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Taha Tesser 2c71881f50
Fix Scrollable TabBar for Material 3 (#131409) 
fixes [Material 3 `TabBar` does not take full width when `isScrollable: true`](https://github.com/flutter/flutter/issues/117722)

### Description
1. Fixed the divider doesn't stretch to take all the available width in the scrollable tab bar in M3
2. Added `dividerHeight` property.

### Code sample

<details> 
<summary>expand to view the code sample</summary> 

```dart
import 'package:flutter/material.dart';

/// Flutter code sample for [TabBar].

void main() => runApp(const TabBarApp());

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      home: TabBarExample(),
    );
  }
}

class TabBarExample extends StatefulWidget {
  const TabBarExample({super.key});

  @override
  State<TabBarExample> createState() => _TabBarExampleState();
}

class _TabBarExampleState extends State<TabBarExample> {
  bool rtl = false;
  bool customColors = false;
  bool removeDivider = false;
  Color dividerColor = Colors.amber;
  Color indicatorColor = Colors.red;

  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
      initialIndex: 1,
      length: 3,
      child: Directionality(
        textDirection: rtl ? TextDirection.rtl : TextDirection.ltr,
        child: Scaffold(
          appBar: AppBar(
            title: const Text('TabBar Sample'),
            actions: <Widget>[
              IconButton.filledTonal(
                tooltip: 'Switch direction',
                icon: const Icon(Icons.swap_horiz),
                onPressed: () {
                  setState(() {
                    rtl = !rtl;
                  });
                },
              ),
              IconButton.filledTonal(
                tooltip: 'Use custom colors',
                icon: const Icon(Icons.color_lens),
                onPressed: () {
                  setState(() {
                    customColors = !customColors;
                  });
                },
              ),
              IconButton.filledTonal(
                tooltip: 'Show/hide divider',
                icon: const Icon(Icons.remove_rounded),
                onPressed: () {
                  setState(() {
                    removeDivider = !removeDivider;
                  });
                },
              ),
            ],
          ),
          body: Column(
            children: <Widget>[
              const Spacer(),
              const Text('Scrollable - TabAlignment.start'),
              TabBar(
                isScrollable: true,
                tabAlignment: TabAlignment.start,
                dividerColor: customColors ? dividerColor : null,
                indicatorColor: customColors ? indicatorColor : null,
                dividerHeight: removeDivider ? 0 : null,
                tabs: const <Widget>[
                  Tab(
                    icon: Icon(Icons.cloud_outlined),
                  ),
                  Tab(
                    icon: Icon(Icons.beach_access_sharp),
                  ),
                  Tab(
                    icon: Icon(Icons.brightness_5_sharp),
                  ),
                ],
              ),
              const Text('Scrollable - TabAlignment.startOffset'),
              TabBar(
                isScrollable: true,
                tabAlignment: TabAlignment.startOffset,
                dividerColor: customColors ? dividerColor : null,
                indicatorColor: customColors ? indicatorColor : null,
                dividerHeight: removeDivider ? 0 : null,
                tabs: const <Widget>[
                  Tab(
                    icon: Icon(Icons.cloud_outlined),
                  ),
                  Tab(
                    icon: Icon(Icons.beach_access_sharp),
                  ),
                  Tab(
                    icon: Icon(Icons.brightness_5_sharp),
                  ),
                ],
              ),
              const Text('Scrollable - TabAlignment.center'),
              TabBar(
                isScrollable: true,
                tabAlignment: TabAlignment.center,
                dividerColor: customColors ? dividerColor : null,
                indicatorColor: customColors ? indicatorColor : null,
                dividerHeight: removeDivider ? 0 : null,
                tabs: const <Widget>[
                  Tab(
                    icon: Icon(Icons.cloud_outlined),
                  ),
                  Tab(
                    icon: Icon(Icons.beach_access_sharp),
                  ),
                  Tab(
                    icon: Icon(Icons.brightness_5_sharp),
                  ),
                ],
              ),
              const Spacer(),
              const Text('Non-scrollable - TabAlignment.fill'),
              TabBar(
                tabAlignment: TabAlignment.fill,
                dividerColor: customColors ? dividerColor : null,
                indicatorColor: customColors ? indicatorColor : null,
                dividerHeight: removeDivider ? 0 : null,
                tabs: const <Widget>[
                  Tab(
                    icon: Icon(Icons.cloud_outlined),
                  ),
                  Tab(
                    icon: Icon(Icons.beach_access_sharp),
                  ),
                  Tab(
                    icon: Icon(Icons.brightness_5_sharp),
                  ),
                ],
              ),
              const Text('Non-scrollable - TabAlignment.center'),
              TabBar(
                tabAlignment: TabAlignment.center,
                dividerColor: customColors ? dividerColor : null,
                indicatorColor: customColors ? indicatorColor : null,
                dividerHeight: removeDivider ? 0 : null,
                tabs: const <Widget>[
                  Tab(
                    icon: Icon(Icons.cloud_outlined),
                  ),
                  Tab(
                    icon: Icon(Icons.beach_access_sharp),
                  ),
                  Tab(
                    icon: Icon(Icons.brightness_5_sharp),
                  ),
                ],
              ),
              const Spacer(),
              const Text('Secondary - TabAlignment.fill'),
              TabBar.secondary(
                tabAlignment: TabAlignment.fill,
                dividerColor: customColors ? dividerColor : null,
                indicatorColor: customColors ? indicatorColor : null,
                dividerHeight: removeDivider ? 0 : null,
                tabs: const <Widget>[
                  Tab(
                    icon: Icon(Icons.cloud_outlined),
                  ),
                  Tab(
                    icon: Icon(Icons.beach_access_sharp),
                  ),
                  Tab(
                    icon: Icon(Icons.brightness_5_sharp),
                  ),
                ],
              ),
              const Text('Secondary - TabAlignment.center'),
              TabBar.secondary(
                tabAlignment: TabAlignment.center,
                dividerColor: customColors ? dividerColor : null,
                indicatorColor: customColors ? indicatorColor : null,
                dividerHeight: removeDivider ? 0 : null,
                tabs: const <Widget>[
                  Tab(
                    icon: Icon(Icons.cloud_outlined),
                  ),
                  Tab(
                    icon: Icon(Icons.beach_access_sharp),
                  ),
                  Tab(
                    icon: Icon(Icons.brightness_5_sharp),
                  ),
                ],
              ),
              const Spacer(),
            ],
          ),
        ),
      ),
    );
  }
}
``` 
	
