GetWindowLong
The GetWindowLong
function retrieves information about the specified window. The function also
retrieves the 32-bit (long) value at the specified offset into the extra window
memory of a window.
LONG GetWindowLong(
|
HWND hWnd, |
// handle of window |
|
int nIndex |
// offset of value
to retrieve |
|
); |
|
Parameters
hWnd
Identifies
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 |
Action |
|
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_HINSTANCE |
Retrieves
the handle of the application instance. |
|
GWL_HWNDPARENT |
Retrieves
the handle of the parent window, if any. |
|
GWL_ID |
Retrieves
the identifier of the window. |
|
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. |
The following
values are also available when the hWnd parameter identifies a dialog
box:
|
Value |
Action |
|
DWL_DLGPROC |
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 |
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
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
window memory by specifying a nonzero value in the cbWndExtra member of
the WNDCLASS structure used with the RegisterClass function.
See Also