From: Kester Maddock <dmaddock AT xtra DOT co DOT nz>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Help. Winallegro
Date: Sun, 14 Feb 1999 18:02:38 +1300
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To: djgpp AT delorie DOT com
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If set_gfx_mode returns a negative number, you can assume that the
selected colour depth does not work.  This goes for DOS Allegro
too.  WinAllegro uses DirectX, and apparently not all colour depths
are supported properly.
    int colours[] = {8, 15, 16, 24, 32};
    int i, e;
    for (i = 0; i < sizeof(colours)/sizeof(colours[0]); i++)
    {
      set_color_depth(colours[i]);
      e = set_gfx_mode(GFX_AUTODETECT, 640, 480, 0, 0);
      if (!e)
        break;
    }
    if (e < 0)
    {
       /* Do some error condition: Graphics failed */
    }

Kester
dmaddock AT xtra DOT co DOT nz

Gary Smith wrote:

> By changing the colour depth to 15 bit, the program runs at the correct
> frame rate.
>
> If I set the colour depth to 16bit, and then call  'set_gfx_mode', this
> causes the program to crash.  How can I tell if the colour depth that is
> selected will work on someone elses computer.
>
> Gary Smith
>
> Gary Smith wrote in message <7a4ma6$kv4$1 AT nclient3-gui DOT server DOT virgin DOT net>...
> >Help.
> >
> >I have been working on a program using Winallegro as the graphics library.
> >
> >I have just upgraded my graphics card from a Matrox Mystique, 4MB to an ATI
> >Rage LT PRO, 8MB.
> >
> >With the Matrox card, I could run the program in 15bit, 16bit, 24bit & 32
> >bit at a reasonable frame rate.   With the ATI card, the program now runs
> at
> >approximately 10% of its previous speed.
> >
> >The ATI card should be faster than the Matrox card.
> >
> >I have tried setting various colour depths with no luck.
> >
> >Any suggestions.
> >
> >Gary Smith
> >
> >
> >
> >