From: Joseph Morris <jpm AT it-he DOT org>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: svga
Date: Tue, 06 Jun 2000 20:52:24 +0100
Lines: 31
Message-ID: <393D5678.9F7AA087@it-he.org>
References: <393A97A6 DOT 68C0EB6 AT ne DOT infi DOT net> <393A9867 DOT 8872DAEE AT it-he DOT org> <8heat2$cho$1 AT supernews DOT com> <393C606A DOT 174FA10D AT ne DOT infi DOT net>
NNTP-Posting-Host: jpmorris.force9.co.uk (212.56.119.112)
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Trace: fu-berlin.de 960321129 3389521 212.56.119.112 (16 [28722])
X-Mailer: Mozilla 4.7 [en] (X11; I; Linux 2.2.14-15mdk i586)
X-Accept-Language: en
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

Martell wrote:
> 
....
> I would like to write the graphical functions myself, just for the knowledge of
> how they work, so using pre-written functions is not what im looking for here.

Ok then.  Have you considered using FAR pointers instead?
The technique I used in my ITG library before I switched to Allegro was to use a
307K back-buffer and blit this to the screen with a suitable 'driver' written
in ASM.  I was also able to use an SDL 'driver' to do the blit work in Linux,
Windows and BeOS. (But it got tangled eventually, hence Allegro)

I allocated a segment to point to the video display using C.w. Sandmann's SVGA
examples, and then used rep movsd to copy the back-buffer to the screen.

I had a banked driver that copied this in 64k chunks, but I had ot be careful to
set the destination pointer back to 0 each time.  You are doing this, yes?

If you're interested, the source code for the ITG drivers is in the IRE project,
at http://fly.to/ire where you can download the source and have a look.
The next release will use Allegro.

> 
> -Jeremiah

-- 
JP Morris - aka DOUG the Eagle (Dragon) -=UDIC=-  doug AT it-he DOT org
Fun things to do with the Ultima games            (http://www.it-he.org)
Developing a U6/U7 clone                          (http://fly.to/ire)
d+++ e+ N+ T++ Om U1234!56!7'!S'!8!9!KA u++ uC+++ uF+++ uG---- uLB----
uA--- nC+ nR---- nH+++ nP++ nI nPT nS nT wM- wC- y a(YEAR - 1976)