+ shared_ptr<ViewItem> get_mouse_over_item(const QPoint &pt);
+
+ /**
+ * Sets this item into the dragged state.
+ */
+ void drag();
+
+ /**
+ * Drag the background by the delta offset.
+ * @param delta the drag offset in pixels.
+ */
+ void drag_by(const QPoint &delta);
+
+ /**
+ * Sets this item into the un-dragged state.
+ */
+ void drag_release();