        bell volume, Manipulating the Keyboard and Pointer
                Settings

        bit vector, Manipulating the Keyboard and Pointer Settings
        grabbing, Keyboard Grabbing, Glossary
        keyclick volume, Manipulating the Keyboard and Pointer
                Settings

        ungrabbing, Keyboard Grabbing

   KeymapNotify, Key Map State Notification Events
   KeyPress, Keyboard and Pointer Events
   KeyRelease, Keyboard and Pointer Events
   Keysym, Glossary

L

   LastKnownRequestProcessed, Display Macros
   Latin Portable Character Encoding, Glossary
   Latin-1, Glossary
   LeaveNotify, Window Entry/Exit Events
   Lines

        drawing, Drawing Single and Multiple Lines

   Locale, Glossary
   Locale name, Glossary
   Localization, Glossary
   LockDisplay, Locking Data Structures

M

   MapNotify, MapNotify Events
   Mapped window, Glossary
   MappingNotify, MappingNotify Events
   MapRequest, MapRequest Events
   MaxCmapsOfScreen, Screen Information Macros
   Menus, Grabbing the Server
   MinCmapsOfScreen, Screen Information Macros
   Modifier keys, Glossary
   Monochrome, Glossary
   MotionNotify, Keyboard and Pointer Events
   Mouse

        programming, Manipulating the Keyboard and Pointer
                Settings

   Multibyte, Glossary

N

   NextRequest, Display Macros
   NoExpose, GraphicsExpose and NoExpose Events
   None, Generic Values and Types

O

   Obscure, Glossary
   Occlude, Glossary
   Output Control, Event Types

P

   Padding, Glossary
   Parent Window, Overview of the X Window System, Obtaining
          Window Information

   Passive grab, Pointer Grabbing, Glossary
   Pixel value, Manipulating Graphics Context/State, Glossary
   Pixmap, Overview of the X Window System, Glossary
   Plane, Glossary

        copying, Copying Areas
        mask, Manipulating Graphics Context/State, Glossary

   PlanesOfScreen, Screen Information Macros
   Pointer, Glossary

        grabbing, Pointer Grabbing, Pointer Grabbing, Glossary
        ungrabbing, Pointer Grabbing

   Pointing device, Glossary
   Points

        drawing, Drawing Single and Multiple Points

   Polygons

        drawing, Drawing Single and Multiple Lines
        filling, Filling a Single Polygon

   POSIX, Glossary
   POSIX Portable Filename Character Set, Glossary
   POSIX System Call

        fork, Display Macros

   PreeditCaretCallback, Preedit Caret Callback
   PreeditDoneCallback, Preedit State Callbacks
   PreeditDrawCallback, Preedit Draw Callback
   PreeditStartCallback, Preedit State Callbacks
   PreeditStateNotifyCallback, Preedit State Notify Callback
   Property, Glossary

        appending, Obtaining and Changing Window Properties
        changing, Obtaining and Changing Window Properties
        deleting, Obtaining and Changing Window Properties
        format, Obtaining and Changing Window Properties
        getting, Obtaining and Changing Window Properties
        listing, Obtaining and Changing Window Properties
        prepending, Obtaining and Changing Window Properties
        replacing, Obtaining and Changing Window Properties
        type, Obtaining and Changing Window Properties

   Property list, Glossary
   PropertyNotify, PropertyNotify Events
   Protocol

        DECnet, Opening the Display
        TCP, Opening the Display

   ProtocolRevision, Display Macros
   ProtocolVersion, Display Macros
   PseudoColor, Glossary
   Psychometric Chroma, CIELab Queries, CIELab Queries, CIELuv
          Queries, CIELuv Queries

        maximum, CIELab Queries, CIELab Queries, CIELuv Queries,
                CIELuv Queries

   Psychometric Hue Angle, CIELab Queries, CIELab Queries, CIELab
          Queries, CIELab Queries, CIELuv Queries, CIELuv Queries,
          CIELuv Queries, CIELuv Queries

Q

   QLength, Display Macros

R

   Read-only colormap cells, Allocating and Freeing Color Cells

        allocating, Allocating and Freeing Color Cells, Allocating
                and Freeing Color Cells, Allocating and Freeing
                Color Cells, Allocating and Freeing Color Cells

   read-only colormap cells, Allocating and Freeing Color Cells
   Read/write colormap cells, Allocating and Freeing Color Cells

        allocating, Allocating and Freeing Color Cells

   Read/write colormap planes

        allocating, Allocating and Freeing Color Cells

   Rectangle, Glossary

        filling, Filling Single and Multiple Rectangles

   Rectangles

        drawing, Drawing Single and Multiple Rectangles

   Redirecting control, Glossary
   ReparentNotify, ReparentNotify Events
   Reply, Glossary
   Request, Glossary
   ResizeRequest, ResizeRequest Events
   Resource, Glossary
   Resource IDs, Overview of the X Window System, Closing the
          Display, Associating User Data with a Value

        Colormap, Overview of the X Window System
        Cursor, Overview of the X Window System
        Font, Overview of the X Window System
        freeing, Window Attributes, Changing Window Attributes,
                Changing Window Attributes

        GContext, Overview of the X Window System
        Pixmap, Overview of the X Window System
        Window, Overview of the X Window System

   RGB values, Glossary
   Root, Glossary
   RootWindow, Display Macros
   RootWindowOfScreen, Screen Information Macros

S

   Save set, Glossary
   Save Unders, Save Under Flag
   Scanline, Glossary

        order, Glossary

   Screen, Overview of the X Window System, Opening the Display,
          Glossary

        structure, Glossary

   Screen White Point, Gamut Querying Functions
   ScreenCount, Display Macros
   ScreenNumberOfCCC, Color Conversion Context Macros
   ScreenOfDisplay, Display Macros
   ScreenWhitePointOfCCC, Color Conversion Context Macros
   Selection, Selections, Glossary

        converting, Selections
        getting the owner, Selections
        setting the owner, Selections

   SelectionClear, SelectionClear Events
   SelectionNotify, SelectionNotify Events
   SelectionRequest, SelectionRequest Events
   Serial Number, Using the Default Error Handlers
   Server, Glossary

        grabbing, Grabbing the Server, Glossary

   ServerVendor, Display Macros
   Shift sequence, Glossary
   Sibling, Glossary
   Source, Manipulating Graphics Context/State
   Stacking order, Overview of the X Window System, Glossary
   Standard Colormaps, Standard Colormap Properties and Atoms
   State-dependent encoding, Glossary
   State-independent encoding, Glossary
   StaticColor, Glossary
   StaticGray, Glossary
   Status, Errors, Glossary
   StatusDoneCallback, Status Callbacks
   StatusDrawCallback, Status Callbacks
   StatusStartCallback, Status Callbacks
   Stipple, Glossary
   String Equivalence, Glossary
   StringConversionCallback, String Conversion Callback
   Strings

        drawing, Drawing Text Characters

T

   Text

        drawing, Drawing Complex Text

   Tile, Overview of the X Window System, Glossary

        mode, Window Attributes
        pixmaps, Window Attributes

   Time, Pointer Grabbing
   Timestamp, Glossary
   True, Generic Values and Types
   TrueColor, Glossary
   Type, Glossary

