+ /**
+ * Returns true if the selection of row items allows dragging.
+ * @return Returns true if the drag is acceptable.
+ */
+ virtual bool accept_drag() const = 0;
+
+ /**
+ * Drag the dragging items by the delta offset.
+ * @param delta the drag offset in pixels.
+ */
+ virtual void drag_items(const QPoint &delta) = 0;
+