GetClassWord function (winuser.h)

Article
02/22/2024

Retrieves the 16-bit (WORD) value at the specified offset into the extra class memory for the window class to which the specified window belongs.

Note This function is deprecated for any use other than nIndex set to GCW_ATOM. The function is provided only for compatibility with 16-bit versions of Windows. Applications should use the GetClassLong or GetClassLongPtr function.

Syntax

WORD GetClassWord(
  [in] HWND hWnd,
  [in] int  nIndex
);

Parameters

[in] hWnd

Type: HWND

A handle to the window and, indirectly, the class to which the window belongs.

[in] nIndex

Type: int

The zero-based byte offset of the value to be retrieved. Valid values are in the range zero through the number of bytes of class memory, minus two; for example, if you specified 10 or more bytes of extra class memory, a value of eight would be an index to the fifth 16-bit integer. There is an additional valid value as shown in the following table.

Value	Meaning
GCW_ATOM -32	Retrieves an ATOM value that uniquely identifies the window class. This is the same atom that the RegisterClass or RegisterClassEx function returns.

Return value

Type: WORD

If the function succeeds, the return value is the requested 16-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.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	winuser.h (include Windows.h)
Library	User32.lib
DLL	User32.dll
API set	ext-ms-win-ntuser-windowclass-l1-1-2 (introduced in Windows 10, version 10.0.10240)