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Overview |
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Group |
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Quick Info
Windows NT
| Yes
| Win95
| Yes
| Win32s
| Yes
| Import Library
| user32.lib
| Header File
| winuser.h
| Unicode
| WinNT
| Platform Notes
| None
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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
| );
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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.
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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.
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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
CallWindowProc, GetWindowWord, RegisterClass, SetParent, SetWindowLong, SetWindowWord, WNDCLASS
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Unix Manual Pages
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