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  1. 05 Aug, 2023 1 commit
  3. 04 Aug, 2023 3 commits
    • gaaclarke's avatar
      Sped up the time to find macrobenchmarks. (#131959) · 11025e4a
      gaaclarke authored 
      This reduce the execution time of macrobenchmarks driver tests.

I tried to find the exact size to scroll the screen but I couldn't find a way to do that with driver tests.
      11025e4a
    • Justin McCandless's avatar
      Predictive back support for root routes (#120385) · dedd100e
      Justin McCandless authored 
      This PR aims to support Android's predictive back gesture when popping the entire Flutter app.  Predictive route transitions between routes inside of a Flutter app will come later.

<img width="200" src="https://user-images.githubusercontent.com/389558/217918109-945febaa-9086-41cc-a476-1a189c7831d8.gif" />

### Trying it out

If you want to try this feature yourself, here are the necessary steps:

  1. Run Android 33 or above.
  1. Enable the feature flag for predictive back on the device under "Developer
     options".
  1. Create a Flutter project, or clone [my example project](https://github.com/justinmc/flutter_predictive_back_examples).
  1. Set `android:enableOnBackInvokedCallback="true"` in
     android/app/src/main/AndroidManifest.xml (already done in the example project).
  1. Check out this branch.
  1. Run the app. Perform a back gesture (swipe from the left side of the
     screen).

You should see the predictive back animation like in the animation above and be able to commit or cancel it.

### go_router support

go_router works with predictive back out of the box because it uses a Navigator internally that dispatches NavigationNotifications!

~~go_router can be supported by adding a listener to the router and updating SystemNavigator.setFrameworkHandlesBack.~~

Similar to with nested Navigators, nested go_routers is supported by using a PopScope widget.

<details>

<summary>Full example of nested go_routers</summary>

```dart
// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:go_router/go_router.dart';

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

void main() => runApp(_MyApp());

class _MyApp extends StatelessWidget {
  final GoRouter router = GoRouter(
    routes: <RouteBase>[
      GoRoute(
        path: '/',
        builder: (BuildContext context, GoRouterState state) => _HomePage(),
      ),
      GoRoute(
        path: '/nested_navigators',
        builder: (BuildContext context, GoRouterState state) => _NestedGoRoutersPage(),
      ),
    ],
  );

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      routerConfig: router,
    );
  }
}

class _HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Nested Navigators Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text('Home Page'),
            const Text('A system back gesture here will exit the app.'),
            const SizedBox(height: 20.0),
            ListTile(
              title: const Text('Nested go_router route'),
              subtitle: const Text('This route has another go_router in addition to the one used with MaterialApp above.'),
              onTap: () {
                context.push('/nested_navigators');
              },
            ),
          ],
        ),
      ),
    );
  }
}

class _NestedGoRoutersPage extends StatefulWidget {
  @override
  State<_NestedGoRoutersPage> createState() => _NestedGoRoutersPageState();
}

class _NestedGoRoutersPageState extends State<_NestedGoRoutersPage> {
  late final GoRouter _router;
  final GlobalKey<NavigatorState> _nestedNavigatorKey = GlobalKey<NavigatorState>();

  // If the nested navigator has routes that can be popped, then we want to
  // block the root navigator from handling the pop so that the nested navigator
  // can handle it instead.
  bool get _popEnabled {
    // canPop will throw an error if called before build. Is this the best way
    // to avoid that?
    return _nestedNavigatorKey.currentState == null ? true : !_router.canPop();
  }

  void _onRouterChanged() {
    // Here the _router reports the location correctly, but canPop is still out
    // of date.  Hence the post frame callback.
    SchedulerBinding.instance.addPostFrameCallback((Duration duration) {
      setState(() {});
    });
  }

  @override
  void initState() {
    super.initState();

    final BuildContext rootContext = context;
    _router = GoRouter(
      navigatorKey: _nestedNavigatorKey,
      routes: [
        GoRoute(
          path: '/',
          builder: (BuildContext context, GoRouterState state) => _LinksPage(
            title: 'Nested once - home route',
            backgroundColor: Colors.indigo,
            onBack: () {
              rootContext.pop();
            },
            buttons: <Widget>[
              TextButton(
                onPressed: () {
                  context.push('/two');
                },
                child: const Text('Go to another route in this nested Navigator'),
              ),
            ],
          ),
        ),
        GoRoute(
          path: '/two',
          builder: (BuildContext context, GoRouterState state) => _LinksPage(
            backgroundColor: Colors.indigo.withBlue(255),
            title: 'Nested once - page two',
          ),
        ),
      ],
    );

    _router.addListener(_onRouterChanged);
  }

  @override
  void dispose() {
    _router.removeListener(_onRouterChanged);
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return PopScope(
      popEnabled: _popEnabled,
      onPopped: (bool success) {
        if (success) {
          return;
        }
        _router.pop();
      },
      child: Router<Object>.withConfig(
        restorationScopeId: 'router-2',
        config: _router,
      ),
    );
  }
}

class _LinksPage extends StatelessWidget {
  const _LinksPage ({
    required this.backgroundColor,
    this.buttons = const <Widget>[],
    this.onBack,
    required this.title,
  });

  final Color backgroundColor;
  final List<Widget> buttons;
  final VoidCallback? onBack;
  final String title;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: backgroundColor,
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(title),
            //const Text('A system back here will go back to Nested Navigators Page One'),
            ...buttons,
            TextButton(
              onPressed: onBack ?? () {
                context.pop();
              },
              child: const Text('Go back'),
            ),
          ],
        ),
      ),
    );
  }
}
```

