Extra lines above shaper editor when working with large shaper

[philrz]

Repro is with Zui commit 18dc5e8.

I'm working with the large attached shaper.txt. As shown in the attached video, as I scroll up and down in the shaper editor, a line or block of lines from the shaper get highlighted in an area above the editor, e.g., at first its lines 80-81, then line 14, then later after I make the editor taller it's lines 80-83. After fiddling with it enough I got the impression that it might be trying to show me the code that precedes a block of code I'm actively working with inside the editor. However, even if that's the case, this was very much not obvious to me as first as a user and I mostly thought I was seeing a bug, and even if it's not a bug it feels distracting. My first instinct is to see if it would be possible to disable this behavior.

Repro.mp4