U

   Ungrabbing

        buttons, Pointer Grabbing
        keyboard, Keyboard Grabbing
        keys, Keyboard Grabbing
        pointer, Pointer Grabbing

   UnlockDisplay, Locking Data Structures
   UnmapNotify, UnmapNotify Events
   UnmapNotify Event, Unmapping Windows, Unmapping Windows

V

   Value, TekHVC Queries, TekHVC Queries, TekHVC Queries, TekHVC
          Queries

        maximum, TekHVC Queries, TekHVC Queries, TekHVC Queries
        minimum, TekHVC Queries

   VendorRelease, Display Macros
   Vertex, Drawing and Filling Polygons and Curves
   VertexCurved, Drawing and Filling Polygons and Curves
   VertexDontDraw, Drawing and Filling Polygons and Curves
   VertexEndClosed, Drawing and Filling Polygons and Curves
   VertexRelative, Drawing and Filling Polygons and Curves
   VertexStartClosed, Drawing and Filling Polygons and Curves
   Viewable, Glossary
   VisibilityNotify, VisibilityNotify Events
   Visible, Glossary
   Visual, Visual Types
   Visual Classes

        GrayScale, Visual Types
        PseudoColor, Visual Types
        StaticColor, Visual Types, Visual Types
        StaticGray, Visual Types
        TrueColor, Visual Types

   Visual Type, Visual Types
   VisualOfCCC, Color Conversion Context Macros

W

   White point, Color Conversion Contexts and Gamut Mapping
   White point adjustment, Color Conversion Contexts and Gamut
          Mapping

        client data, Modifying Attributes of a Color Conversion
                Context

        procedure, Modifying Attributes of a Color Conversion
                Context

        setting in Color Conversion Context, Modifying Attributes
                of a Color Conversion Context

   WhitePixel, Display Macros
   WhitePixelOfScreen, Screen Information Macros
   Whitespace, Glossary
   WidthMMOfScreen, Screen Information Macros
   WidthOfScreen, Screen Information Macros
   Window, Overview of the X Window System, Window Attributes

        attributes, Window Attributes
        background, Changing Window Attributes
        clearing, Clearing Areas
        defining the cursor, Changing Window Attributes
        determining location, Parsing the Window Geometry, Parsing
                Window Geometry

        gravity, Glossary
        icon name, Setting and Reading the WM_ICON_NAME Property
        IDs, Associating User Data with a Value
        InputOnly, Creating Windows, Glossary
        InputOutput, Glossary
        manager, Glossary
        managers, Grabbing the Server
        mapping, Window Attributes
        name, Setting and Reading the WM_NAME Property
        parent, Glossary
        root, Glossary
        RootWindow, Display Macros
        undefining the cursor, Changing Window Attributes
        XRootWindow, Display Macros

X

   X Portable Character Set, Glossary
   X10 compatibility

        XDraw, Drawing and Filling Polygons and Curves, Drawing
                and Filling Polygons and Curves

        XDrawDashed, Drawing and Filling Polygons and Curves,
                Drawing and Filling Polygons and Curves

        XDrawFilled, Drawing and Filling Polygons and Curves,
                Drawing and Filling Polygons and Curves

        XDrawPatterned, Drawing and Filling Polygons and Curves,
                Drawing and Filling Polygons and Curves

        XDrawTiled, Drawing and Filling Polygons and Curves,
                Drawing and Filling Polygons and Curves

   X11/cursorfont.h, Standard Header Files
   X11/keysym.h, Standard Header Files, Manipulating the Keyboard
          Encoding

   X11/keysymdef.h, Standard Header Files, Manipulating the
          Keyboard Encoding, Using Keyboard Utility Functions

   X11/X.h, Overview of the X Window System, Standard Header
          Files, Manipulating Graphics Context/State, Event Types,
          Event Masks

   X11/X10.h, Standard Header Files, Drawing and Filling Polygons
          and Curves, Drawing and Filling Polygons and Curves

   X11/Xatom.h, Standard Header Files, Properties and Atoms,
          Loading and Freeing Fonts, Standard Colormap Properties
          and Atoms

   X11/Xcms.h, Standard Header Files, Color Management Functions
   X11/Xlib.h, Standard Header Files, Opening the Display, Color
          Management Functions, Event Structures, Manipulating
          Images

   X11/Xlibint.h, Standard Header Files
   X11/Xproto.h, Standard Header Files, GraphicsExpose and
          NoExpose Events

   X11/Xprotostr.h, Standard Header Files
   X11/Xresource.h, Standard Header Files, Resource Manager
          Functions

   X11/Xutil.h, Standard Header Files, Setting and Reading the
          WM_HINTS Property, Setting and Reading the
          WM_NORMAL_HINTS Property, Setting and Reading the
          WM_CLASS Property, Setting and Reading the WM_ICON_SIZE
          Property, Parsing the Window Geometry, Manipulating
          Regions, Determining the Appropriate Visual Type,
          Manipulating Images, Using the Context Manager, Setting
          and Getting Window Sizing Hints

   XActivateScreenSaver, Controlling the Screen Saver
   XAddExtension, Hooking into Xlib
   XAddHost, Adding, Getting, or Removing Hosts
   XAddHosts, Adding, Getting, or Removing Hosts
   XAddPixel, Manipulating Images
   XAddToExtensionList, Hooks onto Xlib Data Structures
   XAddToSaveSet, Controlling the Lifetime of a Window
   XAllocClassHint, Setting and Reading the WM_CLASS Property
   XAllocColor, Allocating and Freeing Color Cells, Allocating and
          Freeing Color Cells

   XAllocColorCells, Allocating and Freeing Color Cells,
          Allocating and Freeing Color Cells

   XAllocColorPlanes, Allocating and Freeing Color Cells,
          Allocating and Freeing Color Cells

   XAllocID, Hooks onto Xlib Data Structures
   XAllocIDs, Hooks onto Xlib Data Structures
   XAllocNamedColor, Allocating and Freeing Color Cells,
          Allocating and Freeing Color Cells

