Bug 505029

Summary:	Sub-pixel font smoothing is disabled on translucent backgrounds
Product:	[I don't know] kde	Reporter:	Tech-Tac <im.tech.tac>
Component:	general	Assignee:	Unassigned bugs <unassigned-bugs-null>
Status:	RESOLVED UPSTREAM
Severity:	normal	CC:	nate
Priority:	NOR
Version First Reported In:	unspecified
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

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.