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Window Procedures

Every window has an associated window procedure — a function that processes all messages sent or posted to all windows of the class. All aspects of a window's appearance and behavior depend on the window procedure's response to these messages.

In This Section

About Window Procedures

Discusses window procedures. Each window is a member of a particular window class. The window class determines the default window procedure that an individual window uses to process its messages.

Using Window Procedures

Covers how to perform the following tasks associated with window procedures.

Window Procedure Reference

Contains the API reference.




Passes message information to the specified window procedure.


Calls the default window procedure to provide default processing for any window messages that an application does not process. This function ensures that every message is processed. DefWindowProc is called with the same parameters received by the window procedure.


An application-defined function that processes messages sent to a window. The WNDPROC type defines a pointer to this callback function. WindowProc is a placeholder for the application-defined function name.