   XAllowEvents, Resuming Event Processing
   XAllPlanes, Display Macros
   XAnyEvent, Event Structures
   XArc, Drawing Points, Lines, Rectangles, and Arcs
   XAutoRepeatOff, Manipulating the Keyboard and Pointer Settings
   XAutoRepeatOn, Manipulating the Keyboard and Pointer Settings
   XBaseFontNameListOfFontSet, Creating and Freeing a Font Set
   XBell, Manipulating the Keyboard and Pointer Settings
   XBitmapBitOrder, Image Format Functions and Macros
   XBitmapPad, Image Format Functions and Macros
   XBitmapUnit, Image Format Functions and Macros
   XBlackPixel, Display Macros
   XBlackPixelOfScreen, Screen Information Macros
   XCellsOfScreen, Screen Information Macros
   XChangeActivePointerGrab, Pointer Grabbing
   XChangeGC, Manipulating Graphics Context/State
   XChangeKeyboardControl, Manipulating the Keyboard and Pointer
          Settings

   XChangeKeyboardMapping, Manipulating the Keyboard Encoding
   XChangePointerControl, Manipulating the Keyboard and Pointer
          Settings

   XChangeProperty, Obtaining and Changing Window Properties
   XChangeSaveSet, Controlling the Lifetime of a Window
   XChangeWindowAttributes, Changing Window Attributes
   XChar2b, Font Metrics
   XCharStruct, Font Metrics
   XCheckIfEvent, Selecting Events Using a Predicate Procedure
   XCheckMaskEvent, Selecting Events Using a Window or Event Mask
   XCheckTypedEvent, Selecting Events Using a Window or Event Mask
   XCheckTypedWindowEvent, Selecting Events Using a Window or
          Event Mask

   XCheckWindowEvent, Selecting Events Using a Window or Event
          Mask, Selecting Events Using a Window or Event Mask

   XCirculateEvent, CirculateNotify Events
   XCirculateRequestEvent, CirculateRequest Events
   XCirculateSubwindows, Changing Window Stacking Order
   XCirculateSubwindowsDown, Changing Window Stacking Order
   XCirculateSubwindowsUp, Changing Window Stacking Order
   XClassHint, Setting and Reading the WM_CLASS Property
   XClearArea, Clearing Areas
   XClearWindow, Clearing Areas
   XClientMessageEvent, ClientMessage Events
   XClipBox, Computing with Regions
   XCloseDisplay, Closing the Display, Closing the Display
   XCloseIM, Input Method Functions
   XCloseOM, Output Method Functions
   XcmsAddColorSpace, Adding Device-Independent Color Spaces
   XcmsAddFunctionSet, Adding Function Sets
   XcmsAllocColor, Allocating and Freeing Color Cells
   XcmsAllocNamedColor, Allocating and Freeing Color Cells
   XcmsCCCOfColormap, Getting and Setting the Color Conversion
          Context of a Colormap

   XcmsCIELab, Color Structures
   XcmsCIELabQueryMaxC, CIELab Queries
   XcmsCIELabQueryMaxL, CIELab Queries
   XcmsCIELabQueryMaxLC, CIELab Queries
   XcmsCIELabQueryMinL, CIELab Queries
   XcmsCIELuv, Color Structures
   XcmsCIELuvQueryMaxC, CIELuv Queries
   XcmsCIELuvQueryMaxL, CIELuv Queries
   XcmsCIELuvQueryMaxLC, CIELuv Queries
   XcmsCIELuvQueryMinL, CIELuv Queries
   XcmsCIEuvY, Color Structures
   XcmsCIExyY, Color Structures
   XcmsCIEXYZ, Color Structures
   XcmsClientWhitePointOfCCC, Color Conversion Context Macros
   XcmsColor, Color Structures
   XcmsCompressionProc, Prototype Gamut Compression Procedure
   XcmsConvertColors, Converting between Color Spaces
   XcmsCreateCCC, Creating and Freeing a Color Conversion Context
   XcmsDefaultCCC, Obtaining the Default Color Conversion Context
   XcmsDisplayOfCCC, Color Conversion Context Macros
   XcmsFormatOfPrefix, Querying Color Space Format and Prefix
   XcmsFreeCCC, Creating and Freeing a Color Conversion Context
   XcmsLookupColor, Mapping Color Names to Values
   XcmsPad, Color Structures
   XcmsParseStringProc, Parse String Callback
   XcmsPrefixOfFormat, Querying Color Space Format and Prefix
   XcmsQueryBlack, Red, Green, and Blue Queries
   XcmsQueryBlue, Red, Green, and Blue Queries
   XcmsQueryColor, Modifying and Querying Colormap Cells
   XcmsQueryColors, Modifying and Querying Colormap Cells
   XcmsQueryGreen, Red, Green, and Blue Queries
   XcmsQueryRed, Red, Green, and Blue Queries
   XcmsQueryWhite, Red, Green, and Blue Queries
   XcmsRGB, Color Structures
   XcmsRGBi, Color Structures
   XcmsScreenInitProc, Creating Additional Function Sets
   XcmsScreenNumberOfCCC, Color Conversion Context Macros
   XcmsScreenWhitePointOfCCC, Color Conversion Context Macros
   XcmsSetCCCOfColormap, Getting and Setting the Color Conversion
          Context of a Colormap

   XcmsSetCompressionProc, Modifying Attributes of a Color
          Conversion Context

   XcmsSetWhiteAdjustProc, Modifying Attributes of a Color
          Conversion Context

   XcmsSetWhitePoint, Modifying Attributes of a Color Conversion
          Context

   XcmsStoreColor, Modifying and Querying Colormap Cells
   XcmsStoreColors, Modifying and Querying Colormap Cells
   XcmsTekHVC, Color Structures
   XcmsTekHVCQueryMaxC, TekHVC Queries
   XcmsTekHVCQueryMaxV, TekHVC Queries
   XcmsTekHVCQueryMaxVC, TekHVC Queries
   XcmsTekHVCQueryMaxVSamples, TekHVC Queries
   XcmsTekHVCQueryMinV, TekHVC Queries
   XcmsVisualOfCCC, Color Conversion Context Macros
   XcmsWhiteAdjustProc, Prototype White Point Adjustment Procedure
   XColor, Color Structures
   XColormapEvent, Colormap State Change Events
   XConfigureEvent, ConfigureNotify Events
   XConfigureRequestEvent, ConfigureRequest Events
   XConfigureWindow, Configuring Windows
   XConnectionNumber, Display Macros
   XContextDependentDrawing, Obtaining Font Set Metrics
   XContextualDrawing, Obtaining Font Set Metrics
   XConvertCase, Using Keyboard Utility Functions
   XConvertSelection, Selections
   XCopyArea, Copying Areas
   XCopyColormapAndFree, Creating, Copying, and Destroying
          Colormaps

