What needs to be done from what I currently understand:

• The private-dict always processes blends. We need a specialization for the subset case that stores them, like the cs-interpretter does.

• Both need to gain support for partial instancing. Not sure were to put all the region expensions. Perhaps the CFF2 subset accel.

• The varstore needs to be pruned of unused regions.

Humm. Maybe easier to do in fonttools first...

I actually implemented this in FontTools. Wasn't too bad there. I hope we can use some of the same design here.

@qxliu76 is this something you can take on?

@garretrieger

I actually implemented this in FontTools. Wasn't too bad there. I hope we can use some of the same design here.

fonttools/fonttools#3506

I rebased this but don't think I'd have time any time soon to get back to this. :(