When "Show selected window" is enabled under system settings, weird artifacts can be observed on the alt-tab switcher. They seem to happen all the time when you don't let the switcher finish animating before releasing alt-tab, and also seem to happen if you release alt-tab while the slide animation of the box is happening This seems to have been a problem since at least Plasma 5.2, and doesn't seem to depend heavily on drivers or other specific configuration (see attached reddit thread) It is most noticeable on the Breeze switcher, but does appear to happen on other similar style switchers too (large thumbnails, details). Turning off "Show selected window" seems to completely fix the problem for me. Reproducible: Always Steps to Reproduce: 1. Press alt-tab quickly, slow enough that the dialog appears, but quick enough that it doesn't fully fade in - OR - 2. Press alt-tab normally, cycle through windows, while the highlighted window is changing, release alt-tab Actual Results: The alt-tab switcher fades out a bit, then fades in, then fades out. Happens very quickly, so it looks like flickering. Expected Results: The alt-tab switcher smoothly fades out
Can you please attach the output of "qdbus org.kde.KWin /KWin supportInformation" It's not reproducible here, not even with very slow animations - is the flicker persistent or just a singleton? Can you record a video of the problem?
Created attachment 96863 [details] Output of qdbus org.kde.KWin /KWin supportInformation This is the output from my desktop, running the binary Nvidia drivers. However, the exact same problem appears on my laptop (using the open source Intel drivers). Tweaking VSync / Compositor settings don't seem to make a difference (it still happens with XRender compositing).
I posted a link to a Reddit thread: https://www.reddit.com/r/kde/comments/31s438/plasma_52_flickering_on_short_alttab/ that has my original YouTube video showing the problem in Plasma 5.2 ( https://www.youtube.com/watch?v=NJPUF8iT0UY ), as well as a few "me toos". I've taken some new videos now (on the exact machine that the support info is from): Showing the bug (Show selected window enabled): https://www.youtube.com/watch?v=b-05weuHDUM&feature=youtu.be (slow speed) https://www.youtube.com/watch?v=Pa2YjI-ikMA&feature=youtu.be (normal speed) Not showing the bug (Show selected window disabled): https://www.youtube.com/watch?v=n8IZLYs3D0A&feature=youtu.be (normal speed) https://www.youtube.com/watch?v=BF_7qM0-QVA&feature=youtu.be (slow speed) The behavior mirrors what I see exactly (ie, there are no screen recording artifacts). I'm not sure what you mean about the flicker being persistent? It happens every time I alt-tab, but once it has happened (ie, done alt-tabbing) everything is normal.
With slow animation speed I'm able to reproduce. My guess is it's a mishandling in either sliding popup or blur effect.
(In reply to Martin Gräßlin from comment #4) > My guess is it's a mishandling in either sliding popup or blur effect. Ahh, *only* breeze switcher ... sorry ;-) The sliding is completely broken in this contexts: a) the thumbnails are in static position during the slide b) the switcher slides in, but not out c) since the slide effect doesn't control the close, it cannot (no idea whether it actually can) revert from the current position, but quits and the fade out effect fades out the window. The "Show window" setting is actually a red herring, all problems occur without just as much.
I'm not able to reproduce with the "Show window" setting disabled. So I don't think it's a red herring. Also after discussing with Marco I changed it to not use Slidingpopups and it's still reproduceable with it disabled.
We must be seeing different things then - i've no problems when turning off sliding popups - highlight effect invoked or not. The only "odd" thing is the instant disappearing of the thumbnails, but that's unrelated to anything.
Is this issue still the case?
(In reply to Thomas Lübking from comment #5) > c) since the slide effect doesn't control the close, it cannot (no idea > whether it actually can) revert from the current position, but quits and the > fade out effect fades out the window. This makes sense. On the attached videos, flickering looks like a conflict between hte sliding popups effect and the fade effect. Anyway, I personally can't reproduce the bug.
Cannot reproduce. If you're still able to reproduce this bug, please reopen this bug report.