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Old 02 April 2020, 04:57   #1
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Bitmap Scrolling in Amiga Mode?

Can bitmap scrolling be achieved in Amiga Mode?
Its mostly done by DisplayBitmap command in Blitz mode.

I am asking because creating and displaying something in Blitz Mode and Display Library
always shifts the whole display to the right. It makes me mad - I can't center it.
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Old 02 April 2020, 10:01   #2
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I am not a Blitz expert, but IIRC the Display Library on Blitz lets you use a custom Copper list. You should be able to use that to center or scroll the screen as you see fit. Perhaps a proper Blitz coder can give you an example, because I sadly don't have any for you.
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Old 02 April 2020, 10:12   #3
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The shifting to the right is normal unfortunately - you'll see it in a lot of games. Unfortunately, doing scrolling directly on an intuition screen isn't as easy as it is in Blitz mode, where you can simply give the bitmap coordinates you want to display. In Amiga mode, the simplest way might be to use a single borderless window and use the BitmapToWindow command, which lets you set coordinates. But that will be slow since it's copying the screen's data rather than simply displaying another part of it.

You could probably modify the Intuition screen's struct directly to modify the addresses used to build the display. This is what the Blitz scrolling routines do internally, but there are intricacies to take care of there that I'm not entirely familiar with so I can't guide you on that method.
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