+#include "note-collision.hh"
+
+#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_;
+ Link_array<Grob> note_columns_;
+
+protected:
+ virtual void acknowledge_grob (Grob_info);
+ virtual void process_acknowledged_grobs ();
+ virtual void stop_translation_timestep ();
+public:
+ TRANSLATOR_DECLARATIONS (Collision_engraver);
+};
+