Bug 460840

Summary: KWin doesn't respect sub-pixel rendering setting for window titles
Product: [Plasma] kwin Reporter: Adam Fontenot <adam.m.fontenot+kde>
Component: decorationsAssignee: KWin default assignee <kwin-bugs-null>
Status: CONFIRMED ---    
Severity: normal CC: alvisebruniera, im.tech.tac, jan.rathmann, kzn.hartwig1, nate, zawertun
Priority: NOR    
Version First Reported In: 6.0.0   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Adam Fontenot 2022-10-22 06:36:20 UTC 
SUMMARY
I have RGB sub-pixel rendering enabled. It works as expected everywhere inside KDE / QT applications, but window titles are rendered with only grayscale anti-aliasing.

From what I can tell looking at some old screenshots, the issue first appeared sometime in 2018 or 2019. 

I think this probably affects anywhere that KWin draws text, but I'm not sure where that is besides the window title, so I can't verify. Text drawn as part in Plasma (e.g. in the task bar) respects the rendering settings.

STEPS TO REPRODUCE
1. Enable RGB sub-pixel rendering for fonts in your system settings. (I also have anti-aliasing enabled and hinting disabled, although this shouldn't matter.)
2. Restart KWin and see if window titles are subpixel rendered. (If you take a screenshot and zoom in close, you should see color fringing around the glyphs.)

OBSERVED RESULT
Window titles are not subpixel rendered.

EXPECTED RESULT
They should be.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 5.26.0
KDE Frameworks Version: 5.99.0
Qt Version: 5.15.6
Kernel Version: 6.0.1-arch1-1 (64-bit)
Graphics Platform: X11
Comment 1 Nate Graham 2022-10-24 19:10:49 UTC 
Can reproduce.
Comment 2 Adam Fontenot 2024-03-04 21:38:30 UTC 
Reproduced on 6.0.0.

Operating System: Arch Linux 
KDE Plasma Version: 6.0.0
KDE Frameworks Version: 6.0.0
Qt Version: 6.6.2
Kernel Version: 6.7.6-arch1-1 (64-bit)
Graphics Platform: Wayland
Comment 3 Nate Graham 2025-03-31 18:57:58 UTC 
*** Bug 502136 has been marked as a duplicate of this bug. ***
Comment 4 Tech-Tac 2025-05-30 18:47:03 UTC 
These seems to apply to Breeze and Oxygen themes only, not Plastique