 Since the source decides the shape of the cursor, the source must receive a response from the target in order to update the cursor.In addition, since the target may need to draw a bombsight to indicate where the drop will occur, and since acceptance of the drop may depend on the exact location of the cursor, this exchange must happen repeatedly as the cursor moves.In fact, even if the cursor does not move, messages must be exchanged to allow the target to scroll when the cursor is near an edge of the viewing area.