Bug 505029 - Sub-pixel font smoothing is disabled on translucent backgrounds
Summary: Sub-pixel font smoothing is disabled on translucent backgrounds
Status: RESOLVED UPSTREAM
Alias: None
Product: kde
Classification: I don't know
Component: general (other bugs)
Version First Reported In: unspecified
Platform: Other Linux
: NOR normal
Target Milestone: ---
Assignee: Unassigned bugs
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2025-05-30 18:46 UTC by Tech-Tac
Modified: 2025-05-30 19:07 UTC (History)
1 user (show)

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Description Tech-Tac 2025-05-30 18:46:13 UTC 
When sub-pixel font smoothing is enabled in font settings, it would work everywhere* except in places where the background of the text is semi-transparent (which is quite common in modern themes) where it instead reverts to full-pixel grayscale anti-aliasing.

This doesn't seem to apply to shell widgets.

EXAMPLES
1. All menus when setting menu transparency to any value other than 100% in Breeze application style config
2. Konsole when background color transparency is enabled
3. Window titles when Breeze or Oxygen window decoration themes are selected, but not Plastique (https://bugs.kde.org/show_bug.cgi?id=460840), though not sure this is because of transparency

OBSERVED RESULT
Grayscale anti-aliasing

EXPECTED RESULT
Blended sub-pixel RGB smoothing

SOFTWARE/OS VERSIONS
Arch Linux
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.0

ADDITIONAL INFORMATION
This may be a Qt issue
Comment 1 Nate Graham 2025-05-30 19:07:59 UTC 
I'm afraid this is something that's up to Qt's font rendering engine, not us.