https://bugs.kde.org/show_bug.cgi?id=421068
Bug ID: 421068
Summary: Kwin sends out undated WM_TAKE_FOCUS messages that
goad firefox into stealing focus
Product: kwin
Version: 5.14.5
Platform: Debian stable
OS: Linux
Status: REPORTED
Severity: grave
Priority: NOR
Component: core
Assignee: kwin-bugs-n...@kde.org
Reporter: k...@kde.lka.org.lu
Target Milestone: ---
SUMMARY
Kwin sends out undated WM_TAKE_FOCUS client messages. Gtk based applications
such as Firefox react to these by handing focus to one of their subwindows
using XSetInputFocus(), and pass on the null time field that they received in
the client message to XSetInputFocus(). If for whatever reason the application
(firefox) is slow to process the event, it might issue that XSetInputFocus()
message at a time when it has already lost focus to the next application. This
results in Firefox stealing back the focus from the next application. Normally,
such an occurrence would not happen, as the server could tell by the time field
that the message is stale.
STEPS TO REPRODUCE
1. Open Firefox
2. Open Web Console Window (by using Inspect element)
3. Open another window (for example, a konsole), and place it such that it
covers the top of the firefox web console
4. Open another window (another konsole) and place it such that it covers the
bottom of the firexfox web console, leaving a narrow gap between both where web
console is visible behind them.
5. Move mouse back and forth between the top and the bottom konsole, crossing
the web console each time.
6. Whenever you are in a konsole with the mouse, observe the cursor shape.
7. Pretty quickly you see that your konsole does not have focus (hollow
cursor) even the mouse is in the window.
8. Press cursor keys: you see that it's the Firefox web console who has focus!
OBSERVED RESULT
Firefox web console has focus
EXPECTED RESULT
Konsole should have focus
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Debian 10, 5.14.5.1-1
(available in About System)
KDE Plasma Version: 5.14.5.1-1
KDE Frameworks Version:
Qt Version: 4.8.7+dfsg-18
ADDITIONAL INFORMATION
Bug initially reported to gtk under
https://gitlab.gnome.org/GNOME/gtk/-/issues/2699
xtruss line showing the bad message WM_TAKE_FOCUS message:
--- SendEvent-generated ClientMessage(window=w#04000003, type=a#306, format=32,
data=00000133:00000000:00000000:00000000:00000000)
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