GetClassLong info  Overview  Group

The GetClassLong function retrieves the specified 32-bit (long) value from the WNDCLASS structure associated with the specified window.

DWORD GetClassLong(

Parameters

hWnd

Identifies the window and, indirectly, the class to which the window belongs.

nIndex

Specifies the 32-bit value to retrieve. To retrieve a 32-bit value from the extra class memory, specify the positive, zero-based byte offset of the value to be retrieved. Valid values are in the range zero through the number of bytes of extra class memory, minus four; for example, if you specified 12 or more bytes of extra class memory, a value of 8 would be an index to the third 32-bit integer. To retrieve any other value from the WNDCLASS structure, specify one of the following values:

Value	Action
GCW_ATOM	Retrieves an ATOM value that uniquely identifies the window class. This is the same atom that the RegisterClass function returns.
GCL_CBCLSEXTRA	Retrieves the size, in bytes, of the extra memory associated with the class.
GCL_CBWNDEXTRA	Retrieves the size, in bytes, of the extra window memory associated with each window in the class. For information on how to access this memory, see GetWindowLong and GetWindowWord .
GCL_HBRBACKGROUND	Retrieves the handle of the background brush associated with the class.
GCL_HCURSOR	Retrieves the handle of the cursor associated with the class.
GCL_HICON	Retrieves the handle of the icon associated with the class.
GCL_HICONSM	Retrieves the handle of the small icon associated with the class.
GCL_HMODULE	Retrieves the handle of the module that registered the class.
GCL_MENUNAME	Retrieves the address of the menu name string. The string identifies the menu resource associated with the class.
GCL_STYLE	Retrieves the window-class style bits.
GCL_WNDPROC	Retrieves the address of the window procedure associated with the class.

Return Values

If the function succeeds, the return value is the requested 32-bit value.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

Reserve extra class memory by specifying a nonzero value in the cbClsExtra member of the WNDCLASS structure used with the RegisterClass function.

See Also

GetClassWord, GetWindowLong, GetWindowWord, RegisterClass, SetClassLong, SetClassWord, WNDCLASS 

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