+ for (vsize i = 0; i < heads.size (); i++)
+ {
+ if (Grob *s = Rhythmic_head::get_stem (heads[i]))
+ stems.push_back (s);
+ }
+
+ vector_sort (stems, less<Grob*> ());
+ uniq (stems);
+
+ common[Y_AXIS] = common_refpoint_of_array (heads, common[Y_AXIS], Y_AXIS);
+ common[Y_AXIS] = common_refpoint_of_array (stems, common[Y_AXIS], Y_AXIS);
+