WindowProc
It is proposed that this article be deleted because of the following concern:
If you can address this concern by improving, copyediting, sourcing, renaming, or merging the page, please edit this page and do so. You may remove this message if you improve the article or otherwise object to deletion for any reason. Although not required, you are encouraged to explain why you object to the deletion, either in your edit summary or on the talk page. If this template is removed, do not replace it. This message has remained in place for seven days, so the article may be deleted without further notice. Find sources: "WindowProc" – news · newspapers · books · scholar · JSTOR Nominator: Please consider notifying the author/project: {{subst:proposed deletion notify|WindowProc|concern=Fails [[WP:NSOFT]]}} ~~~~Timestamp: 20250317201624 20:16, 17 March 2025 (UTC) Administrators: delete |
In Win32 application programming, WindowProc (or window procedure), also known as WndProc is a user-defined callback function that processes messages sent to a window. This function is specified when an application registers its window class and can be named anything (not necessarily WindowProc).
Message handling
The window procedure is responsible for handling all messages that are sent to a window. The function prototype of WindowProc is given by:
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
hwnd is a handle to the window to which the message was sent and uMsg identifies the actual message by its identifier, as specified in winuser.h.
wParam and lParam are parameters whose meaning depends on the message. An application should identify the message and take the required action.
Default processing
Hundreds of different messages are produced as a result of various events taking place in the system, and typically, an application processes only a small fraction of these messages. In order to ensure that all messages are processed, Windows provides a default window procedure called DefWindowProc that provides default processing for messages that the application itself does not process.
An application usually calls DefWindowProc at the end of its own WindowProc function, so that unprocessed messages can be passed down to the default procedure.