> On 2019-10-18, at 09:56, Anders Carlsson <anders.carlsson_at_sfks.se> wrote: > > silverdr_at_wfmh.org.pl wrote: >> When printing to 64 screen, I remember that the content gets scrolled sometimes one and sometimes two lines at once. Does it have something to do with "logical" vs. "physical" screen lines? And how to detect how many lines the content will be scrolled before it happens? > > There is a line link table at $00D9 - $00F2. Whenever you have printed (not POKE) a character in the rightmost column, it will link two physical lines into one logical one and scrolling will occur based on that. It appears this happens by clearing the MSB on the link that exceeds the rightmost column. You could try to ORA all those addresses by $80 and see if you get consistent scrolling of one line at a time. Anders, thanks for good hint! The routine at $E8EA checks there "if the top logical line is two physical lines long" and all lines are moved up two lines if true. Which means it should suffice to check the MSB of second line to determine how many lines long the scroll will be. And to set MSB on the second line to ensure single-line scroll. -- SD!Received on 2020-05-29 23:14:17
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