No desktop effects; System Settings seg faults when I click on "Desktop"

[EssexEagle]

Recently, all desktop effects have stopped working for me in KDE. (A few days ago I plugged my laptop into a TV screen via an HDMI cable and I think it was after that that the problem started, but I don't recall fiddling with any desktop effect settings.) If I click on System Settings then Desktop, System Settings always crashes with the error message "Executable: systemsettings PID: nnnnn Signal: 11 (Segmentation fault)". In the brief split-second before it crashes I can see a line of text claiming that compositing is disabled, but this never used to be the case.

Could anyone help me to figure out: a) why compositing appears to have been disabled, and b) why System Settings always seg faults when I click on Desktop?

Many thanks :-)

[EssexEagle]

Also, if I run systemsettings from the command line, the output is as follows:

simon@simon-laptop:~$ systemsettings 
QInotifyFileSystemWatcherEngine::addPaths: inotify_add_watch failed: No such file or directory
QFileSystemWatcher: failed to add paths: /home/simon/.config/ibus/bus
Bus::open: Can not get ibus-daemon's address. 
IBusInputContext::createInputContext: no connection to ibus-daemon 
simon@simon-laptop:~$ systemsettings(10581)/kwin KWin::Extensions::init: Extensions: shape: 0x "11"  composite: 0x "4"  render: 0x "a"  fixes: 0x "40"
Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
QSocketNotifier: Invalid socket 11 and type 'Read', disabling...
KCrash: Application 'systemsettings' crashing...
sock_file=/home/simon/.kde/socket-simon-laptop/kdeinit4__0

[Snowhog]

First question: Is this behavior occurring with your HDMI connection unplugged? If 'yes', do you experience the same behavior if you plug your HDMI connection back in?

[EssexEagle]

Yes, this is without the HDMI cable plugged in. Unfortunately, I'm not at home at the moment (Christmas etc.) and don't have access to the cable so I shan't be able to check for nearly a week. I might have to come back to this in a few days' time...

[oshunluvr]

First guess as to why compositing has been disabled is your video system slowed significantly when you plugged in the second monitor and it turned off compositing.

ALT-SHIFT-F12 should turn it back on (video restart may be required).

The segfault may or may not be related. A faulty user setting could cause it. Try creating a new user and logging in as that user to see if the segfault goes away. If it does, compare your .kwinrc files and see what's different.

[EssexEagle]

First guess as to why compositing has been disabled is your video system slowed significantly when you plugged in the second monitor and it turned off compositing.

ALT-SHIFT-F12 should turn it back on (video restart may be required).

Alt+Shift+F12 has no effect (even with a restart).

The segfault may or may not be related. A faulty user setting could cause it. Try creating a new user and logging in as that user to see if the segfault goes away. If it does, compare your .kwinrc files and see what's different.

I've tried with a brand new user and exactly the same behaviour occurs.

[oshunluvr]

Please verify your system is fully updated:

sudo apt-get update
sudo apt-get dist-upgrade