"Subpixel offsets break glyph caches"

I once resolved that by keeping a vertically shrunken but really wide glyph around in a cache. Just resample it for a different horizontal offset.

The AGG (“Anti-Grain Geometry”) library does something similar[1], from what I understand.

Also, I had (though never tested) the impression that in the Windows world ClearType uses 3x the horizontal resolution internally (I vaguely remember that being mentioned in the horror novel^W^W Raster Tragedy[2] somewhere?..). Given many font designers’ testing process for their hinting bytecode seems to be to run it through ClearType and check if it looks OK (not unlike firmware programmers...), we all, including Microsoft, are essentially stuck with that choice forever (or at least until people with painfully low-res displays become rare enough that the complaining about blurry text can be disregarded). So I’d expect 1/3 of a pixel to be the natural resolution for a glyph cache, not 1/4? Or have things changed in the transition from GDI to GDI+ to DirectWrite?

[1] https://agg.sourceforge.net/antigrain.com/research/font_rast...

[2] http://rastertragedy.com/