internal static extern IntPtr WindowFromPoint(POINT point);
internal static extern bool ClientToScreen(IntPtr hWnd, ref POINT pt);
internal static extern bool UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst, ref POINT pptDst, ref SIZE psize, IntPtr hdcSrc, ref POINT pprSrc, Int32 crKey, ref BLENDFUNCTION pblend, Int32 dwFlags);
internal static extern bool ScreenToClient(IntPtr hWnd, ref POINT pt);