@direction: the #hb_direction_t of the buffer, see hb_buffer_set_direction(). @script: the #hb_script_t of the buffer, see hb_buffer_set_script(). @language: the #hb_language_t of the buffer, see hb_buffer_set_language().
The structure that holds various text properties of an #hb_buffer_t. Can be set and retrieved using hb_buffer_set_segment_properties() and hb_buffer_get_segment_properties(), respectively.