Window subclassing is a way to hook up into standard window procedure and to modify or extend its default behavior. An application subclasses a window by replacing the the window's original window procedure with a new window procedure. This new window procedure receives any messages sent or posted to the window.
|hWnd||The handle of the window to subclass.|
|SubclassProc||The subclass callback procedure.|
|SubclassId||User specified ID to identify the subclass, together with the subclass procedure uniquely identifies a subclass. It can simply be an arbitrary consecutive number.|
|RefData||User specified data. The meaning is determined by the application. It is passed to the subclass callback in unmodified way. It could be an object pointer to a class instance for example.|