gtk/docs/reference/gdk/tmpl/general.sgml

<!-- ##### SECTION Title ##### -->
General

<!-- ##### SECTION Short_Description ##### -->
library initialization and miscellaneous functions.

<!-- ##### SECTION Long_Description ##### -->
<para>
This section describes the GDK initialization functions and miscellaneous
utility functions.
</para>

<!-- ##### SECTION See_Also ##### -->
<para>

</para>

<!-- ##### FUNCTION gdk_init ##### -->
<para>
Initializes the GDK library and connects to the X server.
If initialization fails, a warning message is output and the application
terminates with a call to <literal>exit(1)</literal>.
</para>
<para>
Any arguments used by GDK are removed from the array and @argc and @argv are
updated accordingly.
</para>
<para>
GTK+ initializes GDK in gtk_init() and so this function is not usually needed
by GTK+ applications.
</para>

@argc: the number of command line arguments.
@argv: the array of command line arguments.


<!-- ##### FUNCTION gdk_init_check ##### -->
<para>
Initializes the GDK library and connects to the X server, returning %TRUE on
success.
</para>
<para>
Any arguments used by GDK are removed from the array and @argc and @argv are
updated accordingly.
</para>
<para>
GTK+ initializes GDK in gtk_init() and so this function is not usually needed
by GTK+ applications.
</para>

@argc: the number of command line arguments.
@argv: the array of command line arguments.
@Returns: %TRUE if initialization succeeded.


<!-- ##### FUNCTION gdk_set_locale ##### -->
<para>
Initializes the support for internationalization by calling the <function>setlocale()</function>
system call. This function is called by gtk_set_locale() and so GTK+
applications should use that instead.
</para>
<para>
The locale to use is determined by the <envar>LANG</envar> environment variable,
so to run an application in a certain locale you can do something like this:
<informalexample>
<programlisting>
  export LANG="fr"
  ... run application ...
</programlisting>
</informalexample>
</para>
<para>
If the locale is not supported by X then it is reset to the standard "C"
locale.
</para>

@Returns: the resulting locale.


<!-- ##### FUNCTION gdk_set_sm_client_id ##### -->
<para>
Sets the <literal>SM_CLIENT_ID</literal> property on the application's leader window so that
the window manager can save the application's state using the X11R6 ICCCM
session management protocol.
</para>
<para>
The leader window is automatically created by GDK and never shown. It's only
use is for session management. The <literal>WM_CLIENT_LEADER</literal> property is automatically
set on all X windows created by the application to point to the leader window.
</para>
<para>
See the X Session Management Library documentation for more information on
session management and the Inter-Client Communication Conventions Manual
(ICCCM) for information on the <literal>WM_CLIENT_LEADER</literal> property. 
(Both documents are part of the X Window System distribution.)
</para>

@sm_client_id: the client id assigned by the session manager when the
connection was opened, or %NULL to remove the property.


<!-- ##### FUNCTION gdk_exit ##### -->
<para>
Exits the application using the <function>exit()</function> system call.
</para>
<para>
This routine is provided mainly for backwards compatibility, since it used to
perform tasks necessary to exit the application cleanly. Those tasks are now
performed in a function which is automatically called on exit (via the use
of g_atexit()).
</para>

@error_code: the error code to pass to the <function>exit()</function> call.


<!-- ##### FUNCTION gdk_get_program_class ##### -->
<para>
Gets the program class. Unless the program class has explicitly
been set with gdk_set_program_class() or with the <option>--class</option> 
commandline option, the default value is the program name (determined 
with g_get_prgname()) with the first character converted to uppercase. 
</para>

@Returns: the program class.


<!-- ##### FUNCTION gdk_set_program_class ##### -->
<para>
Sets the program class. The X11 backend uses the program class to set
the class name part of the <literal>WM_CLASS</literal> property on
toplevel windows; see the ICCCM.
</para>

@program_class: a string.


<!-- ##### FUNCTION gdk_get_display ##### -->
<para>
Gets the name of the display, which usually comes from the <envar>DISPLAY</envar>
environment variable or the <option>--display</option> command line option.
</para>

@Returns: the name of the display.


