From:	"Duncan Coutts" <Duncan DOT Coutts AT dial DOT pipex DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Graphics in djgpp and inline asm in djgpp
Date:	Wed, 22 Sep 1999 23:03:49 +0100
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>I need help with 2 things:
>
>1. I need to convert this asm code for waiting for the vertical
>retrace converted to a function that djgpp accepts.

[snip]
>2. I used these routines(below) for graphics before
>i changed to djgpp. When i use djgpp they dont
>work(execept set_mode). I have figured out its beacause you cant
>use far pointers and different memory models in djgpp.
>If some1 could help me to port this code to djgpp code
>or has any other code for graphics in djgpp it would be very help
full
>if you sent them to my(i dont want to use allergo).

[snip]

The change to protected mode is quite important especially at a low
level. You can't just access arbitrary memory locations (such as A000
or the byte you are checking for in your WaitForRetrace function).
Getting around the memory protection is a bit complicated. I suggest
you read the DJGPP FAQ as it mentions these issues.

My favourite solution is to allocate a selector and to use the farptr
functions. If you know what you are doing then this can be done is
asm.

Consider for using vesa rather than vga. It is fairly standard these
days and it still allows fast routines along with higher resolutions
and colour depths. 16bit colour modes are quite good for example. I
have managed to make VBE2.0 LFB (Linear Frame Buffer) with page
swapping work under DJGPP. Do some research on the web, but I can send
code if you like.

Duncan Coutts.

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