+#include "engraver.hh"
+#include "axis-group-interface.hh"
+
+/*
+ collect Note_column, and as soon as there are 2 or more, put them in
+ a collision object. */
+class Collision_engraver : public Engraver {
+ Item * col_p_;
+ Link_array<Grob> note_column_l_arr_;
+
+protected:
+ virtual void acknowledge_grob (Grob_info);
+ virtual void create_grobs ();
+ virtual void stop_translation_timestep ();
+public:
+ TRANSLATOR_DECLARATIONS(Collision_engraver);
+};
+
+