+Interval
+Staff_symbol::line_span (Grob *me)
+{
+ SCM line_positions = me->get_property ("line-positions");
+ Interval iv;
+
+ if (scm_is_pair (line_positions))
+ for (SCM s = line_positions; scm_is_pair (s); s = scm_cdr (s))
+ iv.add_point (scm_to_double (scm_car (s)));
+ else
+ {
+ int count = line_count (me);
+ return Interval (-count + 1, count - 1);
+ }
+
+ return iv;
+}
+