how to change title bar icon in flutter desktop?

To change the title bar icon in a Flutter desktop application, you can follow these steps:

1. Import the flutter_desktop_embedding package in your project.
2. Create a .ico file with the icon you want to use and add it to your project. You can use a free online icon generator such as https://www.favicon-generator.org/ to create the icon file.
3. In your main function, call the flutter_desktop_embedding.registerTitleBarVisibilityChangedCallback method to register a callback function that will be called when the title bar visibility changes.
4. In the callback function, use the flutter_desktop_embedding.setWindowTitleProperties method to set the title bar icon with the path to the .ico file.

Here's an example code snippet:

import 'dart:io';
import 'package:flutter_desktop_embedding/flutter_desktop_embedding.dart';

void main() {
  // Register callback function for title bar visibility changes
  flutter_desktop_embedding.registerTitleBarVisibilityChangedCallback(setTitleBarIcon);
  
  // Run the app
  runApp(MyApp());
}

void setTitleBarIcon(bool visible) {
  if (Platform.isWindows) {
    // Set the title bar icon
    final String iconPath = 'assets/icon.ico';
    flutter_desktop_embedding.setWindowTitleProperties(iconPath: iconPath);
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'My App',
      home: MyHomePage(),
    );
  }
}

In this example, we registered the setTitleBarIcon function as the callback function for title bar visibility changes. Inside setTitleBarIcon, we used the setWindowTitleProperties method to set the title bar icon with the path to the .ico file.

Note that this example code sets the title bar icon only on Windows OS. If you want to support other platforms, you can use platform-specific code to set the title bar icon accordingly.