#hb_face_t to work upon
#HB_OT_TAG_GSUB or #HB_OT_TAG_GPOS
The index of the requested script tag
The index of the requested language tag
#hb_tag_t of the feature tag requested
The index of the requested feature
true if the feature is found, false otherwise
Fetches the index of a given feature tag in the specified face's GSUB table or GPOS table, underneath the specified script and language.