internal void AddMouseDownListener(Utility.EventImplPriority priority, System.Action <Event, MouseButton, bool> action) => onMouseDownEvent.AddListener(priority, action);
internal void AddEndDragListener(Utility.EventImplPriority priority, System.Action <Event, MouseButton, bool> action) => onEndDragEvent.AddListener(priority, action);
internal void AddKeyUpListener(Utility.EventImplPriority priority, System.Action <Event, bool> action) => onKeyUpEvent.AddListener(priority, action);