DECLARE_SCHEME_CALLBACK (calc_pure_relevant_grobs, (SCM));
DECLARE_SCHEME_CALLBACK (height, (SCM));
DECLARE_SCHEME_CALLBACK (calc_pure_height, (SCM, SCM, SCM));
DECLARE_SCHEME_CALLBACK (calc_pure_relevant_grobs, (SCM));
DECLARE_SCHEME_CALLBACK (height, (SCM));
DECLARE_SCHEME_CALLBACK (calc_pure_height, (SCM, SCM, SCM));