From: mert0407 AT sable DOT ox DOT ac DOT uk (George Foot)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: wierd problem in Allegro 3.0
Date: Sat, 18 Apr 1998 03:50:38 GMT
Organization: [posted via] Easynet UK	
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Message-ID: <353821bd.10390868@news.easynet.co.uk>
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To: djgpp AT delorie DOT com
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On Thu, 16 Apr 1998 08:33:32 -0500, Count Razumovsky
<umyumm AT cc DOT umanitoba DOT ca> wrote:

>#include<allegro.h>
>
>int main(){
>	
>	allegro_init();
>
>	install_keyboard();
>
>	set_gfx_mode(GFX_AUTODETECT,640,480,0,0); /* ******* */

You didn't check the return value.  set_gfx_mode cannot always set the
mode you want; if it fails, it returns a negative number, and you
shouldn't try to draw any graphics to the screen if it does fail.  Try
this:

  if (set_gfx_mode(.....) < 0) {
    fprintf (stderr, "Can't set graphics mode: %s\n", allegro_error);
    exit (1);
  }

>
>	textout_centre(screen,font,"HI",160,100,255);
>
>	readkey();
>
>	return 0;
>}

>funny thing is that the line with the ******* will run just fine if I
>have:
>
>set_gfx_mode(GFX_AUTODETECT,320,200,0,0);
>
>but once I try to go to 640 by 480 I get that wierd message.  I can't
>see what the problem would be.

That's because almost all cards support 320x200x256, but not all
support 640x480x256.  You might have more luck if you install a VESA
driver, such as UniVBE.  I suggest you play around with either the
demo game (in the `demo' directory) or the test program (in the `test'
directory), both of which let you try out different graphics modes.

-- 
george DOT foot AT merton DOT oxford DOT ac DOT uk