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set_gfx_mode(3)			Allegro	manual		       set_gfx_mode(3)

       set_gfx_mode  - Sets a graphic video mode. Allegro game programming li-

       #include	<allegro.h>

       int set_gfx_mode(int card, int w, int h,	int v_w, int v_h);

       Switches	into graphics mode. The	card parameter should usually  be  one
       of  the	Allegro	 magic drivers (read introduction of chapter "Graphics
       modes") or see the platform specific documentation for a	 list  of  the
       available  drivers.  The	w and h	parameters specify what	screen resolu-
       tion you	want.  The color depth of the graphic mode has to be specified
       before calling this function with set_color_depth().

       The  v_w	and v_h	parameters specify the minimum virtual screen size, in
       case you	need a large virtual screen for	 hardware  scrolling  or  page
       flipping.  You should set them to zero if you don't care	about the vir-
       tual screen size.

       When you	call set_gfx_mode(), the v_w and v_h parameters	represent  the
       minimum size of virtual screen that is acceptable for your program. The
       range of	possible sizes is usually very restricted, and Allegro may end
       up creating a virtual screen much larger	than the one you request.  Al-
       lowed sizes are driver dependent	and some drivers do not	allow  virtual
       screens	that  are  larger than the visible screen at all: don't	assume
       that whatever you pass will always work.

       In mode-X the virtual width can be any multiple of eight	 greater  than
       or  equal  to the physical screen width,	and the	virtual	height will be
       set accordingly (the VGA	has 256k of vram, so the virtual  height  will
       be 256*1024/virtual_width).

       Currently,  using  a big	virtual	screen for page	flipping is considered
       bad practice.  There are	platforms which	don't support virtual  screens
       bigger than the physical	screen but can create different	video pages to
       flip back and forth. This means that, if	you  want  page	 flipping  and
       aren't  going to	use hardware scrolling,	you should call	set_gfx_mode()
       with (0,0) as the virtual screen	size and later	create	the  different
       video  pages with create_video_bitmap().	Otherwise your program will be
       limited to the platforms	supporting hardware scrolling.

       After you select	a graphics mode, the physical and virtual screen sizes
       can  be checked with the	macros SCREEN_W, SCREEN_H, VIRTUAL_W, and VIR-

       Returns zero on success.	On  failure  returns  a	 negative  number  and
       stores a	description of the problem in allegro_error.

       set_color_depth(3),  request_refresh_rate(3),  screen(3), gfx_capabili-
       ties(3),	allegro_error(3), create_video_bitmap(3),  get_desktop_resolu-
       tion(3),	SCREEN_W(3), SCREEN_H(3), VIRTUAL_W(3),	VIRTUAL_H(3)

Allegro				 version 4.4.3		       set_gfx_mode(3)


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