To: Frank Sandy <fsandy AT max DOT tiac DOT net>
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: Can't Get Graphics 
Date: Wed, 06 Apr 94 12:55:18 +0200
From: eliz AT is DOT elta DOT co DOT il

> I expected the following trivial program to draw a single red
> line.  The go32 environment variable is undefined.  I expected that I
> would use the default VGA driver for now.

  The default graphics driver is for VESA BIOS.  This driver is what actually
gets invoked when your GO32 variable is undefined.  If your VGA doesn't have
VESA BIOS extensions (either on-board as external BIOS, or as a TSR which you
install before running your program), then your graphics screen will be
garbled.  If you want a standard VGA driver, use vga.gdr which is included in
the drivers/ subdirectory of the directory where you've installed GCC.  To use
it, define GO32=driver c:/....<whatever>/drivers/vga.gdr .  Also be sure you
don't have a DPMI server (like QEMM's QDPMI.SYS) installed; if you do, then
add ``nodpmi'' to the above GO32 line, or else graphics will fail with
general protection failure).
  It will also help, if you insert a pause (e.g. getch()) before going back
to text mode, so you'l have time to see your red line.
  To test if your graphics configuration works, you may use the t05 (I think)
test program which came with djgpp (in the tests/ subdirectory) which also
draws a line, but has an advantage of relieving your doubts about the
correctness of your code.

  Hope this helps.

		Eli Zaretskii