Bug 477177 - Strange scaling behavior with xwayland scaling settings on mixed DPI setups
Summary: Strange scaling behavior with xwayland scaling settings on mixed DPI setups
Status: RESOLVED DUPLICATE of bug 474738
Alias: None
Product: kwin
Classification: Plasma
Component: multi-screen (show other bugs)
Version: 5.27.80
Platform: Arch Linux Linux
: NOR major
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords: qt6
Depends on:
Blocks:
 
Reported: 2023-11-18 08:09 UTC by [object Object]
Modified: 2024-06-25 22:57 UTC (History)
2 users (show)

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Description [object Object] 2023-11-18 08:09:35 UTC
SUMMARY
When on a mixed DPI setup (i.e. two 4k monitors at 195% and one 1440p ultrawide at 130%) and the xwayland "apply scaling themselves" option is set, some clients (including those not running on xwayland) render at an extremely high resolution (in this case, 5159x2184). If only one display is enabled, or all displays are using the same scaling factor, the problem goes away and windows are rendered at the native resolution of the monitor again.

Some examples of non-xwayland apps being affected by this are:
- Gamescope
- Minecraft (using `glfw_wayland`)

I've had this issue since I started using the Plasma wayland session, but I haven't gotten around to making a bug report until now.

STEPS TO REPRODUCE
1. Have a mixed DPI setup
2. Set different DPI levels on two monitors
3. Open 

OBSERVED RESULT
Games/apps rendering at an extremely high resolution

EXPECTED RESULT
Games/apps rendering at the native resolution of the monitor, as they do when all monitor have the same scaling factor

SOFTWARE/OS VERSIONS
Linux: 6.6.1
(available in About System)
KDE Plasma Version: 5.27.80
KDE Frameworks Version: 5.245.0
Qt Version: 6.6.0

ADDITIONAL INFORMATION
Marked severity as major as this effects gaming on all multi-dpi setups, as far as I can tell.
Comment 1 Nate Graham 2023-11-26 16:25:09 UTC
Could you attach a screenshot of the all screens that shows the issue?

Possibly a variant of Bug 474738?
Comment 2 [object Object] 2023-12-02 00:55:14 UTC
I'm not sure how I could show the issue, since it's a problem with the resolution of the windows (they otherwise work fine). Is there a debug app that displays the resolution it's rendering at or something?
Comment 3 Bug Janitor Service 2023-12-17 03:45:45 UTC
Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

If you have already provided the requested information, please
mark the bug as REPORTED so that the KDE team knows that the bug is
ready to be confirmed.

Thank you for helping us make KDE software even better for everyone!
Comment 4 Bug Janitor Service 2024-01-01 03:46:07 UTC
This bug has been in NEEDSINFO status with no change for at least
30 days. The bug is now closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

Thank you for helping us make KDE software even better for everyone!
Comment 5 [object Object] 2024-03-27 03:02:37 UTC
I've done more testing and this doesn't seem to apply to wayland-native apps. Not sure if something got fixed, or if I was just testing it incorrectly before. Running minecraft with glfw-wayland will render at the native 3440x1440 resolution of my monitor while running it in xwayland will set the resolution to 5159x2184. This seems to hold true for every other game I've tested, so I'm currently running all my games in gamescope so they render at the correct resolution.
Comment 6 [object Object] 2024-05-12 06:06:26 UTC
Someone else on Reddit seems to also be having this issue: https://reddit.com/r/linux_gaming/comments/1cp7hgu/plasma_multimonitor_gaming_woes/
Comment 7 Nate Graham 2024-06-25 22:56:57 UTC

*** This bug has been marked as a duplicate of bug 474738 ***