CWindow.SetControlSubclassmethod

Installs or updates a control subclass callback.

WindowsmethodCWindow.incdocumented

Syntax

FUNCTION SetControlSubclass (BYVAL hCtl AS HWND, BYVAL pfnSubclass AS ANY PTR, BYVAL uIdSubclass AS UINT_PTR, BYVAL dwRefData AS ANY PTR) AS BOOLEAN

FUNCTION SetControlSubclass (BYVAL hCtl AS HWND, BYVAL pfnSubclass AS ANY PTR, BYVAL uIdSubclass AS UINT_PTR, BYVAL dwRefData AS DWORD_PTR) AS BOOLEAN

Parameters

Name		Description
`hCtl`		The handle of the control being subclassed.
`pfnSubclass`		A pointer to a window procedure. This pointer and the subclass ID uniquely identify this subclass callback.
`uIdSubclass`		The subclass ID. This ID together with the subclass procedure uniquely identify a subclass. To remove a subclass, pass the subclass procedure and this value to the RemoveWindowSubclass function. This value is passed to the subclass procedure in the uIdSubclass parameter.
`dwRefData`		DWORD_PTR to reference data. The meaning of this value is determined by the calling application. This value is passed to the subclass procedure in the dwRefData parameter. A different dwRefData is associated with each combination of window handle, subclass procedure and uIdSubclass.

Return value

TRUE if the subclass callback was successfully installed; otherwise, FALSE.

Description

Installs or updates a control subclass callback.

Remarks

Subclass callbacks are identified by the combination of the callback address and the caller-defined subclass ID. If the callback address and ID pair have not yet been installed, then this function installs the subclass. If the pair has already been installed, then this function just updates the reference data.

Each callback can store a single DWORD_PTR 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 SetControlSubclass to alter the value of its reference data element.

Warning: You cannot use the subclassing helper functions to subclass a window across threads.

Reference

Include file CWindow.inc
Defined in AfxNova/CWindow.inc:1902
Documented in Windows/Windows GUI/CWindow Class.md
Topic: CWindow Class