   XCopyGC, Manipulating Graphics Context/State
   XCopyPlane, Copying Areas
   XCreateAssocTable, Associating User Data with a Value
   XCreateBitmapFromData, Manipulating Bitmaps
   XCreateColormap, Creating, Copying, and Destroying Colormaps
   XCreateFontCursor, Creating, Recoloring, and Freeing Cursors
   XCreateFontSet, Creating and Freeing a Font Set
   XCreateGC, Manipulating Graphics Context/State
   XCreateGlyphCursor, Creating, Recoloring, and Freeing Cursors
   XCreateIC, Input Context Functions
   XCreateImage, Manipulating Images
   XCreateOC, Output Context Functions
   XCreatePixmap, Creating and Freeing Pixmaps
   XCreatePixmapCursor, Creating, Recoloring, and Freeing Cursors
   XCreatePixmapFromBitmapData, Manipulating Bitmaps
   XCreateSimpleWindow, Creating Windows
   XCreateWindow, Creating Windows
   XCreateWindowEvent, CreateNotify Events
   XCrossingEvent, Window Entry/Exit Events
   XDefaultColormap, Display Macros
   XDefaultColormapOfScreen, Screen Information Macros
   XDefaultDepth, Display Macros
   XDefaultDepthOfScreen, Screen Information Macros
   XDefaultGC, Display Macros
   XDefaultGCOfScreen, Screen Information Macros
   XDefaultRootWindow, Display Macros
   XDefaultScreen, Display Macros
   XDefaultScreenOfDisplay, Display Macros
   XDefaultVisual, Display Macros
   XDefaultVisualOfScreen, Screen Information Macros
   XDefineCursor, Creating Windows, Changing Window Attributes
   XDeleteAssoc, Associating User Data with a Value
   XDeleteContext, Using the Context Manager
   XDeleteModifiermapEntry, Manipulating the Keyboard Encoding
   XDeleteProperty, Obtaining and Changing Window Properties
   XDestroyAssocTable, Associating User Data with a Value
   XDestroyIC, Input Context Functions
   XDestroyImage, Manipulating Images
   XDestroyOC, Output Context Functions
   XDestroyRegion, Creating, Copying, or Destroying Regions
   XDestroySubwindows, Destroying Windows
   XDestroyWindow, Destroying Windows
   XDestroyWindowEvent, DestroyNotify Events
   XDirectionalDependentDrawing, Obtaining Font Set Metrics
   XDisableAccessControl, Changing, Enabling, or Disabling Access
          Control

   XDisplayCells, Display Macros
   XDisplayHeight, Image Format Functions and Macros
   XDisplayHeightMM, Image Format Functions and Macros
   XDisplayKeycodes, Manipulating the Keyboard Encoding
   XDisplayMotionBufferSize, Getting Pointer Motion History
   XDisplayName, Using the Default Error Handlers
   XDisplayOfIM, Input Method Functions
   XDisplayOfOM, Output Method Functions
   XDisplayOfScreen, Screen Information Macros
   XDisplayPlanes, Display Macros
   XDisplayString, Display Macros
   XDisplayWidth, Image Format Functions and Macros
   XDisplayWidthMM, Image Format Functions and Macros
   XDoesBackingStore, Screen Information Macros
   XDoesSaveUnders, Screen Information Macros
   xDoSomethingReply, Request Format
   xDoSomethingReq, Request Format
   XDrawArc, Drawing Single and Multiple Arcs, Drawing Single and
          Multiple Arcs

   XDrawArcs, Drawing Single and Multiple Arcs, Drawing Single and
          Multiple Arcs

   XDrawImageString, Drawing Image Text Characters, Drawing Image
          Text Characters

   XDrawImageString16, Drawing Image Text Characters, Drawing
          Image Text Characters

   XDrawLine, Drawing Single and Multiple Lines, Drawing Single
          and Multiple Lines

   XDrawLines, Drawing Single and Multiple Lines, Drawing Single
          and Multiple Lines, Drawing and Filling Polygons and
          Curves

   XDrawPoint, Drawing Single and Multiple Points, Drawing Single
          and Multiple Points

   XDrawPoints, Drawing Single and Multiple Points, Drawing Single
          and Multiple Points

   XDrawRectangle, Drawing Single and Multiple Rectangles, Drawing
          Single and Multiple Rectangles

   XDrawRectangles, Drawing Single and Multiple Rectangles,
          Drawing Single and Multiple Rectangles

   XDrawSegments, Drawing Single and Multiple Lines, Drawing
          Single and Multiple Lines, Drawing and Filling Polygons
          and Curves

   XDrawString, Drawing Text Characters
   XDrawString16, Drawing Text Characters
   XDrawText, Drawing Complex Text
   XDrawText16, Drawing Complex Text
   XEHeadOfExtensionList, Hooks onto Xlib Data Structures
   XEmptyRegion, Determining if Regions Are Empty or Equal
   XEnableAccessControl, Changing, Enabling, or Disabling Access
          Control

   XEnterWindowEvent, Window Entry/Exit Events
   XEqualRegion, Determining if Regions Are Empty or Equal
   XErrorEvent, Using the Default Error Handlers
   XESetBeforeFlush, Hooks into the Library
   XESetCloseDisplay, Hooks into the Library
   XESetCopyGC, Hooks into the Library
   XESetCreateFont, Hooks into the Library
   XESetCreateGC, Hooks into the Library
   XESetError, Hooks into the Library
   XESetErrorString, Hooks into the Library
   XESetEventToWire, Hooks into the Library
   XESetFlushGC, Hooks into the Library
   XESetFreeFont, Hooks into the Library
   XESetPrintErrorValues, Hooks into the Library
   XESetWireToError, Hooks into the Library
   XESetWireToEvent, Hooks into the Library
   XEvent, Event Structures
   XEventMaskOfScreen, Screen Information Macros
   XEventsQueued, Event Queue Management
   XExposeEvent, Expose Events
   XExtCodes, Hooking into Xlib
   XExtData, Hooks onto Xlib Data Structures
   XExtendedMaxRequestSize, Display Macros
   XExtentsOfFontSet, Obtaining Font Set Metrics
   XFetchBuffer, Using Cut Buffers
   XFetchBytes, Using Cut Buffers
   XFetchName, Setting and Reading the WM_NAME Property
   XFillArc, Filling Single and Multiple Arcs, Filling Single and
          Multiple Arcs

   XFillArcs, Filling Single and Multiple Arcs
   XFillPolygon, Filling a Single Polygon
   XFillRectangle, Filling Single and Multiple Rectangles, Filling
          Single and Multiple Rectangles

   XFillRectangles, Filling Single and Multiple Rectangles,
          Filling Single and Multiple Rectangles

