+ extract_grob_set (me, "stems", stems);
+ for (vsize i = 0; i < stems.size (); i++)
+ {
+ Grob *stem = stems[i];
+ common = common->common_refpoint (Staff_symbol_referencer::get_staff_symbol (stem),
+ Y_AXIS);
+ }
+
+ Interval heads;
+ Real my_y = me->relative_coordinate (common, Y_AXIS);
+
+ for (vsize i = 0; i < stems.size (); i++)
+ {
+ Grob *stem = stems[i];
+ Grob *ss = Staff_symbol_referencer::get_staff_symbol (stem);
+ Interval iv = Stem::head_positions (stem);
+ iv *= Staff_symbol::staff_space (ss) / 2.0;
+ heads.unite (iv + ss->relative_coordinate (common, Y_AXIS) - my_y);
+ }
+
+ Real lt = me->layout ()->get_dimension (ly_symbol2scm ("line-thickness"));
+ Real sp = 1.5 * Staff_symbol_referencer::staff_space (me);
+ Real dy = heads.length () + sp;
+ Real x = 0.7;
+
+ Stencil mol (Lookup::bracket (Y_AXIS, Interval (0, dy), lt, x, lt));
+ mol.translate_axis (heads[LEFT] - sp / 2.0, Y_AXIS);
+ return mol.smobbed_copy ();