The documentation for SetWindowPos says the following for the X and Y parameters: X [in] Type: int The new position of the left side of the window, in client coordinates. Y [in] Type: int The new position of the top of the window, in client coordinates. By "client coordinates", does it mean that the parameters specify the position of the client area of the window, or that they specify the position of the window (not the client area) relative to the parent window's client area? Or something else?