I'm not sure it's window system or KWin related issue
X11, single display, 96DPI
STEPS TO REPRODUCE
1. Open for e.g. Kate
2. Make height to be full and restart application
3. Maximize window
4. Restore it
5. Window is half of previous height
Window after restore from maximize is half of previous height
Window after restore from maximize to equal to previous height
Linux/KDE Plasma: 5.22.4
(available in About System)
KDE Plasma Version: 5.22.4
KDE Frameworks Version: 5.84
Qt Version: 5.15.5 (KDE patches)
Actually this bug is pretty aged. It happens only after first run, if you make it full height again, maximize/restore works correct.
Created attachment 140588 [details]
Open Kate -> resize to full height -> restart app -> maximize -> restore -> half height
After a bit thinking it's not a half height just a previous height (before resize to full height)
I have heard other reports of this, but have never been able to reproduce the issue myself.
Does it affect all KXMLGui-using windows? How about a window from an app that does not use KXMLGui like Discover or Elisa or System Monitor? What about a 3rd-party SSD-using app?
Yup it affects all KXMLGui apps, probably bug is there. See attached video.
Firefox is affected, Steam not.
Is Firefox running in CSD mode, or SSD mode?
If firefox is affected, that would seem to suggest that KXMLGUI is not to blame, as it certainly does use that framework. Moving to KWin.