   XFilterEvent, Event Filtering
   XFindContext, Using the Context Manager
   XFindOnExtensionList, Hooks onto Xlib Data Structures
   XFlush, Handling the Output Buffer
   XFlushGC, Manipulating Graphics Context/State
   XFocusChangeEvent, Input Focus Events
   XFocusInEvent, Input Focus Events
   XFocusOutEvent, Input Focus Events
   XFontProp, Font Metrics
   XFontSetExtents, Obtaining Font Set Metrics
   XFontsOfFontSet, Creating and Freeing a Font Set
   XFontStruct, Font Metrics
   XForceScreenSaver, Controlling the Screen Saver
   XFree, Freeing Client-Created Data
   XFreeColormap, Creating, Copying, and Destroying Colormaps
   XFreeColors, Allocating and Freeing Color Cells
   XFreeCursor, Creating, Recoloring, and Freeing Cursors
   XFreeExtensionList, Basic Protocol Support Routines
   XFreeFont, Loading and Freeing Fonts
   XFreeFontInfo, Obtaining and Freeing Font Names and Information
   XFreeFontNames, Obtaining and Freeing Font Names and
          Information

   XFreeFontPath, Setting and Retrieving the Font Search Path
   XFreeFontSet, Creating and Freeing a Font Set
   XFreeGC, Manipulating Graphics Context/State
   XFreeModifiermap, Manipulating the Keyboard Encoding
   XFreePixmap, Creating and Freeing Pixmaps
   XFreeStringList, Converting String Lists
   XGContextFromGC, Manipulating Graphics Context/State
   XGeometry, Parsing Window Geometry
   XGetAtomName, Properties and Atoms
   XGetAtomNames, Properties and Atoms
   XGetClassHint, Setting and Reading the WM_CLASS Property
   XGetCommand, Setting and Reading the WM_COMMAND Property
   XGetDefault, Getting the X Environment Defaults
   XGetErrorDatabaseText, Using the Default Error Handlers
   XGetErrorText, Using the Default Error Handlers
   XGetFontPath, Setting and Retrieving the Font Search Path
   XGetFontProperty, Loading and Freeing Fonts
   XGetGCValues, Manipulating Graphics Context/State
   XGetGeometry, Obtaining Window Information
   XGetIconName, Setting and Reading the WM_ICON_NAME Property
   XGetIconSizes, Setting and Reading the WM_ICON_SIZE Property
   XGetICValues, Input Context Functions
   XGetImage, Transferring Images between Client and Server
   XGetIMValues, Input Method Functions
   XGetInputFocus, Controlling Input Focus
   XGetKeyboardControl, Manipulating the Keyboard and Pointer
          Settings, Manipulating the Keyboard and Pointer Settings

   XGetKeyboardMapping, Manipulating the Keyboard Encoding
   XGetModifierMapping, Manipulating the Keyboard Encoding
   XGetMotionEvents, Getting Pointer Motion History
   XGetNormalHints, Setting and Getting Window Sizing Hints
   XGetOCValues, Output Context Functions
   XGetOMValues, Output Method Functions
   XGetPixel, Manipulating Images
   XGetPointerControl, Manipulating the Keyboard and Pointer
          Settings

   XGetPointerMapping, Manipulating the Keyboard and Pointer
          Settings

   XGetRGBColormaps, Setting and Obtaining Standard Colormaps
   XGetScreenSaver, Controlling the Screen Saver
   XGetSelectionOwner, Selections
   XGetSizeHints, Setting and Getting Window Sizing Hints
   XGetStandardColormap, Getting and Setting an XStandardColormap
          Structure

   XGetSubImage, Transferring Images between Client and Server
   XGetTextProperty, Setting and Reading Text Properties
   XGetTransientForHint, Setting and Reading the WM_TRANSIENT_FOR
          Property

   XGetVisualInfo, Determining the Appropriate Visual Type
   XGetWindowAttributes, Obtaining Window Information
   XGetWindowProperty, Obtaining and Changing Window Properties
   XGetWMClientMachine, Setting and Reading the WM_CLIENT_MACHINE
          Property

   XGetWMColormapWindows, Setting and Reading the
          WM_COLORMAP_WINDOWS Property

   XGetWMHints, Setting and Reading the WM_HINTS Property
   XGetWMIconName, Setting and Reading the WM_ICON_NAME Property
   XGetWMName, Setting and Reading the WM_NAME Property
   XGetWMNormalHints, Setting and Reading the WM_NORMAL_HINTS
          Property

   XGetWMProtocols, Setting and Reading the WM_PROTOCOLS Property
   XGetWMSizeHints, Setting and Reading the WM_NORMAL_HINTS
          Property

   XGetZoomHints, Setting and Getting Window Sizing Hints
   XGrabButton, Pointer Grabbing
   XGrabKey, Keyboard Grabbing
   XGrabKeyboard, Keyboard Grabbing
   XGrabPointer, Pointer Grabbing
   XGrabServer, Grabbing the Server
   XGraphicsExposeEvent, GraphicsExpose and NoExpose Events
   XGravityEvent, GravityNotify Events
   XHeightMMOfScreen, Screen Information Macros
   XHeightOfScreen, Screen Information Macros
   XHostAddress, Adding, Getting, or Removing Hosts
   XIconifyWindow, Manipulating Top-Level Windows
   XIconSize, Setting and Reading the WM_ICON_SIZE Property,
          Setting and Reading the WM_ICON_SIZE Property

   XID, Generic Values and Types
   XIfEvent, Selecting Events Using a Predicate Procedure
   XIMAbsolutePosition, Preedit Caret Callback
   XImage, Transferring Images between Client and Server
   XImageByteOrder, Image Format Functions and Macros
   XIMBackwardChar, Preedit Caret Callback
   XIMBackwardWord, Preedit Caret Callback
   XIMCallback, Preedit and Status Callbacks
   XIMCaretDirection, Preedit Caret Callback
   XIMCaretDown, Preedit Caret Callback
   XIMCaretStyle, Preedit Caret Callback
   XIMCaretUp, Preedit Caret Callback
   XIMDontChange, Preedit Caret Callback
   XIMForwardChar, Preedit Caret Callback
   XIMForwardWord, Preedit Caret Callback
   XIMHighlight, Preedit Draw Callback
   XIMInitialState, Reset State
   XIMLineEnd, Preedit Caret Callback
   XIMLineStart, Preedit Caret Callback
   XIMNextLine, Preedit Caret Callback
   XIMOfIC, Input Context Functions
   XIMPreeditArea, Query Input Style, Query Input Style
   XIMPreeditCallbacks, Query Input Style, Query Input Style
   XIMPreeditCaretCallbackStruct, Preedit Caret Callback
   XIMPreeditDisable, Preedit State
   XIMPreeditDrawCallbackStruct, Preedit Draw Callback
   XIMPreeditEnable, Preedit State
   XIMPreeditNone, Query Input Style, Query Input Style
   XIMPreeditNothing, Query Input Style, Query Input Style
   XIMPreeditPosition, Query Input Style, Query Input Style
   XIMPreeditStateNotifyCallbackStruct, Preedit State Notify
          Callback

