public static extern ulong FlutterDesktopProcessMessages(FlutterDesktopViewControllerRef controller);
 public static extern FlutterDesktopPluginRegistrarRef FlutterDesktopGetPluginRegistrar(FlutterDesktopViewControllerRef controller,
                                                                                        [MarshalAs(UnmanagedType.LPStr)] string pluginName);
 public static extern FlutterDesktopViewRef FlutterDesktopGetView(FlutterDesktopViewControllerRef controller);