/ add the drag selection position
				// the position is used to delete the selection on a DROP_MOVE
				// and it can be used by the drop target to determine if it should
				// allow the drop (e.g. if drop location overlaps selection)
/ add the drag selection position
				// the position is used to delete the selection on a DROP_MOVE
				// and it can be used by the drop target to determine if it should
				// allow the drop (e.g. if drop location overlaps selection) | TextViewerDragAdapter.java