(This belongs to the Plasma 5 forum, which I discovered after posting this.)
I'm using KDE Plasma 5.2 on openSUSE 13.2 on a nvidia gpu with the binary driver.
After a short while of no activity the display will go into power saving mode, as it should. When I "wake" the display up however, e.g. by moving the mouse, the image of the desktop will very corrupted, dominated by strange triangle shapes and momentary glimpses on the open windows. It is unusable. It also happened at least once when returning from suspend or sleep.
By chance I found out that repeated switching of the virtual terminal (?) by ctrl-alt-F1 and then ctrl-alt-F7 can "restore" the desktop. Usually I have to switch back and forth two times.
I have no idea whether this is really related to plasma but I figured this is a good starting point. Has anybody experienced similar behavior or an idea how it could be fixed? (Ubuntu Unity sometimes also looks a bit shaken up after returning from power saving mode, but it happens much less frequently.)

to to Plasma 5 forum

https://bugs.kde.org/show_bug.cgi?id=344326