+Interval
+Beam::no_visible_stem_positions (Grob *me, Interval default_value)
+{
+ extract_grob_set (me, "stems", stems);
+ if (stems.empty ())
+ return default_value;
+
+ Interval head_positions;
+ Slice multiplicity;
+ for (vsize i = 0; i < stems.size(); i++)
+ {
+ head_positions.unite (Stem::head_positions (stems[i]));
+ multiplicity.unite (Stem::beam_multiplicity (stems[i]));
+ }
+
+ Direction dir = get_grob_direction (me);
+ Real y = head_positions[dir]
+ * 0.5 * Staff_symbol_referencer::staff_space (me)
+ + dir * get_beam_translation (me) * (multiplicity.length () + 1);
+
+ y /= Staff_symbol_referencer::staff_space (me);
+ return Interval (y,y);
+}
+