Repository: flutter
Issue: [web:a11y] respect text spacing browser settings
Labels: engine,a: accessibility,platform-web,c: proposal,P1,customer: quake (g3),customer: castaway,team-web,triaged-web

Internal bug: b/338058572

### Use case

Independent of the web renderers is it not possible to fulfil the WCAG Success Criterion 1.4.12 Text Spacing as described here: https://codepen.io/2kool2/pen/LYzVeLO.

The criterion requires text spacing depending on user settings.

### Proposal

The web engine should respect the user settings or should allow the style manipulation to fulfil the mentioned criterion.

Tested with flutter version: `Flutter (Channel stable, 3.16.9, on macOS 14.3 23D56 darwin-arm64, locale de-DE)`

https://github.com/flutter/flutter/assets/122024451/06d81da7-1f4a-44a1-8801-3b84176c69fe


<details>
  <summary>
  Used the flutter demo project:
  </summary>

  ```dart
import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // TRY THIS: Try running your application with "flutter run". You'll see
        // the application has a purple toolbar. Then, without quitting the app,
        // try changing the seedColor in the colorScheme below to Colors.green
        // and then invoke "hot reload" (save your changes or press the "hot
        // reload" button in a Flutter-supported IDE, or press "r" if you used
        // the command line to start the app).
        //
        // Notice that the counter didn't reset back to zero; the application
        // state is not lost during the reload. To reset the state, use hot
        // restart instead.
        //
        // This works for code too, not just values: Most code changes can be
        // tested with just a hot reload.
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // TRY THIS: Try changing the color here to a specific color (to
        // Colors.amber, perhaps?) and trigger a hot reload to see the AppBar
        // change color while the other colors stay the same.
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          //
          // TRY THIS: Invoke "debug painting" (choose the "Toggle Debug Paint"
          // action in the IDE, or press "p" in the console), to see the
          // wireframe for each widget.
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
            const Spacer(),
            const Text(
                "Irure minim pariatur incididunt laboris aliquip dolor amet mollit excepteur. Laboris sed irure in adipiscing excepteur ut occaecat mollit commodo laborum aliquip id amet. Nostrud aliquip velit sit amet enim non commodo occaecat cillum fugiat minim reprehenderit tempor anim. Laborum ut eiusmod sunt quis adipiscing magna aliqua qui culpa lorem commodo cupidatat aute pariatur sint officia minim tempor. Irure do mollit sunt sint ut ipsum ex in proident pariatur quis laboris cillum nisi mollit occaecat. Sint excepteur voluptate nostrud nostrud aliqua nulla ad sint cillum anim nisi cupidatat non consectetur aliquip aliquip ut."),
            const Text(
                "Proident officia consectetur laborum in aute sint aute commodo amet incididunt. Enim officia in id duis pariatur occaecat dolore eu magna dolor magna excepteur enim eiusmod lorem velit esse. Dolor ea proident sunt ullamco nostrud deserunt nulla ipsum velit voluptate nisi aliquip do deserunt fugiat ipsum occaecat cupidatat."),
            const Text(
                "Duis dolor duis ad sed pariatur magna eiusmod velit et in nulla anim ut sunt irure incididunt do. Nisi veniam cillum consequat aliquip non ipsum minim elit tempor fugiat esse est proident minim dolore elit dolore duis. In ad aliquip sit enim mollit officia exercitation ad ut consequat. Aliqua voluptate aute aliquip enim dolore nulla aliqua enim non sunt laborum occaecat mollit deserunt."),
            const Text(
                "Ullamco lorem lorem cupidatat adipiscing deserunt id eiusmod magna velit. Elit aute elit duis fugiat sed labore amet cupidatat do incididunt labore ea. Amet sit laborum qui sint anim nisi ipsum nulla officia et officia. Duis irure et ipsum sint exercitation culpa lorem aute cupidatat pariatur reprehenderit fugiat. Veniam est consectetur ex mollit ipsum mollit incididunt commodo do tempor nulla enim veniam laboris ullamco ad minim culpa eu. Aliquip esse et esse ullamco eu nisi laboris irure magna."),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}
```

Flutter run commands: 
- `flutter run -d chrome --web-renderer canvaskit`
- `flutter run -d chrome --web-renderer html`

Pasted in terminal to reproduce the user setting:
```
javascript:(function(){const style=document.createElement('style');style.setAttribute('rel','stylesheet'),style.textContent='*{line-height:1.5 !important;letter-spacing:0.12em !important;word-spacing,0.16em !important;}p{margin-bottom:2em !important;}',document.head.appendChild(style);})();
```

</details>