public static extern bool InvalidateRect(IntPtr hWnd, ref GDI.RECT lpRect, bool bErase);
public static extern bool GetClientRect(IntPtr hWnd, out GDI.RECT lpRect);
public static extern bool GetWindowRect(IntPtr hWnd, out GDI.RECT lpRect);
public static extern int ScrollWindow(IntPtr hwnd, int cx, int cy, ref GDI.RECT rectScroll, ref GDI.RECT rectClip);