This previously incorrectly collected lookups that could be reached via feature variations that are dropped and not activated by the current instance position.
Also updated the script that is used to generate tests.With fonttools,
we now do instancing first and then subsetting.
With different order of subsetting and instancing operations on the same
VF file, fonttools seems to generate 2 different font files with different
glyph set.
1. do subsetting and then instancing: this seems result in a larger glyph
set in the font file. Lookups are collected from both retained features
and all possible alternate featurevariations, this leads to a larger
glyph set after glyph closurei. And instancer doesn't redo glyph
closure, it does lookups pruning only.
2. do instancing and then subsetting: lookups are collected from
features that are replaced already and possible alternate feature
variations
Garret Rieger
Qunxin Liu