must follow fvar axes order when building gvar GlyphDeltas

[anthrotype]

TupleBuilder was iterating over VariationRegion's axis_tents which is a BTreeMap, but it should instead iterate over the region's tents following the fvar's axis order, that's what the gvar Tuples must follow. Otherwise we store deltas for the wrong axes!

[dfrg]

Good catch! I wonder if VariationRegion should be changed to store tents in axis order rather than using a map but I see at least one place where lookup is done by tag and changing that might be more invasive so this solution looks good to me.

[anthrotype]

I wonder if VariationRegion should be changed to store tents in axis order

I wondered the same, maybe we can revise this later. I'll merge this for now

[rsheeter]

Good catch, ty!

I wonder if VariationRegion should be changed to store tents in axis order

I wondered the same, maybe we can revise this later. I'll merge this for now

This looks pretty clear, I wouldn't worry about it unless we start seeing it cause problems.