Create a segment_properties.SegmentProperties boxed type.
the #hb_direction_t of the buffer, see harfbuzz.global.bufferSetDirection.
the #hb_script_t of the buffer, see harfbuzz.global.bufferSetScript.
the #hb_language_t of the buffer, see harfbuzz.global.bufferSetLanguage.
Create a segment_properties.SegmentProperties boxed type.