A control can only display some types of information, and emphasize items in a control-specific manner. Therefore, if special items are to be displayed or emphasized in a special manner, this must be done by the owner window of the control.

The control window procedure generates this message and sends it to the owner of the control, informing the owner that an item is to be drawn, offering the owner the opportunity to draw that item and to indicate that either the item has been drawn or that the control is to draw it.