From:	Oon Lin <sci-okl AT jcu DOT edu DOT au>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Using A Higher Resolution Than 320 *200(Mode 13h)
Date:	Mon, 13 Oct 1997 16:51:35 +1000
Organization:	University of Queensland
Lines:	89
Message-ID:	<Pine.OSF.3.93.971013155642.32105B-100000@sailfish.jcu.edu.au>
References:	<971002235232 DOT n0000350 DOT alter AT mail DOT clara DOT net>
NNTP-Posting-Host:	cuda.jcu.edu.au
Mime-Version:	1.0
In-Reply-To:	<971002235232.n0000350.alter@mail.clara.net>
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Hi !

> I'm wondering if anyone can help me.  I'm new to graphics programming in dos,
> and seem to be having problems selecting a higher video mode than 13h.

I'd like to give you a hand here (I'm new to graphics programming but I've
been able to get some VESA modes going...but still no expert...:) )

> I'm not really sure of the technical terms as I'm just learning about the
> various video modes
> that you can get, but I believe it be VESA modes that I can't obtain. 

Any graphic modes equal or more than 640 * 480 with 256 colors are VESA
modes.

If your using VESA functions , please check what version does your video
card supports (like version 1.2 or v 2.0) and if you're programming using
the functions supported by that version. VBE 2.0 has some extra features
which VBE 1.2 doesn't have. * VBE = Vesa Bios Extension *

> I'm not really too sure about
> where to obtain a comprehsive reference on the problem. I downloaded a demo
> (from where I can't
> remember that should run in VESA but it just crashes the machine (it compiled
> with no errors), the screen top and bottoms come down a bit and that's it.
 
1) Does the code accounts for Protected Mode environment ? It's a wee bit
different from Real Mode's codes. DJGPP creates Protected Mode programs.
It could compile perfectly with real mode codes but the program will trash
real bad if bad memory references are made (it could be legal memory
reference in Real Mode but illegal in Protected Mode...)

2) Is it a DJGPP specific code ? If your not sure , try looking for the
functions __djgpp_nearptr_enable() , _djgpp_nearptr_disable() ,
__farpokeb()  or words like __djgpp_conventional_base. If you could find
some of the words , it is likely that the code is DJGPP specific and most
likely the problem will be somewhere else (provided the author had
tested the code thoroughly....)

>       I believe that the make of the video card maybe the problem, and that
> there may be a way roundit.

Yup , it could be...again ,does it support VBE ? (Please refer to first
question) VESA IS the way round incompatibilities between video cards...Oh
yeah , UNIVIBE is another way....

>       If anyone could shed anylight on the situation.(with possible some
> reference URLs) 

URL coming up...

http://www.rt66.com/~brennan/djgpp/

Awesome page ! Brennan's DJGPP2+Games Resources has infos in SVGA
programming using DJGPP.


> I really would be extremely grateful caus 320*200 is quite a poor
> resolution to be working with and I want to do a graphicly based demo.

I agree..Tried Mode X ?? :)

>       (Just looked at a FAQ, it mentioned that you maybe able to use a VESA
> emulator - UNIVIBE, is this the solution, what do  I need?)

Sorry , I had never used UNIVIBE before....

Maybe you should post a copy of your code (the important sections , of
course..) so that everyone can have a look...?
Include the codes for checking the SVGA modes available , setting up SVGA
mode , plotting a pixel (if the code has..) , bank switching (if
applicable) or linear memory addressing or protected mode interface (the
last two are only supported by VBE 2.0). Including The coding inside the
main function would be nice...

With A Humble Help ,
Kean

/****************************************************************************/
  Lin Oon Kean
  email : Oon DOT Lin AT jcu DOT edu DOT au
  http://lionfish.jcu.edu.au/~sci-okl
  http://www.geocities.com/SunsetStrip/Palladium/6730

  "People are killing the babies , Crying 'Save the Whales Today !' "
                                                        - The Kry
/****************************************************************************/ 

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