   XIMPreeditUnknown, Preedit State
   XIMPreviousLine, Preedit Caret Callback
   XIMPrimary, Preedit Draw Callback
   XIMProc, Preedit and Status Callbacks
   XIMReverse, Preedit Draw Callback
   XIMSecondary, Preedit Draw Callback
   XIMStatusArea, Query Input Style, Query Input Style
   XIMStatusCallbacks, Query Input Style, Query Input Style
   XIMStatusDataType, Status Callbacks
   XIMStatusDrawCallbackStruct, Status Callbacks
   XIMStatusNone, Query Input Style, Query Input Style
   XIMStatusNothing, Query Input Style, Query Input Style
   XIMStringConversionCallbackStruct, String Conversion Callback
   XIMStyle, Query Input Style
   XIMStyles, Query Input Style
   XIMTertiary, Preedit Draw Callback
   XIMText, Preedit Draw Callback
   XIMUnderline, Preedit Draw Callback
   XIMVisibleToBackward, Preedit Draw Callback
   XIMVisibleToCenter, Preedit Draw Callback
   XIMVisibleToForward, Preedit Draw Callback
   XInitExtension, Hooking into Xlib
   XInitImage, Transferring Images between Client and Server
   XInitThreads, Using Xlib with Threads
   XINPreserveState, Reset State
   XInsertModifiermapEntry, Manipulating the Keyboard Encoding
   XInstallColormap, Managing Installed Colormaps
   XInternalConnectionNumbers, Using Internal Connections
   XInternAtom, Properties and Atoms
   XInternAtoms, Properties and Atoms
   XIntersectRegion, Computing with Regions
   XKeyboardState, Manipulating the Keyboard and Pointer Settings
   XKeycodeToKeysym, Using Keyboard Utility Functions
   XKeymapEvent, Key Map State Notification Events
   XKeysymToKeycode, Using Keyboard Utility Functions
   XKeysymToString, Using Keyboard Utility Functions
   XKillClient, Killing Clients
   XLastKnownRequestProcessed, Display Macros
   XLeaveWindowEvent, Window Entry/Exit Events
   XLFD, Glossary
   XlibSpecificationRelease, Standard Header Files
   XListDepths, Display Macros
   XListExtensions, Basic Protocol Support Routines
   XListFonts, Obtaining and Freeing Font Names and Information
   XListFontsWithInfo, Obtaining and Freeing Font Names and
          Information

   XListHosts, Adding, Getting, or Removing Hosts
   XListInstalledColormaps, Managing Installed Colormaps
   XListPixmapFormats, Image Format Functions and Macros
   XListProperties, Obtaining and Changing Window Properties
   XLoadFont, Loading and Freeing Fonts
   XLoadQueryFont, Loading and Freeing Fonts
   XLocaleOfFontSet, Creating and Freeing a Font Set
   XLocaleOfIM, Input Method Functions
   XLocaleOfOM, Output Method Functions
   XLockDisplay, Using Xlib with Threads
   XLookUpAssoc, Associating User Data with a Value
   XLookupColor, Mapping Color Names to Values
   XLookupKeysym, Using Keyboard Utility Functions
   XLookupString, Using Latin-1 Keyboard Event Functions
   XLowerWindow, Changing Window Stacking Order
   XMakeAssoc, Associating User Data with a Value
   XMapEvent, MapNotify Events
   XMappingEvent, MappingNotify Events
   XMapRaised, Mapping Windows
   XMapRequestEvent, MapRequest Events
   XMapSubwindows, Mapping Windows, Mapping Windows
   XMapWindow, Window Attributes, Mapping Windows, Mapping Windows
   XMaskEvent, Selecting Events Using a Window or Event Mask
   XMatchVisualInfo, Determining the Appropriate Visual Type
   XMaxCmapsOfScreen, Screen Information Macros
   XMaxRequestSize, Display Macros
   XmbDrawImageString, Drawing Text Using Font Sets
   XmbDrawString, Drawing Text Using Font Sets
   XmbDrawText, Drawing Text Using Font Sets
   XmbLookupString, Getting Keyboard Input
   XmbResetIC, Input Context Functions
   XmbSetWMProperties, Using Window Manager Convenience Functions
   XmbTextEscapement, Obtaining Font Set Metrics
   XmbTextExtents, Obtaining Font Set Metrics
   XmbTextItem, Drawing Text Using Font Sets
   XmbTextListToTextProperty, Converting String Lists
   XmbTextPerCharExtents, Obtaining Font Set Metrics
   XmbTextPropertyToTextList, Converting String Lists
   XMinCmapsOfScreen, Screen Information Macros
   XModifierKeymap, Manipulating the Keyboard Encoding
   XMoveResizeWindow, Configuring Windows
   XMoveWindow, Configuring Windows
   XNArea, Area
   XNAreaNeeded, Area Needed
   XNBackground, Foreground and Background
   XNClientWindow, Client Window
   XNColormap, Colormap
   XNCursor, Cursor
   XNewModifiermap, Manipulating the Keyboard Encoding
   XNextEvent, Handling the Output Buffer, Returning the Next
          Event

   XNextRequest, Display Macros
   XNFilterEvents, Filter Events
   XNFocusWindow, Focus Window
   XNFontSet, Font Set
   XNForeground, Foreground and Background
   XNGeometryCallback, Geometry Callback
   XNoExposeEvent, GraphicsExpose and NoExpose Events
   XNoOp, Generating a NoOperation Protocol Request
   XNPreeditAttributes, Preedit and Status Attributes
   XNPreeditCaretCallback, Preedit and Status Callbacks
   XNPreeditDoneCallback, Preedit and Status Callbacks
   XNPreeditDrawCallback, Preedit and Status Callbacks
   XNPreeditStartCallback, Preedit and Status Callbacks
   XNResourceClass, Resource Name and Class
   XNResourceName, Resource Name and Class
   XNSpotLocation, Spot Location
   XNStatusAttributes, Preedit and Status Attributes
   XNStatusDoneCallback, Preedit and Status Callbacks
   XNStatusDrawCallback, Preedit and Status Callbacks
   XNStatusStartCallback, Preedit and Status Callbacks
   XNStdColormap, Colormap
   XOffsetRegion, Moving or Shrinking Regions
   XOMCharSetList, Required Char Set
   XOMOfOC, Output Context Functions
   XOpenDisplay, Opening the Display
   XOpenIM, Input Method Functions
   XOpenOM, Output Method Functions
   XParseColor, Mapping Color Names to Values
   XParseGeometry, Parsing the Window Geometry
   XPeekEvent, Returning the Next Event
   XPeekIfEvent, Selecting Events Using a Predicate Procedure
   XPending, Handling the Output Buffer, Event Queue Management
   Xpermalloc, Allocating Permanent Storage
   XPixmapFormatValues, Image Format Functions and Macros
   XPlanesOfScreen, Screen Information Macros
   XPoint, Drawing Points, Lines, Rectangles, and Arcs
   XPointer, Generic Values and Types
   XPointInRegion, Locating a Point or a Rectangle in a Region
   XPolygonRegion, Creating, Copying, or Destroying Regions
   XProcessInternalConnection, Using Internal Connections
   XPropertyEvent, PropertyNotify Events
   XProtocolRevision, Display Macros
   XProtocolVersion, Display Macros
   XPutBackEvent, Putting an Event Back into the Queue
   XPutImage, Transferring Images between Client and Server
   XPutPixel, Manipulating Images
   XQLength, Display Macros
   XQueryBestCursor, Creating, Recoloring, and Freeing Cursors,
          Creating, Recoloring, and Freeing Cursors

