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Old 29 January 2012, 15:40   #66
Mrs Beanbag
Glastonbridge Software
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Join Date: Jan 2012
Location: Edinburgh/Scotland
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Originally Posted by Thorham View Post
With scrolling, the blitter doesn't have to copy the whole screen. There's a method of scrolling the screen which is very easy on the blitter (and doesn't do any copying with cpu).
You're teaching a grandma to suck eggs, here.

Although my own code uses CPU and blitter in parallel...

You only have to draw the area of the screen that's been revealed by the screen offset changing. You maintain a screen slightly wider than the visible area and redraw a strip down the edge when required. Obviously drawing a 32 pixel strip is more work than drawing a 16 pixel strip, but 16 pixels is pretty fast scrolling anyway.
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