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set_display_switch_mode(3)	Allegro	manual	    set_display_switch_mode(3)

       set_display_switch_mode	-  Tells Allegro how the program handles back-
       ground switching.

       #include	<allegro.h>

       int set_display_switch_mode(int mode);

       Sets how	the program should handle being	switched into the  background,
       if  the	user  tabs away	from it. Not all of the	possible modes will be
       supported by every graphics driver on  every  platform.	The  available
       modes are:


       Disables	 switching. This is the	default	in single-tasking systems like
       DOS. It may be supported	on other platforms, but	you should use it with
       caution,	 because  your users won't be impressed	if they	want to	switch
       away from your program, but you don't let them!


       Pauses the program whenever it is in the	background. Execution will  be
       resumed as soon as the user switches back to it.	This is	the default in
       most fullscreen multitasking environments, for example the  Linux  con-
       sole, but not under Windows.


       Like  SWITCH_PAUSE,  but	 this mode doesn't bother to remember the con-
       tents of	video memory, so the screen, and any video  bitmaps  that  you
       have created, will be erased after the user switches away and then back
       to your program.	This is	not a terribly useful mode to have, but	it  is
       the default for the fullscreen drivers under Windows because DirectDraw
       is too dumb to implement	anything better.


       The program will	carry on running in the	background,  with  the	screen
       bitmap  temporarily being pointed at a memory buffer for	the fullscreen
       drivers.	You must take special care when	using this mode,  because  bad
       things  will  happen if the screen bitmap gets changed around when your
       program isn't expecting it (see below).


       Like SWITCH_BACKGROUND, but this	mode doesn't bother  to	 remember  the
       contents	 of  video  memory  (see SWITCH_AMNESIA). It is	again the only
       mode supported by the fullscreen	drivers	under Windows  that  lets  the
       program keep running in the background.

       Note  that  you should be very careful when you are using graphics rou-
       tines in	the switching context: you must	always	call  acquire_screen()
       before the start	of any drawing code onto the screen and	not release it
       until you are completely	finished, because the automatic	locking	mecha-
       nism  may not be	good enough to work when the program runs in the back-
       ground or has just been raised in the foreground.

       Returns zero on success,	invalidating at	the same  time	all  callbacks
       previously registered with set_display_switch_callback(). Returns -1 if
       the requested mode is not currently possible.

       set_display_switch_callback(3), get_display_switch_mode(3),  exmidi(3),
       exsample(3), exstream(3), exswitch(3)

Allegro				 version 4.4.3	    set_display_switch_mode(3)


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