SUMMARY When I open and maximise a Firefox window in wayland, while fractional scaling is enabled, desktop animations have dropped frames. Animations such as minimising and maximising other windows, opening and closing start menu, opening new application windows and such. STEPS TO REPRODUCE 1. Enable fractional scaling to any % on wayland 2. Open Firefox, maximise it and make sure no other window is in front or in focus. 3. Open and close start menu or do anything else that has a desktop animation. OBSERVED RESULT Animations seem to have dropped frames / are laggy. EXPECTED RESULT Animations are smooth. SOFTWARE/OS VERSIONS OS: Arch Linux KDE Plasma Version: 6.1.1 KDE Frameworks Version: 6.3.0 Qt Version: 6.7.2 ADDITIONAL INFORMATION Occurs on other distros that I have tried on USB. Does not occur with scaling at 100% Does not occur in X11 with or without fractional scaling. If another window is in front of Firefox (FF is not in focus) the animations are smooth as expected. Does not occur if FF is windowed / not maximised If you set FF to work under Xwayland instead, the bug does not occur.
I'd just like to add that at 100% scaling, so fractional scaling disabled, some animations have dropped frames while FF is in focus and maximised. For instance, the opening animation for dolphin has dropped frames but the closing animation is smooth. Another weird thing I noticed with 100% scaling was when you have FF in focus+maximised and have a video iframe on the active tab like the homepage video of a youtube channel, doesn't matter if the video is actively playing or not, the desktop has dropped frames when switching virtual desktops via keyboard shortcuts. Specifically when going from another virtual desktop back to the desktop with FF in focus. If you switch desktops fast enough, it seems like only the first animation back to the desktop with FF lags and the rest are smooth. However, if you switch desktops with a 3 second-ish delay, then each animation going back to the desktop with FF has dropped frames.
Is this on an integrated GPU? Unfortunately Firefox doesn't properly support fractional scaling and thus renders at a higher resolution than native. As GPU drivers don't do proper prioritization of GPU tasks, it can in some cases simply take away the rendering power KWin needs to render animations smoothly.
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🐛🧹 This bug has been in NEEDSINFO status with no change for at least 30 days. Closing as RESOLVED WORKSFORME.