Unlike radio buttons, an owner-drawn button is painted by the application, not by Windows, and has no predefined appearance or usage. Its purpose is to provide a button whose appearance and behavior are defined by the application alone. There is only one owner-drawn button style: BS_OWNERDRAW.
When the user selects an owner-drawn button, Windows sends the button's parent window a WM_COMMAND message containing the BN_CLICKED notification code, just as it does for a button that is not owner-drawn. The application must respond appropriately.