The UpdateWindow function updates the client area of the specified window by sending a WM_PAINT message to the window if the window's update region is not empty. The function sends a WM_PAINT message directly to the window procedure of the specified window, bypassing the application queue. If the update region is empty, no message is sent.
BOOL UpdateWindow(
HWND hWnd // handle of window
);
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero.
Windows NT: To get extended error information, call GetLastError.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in winuser.h.
Import Library: Use user32.lib.
Painting and Drawing Overview, Painting and Drawing Functions, ExcludeUpdateRgn, GetUpdateRect, GetUpdateRgn, InvalidateRect, InvalidateRgn, WM_PAINT