gtk2/docs/gdk.texi

\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename gdk.info
@settitle GDK
@setchapternewpage odd
@c %**end of header

@set edition 1.0
@set update-date 16 May 1996
@set update-month May 1996

@ifinfo
This file documents GDK, the General Drawing Kit

Copyright (C) 1996 Peter Mattis

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies

@ignore
Permission is granted to process this file throught TeX and print the
results, provided the printed document carries copying permission notice
identical to this one except for the removal of this paragraph (this
paragraph not being relevant to the printed manual).

@end ignore
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation
approved by Peter Mattis.
@end ifinfo

@titlepage
@title The General Drawing Kit
@subtitle Version 1.0
@subtitle @value{update-month}
@author by Peter Mattis

@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1996 Peter Mattis

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation
approved by Peter Mattis.
@end titlepage

@dircategory User Interface Toolkit
@direntry
* GDK: (gdk).		The General Drawing Kit
@end direntry

@node Top, Copying, (dir), (dir)
@top The General Drawing Kit
@ifinfo
This is edition @value{edition} of the GDK documentation,
@w{@value{update-date}}.
@end ifinfo

@menu
* Copying::                     Your rights.
* Overview::                    What is GDK?
* Initialization::              Initialization and exit.
* Events::                      Event handling.
* Visuals::                     Understanding and using visuals.
* Windows::                     Creating and using windows.
* Graphics Contexts::           Creating and modifying GCs.
* Pixmaps::                     Creating pixmaps.
* Images::                      Creating images.
* Color::                       Specifying color.
* Fonts::                       Creating fonts.
* Drawing::                     Drawing commands.
* XInput Support::              Using extended devices.
* Miscellany::                  Other stuff.
* Examples::                    Using GDK.
* Function Index::              Index of functions
* Concept Index::               Index of concepts
@end menu

@node Copying, Overview, Top, Top
@comment node-name, next, previous, up
@chapter Copying

GDK is @dfn{free}; this means that everyone is free to use it and free
to redestribute it on a free basis. GDK is not in the public domain; it
is copyrighted and there are restrictions on its distribution, but these
restrictions are designed to permit everything that a good cooperating
citizen would want to do. What is not allowed is to try to prevent
others from further sharing any version of GDK that they might get from
you.

Specifically, we want to make sure that you have the right to give away
copies of GDK, that you receive source code or else can get it if you
want it, that you can change GDK or use pieces of it in new free
programs, and that you know you can do these things.

To make sure that everyone has such rights, we have to forbid you to
deprive anyone else of these rights. For example, if you distribute
copies of GDK, you must give the recipients all the rights that you
have. You must make sure that they, too, receive or can get the source
code. And you must tell them their rights.

Also, for my own protection, we must make certain that everyone finds
out that there is no warranty for GDK. If GDK is modified by someone
else and passed on, we want their recipients to know that what they have
is not what we distributed, so that any problems introduced by others
will no reflect on our reputation.

The precise conditions of the licenses for GDK are found in the General
Public Licenses that accompanies it.


@node Overview, Initialization, Copying, Top
@comment node-name, next, previous, up
@chapter What is GDK?
@cindex Overview

GDK is designed as a wrapper library that lies on top of Xlib. It
performs many common and desired operations for a programmer instead
of the programmer having to explicitly ask for such functionality from
Xlib directly. For example, GDK provides a common interface to both
regular and shared memory XImage types. By doing so, an application
can nearly transparently use the fastest image type available. GDK
also provides routines for determining the best available color depth
and the best available visual which is not always the default visual
for a screen.

@node Initialization, Events, Overview, Top
@comment node-name, next, previous, up
@chapter Initialization and exit
@cindex Initialization
@cindex Exit

Initializing GDK is easy. Simply call @code{gdk_init} passing in the
@var{argc} and @var{argv} parameters. Exit is similarly easy. Just
call @code{gdk_exit}.

