virtual void prepare_for_cleanup () = 0;
virtual void finish_cleanup () = 0;
virtual void reset_x_origin (framepos_t frame) = 0;
virtual double get_y_origin () const = 0;
virtual void reset_y_origin (double pos) = 0;
virtual void prepare_for_cleanup () = 0;
virtual void finish_cleanup () = 0;
virtual void reset_x_origin (framepos_t frame) = 0;
virtual double get_y_origin () const = 0;
virtual void reset_y_origin (double pos) = 0;