Bright text is too faint/weak

[emilk]

Compare white text on black with black text on white:

Even though the text colors are #fffff and #00000 they do not appear as such. ab_glyph computes per-pixel coverage values, and no pixels in the text are fully covered by the glyph. This makes the text looks a bit too faint in both cases.

This problem is much more pronounced on the bright text. The effect of this is that the bright text looks fainter, thinner and weaker than the black text. This just makes bright mode worse overall in egui.

It is possible this could be solved by either by switching to gamma-blending, or by tweaking how we interpret/store the coverage values we get from ab_glyph.