From: Tom <junkyard AT sunholme DOT demon DOT co DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Allegro and SVGA
Date: Fri, 2 Jan 1998 20:08:29 +0000
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In article <68iggd$nvj AT mtinsc04 DOT worldnet DOT att DOT net>, Walter Luke
<NightWatchman AT Sacrilege DOT com> writes
>   I've written a procedure using Allegro to read in a 256 color bitmap
>from disk and display it on the screen. Using GFX_AUTODETECT, the colors
>came out all wrong. Upon further exploration, I discovered that the
>colors come out wrong when I use VESA2B or 2L modes, but work fine with
>VESA1.
>
>   Does anyone have any reason why VESA 2.0 isn't working properly?
>Also, how concerned should I be? Using the VESA 1.x mode the code should
>run on any decent computer, no?

Firstly, are you using the inline or function version of set_color? The
inline version is only guaranteed to work in VGA-compatible modes, and
it is possible that when you use VESA 2.0 the card is in a different
mode from when it is being VGA-compatible.

Alternatively, your video card's VESA BIOS might be buggy. (In fact this
is quite probable.) Video cards rarely have fully working VESA BIOSes,
so to find out who is at fault get Scitech Display Doctor
(http://www.scitechsoft.com/) and try your program again. If it doesn't
work, it's you; if it works fine, it's your card's VESA BIOS.

As for requiring VESA 1.x, most cards support it and of these most cards
support it reasonably well...

--Tom
My real e-mail address is tom AT sunholme DOT demon DOT co DOT uk