This message is sent when the clipboard contains a data handle for the CF_OWNERDISPLAY format (specifically the clipboard owner should display the clipboard contents) and the Clipboard application's client area needs repainting. The WM_PAINTCLIPBOARD message is sent to the clipboard owner to request repainting of all or part of the Clipboard application's client area.
wParam
Contains a handle to the Clipboard-application window.
lParam
The lParam parameter is a global DDESHARE handle that when locked points to a PAINTSTRUCT structure that defines what part of the client area to paint.
To determine whether the entire client area or just a portion of it needs repainting, the clipboard owner must compare the dimensions of the drawing area given in the rcpaint member of the PAINTSTRUCT structure to the dimensions given in the most recent WM_SIZECLIPBOARD message.
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 returns.
GlobalUnlock, WM_SIZECLIPBOARD