From: Christopher Matthews Keane <keane AT earthsun DOT umd DOT edu>
Subject: Direct Graphics Memory Writing
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Date: Thu, 24 Jun 1993 21:51:26 -0400 (EDT)


I am using DJGPP 1.09 with GRX in developing some image processing
programs.  I currently have the screen refresh being done by indexing
the color to the LUT - and plotting the point via GrPlot(x, y, c);

In 1024x768, this is *relatively* slow and I am trying to speed the
process up some by directly writing to video RAM.  I have written my
own direct write simply by

*(screen_base+y*width+x)=(char)c;
where screen_base = 0xd0000000.

This works like a charm and is somewhat faster - but I don't think it
is any different than the NoClipping GrPlot().....

I have tried to memcpy( (screen_base+y*width), line, width);
where line is a char array of size width.  But in this case I get
garbage on the screen.  What am I doing wrong?  Anyone know of a
routine to move whole lines via direct video writing at a fast
rate....  I must admit that this garbage is comes up on the screen
VERY quickly!

Any help will be greatly appreciated....
Cheers
Christopher Keane
keane AT earthsun DOT umd DOT edu