https://bugs.kde.org/show_bug.cgi?id=521073
Bug ID: 521073
Summary: XWayland games receive scaled desktop resolution
instead of physical monitor resolution when fractional
scaling is enabled
Classification: Plasma
Product: kwin
Version First git-stable-Plasma/6.3
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: compatibility
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 192890
--> https://bugs.kde.org/attachment.cgi?id=192890&action=edit
screenshot from witcher 3 with "aplications scaled by system" using plasma in
4k with 145% scaling, this is the highes avaliable resolution ingame.
Title:
Fractional scaling causes fullscreen games to receive scaled virtual
resolutions instead of physical monitor modes
Description:
When using KDE Plasma Wayland with fractional scaling enabled and X11
applications configured to be scaled by the system, fullscreen games launched
through Steam/Proton do not receive the monitor's physical display modes.
Instead, the games receive resolutions derived from the desktop's logical
scaled resolution.
System:
* KDE Plasma Wayland
* 3840x2160 monitor
* Global Scale: 145%
* AMD Radeon RX 9070 XT
* Steam + Proton
* Distribution: Bazzite
Steps to reproduce:
1. Set monitor resolution to 3840x2160.
2. Set KDE Global Scale to 145%.
3. Configure "Legacy X11 Applications" to be scaled by the system.
4. Launch a fullscreen game through Steam/Proton.
5. Open the game's graphics/display settings.
Observed result:
The game does not expose the monitor's native 3840x2160 mode.
Instead, the highest available resolution becomes approximately 2648x1490,
which corresponds to the desktop's logical scaled resolution.
Example:
* Physical monitor resolution: 3840x2160
* KDE Global Scale: 145%
* Resolution reported to the game: 2648x1490
Expected result:
Fractional UI scaling should not affect the physical display modes exposed to
fullscreen games.
Games should still be able to access and select the monitor's native
resolutions, such as:
* 3840x2160
* 2560x1440
* 1920x1080
regardless of the desktop scaling factor.
Additional observations:
* Changing the KDE scaling factor back to 100% immediately restores the correct
3840x2160 resolution list inside games.
* Changing the "Legacy X11 Applications" setting to "Applications scale
themselves" also restores the correct 3840x2160 resolution list.
* However, this causes many X11 applications (including Steam) to become
extremely small and difficult to use on a 4K display.
* The issue is therefore not a complete lack of functionality, but rather that
users currently must choose between:
* Correct application scaling with incorrect game resolutions, or
* Correct game resolutions with unusably small X11 applications.
Why this matters:
Users of 4K displays often rely on fractional scaling for accessibility and
readability reasons. Desktop UI scaling should not prevent fullscreen
applications from accessing the monitor's physical display modes.
The current behavior effectively ties game resolution availability to desktop
scaling settings, which is unexpected and makes it difficult to use native
monitor resolutions without workarounds such as Gamescope.
Additional note:
Gamescope/Scope Buddy works around the problem by exposing a virtual 3840x2160
display to the game, which suggests that the issue is related to how display
modes are exposed to X11/XWayland applications when fractional scaling is
enabled.
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