<!-- ##### FUNCTION gdk_flush ##### -->
<para>
Flushes the X output buffer and waits until all requests have been processed
by the server. This is rarely needed by applications. It's main use is for
trapping X errors with gdk_error_trap_push() and gdk_error_trap_pop().
</para>



<!-- ##### FUNCTION gdk_screen_width ##### -->
<para>
Returns the width of the screen in pixels.
</para>

@Returns: the width of the screen in pixels.


<!-- ##### FUNCTION gdk_screen_height ##### -->
<para>
Returns the height of the screen in pixels.
</para>

@Returns: the height of the screen in pixels.


<!-- ##### FUNCTION gdk_screen_width_mm ##### -->
<para>
Returns the width of the screen in millimeters.
Note that on many X servers this value will not be correct.
</para>

@Returns: the width of the screen in millimeters, though it is not always
correct.


<!-- ##### FUNCTION gdk_screen_height_mm ##### -->
<para>
Returns the height of the screen in millimeters.
Note that on many X servers this value will not be correct.
</para>

@Returns: the height of the screen in millimeters, though it is not always
correct.


<!-- ##### FUNCTION gdk_pointer_grab ##### -->
<para>
Grabs the pointer (usually a mouse) so that all events are passed to this
application until the pointer is ungrabbed with gdk_pointer_ungrab(), or
the grab window becomes unviewable.
This overrides any previous pointer grab by this client.
</para>
<para>
Pointer grabs are used for operations which need complete control over mouse
events, even if the mouse leaves the application.
For example in GTK+ it is used for Drag and Drop, for dragging the handle in
the #GtkHPaned and #GtkVPaned widgets, and for resizing columns in #GtkCList
widgets.
</para>
<para>
Note that if the event mask of an X window has selected both button press and
button release events, then a button press event will cause an automatic
pointer grab until the button is released.
X does this automatically since most applications expect to receive button
press and release events in pairs.
It is equivalent to a pointer grab on the window with @owner_events set to
%TRUE.
</para>

@window: the #GdkWindow which will own the grab (the grab window).
@owner_events: if %FALSE then all pointer events are reported with respect to
@window and are only reported if selected by @event_mask. If %TRUE then pointer
events for this application are reported as normal, but pointer events outside
this application are reported with respect to @window and only if selected by
@event_mask. In either mode, unreported events are discarded.
@event_mask: specifies the event mask, which is used in accordance with
@owner_events.
@confine_to: If non-%NULL, the pointer will be confined to this
window during the grab. If the pointer is outside @confine_to, it will
automatically be moved to the closest edge of @confine_to and enter
and leave events will be generated as necessary.
@cursor: the cursor to display while the grab is active. If this is %NULL then
the normal cursors are used for @window and its descendants, and the cursor
for @window is used for all other windows.
@time: the timestamp of the event which led to this pointer grab. This usually
comes from a #GdkEventButton struct, though %GDK_CURRENT_TIME can be used if
the time isn't known.
@Returns: %GDK_GRAB_SUCCESS if the grab was successful.


<!-- ##### ENUM GdkGrabStatus ##### -->
<para>
Returned by gdk_pointer_grab() and gdk_keyboard_grab() to indicate 
success or the reason for the failure of the grab attempt.
</para>

@GDK_GRAB_SUCCESS: the resource was successfully grabbed.
@GDK_GRAB_ALREADY_GRABBED: the resource is actively grabbed by another client.
@GDK_GRAB_INVALID_TIME: the resource was grabbed more recently than the 
  specified time.
@GDK_GRAB_NOT_VIEWABLE: the grab window or the @confine_to window are not
  viewable.
@GDK_GRAB_FROZEN: the resource is frozen by an active grab of another client.

<!-- ##### FUNCTION gdk_pointer_ungrab ##### -->
<para>
Ungrabs the pointer, if it is grabbed by this application.
</para>

@time: a timestamp from a #GdkEvent, or %GDK_CURRENT_TIME if no timestamp is
available.


