Comment 12 for bug 847484

I know the cause and have a fix pending, thanks for the information.

It has to do with how QWidget's setfullscreen behaves with regards to KDE's toggle action system. Quassel currently does not follow the KDE fullscreen toggle actions documentation in that one should use its functions to turn on/off fullscreen rather than the regular QWidget ones as the latter include additional changes that are unrelated and more importantly will cause syncness issues.