code: public static IOSPlatform register(UIApplication app, UIWindow window, Config config) {
      IOSPlatform platform = new IOSPlatform(app, window, config);
      PlayN.setPlatform(platform);
      return platform;
    }
docs: Registers your application using the supplied configuration and window.
  
  The window is used for a game integrated as a part of application. An iOS application
  typically just works on one screen so that the game has to share the window created by other
  controllers (typically created by the story board). If no window is specified, the platform
  will create one taking over the whole application.
  
  Note that PlayN will still install a RootViewController on the supplied UIWindow. If a custom
  root view controller is needed, your application should subclass {@link IOSRootViewController}
  or replicate its functionality in your root view controller.