flutter_server_box/macos/Runner/AppDelegate.swift

import Cocoa
import FlutterMacOS

@main
class AppDelegate: FlutterAppDelegate {
  override func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
    return true
  }

  override func applicationSupportsSecureRestorableState(_ app: NSApplication) -> Bool {
    return true
  }

  override func applicationDidFinishLaunching(_ notification: Notification) {
    if let controller = mainFlutterWindow?.contentViewController as? FlutterViewController {
      let channel = FlutterMethodChannel(name: "about", binaryMessenger: controller.engine.binaryMessenger)
      channel.setMethodCallHandler { (call: FlutterMethodCall, result: @escaping FlutterResult) in
        if call.method == "showAboutPanel" {
          NSApp.orderFrontStandardAboutPanel(nil)
          result(nil)
        } else {
          result(FlutterMethodNotImplemented)
        }
      }
    }
    super.applicationDidFinishLaunching(notification)
  }
}