Plasma 6 Wayland: Thin Lined Fonts Display as Rainbow

[spica]

Hi everyone,

I'm encountering an issue with Plasma 6 on Wayland where thin-lined fonts appear with a rainbow-like effect, which is incorrect. The fonts display fine in X11 (Plasma 6) and in GNOME on Wayland, where they look as expected.

Here’s a summary of the issue:

Plasma 6 on Wayland: Thin fonts are displayed with rainbow-like distortion image
Plasma 6 on X11: The fonts are rendered as expected (no rainbow effect) image
GNOME on Wayland: Fonts appear as expected, no distortion.

Has anyone experienced a similar issue or know of a potential solution? I'm using Gentoo and have tested various font configurations, but the issue persists. Any help or suggestions would be greatly appreciated!

This is Noto on the screenshot. Unmerging the noto package makes the font thick, and rainbow disappears.

Thanks in advance.

[rab0171610]

There have been some font rendering issues in QT/KDE Plasma since the upgrade from 5 to 6, however most of that
has been fixed in recent releases/updates.

Under System Settings> Text & Fonts> Fonts, what are you settings for the last four items:
1.) Anti-Aliasing (Enable)
2.) Exclude range from anti-aliasing
3.) Sub-pixel rendering
4.) Hinting

Under System Settings> Display and Monitor> Display, are you using scaling? Have you modified the color profile setting there?

Are you using using a hidpi monitor?

Does this occur with all applications or only specific applications?

To eliminate the possibility that this is a configuration or settings issue, what are the results when logged in as a new user?

[spica]

System Settings> Text & Fonts> Fonts image
1 Anti-Aliasing (Enable) === Enable (checkbox is set)
2 Exclude range from anti-aliasing === Disable (checkbox is empty)
3 Sub-pixel rendering === RGB (image) Also tried None (image)
4 Hinting === tried Slight and Full --- both look the same


System Settings> Display and Monitor> Display image
Scale: 125% (tried 100% --- no effect)
Color profile: None (tried built-in ---no effect)
Legacy applications (X11) --- tried both, no effect


Q: Are you using using a hidpi monitor?
A: This is 1920x1200 14.5" IPS screen (I am not sure what is considered hidpi nowadays, hope the numbers provide the answer)


Q: Does this occur with all applications or only specific applications?
A: First observed in guitarix, also I can reproduce in firefox-bin --- because I can craft a test html page


Q: To eliminate the possibility that this is a configuration or settings issue, what are the results when logged in as a new user?
A: Under a newly created account observations are the same.


Observed with plasma-meta-6.2.5 and 6.3.0


Used this html snippet for testing in firefox-bin:

[Yamakuzure]

I'd look into

[spica]

[muddle]

I had similar issues if I activated HDR on my box.

[Yamakuzure]

Maybe HDR can be an issue. Spicas fontconfig looks pretty solid to me.
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Edited 220,176 times by Yamakuzure