Derp, been too long since my theory class.

I am fairly confident AAT tables are FSMs, so I am curious where the turing completeness comes from. I am certainly not familiar with all truetype/opentype features.

It's the hinting that's normally referred to here as Turing complete, I think.

https://en.wikipedia.org/wiki/TrueType#Hinting_language

I know Mac OS X has ignored a lot of the hinting in fonts. Do they evaluate the entire script regardless?