Dolphin is made with the good old Qtwidgets. Filelight is made with the "new" GPU-Accelerated (not quite...) Qt Quick (not so quick). By now, most KDE apps are built using Qt Quick. Welcome to the new technology nobody really needed.
I am not sure whether this is the case of "Qt Quick bad". When I run filelight with QT_QUICK_BACKEND=software as suggested by another commenter the issue went away.
This confirms what I was saying: GPU acceleration is poorly implemented by Qt. Of course, it may well be down to the drivers, but it’s something you can test with different drivers, so it’s not just the drivers’ fault. I could also suggest you try QSG_USE_SIMPLE_ANIMATION_DRIVER=1 – it sometimes helps (especially if you have different screens with different refresh rates) or you can try the vulkan backend.
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u/SuperGNUser Aug 30 '26
Dolphin is made with the good old Qtwidgets. Filelight is made with the "new" GPU-Accelerated (not quite...) Qt Quick (not so quick). By now, most KDE apps are built using Qt Quick. Welcome to the new technology nobody really needed.