<!-- ##### FUNCTION gdk_pointer_is_grabbed ##### -->
<para>
Returns %TRUE if the pointer is currently grabbed by this application.
</para>
<para>
Note that the return value is not completely reliable since the X server may
automatically ungrab the pointer, without informing the application, if the
grab window becomes unviewable. It also does not take passive pointer grabs
into account.
</para>

@Returns: %TRUE if the pointer is currently grabbed by this application.
Though this value is not always correct.


<!-- ##### FUNCTION gdk_set_double_click_time ##### -->
<para>

</para>

@msec: 


<!-- ##### FUNCTION gdk_keyboard_grab ##### -->
<para>
Grabs the keyboard so that all events are passed to this
application until the keyboard is ungrabbed with gdk_keyboard_ungrab().
This overrides any previous keyboard grab by this client.
</para>

@window: the #GdkWindow which will own the grab (the grab window).
@owner_events: if %FALSE then all keyboard events are reported with respect to
@window. If %TRUE then keyboard events for this application are reported as
normal, but keyboard events outside this application are reported with respect
to @window. Both key press and key release events are always reported,
independant of the event mask set by the application.
@time: a timestamp from a #GdkEvent, or %GDK_CURRENT_TIME if no timestamp is
available.
@Returns: %GDK_GRAB_SUCCESS if the grab was successful.


<!-- ##### FUNCTION gdk_keyboard_ungrab ##### -->
<para>
Ungrabs the keyboard, if it is grabbed by this application.
</para>

@time: a timestamp from a #GdkEvent, or %GDK_CURRENT_TIME if no timestamp is
available.


<!-- ##### FUNCTION gdk_beep ##### -->
<para>
Emits a short beep.
</para>



<!-- ##### FUNCTION gdk_get_use_xshm ##### -->
<para>
Returns %TRUE if GDK will attempt to use the MIT-SHM shared memory extension.
</para>
<para>
The shared memory extension is used for #GdkImage, and consequently for
<link linkend="gdk-GdkRGB">GdkRGB</link>.
It enables much faster drawing by communicating with the X server through
SYSV shared memory calls. However, it can only be used if the X client and
server are on the same machine and the server supports it.
</para>

@Returns: %TRUE if use of the MIT shared memory extension will be attempted.


<!-- ##### FUNCTION gdk_set_use_xshm ##### -->
<para>
Sets whether the use of the MIT shared memory extension should be attempted.
This function is mainly for internal use. It is only safe for an application
to set this to %FALSE, since if it is set to %TRUE and the server does not
support the extension it may cause warning messages to be output.
</para>

@use_xshm: %TRUE if use of the MIT shared memory extension should be attempted.


<!-- ##### FUNCTION gdk_error_trap_push ##### -->
<para>
This function allows X errors to be trapped instead of the normal behavior
of exiting the application. It should only be used if it is not possible to
avoid the X error in any other way.
</para>
<example>
<title>Trapping an X error.</title>
<programlisting>
  gdk_error_trap_push (<!>);

  /* ... Call the X function which may cause an error here ... */

  /* Flush the X queue to catch errors now. */
  gdk_flush (<!>);

  if (gdk_error_trap_pop (<!>))
    {
      /* ... Handle the error here ... */
    }
</programlisting>
</example>



<!-- ##### FUNCTION gdk_error_trap_pop ##### -->
<para>
Removes the X error trap installed with gdk_error_trap_push().
</para>

@Returns: the X error code, or 0 if no error occurred.


<!-- ##### MACRO GDK_WINDOWING_X11 ##### -->
<para>
This macro is defined if GDK is configured to use the X backend.
</para>



<!-- ##### MACRO GDK_WINDOWING_WIN32 ##### -->
<para>
This macro is defined if GDK is configured to use the Win32 backend.
</para>



<!-- ##### MACRO GDK_WINDOWING_FB ##### -->
<para>
This macro is defined if GDK is configured to use the Linux framebuffer backend.
</para>