Bug 506244

Summary:	[Wayland] Fractional scaling: blurry and distorted font rendering
Product:	[Plasma] kwin	Reporter:	nvcosj
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED DUPLICATE
Severity:	normal	CC:	akira.uestc, eifr0980, kdedev, rmallah29, xaver.hugl
Priority:	NOR	Keywords:	multiscreen, wayland-only
Version First Reported In:	6.4.1
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	Font rendering at native scaling, with no fractional scaling on any displays Font rendering at native scaling, second display's scaling set to 125% Font rendering at 125% scaling

Description nvcosj 2025-06-26 23:31:23 UTC

Created attachment 182708 [details]
Font rendering at native scaling, with no fractional scaling on any displays

SUMMARY
On Wayland session in multi-display setup, setting fractional scaling on one or more displays results in fonts appearing distorted in proportions. Additionally, fonts rendered on a display with 100% scaling look blurred.

STEPS TO REPRODUCE
1. Set only one display's scaling to any value other than 100% (125% in my case).
2. Restart plasmashell.

OBSERVED RESULT
Fonts rendered on both displays have changed proportions compared to native scaling. Fonts rendered on display using 100% scaling look blurry, as if they were mapped onto a 1080p display from 1536x864 resolution resulting from scaling the other 1080p display to 125%.

EXPECTED RESULT
After restarting plasmashell, fonts on the display with native scaling look the same as before the restart and have the same (original) proportions on all displays.

SOFTWARE/OS VERSIONS
Operating System: EndeavourOS 
KDE Plasma Version: 6.4.1
KDE Frameworks Version: 6.15.0
Qt Version: 6.9.1
Kernel Version: 6.15.3-arch1-1 (64-bit)

ADDITIONAL INFORMATION
Attached screenshots show how the fonts are rendered before and after changing the settings on Plasma desktop (random desktop filename and app launcher). Both displays have 1920x1080 resolution.

Could be a duplicate of https://bugs.kde.org/show_bug.cgi?id=501715 and maybe is related to https://bugs.kde.org/show_bug.cgi?id=446674

Comment 1 nvcosj 2025-06-26 23:32:45 UTC

Created attachment 182709 [details]
Font rendering at native scaling, second display's scaling set to 125%

Comment 2 nvcosj 2025-06-26 23:45:37 UTC

Created attachment 182710 [details]
Font rendering at 125% scaling

Same font proportions as on the display with 100% scaling, but a lot sharper

Comment 3 TraceyC 2025-07-01 18:09:56 UTC

Thanks for the bug report. From the screenshots, what I see is:
- With scaling on, the text is taller than with no fractional scaling
- Font rendering at 125% scaling the fonts are indeed crisper

I'm able to reproduce this on git-master. As we've seen with other multi-display bugs and fonts, the exact effects will vary depending on the display setup. The main thing is the difference in font crispness when different scaling settings are in use.

Screens in my normal setup:
Laptop 3840 x 2400 @ 150%
2 external monitors 3440 x 1440 @100 % - connected via USB-C dock

With the laptop display at native resolution @175% I see less clear fonts than at 150%, 200% is also fuzzy
With Mon2 set to native resolution @125% I see less crisp fonts than on Mon1 native @ 100%

Comment 4 TraceyC 2025-09-03 20:11:53 UTC

*** Bug 508955 has been marked as a duplicate of this bug. ***

Comment 5 Zamundaaa 2025-09-09 13:58:27 UTC


*** This bug has been marked as a duplicate of bug 501715 ***