main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: Column(
            children: [
              SelectableText.rich(
                TextSpan(
                  text: 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX',
                ),
              ),
              SelectableText.rich(
                TextSpan(
                  text: 'XXXXXXXXXXXXXXXXXXXX',
                  children: [
                    WidgetSpan(
                      alignment: PlaceholderAlignment.middle,
                      baseline: TextBaseline.alphabetic,
                      child: Container(
                        clipBehavior: Clip.hardEdge,
                        decoration: BoxDecoration(
                          border: Border(
                            left: BorderSide(width: 5.2, color: Colors.yellow),
                          ),
                        ),
                        child: Text('X'),
                      ),
                    ),
                    TextSpan(
                      text: 'XXXXXXXXXXXXXXXXXXX',
                    ),
                  ],
                ),
              ),
              SelectableText.rich(
                TextSpan(
                  text: 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX',
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}