GetWindowLong function
Applies to: desktop apps only
Retrieves information about the specified window. The function also retrieves the 32-bit (DWORD) value at the specified offset into the extra window memory.
Note If you are retrieving a pointer or a handle, this function has been superseded by the GetWindowLongPtr function. (Pointers and handles are 32 bits on 32-bit Windows and 64 bits on 64-bit Windows.) To write code that is compatible with both 32-bit and 64-bit versions of Windows, use GetWindowLongPtr.
Syntax
LONG WINAPI GetWindowLong( __in HWND hWnd, __in int nIndex );
Parameters
- hWnd [in]
-
Type: HWND
A handle to the window and, indirectly, the class to which the window belongs.
- nIndex [in]
-
Type: int
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 Meaning - GWL_EXSTYLE
- -20
Retrieves the extended window styles.
- GWL_HINSTANCE
- -6
Retrieves a handle to the application instance.
- GWL_HWNDPARENT
- -8
Retrieves a handle to the parent window, if any.
- GWL_ID
- -12
Retrieves the identifier of the window.
- GWL_STYLE
- -16
Retrieves the window styles.
- GWL_USERDATA
- -21
Retrieves the user data associated with the window. This data is intended for use by the application that created the window. Its value is initially zero.
- GWL_WNDPROC
- -4
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.
The following values are also available when the hWnd parameter identifies a dialog box.
Value Meaning - DWL_DLGPROC
- DWLP_MSGRESULT + sizeof(LRESULT)
Retrieves the address of the dialog box procedure, or a handle representing the address of the dialog box procedure. You must use the CallWindowProc function to call the dialog box procedure.
- DWL_MSGRESULT
- 0
Retrieves the return value of a message processed in the dialog box procedure.
- DWL_USER
- DWLP_DLGPROC + sizeof(DLGPROC)
Retrieves extra information private to the application, such as handles or pointers.
Return value
Type:
Type: LONG
If the function succeeds, the return value is the requested value.
If the function fails, the return value is zero. To get extended error information, call GetLastError.
If SetWindowLong has not been called previously, GetWindowLong returns zero for values in the extra window or class memory.
Remarks
Reserve extra window memory by specifying a nonzero value in the cbWndExtra member of the WNDCLASSEX structure used with the RegisterClassEx function.
Examples
For an example, see Creating, Enumerating, and Sizing Child Windows.
Requirements
|
Minimum supported client | Windows 2000 Professional |
|---|---|
|
Minimum supported server | Windows 2000 Server |
|
Header |
|
|
Library |
|
|
DLL |
|
|
Unicode and ANSI names | GetWindowLongW (Unicode) and GetWindowLongA (ANSI) |
See also
- Reference
- CallWindowProc
- GetWindowLongPtr
- RegisterClassEx
- SetParent
- SetWindowLong
- WNDCLASS
- Conceptual
- Window Classes
Send comments about this topic to Microsoft
Build date: 2/3/2012
- 12/10/2010
- Ben_userdn
- 3/18/2011
- soonrchong
- 4/18/2009
- dmex
- 7/24/2010
- Thomas Lee
Friend Enum WindowLongs As Int32
GWL_EXSTYLE = -20
GWL_STYLE = -16
GWL_WNDPROC = -4
GWL_HINSTANCE = -6
GWL_HWNDPARENT = -8
GWL_ID = -12
GWL_USERDATA = -21
DWL_DLGPROC = 4
DWL_MSGRESULT = 0
DWL_USER = 8
End Enum
In order to obtain current wnd proc of window, you can use this declaration:
Friend Declare Auto Function GetWindowLong Lib "user32.dll" (ByVal hwnd As IntPtr, ByVal nIndex As WindowProcs) As Messages.WndProc
Public Delegate Function WndProc(ByVal hWnd As Integer, ByVal msg As Messages.WindowMessages, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
Friend Enum WindowProcs As Int32
GWL_WNDPROC = WindowLongs.GWL_WNDPROC
DWL_DLGPROC = WindowLongs.DWL_DLGPROC
End Enum
WindwMessages is an enumeration of all known window messages and is of type Int32.
If such-declared function fails, return value is null (nothing).
- 12/7/2007
- Đonny
- 7/12/2010
- liserdarts
- 4/18/2009
- dmex
- 7/12/2010
- liserdarts