   XQueryBestSize, Setting the Fill Tile and Stipple
   XQueryBestStipple, Setting the Fill Tile and Stipple
   XQueryBestTile, Setting the Fill Tile and Stipple
   XQueryColor, Modifying and Querying Colormap Cells
   XQueryColors, Modifying and Querying Colormap Cells
   XQueryExtension, Basic Protocol Support Routines
   XQueryFont, Loading and Freeing Fonts
   XQueryKeymap, Manipulating the Keyboard and Pointer Settings
   XQueryPointer, Translating Screen Coordinates
   XQueryTextExtents, Querying Character String Sizes
   XQueryTextExtents16, Querying Character String Sizes
   XQueryTree, Obtaining Window Information
   XRaiseWindow, Changing Window Stacking Order
   XReadBitmapFile, Manipulating Bitmaps
   XReadBitmapFileData, Manipulating Bitmaps
   XRebindKeysym, Using Latin-1 Keyboard Event Functions
   XRecolorCursor, Creating, Recoloring, and Freeing Cursors
   XReconfigureWMWindow, Manipulating Top-Level Windows
   XRectangle, Drawing Points, Lines, Rectangles, and Arcs
   XRectInRegion, Locating a Point or a Rectangle in a Region
   XRefreshKeyboardMapping, Using Keyboard Utility Functions
   XRegisterIMInstantiateCallback, Input Method Functions
   XRemoveConnectionWatch, Using Internal Connections
   XRemoveFromSaveSet, Controlling the Lifetime of a Window
   XRemoveHost, Adding, Getting, or Removing Hosts
   XRemoveHosts, Adding, Getting, or Removing Hosts
   XReparentEvent, ReparentNotify Events
   XReparentWindow, Changing the Parent of a Window
   XResetScreenSaver, Controlling the Screen Saver
   XResizeRequestEvent, ResizeRequest Events
   XResizeWindow, Configuring Windows
   XResourceManagerString, Creating and Storing Databases
   xResourceReq, Request Format
   XRestackWindows, Changing Window Stacking Order
   XrmCombineDatabase, Merging Resource Databases
   XrmCombineFileDatabase, Merging Resource Databases
   XrmDatabase, Creating and Storing Databases
   XrmDestroyDatabase, Creating and Storing Databases
   XrmEnumerateDatabase, Enumerating Database Entries
   XrmGetDatabase, Creating and Storing Databases
   XrmGetFileDatabase, Creating and Storing Databases
   XrmGetResource, Looking Up Resources
   XrmGetStringDatabase, Creating and Storing Databases
   XrmInitialize, Creating and Storing Databases
   XrmLocaleOfDatabase, Creating and Storing Databases
   XrmMergeDatabases, Merging Resource Databases
   XrmOptionDescRec, Parsing Command Line Options
   XrmOptionKind, Parsing Command Line Options
   XrmParseCommand, Parsing Command Line Options
   XrmPermStringToQuark, Quarks
   XrmPutFileDatabase, Creating and Storing Databases
   XrmPutLineResource, Storing into a Resource Database
   XrmPutResource, Storing into a Resource Database
   XrmPutStringResource, Storing into a Resource Database
   XrmQGetResource, Looking Up Resources
   XrmQGetSearchList, Looking Up Resources
   XrmQGetSearchResource, Looking Up Resources
   XrmQPutResource, Storing into a Resource Database
   XrmQPutStringResource, Storing into a Resource Database
   XrmQuarkToString, Quarks
   XrmSetDatabase, Creating and Storing Databases
   XrmStringToBindingQuarkList, Quarks
   XrmStringToQuark, Quarks
   XrmStringToQuarkList, Quarks
   XrmUniqueQuark, Quarks
   XrmValue, Creating and Storing Databases
   XRootWindow, Display Macros
   XRootWindowOfScreen, Screen Information Macros
   XRotateBuffers, Using Cut Buffers
   XRotateWindowProperties, Obtaining and Changing Window
          Properties

   XSaveContext, Using the Context Manager
   XScreenCount, Display Macros
   XScreenNumberOfScreen, Screen Information Macros
   XScreenOfDisplay, Display Macros
   XScreenResourceString, Creating and Storing Databases
   XSegment, Drawing Points, Lines, Rectangles, and Arcs
   XSelectInput, Selecting Events
   XSelectionClearEvent, SelectionClear Events
   XSelectionEvent, SelectionNotify Events
   XSelectionRequestEvent, SelectionRequest Events
   XSendEvent, Sending Events to Other Applications, Sending
          Events to Other Applications

   XServerInterpretedAddress, Adding, Getting, or Removing Hosts
   XServerVendor, Display Macros
   XSetAccessControl, Changing, Enabling, or Disabling Access
          Control

   XSetAfterFunction, Enabling or Disabling Synchronization
   XSetArcMode, Setting the Arc Mode, Subwindow Mode, and Graphics
          Exposure

   XSetBackground, Setting the Foreground, Background, Function,
          or Plane Mask

   XSetClassHint, Setting and Reading the WM_CLASS Property
   XSetClipMask, Setting the Clip Region
   XSetClipOrigin, Setting the Clip Region
   XSetClipRectangles, Setting the Clip Region
   XSetCloseDownMode, Closing the Display
   XSetCommand, Setting and Reading the WM_COMMAND Property
   XSetDashes, Setting the Line Attributes and Dashes
   XSetErrorHandler, Using the Default Error Handlers
   XSetFillRule, Setting the Fill Style and Fill Rule
   XSetFillStyle, Setting the Fill Style and Fill Rule
   XSetFont, Setting the Current Font
   XSetFontPath, Setting and Retrieving the Font Search Path
   XSetForeground, Setting the Foreground, Background, Function,
          or Plane Mask

   XSetFunction, Setting the Foreground, Background, Function, or
          Plane Mask

   XSetGraphicsExposures, Setting the Arc Mode, Subwindow Mode,
          and Graphics Exposure

