Created attachment 171301 [details]
A video of a window receiving TAB characters while cycling windows.

SUMMARY
For certain applications, walking through windows by hitting Alt+Tab+Tab will send TAB characters (or any other keyboard input) to the current window. It happens with emacs windows; I haven't yet found any other applications where this problem occurs.

STEPS TO REPRODUCE
0. Start a Plasma Wayland session.
1. In settings, make sure the Alt+Tab keyboard shortcut is bound to Walk Through Windows. (This is the default.)
2. Open an `emacs` window as the active window.
3. Hit `Alt+TAB+TAB+...+TAB` to walk through windows. (Hit TAB at least twice while holding down Alt.)

OBSERVED RESULT
The emacs window will receive the TAB key (If you hit TAB n times, then emacs will receive n-1 TAB keys.) Eg, if emacs is in "fundamental-mode", then TAB characters will be inserted in the buffer. (In some other modes, the current line will be indented.)

EXPECTED RESULT
The emacs window never sees the TAB keys, and does not change in any way as windows are cycled.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 6.9.7-arch1-1
KDE Plasma Version: 6.1.1
KDE Frameworks Version: 6.3.0
Qt Version: 6.7.2

ADDITIONAL INFORMATION
* The problem does not seem to happen on X11.
* I tried with a couple other applications, but so far only emacs windows have this issue.
* To reproduce, the emacs window cannot be inside of a console with `emacs -nw`; it needs to be a separate window.
* The problem is more general than just TAB keys. Hit Alt+TAB; while still holding down Alt, press any keys. Emacs will receive all of them.
* The same problem happens if you rebind Walk Through Windows to a different keyboard shortcut. Eg, if you turn off the default binding and rebind it to Alt+q, then hitting Alt+q+q+q+q will send 3 q's to emacs.