Bug 501975 - Wayland: Text Rendering Artifacts When Scaling the Screen
Summary: Wayland: Text Rendering Artifacts When Scaling the Screen
Status: RESOLVED DUPLICATE of bug 499289
Alias: None
Product: kwin
Classification: Plasma
Component: wayland-generic (show other bugs)
Version: 6.3.3
Platform: Neon Linux
: NOR normal
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords: wayland-only
Depends on:
Blocks:
 
Reported: 2025-03-25 11:55 UTC by Alex J Green
Modified: 2025-04-07 15:52 UTC (History)
3 users (show)

See Also:
Latest Commit:
Version Fixed In:
Sentry Crash Report:


Attachments
This is how fonts look like when screen is scaled to 125% (1.62 MB, image/jpeg)
2025-03-25 11:58 UTC, Alex J Green
Details
This is how fonts looks like if the screen is not scaled (i.e. 100%) (3.07 MB, image/jpeg)
2025-03-25 11:58 UTC, Alex J Green
Details

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Description Alex J Green 2025-03-25 11:55:52 UTC
SUMMARY
In the KDE Wayland session, enabling screen scaling causes text to appear jagged, incomplete, and surrounded by colored fringes. This issue does not occur when scaling is set to 100%.

STEPS TO REPRODUCE
1. Start a KDE session on Wayland (I ran Neon from neon-user-20250323-0744.iso)
2. Set display scaling to 125%
3. Open font viewer in Settings
4. Observe rendering artifacts

OBSERVED RESULT
Symbols are jagged, incomplete, and surrounded by colored fringes

EXPECTED RESULT
Text should render clearly, similar to how it appears at 100% scaling


SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Neon from neon-user-20250323-0744.iso

ADDITIONAL INFORMATION
My screen's physical dimensions are 1920x1200
Comment 1 Alex J Green 2025-03-25 11:58:07 UTC
Created attachment 179719 [details]
This is how fonts look like when screen is scaled to 125%
Comment 2 Alex J Green 2025-03-25 11:58:54 UTC
Created attachment 179720 [details]
This is how fonts looks like if the screen is not scaled (i.e. 100%)
Comment 3 Nate Graham 2025-03-25 23:13:56 UTC
Does it happen in a new clean user account with no customizations except for changing the scale factor to 125%? If not, this is probably caused by your font settings somehow.
Comment 4 Alex J Green 2025-03-26 00:18:26 UTC
(In reply to Nate Graham from comment #3)
> Does it happen in a new clean user account with no customizations except for
> changing the scale factor to 125%? If not, this is probably caused by your
> font settings somehow.

Hi! 

This is a clean account. I do only these steps:

1 Write the Neon ISO onto USB stick
2 Boot USB stick
3 Open Display settings, (for me it already shows 105%) change to 125%, press OK
4 Open Settings again, go to Font Management –– observe fonts

I use Neon here only for reproducing this observation. Normally, I run different distributive. It is observed not only on the Font Management, but for other applications too; I think that the Font Management page is good for reproducing it because everyone has this application — this is why I use Font Management screen.
Firstly I found it in my gentoo installation https://forums.gentoo.org/viewtopic-t-1172976.html but that is not something that can be reproduced on another laptop, so I needed some reproducible example and I find Neon is very useful.

Additional observation is that it does not appear in X11, and (just for experiment purposes) I tried to set QT_SCALE_FACTOR with scaling 100% under Wayland session then it is not observed too. 

Maybe, this is related to the graphics card? I run Intel Arc with Xe drivers -- these are relatively new drivers
> 00:02.0 VGA compatible controller: Intel Corporation Meteor Lake-P [Intel Arc Graphics] (rev 08)
> 	Subsystem: Lenovo Device 50e9
> 	Kernel driver in use: i915
> 	Kernel modules: xe

Also, the screen is 14" 1920x1200
Comment 5 Nate Graham 2025-03-26 17:57:35 UTC
Can you clarify some points?

1. Can you attach a few screenshots of the issue in other contexts?
2. Does it happen at both 105% scale as well as 125% scale, or only one?
Comment 6 Alex J Green 2025-03-26 18:30:14 UTC
(In reply to Nate Graham from comment #5)
> Can you clarify some points?
> 
> 1. Can you attach a few screenshots of the issue in other contexts?
> 2. Does it happen at both 105% scale as well as 125% scale, or only one?

A1: It happens not only un Fint browser, but in other applciations. If for example I open in Firefox https://fonts.google.com/noto/specimen/Noto+Sans and set background to black (there is a theme button on the page) and change font (there is a dropdown on that page) from 48px to 20px, then fonts become colored. This is only observed under Wayland session


A2: It happens with 105%, with 125%, with 150% – any non integer scale. Does not happen with 200%.
Here's the video, starting from boot from usb iso, then 105 (corrupted), then 125(corrupted), then 100 (good) https://fex.net/s/4kmkkpe
Comment 7 Alex J Green 2025-03-26 19:02:56 UTC
Here's an example for A1, made here https://fonts.google.com/noto/specimen/Noto+Sans
https://fex.net/s/sevdk7r
It can be seen that characters change their shape when they are slowly moved up-down
Comment 8 Alex J Green 2025-03-27 02:33:22 UTC
Similar bug 499289
Comment 9 Alex Sh 2025-04-04 14:57:07 UTC
I also experience it with software and hardware, listed here: bug 502322
See also: bug 502322, bug 502103
Comment 10 TraceyC 2025-04-07 15:42:26 UTC
(In reply to Alex J Green from comment #8)
> Similar bug 499289

This looks like the same bug as that report. I'm going to mark this as a duplicate of that one. Please follow that report for updates. Thanks!

*** This bug has been marked as a duplicate of bug 499289 ***