1set_gfx_mode(3)                 Allegro manual                 set_gfx_mode(3)
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NAME

6       set_gfx_mode  -  Sets  a  graphic  video mode. Allegro game programming
7       library.
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SYNOPSIS

10       #include <allegro.h>
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13       int set_gfx_mode(int card, int w, int h, int v_w, int v_h);
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DESCRIPTION

16       Switches into graphics mode. The card parameter should usually  be  one
17       of  the  Allegro  magic drivers (read introduction of chapter "Graphics
18       modes") or see the platform specific documentation for a  list  of  the
19       available  drivers.  The w and h parameters specify what screen resolu‐
20       tion you want.  The color depth of the graphic mode has to be specified
21       before calling this function with set_color_depth().
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23       The  v_w and v_h parameters specify the minimum virtual screen size, in
24       case you need a large virtual screen for  hardware  scrolling  or  page
25       flipping.  You should set them to zero if you don't care about the vir‐
26       tual screen size.
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28       When you call set_gfx_mode(), the v_w and v_h parameters represent  the
29       minimum size of virtual screen that is acceptable for your program. The
30       range of possible sizes is usually very restricted, and Allegro may end
31       up  creating  a  virtual  screen  much larger than the one you request.
32       Allowed sizes are driver dependent and some drivers do not  allow  vir‐
33       tual  screens  that  are  larger  than the visible screen at all: don't
34       assume that whatever you pass will always work.
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36       In mode-X the virtual width can be any multiple of eight  greater  than
37       or  equal  to the physical screen width, and the virtual height will be
38       set accordingly (the VGA has 256k of vram, so the virtual  height  will
39       be 256*1024/virtual_width).
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41       Currently,  using  a big virtual screen for page flipping is considered
42       bad practice.  There are platforms which don't support virtual  screens
43       bigger than the physical screen but can create different video pages to
44       flip back and forth. This means that, if you  want  page  flipping  and
45       aren't  going to use hardware scrolling, you should call set_gfx_mode()
46       with (0,0) as the virtual screen size and later  create  the  different
47       video  pages with create_video_bitmap(). Otherwise your program will be
48       limited to the platforms supporting hardware scrolling.
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50       After you select a graphics mode, the physical and virtual screen sizes
51       can  be checked with the macros SCREEN_W, SCREEN_H, VIRTUAL_W, and VIR‐
52       TUAL_H.
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RETURN VALUE

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

60       set_color_depth(3),  request_refresh_rate(3),  screen(3), gfx_capabili‐
61       ties(3), allegro_error(3), create_video_bitmap(3),  get_desktop_resolu‐
62       tion(3), SCREEN_W(3), SCREEN_H(3), VIRTUAL_W(3), VIRTUAL_H(3)
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66Allegro                          version 4.2.2                 set_gfx_mode(3)
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