[vg_head]

Very interesting. Honestly I don't know much about hinting, but I suspect the whole shaping stack that Slug supports:

> kerning, ligature replacement, combining diacritical mark placement, and character composition. Slug also supports a number of OpenType features that include stylistic alternates, small caps, oldstyle figures, subscripts, superscripts, case-sensitive punctuation, and fractions.

Probably still uses the CPU.