如何获取被点击的TextSpan的坐标？

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('TextSpan Click Position')),
        body: Center(child: TextWithPosition()),
      ),
    );
  }
}

class TextWithPosition extends StatefulWidget {
  @override
  _TextWithPositionState createState() => _TextWithPositionState();
}

class _TextWithPositionState extends State<TextWithPosition> {
  String text = "Click me!";
  Offset? tapPosition;

  void _handleTapDown(TapDownDetails details) {
    final RenderBox referenceBox = context.findRenderObject() as RenderBox;
    setState(() {
      tapPosition = referenceBox.globalToLocal(details.globalPosition);
    });
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTapDown: _handleTapDown,
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Text.rich(
            TextSpan(
              text: text,
              style: TextStyle(fontSize: 24),
              recognizer: TapGestureRecognizer()..onTap = () {},
            ),
          ),
          if (tapPosition != null)
            Text('Tap position: (${tapPosition!.dx}, ${tapPosition!.dy})'),
        ],
      ),
    );
  }
}