How do I stop print scrolling?

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Jeff-20
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How do I stop print scrolling?

Post 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.
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srowe
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Re: How do I stop print scrolling?

Post 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
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Jeff-20
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Re: How do I stop print scrolling?

Post 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.
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tokra
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Re: How do I stop print scrolling?

Post 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.
dr.geek
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Re: How do I stop print scrolling?

Post by dr.geek »

print a "home" character at the end of the line???
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Re: How do I stop print scrolling?

Post 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
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