</details>

### Resources

Fixes https://github.com/flutter/flutter/issues/109513
Depends on engine PR https://github.com/flutter/engine/pull/39208 :heavy_check_mark: 
Design doc: https://docs.google.com/document/d/1BGCWy1_LRrXEB6qeqTAKlk-U2CZlKJ5xI97g45U7azk/edit#
Migration guide: https://github.com/flutter/website/pull/8952
      dedd100e
    • Polina Cherkasova's avatar
      Upgrade packages. (#131927) · 2c102959
      Polina Cherkasova authored
      2c102959
  5. 03 Aug, 2023 4 commits
  7. 02 Aug, 2023 3 commits
    • gaaclarke's avatar
      Added standard deviation to rasterizer results. (#131781) · 947367aa
      gaaclarke authored 
      This calculation is important if you want to calculate the probability that one thing is better than another.
      947367aa
    • dependabot[bot]'s avatar
      Bump ubuntu from `f8f6584` to `c9820a4` in /dev/ci/docker_linux (#130292) · 6cf50ef9
      dependabot[bot] authored 
      Bumps ubuntu from `f8f6584` to `c9820a4`.

[![Dependabot compatibility score](https://dependabot-badges.githubapp.com/badges/compatibility_score?dependency-name=ubuntu&package-manager=docker&previous-version=focal&new-version=focal)](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores)

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting `@dependabot rebase`.

---

<details>
<summary>Dependabot commands and options</summary>
<br />

You can trigger Dependabot actions by commenting on this PR:
- `@dependabot rebase` will rebase this PR
- `@dependabot recreate` will recreate this PR, overwriting any edits that have been made to it
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- `@dependabot ignore this dependency` will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)

</details>
      6cf50ef9
    • Taha Tesser's avatar
      Fix Scrollable `TabBar` for Material 3 (#131409) · 2c71881f
      Taha Tesser authored 
      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)
      2c71881f
  9. 01 Aug, 2023 1 commit
  11. 31 Jul, 2023 3 commits
  13. 28 Jul, 2023 2 commits
  15. 27 Jul, 2023 3 commits
  17. 26 Jul, 2023 3 commits
  19. 24 Jul, 2023 2 commits
  21. 21 Jul, 2023 4 commits
  23. 20 Jul, 2023 1 commit
  25. 19 Jul, 2023 1 commit
  27. 18 Jul, 2023 4 commits
  29. 17 Jul, 2023 4 commits
    • Michael Goderbauer's avatar
      Resolve TODOs in channels integration test (#130745) · 2dbf594f
      Michael Goderbauer authored 
      They were helpful in diagnosing the flake in https://github.com/flutter/flutter/issues/116663, but now that that's resolved they have outlived their usefulness. Let's remove 'em!
      2dbf594f
    • LongCatIsLooong's avatar
      Replaces `textScaleFactor` with `TextScaler` (#128522) · b2e22d35
      LongCatIsLooong authored 
      Deprecate `textScaleFactor` in favor of `textScaler`, in preparation for Android 14 [Non-linear font scaling to 200%](https://developer.android.com/about/versions/14/features#non-linear-font-scaling). The `TextScaler` class can be moved to `dart:ui` in the future, if we decide to use the Android platform API or AndroidX to get the scaling curve instead of hard coding the curve in the framework.

I haven't put the Flutter version in the deprecation message so the analyzer checks are failing. Will do so after I finish the migration guide.

**Why `TextScaler.textScaleFactor`**
The author of a `TextScaler` subclass should provide a fallback `textScaleFactor`. By making `TextScaler` also contain the `textScaleFactor` information it also makes it easier to migrate: if a widget overrides `MediaQueryData.textScaler` in the tree, for unmigrated widgets in the subtree it would also have to override `MediaQueryData.textScaleFactor`, and that makes it difficult to remove `MediaQueryData.textScaleFactor` in the future.

