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Author Topic: Pixel modes screen scroling (Read 1921 times)

Offline geco

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Re: Pixel modes screen scroling
« Reply #15 on: 2015.November.21. 14:22:59 »
There's no screen memory wrap like on the cpc so I guess you can't use the "adaptive tile refresh" technique and can't use other techniques from the cpc?...
You can use any technique from CPC, if you use the vertical scrolling of CPC there is one disadvantage on EP, sometimes 1 char row or part of it will be corrupted, but I think it can be avoided to decrease the screen size by 1 char row.

Offline geco

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Re: Pixel modes screen scroling
« Reply #16 on: 2015.November.21. 14:44:47 »
Sorry to all... I thought that I need a backbuffer for every line on the ep... But geco's post made me rethink... So I've tried it and got the scroll to work... Sorry :oops:
No problem :)
This way is the most space efficient scrolling I think, if your scroll moves right 1 byte at 25 fps, and you use a SPECCY size screen (3000h) then you can make a 163 sec scroll in a 16KB page.
Other thing if you need to use bigger screen ex CPC default size (320x200 3e80h) and an alternate screen to avoid flashing then with 3 video segment the scrolling can take 670 sec without redraw of the screen.

screen1 on FC, starts at 0000h
screen2 on FD, starts at 0000h (address on the page)
and FE is used later for scrolling
the scroll can move 0000-0180h FE segment is not needed
when start pos of screen reached 0181h FE segment is involved and screen2 starts on FD segment but ends on FE, screen1 starts on FC and ends on FD.