New blur bug in KWin

[tsujan]

I opened this discussion to inform users that the weird problems they might have started to see with blurring are caused by KWin, not by Kvantum.

Since KWin 5.25 (or, probably, an older version), there's a flickering bug in KWin's blur effect. To reproduce it.

1. Use a Kavntum theme with translucent windows, menus and tooltips.
2. Enable blurring in KWin and also in Kvantum Manager.

Then you may notice that, sometimes, a phantom like rectangle is created in place of closed tool-tips and menus. It may even happen when you close a translucent dialog in front of a window. The ghost like rectangle usually flickers, but it'll disappear once something changes in the window (on mouse-over, for instance).

The bug has been reported in several places. The reporters needed Konsole to see it — they didn't use Kvantum and, without Kvantum, only Konsole and a few other apps can have translucency + blurring.

The video at https://old.reddit.com/r/kde/comments/tarqo8/just_curious_if_theres_been_any_progress_with_the/ shows the problem clearly. That page also contains a long list of reports.

Since Kvantum can apply KWin's blurring anywhere, the problem can get really annoying — it was so annoying to me that, instead of LXQt+KWin, I started to use Wayfire+LXQt (and liked it).

An example:

QTerminal.mp4

[tsujan]

This seems to be fixed in KWin is 5.27.3.