From: alombard AT iiic DOT ethz DOT ch (Andrea Lombardoni)
Newsgroups: comp.os.msdos.djgpp
Subject: Scroll Problem Allegro DJGPP
Date: 30 Apr 1997 22:47:26 GMT
Organization: Dept. Informatik, Swiss Federal Institute of Technology
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Message-ID: <5k8i5u$p81@neptune.ethz.ch>
NNTP-Posting-Host: raf5.inf.ethz.ch
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
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Hello

I'm working with DJGPP and Allegro.
What I'm trying to do is to show a big (ca 1280x1024) picture on the screen.
I want to see only a part of the pics, so I'm using a 320x200 standard VGa
mode.
I do it in the following way:
- blit the desired part of the pic on a bitmap structure (size: 320x200)
- draw something else on the bitmap structure
- call vsync()
- blit the 320x200 bitmap structure on the screen

The problem is that all goes smootly only in some parts of the picture, on
some other there is a slow down, that makes the scroll jerky.
I guess it has something to do with memory allocation of the picture, but I
can't figure out what.
Can anyone hlep or suggest a good scrolling example?

Bye

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Andrea Lombardoni - Computer Science Student
alombard AT iiic DOT ethz DOT ch
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