This message is sent when the clipboard contains a data handle for the CF_OWNER-DISPLAY format (that is, the clipboard owner should display the clipboard contents) and the clipboard-application window has changed size.
| Parameter | Description |
| wParam | Identifies the clipboard-application window. | |
| lParam | The low-order word of the lParam parameter identifies a RECT data structure that specifies the area the clipboard owner should paint. The high-order word is not used. |
A WM_SIZECLIPBOARD message is sent with a null rectangle (0,0,0,0) as the new size when the clipboard application is about to be destroyed or minimized. This permits the clipboard owner to free its display resources.
An application must use the GlobalLock function to lock the memory that contains the PAINTSTRUCT data structure. The application should unlock that memory by using the GlobalUnlock function before it yields or returns control.