Date: Thu, 26 Oct 1995 09:07:34 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Brian Glass <glass AT andrews DOT edu>
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: print screen with GRX2.0


On 25 Oct 1995, Brian Glass wrote:

> I can dump text screen information to the printer with no problem but
> when I try to print graphics I get either a blank page or a totally
> black page.  My theory is that GRX maps the graphics screen to a block
> of memory that DOS's Graphics program doesn't know about and thus 
> prints out garbage from a totally unrelated block of memory.

No, I don't think your theory is correct.  When the graphics image is 
displayed on your screen, the one and only place it have to reside is the 
usual video RAM in the usual addresses, because that's where the video 
refresh circuitry looks for it.  If DJGPP would move the graphics image, 
you won't be able to see it.

I think that the problem might be that DJGPP never passes the software 
interrupt generated by the Print Screen key to its real-mode handler 
(which in this case is the GRAPHICS program), so GRAPHICS doesn't know 
you pressed that key.  One thing to try is to press Print Screen when the 
program is in real mode, like when you call scanf() to read from standard 
input.  You can tell whether the program is in real mode by adding 
``topline'' to your GO32 environment variable and watching the `R' and 
`P' characters at the extreme left of the upper line: `R' means real 
mode.