#hb_face_t to work upon
The #hb_aat_layout_feature_type_t of the requested feature type
offset of the first feature type to retrieve
A buffer pointer. The selectors available for the feature type queries.
The index of the feature's default selector, if any
Number of all available feature selectors
Fetches a list of the selectors available for the specified feature in the given face.
If upon return, default_index is set to #HB_AAT_LAYOUT_NO_SELECTOR_INDEX, then the feature type is non-exclusive. Otherwise, default_index is the index of the selector that is selected by default.