LRESULT CALLBACK WndProc(...)
{
case WM_CREATE:
	....
	return 0;
case WM_DESTROY:
	PostQuitMessage (0) ;

	return 0 ;
	return DefWindowProc (hwnd, message, wParam, lParam) ;

}

WM_CTLCOLORSCROLLBAR

win32 wndproc 返回值