From:	"A.Appleyard" <A DOT APPLEYARD AT fs2 DOT mt DOT umist DOT ac DOT uk>
To:	DJGPP AT SUN DOT SOE DOT CLARKSON DOT EDU
Date:	Wed, 1 Mar 1995 12:27:31 GMT
Subject:	Graphics drivers

  I recently downloaded a graphics program that had been written in Gnu C. So
that it could work, it had to carry about with it a load of graphics drivers
for different graphics chips, and I had to set it up for my graphics chip
instead of being able to use the software at once. Someone with a PC may not
always know what sort of graphics chip his PC has in, and in any case having
to edit the name of the chip into his AUTOEXEC.BAT is one more thing to do. As
it is, my PC's graphics chip (a Cirrus) is not in DJGPP\DRIVERS\, but luckily
I dug its driver up in a remote subdirectory corner of DJGPP\CONTRIB\.
  The only purpose of these graphics drivers seems to be to map the nine GO32
screen modes (0 = 80*25 text, 1 = default text, 2 = CX*DX text, 3 = biggest
text, 4 = 320*200 graphics, 5 = default graphics, 6 = CX*DX graphics, 7 =
biggest non-interlaced graphics, 8 = biggest graphics) onto his PC's graphics
chip's own screen modes (AH=0xff, AL=z, int10: go to GO32 screen mode z).
  But there are ways that a program can for(n=0;n<255;n++) find what mode n is
and what its details are, e.g. the SuperVGA interrupt `AX=0xf401, CX=n,
ES:DI=array, int 10' writes into the array a lot of info re screen mode n.
  In view of this, please can't Gnu C have one graphics driver only, that uses
these find-screen-mode-info interrupts to find the graphics chip's modes? Thus
all the miscellaneous horde of graphics drivers that clutters up djgpp could
be pensioned off. For example Windows Setup can cope easily with different
graphics chips without me having to tell it what graphics chip I have.

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