Created attachment 98920 [details] Support information while the issue is NOT present. Not sure if it's a bug in kwin or plasmashell. I have a kwin rule to disable compositing once mpv launches. Sometimes, this results in plasmashell displaying a stale image - this affects the whole UI. For example, the icon-only task manager shows applications that were running the last time compositing was activated. Starting new applications does neither display the loading circle animation, nor show the application icon once the application starts. The more annoying part about it is that the clock and the widgets are showing stale information, too. I once nearly missed and appointment because both clocks were still saying it's 16:30 while it was starting to get dark... I have also remember being able to trigger it by manually suspending compositing, but that might have been after it was already bugged by launching mpv. Arch linux x64, fully updated as of yesterday, nvidia 340xx blob (260GTX). Has been happening since forever, but that's not surprising since I'm on the legacy branch.
(Likely "the driver", maybe QtQuick/QGraphicsScene/View) * Are other windows affected? * Multiscreen issue? The GL context in plasmashell probably "misses" the unredirection (does resuming the compositor "unfreeze" plasmashell?) and maybe even keeps painting into an offscreen drawable. I guess implicit unredirection with mpv is crucial (ie. explicitly suspending the compositor at some other time by SHIFT+Alt+F12 or implicit suspending for xterm doesn't cause this)? Does mpv -vo x11 video.mp4 cause this as well? (it should make mpv use the not so performant software/x11 render path)
It's really hard to reproduce, sadly. I tried launching it like 50 times and so far it hasn't happened. Same for explicitly disabling the compositor and using -vo x11 Closing mpv/re-enabling compositing does unfreeze plasmashell, however. Also yes, I have two monitors and the clock widget is on the secondary monitor. The panel with the task manager is on the primary monitor, though, so both freeze. I haven't noticed other windows being affected, I'll try looking at e.g. chromium the next time this happens.
Ok, it just happened again. Once it's triggered, any action suspending compositing triggers it again. Once I noticed it, I tried to start mpv with -vo x11, and it also makes the issue re-appear. Restarting kwin using kwin_x11 --replace does fix it. I guess the initial trigger is what is bugging it up - this time it was mpv -vo opengl-hq again.
Created attachment 99036 [details] Support information while the issue is present Not sure if this one is useful
*** Bug 368076 has been marked as a duplicate of this bug. ***
I have this issue, and have had it for quite some time. I can trigger it (almost) 100% of the time by turning off compositing using any method. I've grabbed some screenshots in case it's useful. This: http://i.imgur.com/9NfHLAw.png is the desktop before I disable compositing and close the window. This: http://i.imgur.com/RXXL7qp.png is immediately after I disable compositing. I'm using openSUSE 42.1, kernel 4.1.27, Plasma 5.5.5, and an Nvidia 970 with their driver (367.35). I've seen the issue consistently through at least a few versions of openSUSE, KDE 4 and 5, and three different GPUs (all Nvidia, all proprietary driver), though. I think I've also pretty much always used two or more monitors with that computer. kwin_x11 --replace does fix the issue for me, for a little while. I can then disable compositing and everything functions like it should, for a while. Disabling and re-enabling compositing afterwards will bring the issue back, but not consistently. The issue might resurface the first time I disable compositing again, or it might be ten "cycles" before it happens again.
Is this bug still relevant for you?
*** This bug has been marked as a duplicate of bug 353983 ***