Bug 444420

Summary: XWayland server started by nested KWin Wayland reports incorrect refresh rate
Product: [Plasma] kwin Reporter: sattaxt
Component: platform-wayland-nestedAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED DUPLICATE    
Severity: normal    
Priority: NOR    
Version: 5.23.1   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed In:
Attachments: output from kscreen-doctor-o
output from qdbus
output from xrandr

Description sattaxt 2021-10-26 10:12:45 UTC 
SUMMARY
When using KWin Wayland, the XWayland server started by it will have the wrong refresh rate set. In my case it is 144Hz for a 240Hz monitor. For wayland itself, the refresh rate is correct. 

This bug can be seen when running XWayland apps as well, for example: Chromium and mpv (with xwayland) will report the display refresh rate as 143Hz. This can (and does) result in laggy, juddery experience.

STEPS TO REPRODUCE
1. Start KWin Wayland
2. run xrandr or check X apps

OBSERVED RESULT
XWayland is set to the wrong refresh rate (144Hz in my case)

EXPECTED RESULT
XWayland refresh rate should be in sync with the Wayland one (240Hz)

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux 5.23.1
KDE Plasma Version: 5.23.1
KDE Frameworks Version: 5.87.0
Qt Version: 5.15.2
GPU: NVIDIA Turing

ADDITIONAL INFORMATION
Comment 1 sattaxt 2021-10-26 10:13:18 UTC 
Created attachment 142901 [details]
output from kscreen-doctor-o
Comment 2 sattaxt 2021-10-26 10:13:36 UTC 
Created attachment 142902 [details]
output from qdbus
Comment 3 sattaxt 2021-10-26 10:13:53 UTC 
Created attachment 142903 [details]
output from xrandr
Comment 4 Vlad Zahorodnii 2021-10-26 10:17:38 UTC 
The refresh rate of nested kwin_wayland is hardcoded to 60Hz. Did you mean host kwin_wayland or nested kwin_wayland?
Comment 5 Vlad Zahorodnii 2021-10-26 10:18:33 UTC 
host kwin_wayland => kwin_wayland running on top of DRM
nested kwin_wayland => windowed kwin_wayland
Comment 6 sattaxt 2021-10-26 10:20:00 UTC 
(In reply to Vlad Zahorodnii from comment #4)
> The refresh rate of nested kwin_wayland is hardcoded to 60Hz. Did you mean
> host kwin_wayland or nested kwin_wayland?

I mean kwin_wayland started with "kwin_wayland ... --xwayland ..". This is usually referred to as a "nested session" in KDE documentation I've read, am I using the wrong terminology?
Comment 7 sattaxt 2021-10-26 10:24:46 UTC 
(In reply to Vlad Zahorodnii from comment #5)
> host kwin_wayland => kwin_wayland running on top of DRM
> nested kwin_wayland => windowed kwin_wayland

Host.
Comment 8 Vlad Zahorodnii 2021-10-26 10:39:48 UTC 

*** This bug has been marked as a duplicate of bug 444303 ***