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flat assembler > OS Construction > VGA - 80x25 Text Mode Scroll Screen in protected mode?

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newport



Joined: 08 Jun 2012
Posts: 86
Location: Kentucky, USA
VGA - 80x25 Text Mode Scroll Screen in protected mode?
I've gotten my keyboard 'driver' working - so I can type on the screen, however once I reach the bottom of the screen, I need it to scroll up one line so I can see what I continue to type. I've searched all over, but all the examples on the net are in C code which i'm not interested in at this time. Could someone explain how this works in protected mode without using the bios? Thanks!


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Post 11 Jan 2016, 05:14
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 15096
Location: The Unicomplex
Erm, I thought it would just be copying the screen buffer from the next line into the previous line. A simple "rep movsd" would probably suffice, followed by a clearing of the last line ready for the new text.

You can do fancy tricks with pixel scrolling in text mode to make it move smoothly, but that requires a bit more work.
Post 11 Jan 2016, 08:08
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cod3b453



Joined: 25 Aug 2004
Posts: 616
As revolution says - simply write directly to the video buffer but you'll want to have a set of screen buffer and print functions that maintain the state (cursor colours scrolling/line wrap etc) so you can continue to coherently display text. I personally found it easier to do this right from the start in 16bit so that switching to 32/64 wasn't a problem.
Post 13 Jan 2016, 21:39
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newport



Joined: 08 Jun 2012
Posts: 86
Location: Kentucky, USA
thanks for the replies! think i got it figured out..
Post 14 Jan 2016, 12:38
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