Konsole reports: KDE Frameworks 5.18.0 Qt 5.5.1 (built against 5.5.1) The xcb windowing system I couldn't see KDE version 5.18, so I selected unspecified. I cannot reproduce it but it seems to me it is triggered when I open a "file selection" widget. I cannot switch between windows with ALT+TAB, I cannot iconize or resize windows (no window widgets and handles). If I am lucky I can use the "K" button to logout e log back in. Otherwise I can switch to the system console with CTRL-ALT-F1, log in and run: killall -9 kwin_x11; DISPLAY=:0.0 kwin_x11 --replace &> /dev/null & The kwin_x11 process is not dead. I simply "refresh" it. I filed this to Ubuntu which in turn asked me to file it to kde.org. https://bugs.launchpad.net/bugs/1582246 I am available to help troubleshooting provided that precise directions are provided. Reproducible: Sometimes Steps to Reproduce: 1. I have no way to reproduce it. It's quite annoying.
Please provide the output of: qdbus org.kde.KWin /KWin supportInformation
Created attachment 100947 [details] qdbus org.kde.KWin /KWin supportInformation
Please try switching to the default decoration Breeze.
I just did it. Of course we need to wait some time (a couple of days should suffice). So, stay tuned for the news.
The use of the Breeze windows decorations didn't triggered the problem. I don't know whether it's a bug in the Plastik window decorations (the one I was using previously) or it's about something that the Breeze is not using/doing.
Most likely the well known issue with QtQuick. Marking as duplicate *** This bug has been marked as a duplicate of bug 351839 ***