Thanks for the report. This is now fixed for the next release: https://feedback.objo.dev/bug/1256
The bug was Windows scaling-related. Objo Studio’s ListBox column-width calculation was doing the right thing: for a 300-point bordered ListBox, the usable content width is 298 points. Percentage columns such as 33%,33%,34% resolved to 298 points, and fixed columns such as 100,100,98 also totalled 298 points.
On Windows at 150% display scaling, Avalonia’s underlying DataGrid rounded the final rows viewport down by one physical pixel. That made the DataGrid think there was a tiny horizontal overflow of about 0.6667 points, so it showed the real horizontal scrollbar even though the columns effectively fitted.
