+MAKE_SCHEME_CALLBACK (Line_spanner, calc_cross_staff, 1);
+SCM
+Line_spanner::calc_cross_staff (SCM smob)
+{
+ Spanner *me = unsmob<Spanner> (smob);
+ if (!me)
+ return SCM_BOOL_F;
+
+ if (to_boolean (me->get_bound (LEFT)->get_property ("non-musical"))
+ || to_boolean (me->get_bound (RIGHT)->get_property ("non-musical")))
+ return SCM_BOOL_F;
+
+ return scm_from_bool (Staff_symbol_referencer::get_staff_symbol (me->get_bound (LEFT))
+ != Staff_symbol_referencer::get_staff_symbol (me->get_bound (RIGHT)));
+}
+