From:	"Stefan Viljoen" <rylan AT intekom DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Allegro: scroll_screen problems
Date:	Sun, 8 Aug 1999 22:43:45 +0300
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----- Original Message -----
From: <don_rogers AT my-deja DOT com>
Newsgroups: comp.os.msdos.djgpp
Sent: Sunday, August 08, 1999 6:36 AM
Subject: Allegro: scroll_screen problems


>   Could someone please help me with this problem.
> I am new to Allegro so I decided to keep it
> simple, just draw some shapes on the screen
> (virtual) and then scroll around a bit. So,

I have heard that some of the functions that do scrolling can be hardware
dependant when used - this means that something that Shawn & contributors to
Allegro designed to go vertically and did work on their particular SVGA
setups might not neccessarily go vertically on yours - I thus implemented
software scrolling using oversized bitmaps when I wanted to do scrolling a
while ago. You might want to try this - IMHO it is more reliable than
hardware scrolling due to the various hardware setups your program might
have to run on.

Basically what I did was to set up a large "source" bitmap that is twice as
large as the physical screen, then use a "sliding" bitmap 'window' onto that
source bitmap to blit to the actual screen - implemented correctly it gives
a nice, smooth scrolling or sliding effect.

This message courtesy of
RylanNet rylan AT intekom DOT co DOT za
http://home.intekom.com/rylan/
--
StarWars for ever!.

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