That one has cost me nerves.
What happens is that kwin gets locked trapped in it's strut handling because it already is in an invalid area, also the wrong clipping area was used.
As a solution i check
- are we locked?
- are we changing the screen
--> put window into bounds of the new screens workarea
The patch applies to 4.8, so ideally Kai can test & use it, but i'd rather apply it to master only - it might cause unforeseen regressions...
Testing
Could reprouce test from bug, now the window moves below the titlebar and from there just on.