Overlap oversampling

[Alexei Podtelezhnikov]

Hi everybody,

This is a proof of concept for oversampling to decrease artifacts in
rendering overlaps. The attached images show how the artifact visible
at the top of B, E, F, T decreases as we increase oversampling from
1x1, to 2x2, to 4x4. The price is doubling and quadrupling the
rendering time. The proposal is to have it available as
FT_RENDER_MODE_SLOW specifically for fonts that need it.

I am seeking feedback if 2x2 is good enough, or 4x4 is necessary. I
will also reply with a set of patches to try it and comment on it.

Regards,
Alexei

4x4.png
Description: PNG image

2x2.png
Description: PNG image

1x1.png
Description: PNG image