DefSubclassProc function
Applies to: desktop apps only
Calls the next handler in a window's subclass chain. The last handler in the subclass chain calls the original window procedure for the window.
Syntax
LRESULT DefSubclassProc( __in HWND hWnd, __in UINT uMsg, __in WPARAM WPARAM, __in LPARAM LPARAM );
Parameters
- hWnd [in]
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Type: HWND
A handle to the window being subclassed.
- uMsg [in]
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Type: UINT
A value of type unsigned int that specifies a window message.
- WPARAM [in]
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Type: WPARAM
Specifies additional message information. The contents of this parameter depend on the value of the window message.
- LPARAM [in]
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Type: LPARAM
Specifies additional message information. The contents of this parameter depend on the value of the window message. Note: On 64-bit versions of Windows LPARAM is a 64-bit value.
Return value
Type: LRESULT
The returned value is specific to the message sent. This value should be ignored.
Remarks
You do not need to call the default window procedure; this function calls it automatically.
The SUBCLASS module defines helper functions that are used to subclass windows. The code maintains a single property on the subclassed window and dispatches various subclass callbacks to its clients as required. The client is provided reference data and a default processing API.
A subclass callback is identified by a unique pairing of a callback function pointer and an unsigned ID value. Each callback can also store a single DWORD of reference data, which is passed to the callback function when it is called to filter messages. No reference counting is performed for the callback; it may repeatedly call SetWindowSubclass to alter the value of its reference data element.
Warning You cannot use the subclassing helper functions to subclass a window across threads.
Requirements
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Minimum supported client | Windows XP |
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Minimum supported server | Windows Server 2003 |
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See also
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Build date: 3/7/2012
