As the clipboard owner is responsible for displaying the clipboard contents, this message notifies the clipboard application that its client area needs repainting. The WM_PAINTCLIPBOARD message is sent to the owner of the clipboard to request repainting of all or part of the client area of the clipboard application.
Note: To determine whether the entire client area needs repainting or just a portion of it, the clipboard owner must compare the dimensions of the drawing area to the dimensions given in the most recent WM_SIZECLIPBOARD message.