the buildGSUB function creates an empty GSUB with no FeatureRecords, so the FeatureIndex list should be empty initially; the index of the newly created rvrn feature record will be appended later on by addFeatureVariationsRaw function.
the buildGSUB function creates an empty GSUB with no FeatureRecords, so the FeatureIndex list should be empty initially; the index of the newly created rvrn feature record will be appended later on by addFeatureVariationsRaw function.