https://bugs.kde.org/show_bug.cgi?id=484992
--- Comment #34 from nyanpasu64 <nyanpas...@tuta.io> --- Created attachment 177983 --> https://bugs.kde.org/attachment.cgi?id=177983&action=edit Video of a key being sent to a XWayland app after it's released in Wayland. I'm still getting this bug on KDE Plasma 6.2.5 on Fedora 41. To understand why the bug happens, I installed screenkey, a X11-based program which displays keystrokes on-screen. Since it's a X11 app running under XWayland, it only sees keystrokes delivered to XWayland apps. ## Reproduction To set up keystroke visualization, in Screenkey settings I checked "Persistent window", and under KDE "Special Application Settings" I set all windows from Screenkey to be above other windows. Then I restarted screenkey, dragged the window to a convenient location, then opened a Wayland app (Firefox) and an X11 app (Obsidian Flatpak). To reproduce the bug, I typed into Wayland Firefox while watching screenkey to see what keystrokes it's receiving. I also moved my mouse in circles over X11 Obsidian, which makes XWayland send events to screenkey more quickly. I used GPU Screen Recorder in replay mode to record the screen while I looked for bugs, and in recording mode to capture a screencast of the bug happening. My findings: ## Behavior - Enter, Backspace, Tab, and arrow/Home/End/Page Up/Down keystrokes are delivered to screenkey immediately. If you're not moving the mouse, they get delayed until the next modifier keystroke (like Ctrl or Shift) or a periodic timer. - Modifier shortcuts (like Ctrl+A) are delivered to screenkey immediately. If you're not moving the mouse, they're delayed until you release Ctrl. - If I release Ctrl before A, XWayland usually enters a state where it sends an endless string of A keystrokes to screenkey (which refreshes faster if you're moving your mouse over a X11 app); I think the key repeats forever because kwin_wayland fails to deliver the A key release to XWayland. While the key is repeating, if I mouse-click into a X11 (XWayland) app, there is a 10-50% chance that an erroneous A key gets delivered to the app. I think this happens if a key repeat gets delivered to the app before XWayland realizes A is no longer being pressed. I've reproduced this bug with alphabetic and symbol keys (like ; semicolon). I'm not sure this bug happens with *tab* events after Plasma 6.2; Tab is always sent to XWayland (so letting go of a modifier does *not* cause the key release to not be sent), Alt+Tab does not appear on Screenkey at all, and Ctrl+Tab does not trigger endless repeats on screenkey if I release Ctrl before Tab (I think the endless repeats are what causes stray keystrokes). In any case I'm still posting this report under this bug; I reported the issue with alphabetic keys instead of Tab at Bug 493956, but that got closed as a duplicate of this. ## Fix I'm guessing the fix is that if the user presses Ctrl+A, the A keypress "belongs to a shortcut" and the key release is unconditionally delivered to XWayland, even if Ctrl has been released already. Also, if the user presses A and it's not delivered to XWayland, then presses Ctrl and releases A, it may not be necessary to deliver the key release if you don't deliver key-held events; I don't know if you do or not, or what behavior is ideal. I think this behavior is a result of KDE's implementation of "Allow legacy X11 apps to read keystrokes typed in all apps:" "As above, plus any key typed while the Control, Alt, or Meta keys are pressed" option. Unfortunately this is the default value of the setting. Hopefully this analysis helps find out *why* stray keys are sent to XWayland apps, and fix keys being stuck on repeat on XWayland and being sent to apps when focused. I wonder if there's a similar bug where if you hold Ctrl+A on a Wayland app and click on a X11 app, KWin sends a stray Ctrl+A to the app. I don't think this bug exists, since when you click on a X11 app, screenkey reports a single A keystroke (not a Ctrl+A) and spends a second before repeating Ctrl+A presses. I also tried this procedure 20+ times and did not see the bug. Operating System: Fedora Linux 41 KDE Plasma Version: 6.2.5 KDE Frameworks Version: 6.10.0 Qt Version: 6.8.1 Kernel Version: 6.12.9-200.fc41.x86_64 (64-bit) Graphics Platform: Wayland Processors: 4 × Intel® Core™ i5-3570K CPU @ 3.40GHz Memory: 7.6 GiB of RAM Graphics Processor: Mesa Intel® HD Graphics 4000 Manufacturer: M&A Technology Product Name: DB75EN__ -- You are receiving this mail because: You are watching all bug changes.
