UpdateWindow() vs InvalidateRect()

[J B 0]

Hi guys, Can anyone explain the differences between the following two calls:

UpdateWindow(hWnd);

and

InvalidateRect(hWnd, NULL, FALSE);

If I replace one with another, the app would be drawn differently. But I couldn't tell why by reading the MSDN docs :( Thanks alot

[J B 0]

I think I sort of know now - UpdateWindow(hWnd) only places a WM_PAINT message in the message queue, which leads to an execution of the WM_PAINT's message handler finally. If at that time the client area is all validated already, the window will not be re-painted. On the other hand, InvalidateRect(hWnd, NULL, FALSE) explicitly invalidates the client area and then sends a WM_PAINT message. This makes sure the window will always be re-painted when the WM_PAINT message handler reaches its time. It does two things instead of just one. Please correct me if I am wrong here. Thanks