Created attachment 179823 [details]
Screenshot of dolfin where the issue is observable

SUMMARY

When subpixel rendering is enabled from kde settings, windows decorations still do simple grayscale rendering. The content of the windows renders correctly instead.

STEPS TO REPRODUCE
1. Enable and apply subpixel rendering
2. Log out and in or reboot if you want to make sure that is not the problem, but it doesn't matter
3. Open a window

OBSERVED RESULT

The content of the window is rendered correctly, while the decoration of the window uses greyscale rendering (screenshot attached)

EXPECTED RESULT

All text should do subpixel rendering.

SOFTWARE/OS VERSIONS
Operating System: Fedora Linux 41
KDE Plasma Version: 6.3.3
KDE Frameworks Version: 6.12.0
Qt Version: 6.8.2
Kernel Version: 6.13.8-200.fc41.x86_64 (64-bit)
Graphics Platform: Wayland


ADDITIONAL INFORMATION

The taskbar and kickoff panel render correctly, with subpixel antialiasing.

As a side note, all gtk windows do greyscale rendering, but I'm almost sure that's an entire other matter, so I'll just mention it.