</details>

### Before

![Screenshot 2023-07-27 at 14 12 36](https://github.com/flutter/flutter/assets/48603081/1c08a9d2-ac15-4d33-8fa1-c765b4b10f92)

### After 

![Screenshot 2023-07-27 at 14 13 12](https://github.com/flutter/flutter/assets/48603081/7e662dfe-9f32-46c9-a128-3024a4782882)

This also contains regression test for https://github.com/flutter/flutter/pull/125974#discussion_r1239089151

```dart
  // This is a regression test for https://github.com/flutter/flutter/pull/125974#discussion_r1239089151.
  testWidgets('Divider can be constrained', (WidgetTester tester) async {
```

![Screenshot 2023-07-27 at 14 16 37](https://github.com/flutter/flutter/assets/48603081/ac2ef49b-2410-46d0-8ae2-d9b77236abba)
2023-08-02 00:48:06 +00:00
..
bin
Add support for M3 motion (#129942)
2023-07-19 22:07:59 +02:00
data
Run dart command to update widget defaults (#122557)
2023-03-15 18:53:29 +01:00
generated
Fix Scrollable TabBar for Material 3 (#131409)
2023-08-02 00:48:06 +00:00
lib
Fix Scrollable TabBar for Material 3 (#131409)
2023-08-02 00:48:06 +00:00
test
Improve defaults generation with logging, stats, and token validation (#128244)
2023-06-09 11:28:18 +00:00
pubspec.yaml
Upgrade Flutter libraries. (#131700)
2023-08-01 12:59:47 -07:00
README.md
Improve defaults generation with logging, stats, and token validation (#128244)
2023-06-09 11:28:18 +00:00
test.json
Improve defaults generation with logging, stats, and token validation (#128244)
2023-06-09 11:28:18 +00:00

README.md

Token Defaults Generator

Script that generates component theme data defaults based on token data.

Usage

Run this program from the root of the git repository:

dart dev/tools/gen_defaults/bin/gen_defaults.dart [-v]

This updates generated/used_tokens.csv and the various component theme files.

Templates

There is a template file for every component that needs defaults from the token database. These templates are implemented as subclasses of TokenTemplate. This base class provides some utilities and a structure for adding a new block of generated code to the bottom of a given file.

Templates need to override the generate method to provide the generated code block as a string.

See lib/fab_template.dart for an example that generates defaults for the Floating Action Button.

Tokens

Tokens are stored in JSON files in data/, and are sourced from an internal Google database.

template.dart should provide nearly all useful token resolvers (e.g. color, shape, etc.). For special cases in which one shouldn't be defined, use getToken to get the raw token value. The script, through the various revolvers and getToken, validates tokens, keeps track of which tokens are used, and generates generated/used_tokens.csv.