From:	"Damian Yerrick" <NOSP AT Musenet@pineight.8m.com>
Newsgroups:	comp.os.msdos.djgpp
References:	<fycflpbqrpbz DOT flxb2y0 DOT pminews AT nntp DOT generation DOT net>
Subject:	Re: HELP - GFX programming
Lines:	45
Organization:	Pin Eight Software <http://pineight.8m.com/>
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NNTP-Posting-Date:	Sun, 28 Nov 1999 22:20:53 GMT
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Date:	Sun, 28 Nov 1999 22:20:54 GMT
To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

"sl" <junk AT bbs DOT darktech DOT org> wrote:
>
> I have been studying the VESA 1.2 document and I have
> some technical questions.. I need to know what the following
> things are and what they are used for:

The VESA specs are dense and DOS-only. For an easier, more
portable way to get SVGA in 256, thousands, or millions of colors,
try Allegro.
http://www.talula.demon.co.uk/allegro/
No use reinventing the wheel, but if you insist:

> 1) Memory windows

Has nothing to do with Microsoft Windows 3.x, 95, 98, or NT.
The original SVGA cards had a banked frame buffer so that real-
mode (pre-DJGPP) programs could access all the RAM on the
card. A program would write a bunch of pixels to one bank,
"slide the window," and write to the next bank.

> 2) Window granularity
> 3) Memory banks
> 4) Memory model - How does it help us when we know which
> memory model the card uses?

Planar vs. linear: In planar (16 color or some cards' 16 million color)
modes, red is stored in one bitplane, green in another, and blue in a
third. In linear (256 colors and most cards' high and true color),
modes, the pixels are stored as a straight bitmap.

> 5) If NumberOfImagePages is nonzero and there is space for
> virtual display images/pages, how does one flip between them?
> How does one write into these virtual pages as opposed to the
> displayed page?

By sliding the window to the other pages.

> That's all for now .. Please reply,

Posted and emailed.


Damian Yerrick

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