DECLARE_SCHEME_CALLBACK (calc_left_bound_info_and_text, (SCM));
DECLARE_SCHEME_CALLBACK (calc_right_bound_info, (SCM));
DECLARE_SCHEME_CALLBACK (calc_bound_info, (SCM, Direction));
DECLARE_SCHEME_CALLBACK (calc_left_bound_info_and_text, (SCM));
DECLARE_SCHEME_CALLBACK (calc_right_bound_info, (SCM));
DECLARE_SCHEME_CALLBACK (calc_bound_info, (SCM, Direction));