Comment 4 for bug 182288

I just had the same issue on a machine where previously kwin effects worked OK.
After narrowing down which change actually produced the black screen I found
the following combination to reproducibly trigger the bug:
+ On tab "General" enable desktop effects
+ On tab "All Effects" disable "Login/Login visual effect"
At your next login the screen will stay black.

(It smells like: login with effects enabled switches to a black screen and only
the login effect will turn the light back on, doesn't it??)

So the workaround might be as easy as avoiding the above combination.

BTW: I came into this situation while searching for a set of effects that doesn't
slow me down too much. Since I do a lot of desktop switching (mostly using
keyboard shortcuts), 4 seconds of repaint after each switch wasn't making me happy.
Any hints on which particular effect causes repaint of all windows after desktop switching?
Or is it compositing in general that causes additional repaints?