+ Grob *s = support[i];
+ if (!ss)
+ ss = Staff_symbol_referencer::staff_space (s);
+
+ /* can't inspect Y extent of rest.
+
+ Rest collisions should wait after line breaking.
+ */
+ Interval y;
+ if (Rest::has_interface (s))
+ {
+ base_x.unite (s->extent (commonx, X_AXIS));
+ continue;
+ }
+ else if (Stem::has_interface (s))
+ {
+ Real y1 = Stem::head_positions (s)[-get_grob_direction (s)];
+ Real y2 = y1 + get_grob_direction (s) * 7;
+
+ y.add_point (y1);
+ y.add_point (y2);
+ }
+ else if (Note_head::has_interface (s))
+ y = Interval (-1, 1);
+ else
+ {
+ programming_error ("unknown grob in dot col support");
+ continue;
+ }
+
+ y *= 2 / ss;
+ y += Staff_symbol_referencer::get_position (s);
+
+ Box b (s->extent (commonx, X_AXIS), y);
+ boxes.push_back (b);
+
+ if (Grob *stem = unsmob_grob (s->get_object ("stem")))
+ stems.insert (stem);