- "Grobs can be distinguished in their role in the horizontal spacing.\n"
- "Many grobs define constraints on the spacing by their sizes. For\n"
- "example, note heads, clefs, stems, and all other symbols with a fixed\n"
- "shape. These grobs form a subtype called @code{Item}.\n"
- "\n"
+ cached_pure_height_ = Grob::pure_height (this, start, end);
+ cached_pure_height_valid_ = true;
+ return cached_pure_height_ + pure_relative_y_coordinate (g, start, end);
+}
+
+bool
+Item::less (Grob * const &g1, Grob * const &g2)
+{
+ return dynamic_cast<Item*> (g1)->get_column ()->get_rank () < dynamic_cast<Item*> (g2)->get_column ()->get_rank ();
+}
+
+ADD_INTERFACE (Item,
+ "Grobs can be distinguished in their role in the horizontal"
+ " spacing. Many grobs define constraints on the spacing by"
+ " their sizes, for example, note heads, clefs, stems, and all"
+ " other symbols with a fixed shape. These grobs form a"
+ " subtype called @code{Item}.\n"