https://bugs.kde.org/show_bug.cgi?id=411058
Bug ID: 411058
Summary: Occasional spurious scroll events in apps under
XWayland
Product: kwin
Version: 5.16.4
Platform: Archlinux Packages
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: kwin-bugs-n...@kde.org
Reporter: kaiw...@gmail.com
Target Milestone: ---
I mainly use the two-finger scroll gesture to scroll in applicatios. Since I
began using the Wayland session of KDE in Plasma 5.15.1 / Frameworks 5.55, I
have been triggering a bug that applications running under XWayland sometimes
behave as if I'm scrolling downward.
STEPS TO REPRODUCE
This problem happens occasionally, and I'm sorry that I haven't discovered a
reliable way to reproduce it.
1. Open an application that runs under XWayland (such as chromium or firefox)
2. Open a long document
3. Use touchpad to scroll downward. I'm not sure if a long or jerk scroll has a
higher chance to trigger it.
OBSERVED RESULT
If this bug happens, you will see the page scrolling down rapidly even though
fingers are off the touchpad. Moving the cursor to the tab bar of chromium will
cause the tabs to switch rapidly. The bottom of a more-than-thousand-page PDF
document can be reached instantly in firefox.
Performing a two-finger upward scroll will work (cause the page to move upward)
for a moment. But the page will continue to scroll downward after fingers stop
moving upward.
To stop the spurious scrolling, I can type something into the application or
send a Ctrl-T shortcut to chromium. However, once this bug happens, it will be
more often triggered when I scroll downward in applications, until I reboot my
laptop.
Scrolling upward can also trigger the applications to spuriously scroll upward,
nevertheless I mainly scroll downward.
EXPECTED RESULT
Applications scroll normally.
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 5.2.9-arch1-1-ARCH
KDE Plasma Version: 5.16.4
KDE Frameworks Version: 5.60.0
Qt Version: 5.13.0
libinput version: 1.14.0
ADDITIONAL INFORMATION
I'm able to perform tap-to-click in XWayland applications along with the
spurious scrolling.
This bug doesn't affect native wayland applications including dolphin,
konqueror, kate or gedit. That is, moving cursor into these applications won't
cause them to scroll, while moving it into another nearby xwayland window will
cause it to scroll crazily.
However, if I force them into using XWayland by setting GDK_BACKEND=x11 or
QT_QPA_PLATFORM=xcb, they will scroll downward indefinitely as long as the
cursor is in their windows.
Firefox runs with MOZ_USE_XINPUT2=1. Chromium doesn't use XInput2 because of
https://crbug.com/712737
I have tried applying the kwin patch for bug 404152 to kwin 5.16.4, but I still
triggered this bug moments before.
A similar report can be found on the Internet:
https://forum.manjaro.org/t/xwayland-apps-scrolling-on-their-own-in-a-kwin-wayland-session/58096
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