@deftypefun void gdk_init (int *@var{argc}, char ***@var{argv})
Initializes the GDK library. The arguments @var{argc} and @var{argv}
are scanned and any arguments that GDK recognizes are handled and
removed. The @var{argc} and @var{argv} parameters are the values
passed to @code{main} upon program invocation.
@end deftypefun

@deftypefun void gdk_exit (int @var{errorcode})
Exit GDK and perform any necessary cleanup. @code{gdk_exit} will call
the systems @code{exit} function passing @var{errorcode} as the
parameter.
@end deftypefun

@example
int
main (int argc, char *argv[])
@{
  /* Initialize GDK. */
  gdk_init (&argc, &argv);

  /* Exit from GDK...this call will never return. */
  gdk_exit (0);

  /* Keep compiler from issuing a warning */
  return 0;
@}
@end example


@node Events, Visuals, Initialization, Top
@comment node-name, next, previous, up
@chapter Event handling
@cindex Events

Events are the means by which GDK lets the programmer know of user
interaction. An event is normally a button or key press or some other
indirect user action, such as a the mouse cursor entering or leaving a
window.

There exist only a few functions for getting events and event
information. These are @code{gdk_events_pending},
@code{gdk_event_get}, @code{gdk_events_record} and
@code{gdk_events_playback}. The latter two functions are useful for
automatic testing of a software package and should normally not be
needed in a program.

@deftypefun gint gdk_events_pending (void)
Returns the number of events pending on the event queue.
@end deftypefun

@deftypefun gint gdk_event_get (GdkEvent *@var{event})
Return the next available event in the @var{event}
structure. @code{gdk_event_get} will return @code{TRUE} on success and
@code{FALSE} on failure. Success and failure is determined by whether
an event arrived before the timeout period expired.
@end deftypefun

@deftypefun void gdk_events_record (char *@var{filename})
Turn on recording of events. User events and certain system events will
be saved in the file named by the variable @var{filename}. This stream
of events can later be played back and ``should'' produce the same
results as when the original events were handled. However, the
programmer does need to be careful in that the state of the program must
be the same when @code{gdk_events_record} is called and when
@code{gdk_events_playback} is called. For this reason,
@code{gdk_events_record} is normally not called directly, but is instead
invoked indirectly by specifying the ``-record'' command line option.
@end deftypefun

@deftypefun void gdk_events_playback (char *@var{filename})
Start playback of events from a file. (See the above description of
@code{gdk_events_record}). Normally this function is not called directly
but is invoked by the ``-playback'' command line option.
@end deftypefun

@deftypefun void gdk_events_stop (void)
Stop recording and playback of events.
@end deftypefun

@example
void
handle_event ()
@{
  GdkEvent event;

  if (gdk_event_get (&event))
    @{
      switch (event.type)
       @{
         @dots{}
       @}
    @}
@}
@end example


@node Visuals, Windows, Events, Top
@comment node-name, next, previous, up
@chapter Understanding and using visuals
@cindex Visuals

@node Windows, Graphics Contexts, Visuals, Top
@comment node-name, next, previous, up
@chapter Creating and using windows
@cindex Windows

@node Graphics Contexts, Pixmaps, Windows, Top
@comment node-name, next, previous, up
@chapter Creating and modifying GCs
@cindex Graphics Contexts
@cindex GC

@node Pixmaps, Images, Graphics Contexts, Top
@comment node-name, next, previous, up
@chapter Creating pixmaps
@cindex Pixmaps

@node Images, Color, Pixmaps, Top
@comment node-name, next, previous, up
@chapter Creating images
@cindex Images

@node Color, Fonts, Images, Top
@comment node-name, next, previous, up
@chapter Specifying color
@cindex Color

@node Fonts, Drawing, Color, Top
@comment node-name, next, previous, up
@chapter Creating Fonts
@cindex Fonts

@node Drawing, XInput Support, Fonts, Top
@comment node-name, next, previous, up
@chapter Drawing Commands
@cindex Drawing

@node XInput Support, Miscellany, Drawing, Top
@comment node-name, next, previous, up
@chapter Using extended devices
@cindex Overview
@cindex Using extended device capabilities
@cindex Controlling extended devices

@node Miscellany, Examples, XInput Support, Top
@comment node-name, next, previous, up
@chapter Other stuff
@cindex Timers
@cindex Debugging
@cindex Miscellaneous


@node Examples, Function Index, Miscellany, Top
@comment node-name, next, previous, up
@chapter Using GDK
@cindex Examples


@node Function Index, Concept Index, Examples, Top
@comment node-name, next, previous, up
@unnumbered Variable Index

@printindex fn

@node Concept Index, , Function Index, Top
@comment node-name, next, previous, up
@unnumbered Concept Index

@printindex cp

@summarycontents
@contents
@bye