+ DECLARE_SCHEME_CALLBACK (pure_height, (SCM smob, SCM start, SCM end));
+ DECLARE_SCHEME_CALLBACK (calc_skylines, (SCM smob));
+ DECLARE_SCHEME_CALLBACK (combine_skylines, (SCM smob));
+ DECLARE_SCHEME_CALLBACK (print, (SCM smob));
+ DECLARE_SCHEME_CALLBACK (adjacent_pure_heights, (SCM));
+ DECLARE_SCHEME_CALLBACK (calc_next_staff_spacing, (SCM));
+ DECLARE_SCHEME_CALLBACK (calc_pure_next_staff_spacing, (SCM, SCM, SCM));
+ DECLARE_SCHEME_CALLBACK (calc_pure_relevant_grobs, (SCM));
+ DECLARE_SCHEME_CALLBACK (calc_pure_relevant_items, (SCM));
+ DECLARE_SCHEME_CALLBACK (calc_pure_relevant_spanners, (SCM));
+ DECLARE_SCHEME_CALLBACK (calc_pure_y_common, (SCM));
+ static Interval relative_group_extent (vector<Grob*> const &list,