GetWindowLong

This function retrieves information about the specified window. GetWindowLong also retrieves the 32-bit (long) value at the specified offset into the extra window memory of a window.

A remote application interface (RAPI) version of this function exists, and it is called CeGetWindowLong (RAPI).

LONG GetWindowLong( 
  HWND hWnd, 
  int nIndex
); 

Parameters

• hWnd
  Handle to the window and, indirectly, the class to which the window belongs.

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

  Value	Description
  GWL_EXSTYLE	Retrieves the extended window styles.
  GWL_STYLE	Retrieves the window styles.
  GWL_WNDPROC	Retrieves the address of the window procedure, or a handle representing the address of the window procedure. You must use the CallWindowProc function to call the window procedure.
  GWL_ID	Retrieves the window identifier.
  GWL_USERDATA	Retrieves the 32-bit value associated with the window. Each window has a corresponding 32-bit value intended for use by the application that created the window. Windows CE versions 2.0 and later support this value, but Windows CE versions 1.0 and 1.01 do not.

  The following values are also available when the hWnd parameter identifies a dialog box.

  Value	Description
  DWL_MSGRESULT	Retrieves the return value of a message processed in the dialog box procedure.
  DWL_USER	Retrieves extra information private to the application, such as handles or pointers.

Return Values

The requested 32-bit value indicates success. Zero indicates failure. To get extended error information, call GetLastError.

Remarks

The nIndex parameter must be a multiple of 4 bytes.

Unaligned access is not supported.

Windows CE versions 1.0 and 1.01 also do not support the DWL_DLGPROC value in the nIndex parameter.

Requirements

OS Versions: Windows CE 1.0 and later.
Header: Winuser.h.

See Also

Window Class Functions | CallWindowProc | CeGetWindowLong (RAPI) | RegisterClass | SetParent | SetWindowLong | WNDCLASS

Last updated on Wednesday, April 13, 2005

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