Created attachment 145291 [details] screenshot Since update to KF5 5.90.0, there is a gray line around plasma panels, tooltips, and notifications. The one just above the main panel can move and/or becomes thicker when restarting plasmashell, and moves when resizing the panel. It looks like the shadow, but rendered with an incorrect offset. SOFTWARE/OS VERSIONS Linux/KDE Plasma: Fedora 35 KDE Plasma Version: 5.23.4 KDE Frameworks Version: 5.90.0 Qt Version: 5.15.2 ADDITIONAL INFORMATION The issue is fixed by downgrading kf5-plasma to 5.89.0, even keeping the other KF5 packages to 5.90.0.
Looks like messed up shadows. Does the problem go away if you clear the cache and restart Plasma by using a terminal to run: rm -r ~/.cache/*plasma* ;; killall plasmashell ;; kstart5 plasmashell ?
Created attachment 145345 [details] shadows after erasing cache The bug disappears, but now the shadows are almost invisible, they are extremely light (I don't know if this is expected or not). Is this the expected rendering (see screenshot) ? Maybe there is an alpha blending issue. If I create a default panel on top of the screen, its shadow is is little more visible.
Sounds like it was a cache issue indeed. What Plasma theme are you using and what scale factor is set? The default 100%, or something else?
The Plasma theme is Breeze Dark, the scale is 100%, and the DPI is forced to 96 (if this matters). I don't know if the shadow shown in the plasma theme image in systemsettings is supposed to be realistic, but it's much more visible. With Breeze Light, the shadows are slightly more visible, but that's probably due to the colors. Oxygen plasma theme has visible shadows.
For better or worse, that's what the shadows are supposed to look like now. If you think they're too faint, feel free to file a separate bug report about it. :)