DECLARE_SCHEME_CALLBACK (calc_skylines, (SCM smob));
DECLARE_SCHEME_CALLBACK (combine_skylines, (SCM smob));
DECLARE_SCHEME_CALLBACK (calc_max_stretch, (SCM smob));
DECLARE_SCHEME_CALLBACK (calc_skylines, (SCM smob));
DECLARE_SCHEME_CALLBACK (combine_skylines, (SCM smob));
DECLARE_SCHEME_CALLBACK (calc_max_stretch, (SCM smob));