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How do I stop print scrolling?
Posted: Sun Nov 11, 2018 10:57 pm
by Jeff-20
I recall there is a way to do this, but I don't remember exactly how.
I am PRINTing continuous text to the screen using semicolons with each PRINT command. When the printing reaches the bottom of the screen, the screen data "jumps" upward several lines.
It creates a "jerky" scroll effect. I thought I could turn this feature with a POKE 658,1, but it does not seem to have any effect. Does anyone have any ideas?
In addition, there must be a location that tells the cursor how many spaces to move down with a down cursor command. If I could find this, it could be helpful. I am thinking location 213 - 244 could work in some way, but I haven't been able to figure it out.
Re: How do I stop print scrolling?
Posted: Mon Nov 12, 2018 2:16 am
by srowe
Jeff-20 wrote:
In addition, there must be a location that tells the cursor how many spaces to move down with a down cursor command. If I could find this, it could be helpful. I am thinking location 213 - 244 could work in some way, but I haven't been able to figure it out.
Cursor addressing is done using an index into a table of pointers, the row index is called TBLX
https://eden.mose.org.uk/gitweb/?p=rom- ... =HEAD#l617
The table is built on boot from a table in KERNAL ROM, the stride is hard-coded at 22
https://eden.mose.org.uk/gitweb/?p=rom- ... EAD#l10452
Pressing Crsr-Dwn just increments the index.
https://eden.mose.org.uk/gitweb/?p=rom- ... HEAD#l9911
Re: How do I stop print scrolling?
Posted: Mon Nov 12, 2018 12:39 pm
by Jeff-20
Thanks, srowe! That's very useful information. I figured out a trick to avoid the issue in my specific application. It seems the screen "jumps up" about four rows when I print at the bottom. I thought there was a way to turn that off.
Re: How do I stop print scrolling?
Posted: Tue Nov 13, 2018 2:10 am
by tokra
Yes, you must make sure not to print the last character of the last line to avoid the scroll. There is some nifty PRINT-technique where you use cursor-left and insert in quote mode to push the final character to the last position, but it may be easier to just POKE to that screen destination.
Re: How do I stop print scrolling?
Posted: Tue Jan 08, 2019 8:55 pm
by dr.geek
print a "home" character at the end of the line???
Re: How do I stop print scrolling?
Posted: Tue Jan 08, 2019 8:57 pm
by dr.geek
tokra wrote:Yes, you must make sure not to print the last character of the last line to avoid the scroll. There is some nifty PRINT-technique where you use cursor-left and insert in quote mode to push the final character to the last position, but it may be easier to just POKE to that screen destination.
or just dont use the bottom line...or use it to display score, etc without using the last position