The GetWindowLongPtr function retrieves information about the specified window. The function also retrieves the value at a specified offset into the extra window memory.
If you are retrieving a pointer or a handle, this function supersedes the GetWindowLong function. (Pointers and handles are 32 bits on 32-bit Microsoft 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_PTR GetWindowLongPtr(
HWND hWnd,
int nIndex
);
Parameters
- hWnd
-
[in]
Handle to the window and, indirectly, the class to which the window belongs.
If you are retrieving a pointer or a handle, this function supersedes the GetWindowLong 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.
- nIndex
-
[in] 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 the size of an integer. To retrieve any other value, specify one of the following values.
GWL_EXSTYLE- Retrieves the extended window styles. For more information, see CreateWindowEx.
GWL_STYLE- Retrieves the window styles.
GWLP_WNDPROC- Retrieves the pointer to the window procedure, or a handle representing the pointer to the window procedure. You must use the CallWindowProc function to call the window procedure.
GWLP_HINSTANCE- Retrieves a handle to the application instance.
GWLP_HWNDPARENT- Retrieves a handle to the parent window, if there is one.
GWLP_ID- Retrieves the identifier of the window.
GWLP_USERDATA- 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.
- The following values are also available when the hWnd parameter identifies a dialog box.
DWLP_DLGPROC- Retrieves the pointer to the dialog box procedure, or a handle representing the pointer to the dialog box procedure. You must use the CallWindowProc function to call the dialog box procedure.
DWLP_MSGRESULT- Retrieves the return value of a message processed in the dialog box procedure.
DWLP_USER- Retrieves extra information private to the application, such as handles or pointers.
Return Value
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 or SetWindowLongPtr has not been called previously, GetWindowLongPtr 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.
Function Information
| Minimum DLL Version | user32.dll |
|---|
| Header | Declared in Winuser.h, include Windows.h |
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| Import library | User32.lib |
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| Minimum operating systems |
Windows 95, Windows NT 3.1 |
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| Unicode | Implemented as
ANSI and Unicode versions. |
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See Also