AvaloniaEdit (version 12.0.0) slow vertical scrolling in Ubuntu 26.04

[uapconvnet]

Hi,

steps to reproduce the problem: (Ubuntu 26.04 terminal)

git clone https://github.com/AvaloniaUI/AvaloniaEdit
cd AvaloniaEdit
dotnet build AvaloniaEdit.slnx -c:Release
cd src/AvaloniaEdit.Demo/bin/Release/net10.0
./AvaloniaEdit.Demo

Replace the text in the editor with some larger c# code sample (1000+ lines):
Maximize the AvaloniaEdit.Demo app
Scroll with the vertical scrollbar (with the mouse) through the code.
The vertical scrolling experience is sluggish in Ubuntu 26.04.
In Windows 11 this is not the case.
This problem is introduced in version 12.0.0, it doesn't occur in version 11.4.1.

Thanks

[svbackend]

Same issue here (also on ubuntu 26), and text file doesn't even have to be big (like 1000+ lines) - it lags and very slow even with smaller files, e.g 200 lines. But I checked the changes between 11.4.1 and 12.0.0 in AvaloniaEdit and unfortunately it looks like they are very minimal, so the issue might be on the avaloniaUI side, not in this package

[danipen]

@Gillibald is there any known perf regression in the text engine from 11 to 12?