Version: unspecified (using Devel) OS: Linux I start to notice this bug at the beginning of this month, when the composite was suspended and reenabled, very often plasma pannel stayed with the ugly non-composite theme, all the other composite staff like the shadow and special effects were normal, but for plasma it is like it never get the signal the composite is back on. Reproducible: Sometimes Steps to Reproduce: Press alt+shift+f12 to disable the composite, press the combo again to bring it back Actual Results: plasma changes the theme to the non-composite one when the composite is disabled, but does not switch back to the composite theme when composite is enabled again, and special functions depend on the composite function is still off, like the thumbnail function on taskbar. I have to kill plasma-desktop and restart it to get composite effect back Expected Results: plasma switch back to the composite theme when composite it back. The only other possible reason for the bug beside plasma itself is I am using binary drivers from NVIDIA. I did upgraded the driver recently, and did not try downgrading it.
I added some kDebug code to ThemePrivate::compositingChanged(), this bug is very easy to trigger when the compositing is restarted: changing the advanced options in kwin, remove a monitor in nvidia-settings, etc. the compositingChanged function get the initial disabling signal, but it still consider the compositing is off when it is reenabled. If I disable compositing again using Alt+Shift+F12, compositingChanged works again and received the compositing off signal, but it is NEVER called again no matter how many times I disable/enable compositing after that. I do not know if it is because plasma spend too much time to discard the cache and cannot responding fast enough.
One quite reliable way to reproduce the bug is to restart kwin by kwin --replace, with 6-8 window opened and some special effect like blur enable.
After some debug, this bug seems to be a duplicate of 179042 *** This bug has been marked as a duplicate of bug 179042 ***