+ string glyph_string = ly_scm2string (glyph);
+
+ /* compose span_bar_mol */
+ vector<Interval> extents;
+ vector<bool> make_span_bar;
+ Grob *model_bar = 0;
+ for (vsize i = elements.size (); i--;)
+ {
+ Grob *bar = elements[i];
+ Interval ext = Bar_line::bar_y_extent (bar, refp);
+ if (ext.is_empty ())
+ continue;
+
+ extents.push_back (ext);
+ make_span_bar.push_back (to_boolean (bar->get_property ("allow-span-bar")));
+ model_bar = bar;
+ }
+
+ if (!model_bar)
+ model_bar = me;
+
+ vector_sort (extents, Interval::left_less);
+
+ Stencil span_bar;
+ for (vsize i = 1; i < extents.size (); i++)
+ {
+ Interval prev_extent = extents[i - 1];
+ Interval ext = extents[i];
+ if (!prev_extent.is_empty ())
+ {
+ Interval l (prev_extent [UP],
+ ext[DOWN]);
+
+ if (l.is_empty () || !make_span_bar[i])
+ {
+ /* There is overlap between the bar lines. Do nothing. */
+ }
+ else
+ {
+ Stencil interbar = Bar_line::compound_barline (model_bar,
+ glyph_string,
+ l.length (),
+ false);
+ interbar.translate_axis (l.center (), Y_AXIS);
+ span_bar.add_stencil (interbar);
+ }
+ }
+ prev_extent = ext;
+ }
+
+ span_bar.translate_axis (- me->relative_coordinate (refp, Y_AXIS),
+ Y_AXIS);
+
+ return span_bar.smobbed_copy ();