https://bugs.kde.org/show_bug.cgi?id=413670
Bug ID: 413670
Summary: Keyboard modifier event for Capslock fired
(incorrectly?) on key release in Wayland
Product: kwin
Version: git master
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: kwin-bugs-n...@kde.org
Reporter: k...@jbev.net
Target Milestone: ---
SUMMARY
I am trying to implement the detection of caps lock in my application for
Wayland. This in itself already requires around 30 lines of code using KWayland
(way worse with the plain C API), compared to the single-line solutions for
Windows or macOS or the three lines for X11, but worst of all, I noticed that
the modifier change event is called both on key press and key release with
different bit flags set.
The first activation has bit #2 set, the second activate does not, so my
application thinks that caps lock had been released again until I press any
other key, which triggers the event a third time.
I thought at first that this was just a bug in my implementation, but then I
noticed that the caps lock indicator in the Plasma tray has the same issue and
is only shown as long as I hold caps lock down.
STEPS TO REPRODUCE
1. subscribe to KWayland::Client::Keyboard::modifiersChanged() for a keyboard
2. log the status of the `locked` bitmask
3. press and release caps lock
OBSERVED RESULT
Event is triggered a second time on key release with `locked & 0x10 == 0`.
EXPECTED RESULT
Event is either triggered only on key press or key release does not unset the
caps lock bit
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KDE Neon
KDE Plasma Version: 5.17.80
KDE Frameworks Version: 5.64.0
Qt Version: 5.13.1
ADDITIONAL INFORMATION
I tried using the KDE-proprietary org_kde_kwin_keystate protocol extension as
an alternative that requires fewer LOCs, but the compositor doesn't even
announce this extension.
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