import Cocoa import FlutterMacOS import desktop_multi_window class MainFlutterWindow: NSWindow { override func awakeFromNib() { let flutterViewController = FlutterViewController() let windowFrame = self.frame self.contentViewController = flutterViewController self.setFrame(windowFrame, display: true) RegisterGeneratedPlugins(registry: flutterViewController) FlutterMultiWindowPlugin.setOnWindowCreatedCallback { controller in // Register the plugin which you want access from other isolate. RegisterGeneratedPlugins(registry: controller) } super.awakeFromNib() } }