   XSetICFocus, Input Context Functions
   XSetIconName, Setting and Reading the WM_ICON_NAME Property
   XSetIconSizes, Setting and Reading the WM_ICON_SIZE Property
   XSetICValues, Input Context Functions
   XSetIMValues, Input Method Functions
   XSetInputFocus, Controlling Input Focus
   XSetIOErrorHandler, Using the Default Error Handlers
   XSetLineAttributes, Setting the Line Attributes and Dashes
   XSetLocaleModifiers, X Locale Management
   XSetModifierMapping, Manipulating the Keyboard Encoding
   XSetNormalHints, Setting and Getting Window Sizing Hints
   XSetOCValues, Output Context Functions
   XSetOMValues, Output Method Functions
   XSetPlaneMask, Setting the Foreground, Background, Function, or
          Plane Mask

   XSetPointerMapping, Manipulating the Keyboard and Pointer
          Settings

   XSetRegion, Creating, Copying, or Destroying Regions
   XSetRGBColormaps, Setting and Obtaining Standard Colormaps
   XSetScreenSaver, Controlling the Screen Saver
   XSetSelectionOwner, Selections
   XSetSizeHints, Setting and Getting Window Sizing Hints
   XSetStandardColormap, Getting and Setting an XStandardColormap
          Structure

   XSetStandardProperties, Setting Standard Properties
   XSetState, Setting the Foreground, Background, Function, or
          Plane Mask

   XSetStipple, Setting the Fill Tile and Stipple
   XSetSubwindowMode, Setting the Arc Mode, Subwindow Mode, and
          Graphics Exposure

   XSetTextProperty, Setting and Reading Text Properties
   XSetTile, Setting the Fill Tile and Stipple
   XSetTransientForHint, Setting and Reading the WM_TRANSIENT_FOR
          Property

   XSetTSOrigin, Setting the Fill Tile and Stipple
   XSetWindowAttributes, Window Attributes
   XSetWindowBackground, Changing Window Attributes
   XSetWindowBackgroundPixmap, Changing Window Attributes
   XSetWindowBorder, Changing Window Attributes
   XSetWindowBorderPixmap, Changing Window Attributes
   XSetWindowBorderWidth, Configuring Windows
   XSetWindowColormap, Changing Window Attributes
   XSetWMClientMachine, Setting and Reading the WM_CLIENT_MACHINE
          Property

   XSetWMColormapWindows, Setting and Reading the
          WM_COLORMAP_WINDOWS Property

   XSetWMHints, Setting and Reading the WM_HINTS Property
   XSetWMIconName, Setting and Reading the WM_ICON_NAME Property
   XSetWMName, Setting and Reading the WM_NAME Property
   XSetWMNormalHints, Setting and Reading the WM_NORMAL_HINTS
          Property

   XSetWMProperties, Using Window Manager Convenience Functions
   XSetWMProtocols, Setting and Reading the WM_PROTOCOLS Property
   XSetWMSizeHints, Setting and Reading the WM_NORMAL_HINTS
          Property

   XSetZoomHints, Setting and Getting Window Sizing Hints
   XShrinkRegion, Moving or Shrinking Regions
   XStoreBuffer, Using Cut Buffers
   XStoreBytes, Using Cut Buffers
   XStoreColor, Modifying and Querying Colormap Cells
   XStoreColors, Modifying and Querying Colormap Cells
   XStoreName, Setting and Reading the WM_NAME Property
   XStoreNamedColor, Modifying and Querying Colormap Cells
   XStringListToTextProperty, Converting String Lists
   XStringToKeysym, Using Keyboard Utility Functions
   XSubImage, Manipulating Images
   XSubtractRegion, Computing with Regions
   XSync, Overview of the X Window System, Overview of the X
          Window System, Handling the Output Buffer

   XSynchronize, Enabling or Disabling Synchronization
   XTextExtents, Computing Logical Extents
   XTextExtents16, Computing Logical Extents
   XTextItem, Drawing Text
   XTextItem16, Drawing Text
   XTextProperty, Converting String Lists
   XTextPropertyToStringList, Converting String Lists
   XTextWidth, Computing Character String Sizes, Computing
          Character String Sizes

   XTextWidth16, Computing Character String Sizes, Computing
          Character String Sizes

   XTimeCoord, Getting Pointer Motion History
   XTranslateCoordinates, Translating Screen Coordinates
   XUndefineCursor, Changing Window Attributes
   XUngrabButton, Pointer Grabbing
   XUngrabKey, Keyboard Grabbing
   XUngrabKeyboard, Keyboard Grabbing
   XUngrabPointer, Pointer Grabbing
   XUngrabServer, Grabbing the Server
   XUninstallColormap, Managing Installed Colormaps
   XUnionRectWithRegion, Computing with Regions
   XUnionRegion, Computing with Regions
   XUnloadFont, Loading and Freeing Fonts
   XUnlockDisplay, Using Xlib with Threads
   XUnmapEvent, UnmapNotify Events
   XUnmapSubwindows, Unmapping Windows
   XUnmapWindow, Unmapping Windows, Unmapping Windows
   XUnregisterIMInstantiateCallback, Input Method Functions
   XUnsetICFocus, Input Context Functions
   XVaCreateNestedList, Variable Argument Lists
   XVendorRelease, Display Macros
   XVisibilityEvent, VisibilityNotify Events
   XVisualIDFromVisual, Visual Types
   XWarpPointer, Moving the Pointer
   XwcDrawImageString, Drawing Text Using Font Sets
   XwcDrawString, Drawing Text Using Font Sets
   XwcDrawText, Drawing Text Using Font Sets
   XwcFreeStringList, Converting String Lists
   XwcLookupString, Getting Keyboard Input
   XwcResetIC, Input Context Functions
   XwcTextEscapement, Obtaining Font Set Metrics
   XwcTextExtents, Obtaining Font Set Metrics
   XwcTextItem, Drawing Text Using Font Sets
   XwcTextListToTextProperty, Converting String Lists
   XwcTextPerCharExtents, Obtaining Font Set Metrics
   XwcTextPropertyToTextList, Converting String Lists
   XWhitePixel, Display Macros
   XWhitePixelOfScreen, Screen Information Macros
   XWidthMMOfScreen, Screen Information Macros
   XWidthOfScreen, Screen Information Macros
   XWindowAttributes, Obtaining Window Information
   XWindowChanges, Configuring Windows
   XWindowEvent, Handling the Output Buffer, Selecting Events
          Using a Window or Event Mask

   XWithdrawWindow, Manipulating Top-Level Windows
   XWMGeometry, Parsing the Window Geometry
   XWriteBitmapFile, Manipulating Bitmaps, Manipulating Bitmaps
   XXorRegion, Computing with Regions
   XY format, Glossary

Z

   Z format, Glossary
