Subpixel anti-aliasing is a big mixed bag. Attached is a the main file of a QT Widget Application that draws some text with drawText, on various targets, directly on a QWidget, on a QPixmap with transparancy and one without, and on QImages of all applicable formats.

Also attached the resulting renders from windows 11 and linux with wayland and freetype, blown up 5x.

Expected result:

I expect all options where it makes sense for sub-pixel anti-aliasing (i.e. various forms of RGB without alpha layer) to be sub-pixel anti-aliasing. So, the lines labelled: direct, pixmap, and all the variations of RGB without alpha.

Actual result:

On linux, none at all except directly rendering to a QWidget.

On windows, only 3 correct results (direct, pixmap, RGB32), and one weird result, there is subpixel anti-aliasing on a QImage with an alpha channel (ARGB32 premultiplied).