I have this same issue when opening mpv, although at times it seems kwin will completely crash (all window decorations are gone, I can't switch windows, etc). Making a setting change in the compositor settings does indeed fix the former (though it needs to be done every time after opening mpv), and the latter is fixed when starting kwin.
http://puu.sh/o0zrx/5b9937a48c.png Upon starting kwin again, it actually goes to that state which was originally mentioned--the lack of shadows etc (and noticeable graphical glitches when stepping backward in mpv in fullscreen). $ uname -roms Linux 4.4.5-1-ARCH x86_64 GNU/Linux $ pacman -Qs kwin local/kwin 5.6.1-1 (plasma) $ pacman -Qs xf86-video-intel local/xf86-video-intel 1:2.99.917+587+gc186d4d-1 (xorg-drivers xorg) $ pacman -Qs mesa-libgl local/lib32-mesa-libgl 11.1.2-1 local/mesa-libgl 11.1.2-1
