Date: Tue, 30 Jun 92 13:36:22 EDT
From: DJ Delorie <dj AT ctron DOT com>
To: P DOT W DOT A DOT Stallard AT gdr DOT bath DOT ac DOT uk
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Problems compiling GhostScript with DJGPP

>	Now, I want to add the VGA device so that I can preview the files
>before printing and this is where the problems start.  The device driver
>assumes that I can write directly to the screen memory and when I run the
>program I get a segmentation fault as soon as it attempts a screen write. 

>	How can I make go32 allow me to write to a certain area of memory? I
>don't want to re-write large chunks of code to use higher level graphics
>primitives so what should I do? Has anyone else managed to compiler
>GhostScript under DJGPP?

The video memory, once in graphics mode, appears mapped at 0xd0000000
in the virtual space.  You MUST use this mapping if you want to take
advantage of the SuperVGA modes of the graphics drivers, which will
automagically handle remapping and reconfiguring your SVGA for
different video banks as you access them.

You will still need to initialize the GR/GRX module to get to the
correct mode and figure out the capabilities of the system.  Note that
using the GRX library is recommended if you want to support 16-color
modes.

DJ