Message-ID: <8D53104ECD0CD211AF4000A0C9D60AE337C6F7@probe-2.Acclaim-Euro.net>
From: Shawn Hargreaves <ShawnH AT Probe DOT co DOT uk>
To: djgpp AT delorie DOT com
Subject: Re: Hardware or software scroll?
Date: Tue, 22 Dec 1998 17:48:02 -0000
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Reply-To: djgpp AT delorie DOT com

Programmer <pekkaka AT dlc DOT fi> writes:
> So i was thinking, is software scroll smoother?...it is right?

I would say so, yes. Hardware scrolling is great when it works (ie. 
in mode-X, when you are running under clean DOS), but most SVGA cards 
can't scroll smoothly along the horizontal axis, and a lot of VESA 
drivers are very buggy in their support for the scrolling functions. 
So I think you will almost always be better off using a software 
method, or at least providing both options and letting the user 
select between them.

> how can i write that, that's my problem..

Very simple: you just have to redraw all the parts of the screen that 
have changed! If you have a hardware accelerator (using VBE/AF) you 
could perhaps use a hardware blit to copy the existing screen image 
and then just redraw the new section along the border, but doing 
this will be painfully slow if you don't have acceleration (reading 
from video memory is very slow), so you will be much better off to 
just redraw the entire image.


	Shawn Hargreaves.