Comment 41 for bug 921555

Report it for each application where you see it. Qt cannot be fixed, because rendering into a bitmap cannot add subpixel hinting, because Qt does not know which screen (if at all) the bitmap is going to be copied into.

The respective application developers can then decide to change the code not to render into a bitmap, but directly to the widget's painter. Or maybe they are using Plasma text rendering calls, without being aware of the issue. Or they use Plasma calls intentionally, to get the blurred shadows to be better readable with transparent themes.

You might point them to this bug report, especially comment #21 and comment #33.

Plasma developers could check, if rendering the shadows could be decoupled from rendering the text, but that might cause issues when the metrics does not match accurately.

Anyway, what you see is related, but a completely different issue what this bug is about. Since bug 260943 has been marked upstream, I will do the same for this one.