Created attachment 121031 [details]
This black border occurs on all 4 corners.
There is an ugly black border around the rounded edges when blur is enabled with any theme that isn't Breeze (Tested with Materia KDE and Arc KDE). Disabling blur makes this bug go away. Have seen other reports of this bug so its legit. This bug didn't exist on Plasma prior to version 5.16. Also, this border occurs on GTK applications as well. I read somewhere that this was as a result of blur being rendered for window shadows but I'm not sure.
STEPS TO REPRODUCE
1. Enable blur
Black border at rounded corners
(available in About System)
KDE Plasma Version:
KDE Frameworks Version:
Reports of this bug:
This is a duplicate of two bugs: bug 408594 and bug 395725.
*** This bug has been marked as a duplicate of bug 408594 ***