Bug 417598

Summary: Every other frame inside window being dropped
Product: [Plasma] kwin Reporter: George <Vash63>
Component: scene-openglAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED FIXED    
Severity: normal CC: bugtracking, nate, null, postix
Priority: NOR    
Version First Reported In: 5.20.2   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: https://invent.kde.org/plasma/kwin/-/commit/b8a70e62d53591130a284adea9a56eb20e6d8060 Version Fixed/Implemented In: 5.21
Sentry Crash Report:

Description George 2020-02-13 20:29:53 UTC 
At least with both Firefox and Chrome using the test detailed below, it seems that my display is only receiving every other frame (with perfect cadence) that is rendered by the browsers. I've tested with both OpenGL2.1 and 3.0 compositors and can reproduce on both. I cannot reproduce this on Gnome shell. kwin 5.16 had the same issue a few months ago so this is not a new regression.


STEPS TO REPRODUCE
1. Visit https://www.testufo.com/blackframes#count=2&bonusufo=1&equalizer=1&background=000000 in either Chrome or FF

OBSERVED RESULT
1. The middle UFO is either completely missing (black frames only being shown) or twice the expected brightness (black frames not being shown). 
2. The topmost and bottommost UFOs are operating at the same speed (visibly, both show proper framerates according to the browsers - this is a presentation issue not rendering).

EXPECTED RESULT
1. The middle UFO should look substantially sharper but at the same brightness and speed as the top UFO. This one is using black-frame-insertion. 
2. The bottommost UFO should be showing at twice the framerate (visibly smoother, usually looks slightly 'ahead' as well).

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch with Plasma 5.18.0
KDE Plasma Version: 5.18.0
KDE Frameworks Version: 5.67.0
Qt Version: 5.14.1

ADDITIONAL INFORMATION
This is using the Nvidia binary driver on X11. I have had other people via Discord/IRC duplicate the issue, though it may only impact Nvidia users as no AMD users reported back.
Comment 1 Kitsuna 2020-04-11 23:46:07 UTC 
I can reproduce this on 5700XT using mesa-git 20.1.0_devel.122121.089e1fb287e-1

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch 
KDE Plasma Version: 5.18.4
KDE Frameworks Version: 5.68.0
Qt Version: 5.14.2
Comment 2 George 2020-11-10 19:50:07 UTC 
Update on this, I have just switched to kwinft and can confirm this issue is resolved by avoiding the use of kwin. Also bumping the version on this bug to 5.20.2 as I've confirmed it still exists with the latest kwin upstream release.
Comment 3 Vlad Zahorodnii 2021-01-06 17:01:24 UTC 
Fixed with the compositing scheduling rewrite.