Created attachment 169072 [details] Video of bug *** If you're not sure this is actually a bug, instead post about it at https://discuss.kde.org If you're reporting a crash, attach a backtrace with debug symbols; see https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports *** Lagging/Slow scrolling STEPS TO REPRODUCE 1. Open KDiff3 and do any diff of two files 2. Scroll using the scroll wheel of your mouse 3. OBSERVED RESULT Lagging/slow scrolling EXPECTED RESULT Smooth scrolling SOFTWARE/OS VERSIONS KDE Frameworks Version 6.1.0 Qt Version 6.7.0 (built against 6.7.0) The wayland windowing system ADDITIONAL INFORMATION
I can reproduce a rubberband effect under Wayland, when run as X application it instead just drops the frames. Wonder if that is an issue with kdiff’s painting. Fwiw I made a patch for Qt Wayland to implement backingstore scrolling, so it only has to repaint a small region as you scroll, which should improve performance (when not using fractional scaling) albeit not entirely: https://codereview.qt-project.org/c/qt/qtwayland/+/528803
[CCing after having seen the bug mentioned on the kde-core-devel list, which I follow via gmane.io's list2news service.] Confirming here too. gentoo kdiff3 1.11.4 qt 6.7.2 frameworks live-git (using the gentoo/kde overlay ebuilds) updated Sep 18, reports 6.7.0 plasma live-git desktop, wayland by default, plasmashell reports 6.1.90 I ran kdiff3 with --platform xcb to run in xwayland for the X side test. I'm on decade-old hardware, amdgpu graphics. The scrolling lag was there on wayland but not /horrible/. I ran kdiff3 wayland-native first (it was a fresh build/install so was testing that it'd even run, too) and honestly didn't notice a lag -- I suppose I was subconsciously attributing it to a scrolling animation effect. Only after running it under xwayland and seeing the faster scrolling there did I really notice the wayland-native scroll-lag. Then I ran two windows, one wayland-native one xwayland, flipping between them and scrolling, and the wayland-native scrolling lag became /quite/ obvious. So now CCing and we'll see where this goes. I might try that qtwayland patch if I get time.