+ Item *find_prebroken_piece (Direction) const;
+ Grob *find_broken_piece (System *) const;
+ virtual System *get_system () const;
+ virtual Paper_column *get_column () const;
+ virtual void handle_prebroken_dependencies ();
+ virtual Interval_t<int> spanned_rank_interval () const;
+ virtual Interval pure_height (Grob *ref, int start, int end);
+ DECLARE_GROB_INTERFACE();
+protected:
+ virtual void discretionary_processing ();
+ void copy_breakable_items ();
+ virtual void derived_mark () const;