## A full list of affected APIs in this PR

Deprecated: The method/getter/setter/argument is annotated with a `@Deprecated()` annotation in this PR, and the caller should replace it with `textScaler` instead. Unless otherwise specified there will be a Flutter fix available to help with migration but it's still recommended to migrate case-by-case.
**Replaced**:  The method this `textScaleFactor` argument belongs to is rarely called directly by user code and is not overridden by any of the registered custom tests, so the argument is directly replaced by `TextScaler`.
**To Be Deprecated**:  The method/getter/setter/argument can't be deprecated in this PR because a registered customer test depends on it and a Flutter fix isn't available (or the test was run without applying flutter fixes first). This method/getter/setter/argument will be deprecated in a followup PR once the registered test is migrated.

### `Painting` Library

| Affected API | State of `textScaleFactor` | Comment | 
| --- | --- | --- |
| `InlineSpan.build({ double textScaleFactor = 1.0 })` argument | **Replaced** | | 
| `TextStyle.getParagraphStyle({ double TextScaleFactor = 1.0 })` argument | **Replaced** | |
| `TextStyle.getTextStyle({ double TextScaleFactor = 1.0 })`  argument| Deprecated | Can't replace: https://github.com/superlistapp/super_editor/blob/c47fd38dca4b7f43611690913b551a1773c563d7/super_editor/lib/src/infrastructure/super_textfield/desktop/desktop_textfield.dart#L1903-L1905|
| `TextPainter({ double TextScaleFactor = 1.0 })` constructor argument | Deprecated | |
| `TextPainter.textScaleFactor` getter and setter | Deprecated | No Flutter Fix, not expressible yet |
| `TextPainter.computeWidth({ double TextScaleFactor = 1.0 })` argument | Deprecated | |
| `TextPainter.computeMaxIntrinsicWidth({ double TextScaleFactor = 1.0 })` argument | Deprecated | |

### `Rendering` Library

| Affected API | State of `textScaleFactor` | Comment | 
| --- | --- | --- |
| `RenderEditable({ double TextScaleFactor = 1.0 })` constructor argument | Deprecated | |
| `RenderEditable.textScaleFactor` getter and setter | Deprecated | No Flutter Fix, not expressible yet |
| `RenderParagraph({ double TextScaleFactor = 1.0 })` constructor argument | Deprecated | |
| `RenderParagraph.textScaleFactor` getter and setter | Deprecated | No Flutter Fix, not expressible yet |

### `Widgets` Library

| Affected API | State of `textScaleFactor` | Comment | 
| --- | --- | --- |
| `MediaQueryData({ double TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | https://github.com/flutter/packages/blob/cd7b93532e5cb605a42735e20f1de70fc00adae7/packages/flutter_markdown/test/text_scale_factor_test.dart#LL39C21-L39C35 |
| `MediaQueryData.textScaleFactor` getter | Deprecated | |
| `MediaQueryData.copyWith({ double? TextScaleFactor })` argument | Deprecated | |
| `MediaQuery.maybeTextScaleFactorOf(BuildContext context)` static method | Deprecated | No Flutter Fix, not expressible yet  |
| `MediaQuery.textScaleFactorOf(BuildContext context)` static method | **To Be Deprecated** | https://github.com/flutter/packages/blob/cd7b93532e5cb605a42735e20f1de70fc00adae7/packages/flutter_markdown/lib/src/_functions_io.dart#L68-L70, No Flutter Fix, not expressible yet |
| `RichText({ double TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | https://github.com/flutter/packages/blob/cd7b93532e5cb605a42735e20f1de70fc00adae7/packages/flutter_markdown/lib/src/builder.dart#L829-L843 |
| `RichText.textScaleFactor` getter | **To Be Deprecated** | A constructor argument can't be deprecated right away|
| `Text({ double? TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | https://github.com/flutter/packages/blob/914d120da12fba458c020210727831c31bd71041/packages/rfw/lib/src/flutter/core_widgets.dart#L647 , No Flutter Fix because of https://github.com/dart-lang/sdk/issues/52664 |
| `Text.rich({ double? TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | The default constructor has an argument that can't be deprecated right away. No Flutter Fix because of https://github.com/dart-lang/sdk/issues/52664 |
| `Text.textScaleFactor` getter | **To Be Deprecated** | A constructor argument can't be deprecated right away |
| `EditableText({ double? TextScaleFactor = 1.0 })` constructor argument | Deprecated | No Flutter Fix because of https://github.com/dart-lang/sdk/issues/52664 |
| `EditableText.textScaleFactor` getter | Deprecated | |

### `Material` Library

| Affected API | State of `textScaleFactor` | Comment | 
| --- | --- | --- |
| `SelectableText({ double? TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | https://github.com/flutter/packages/blob/cd7b93532e5cb605a42735e20f1de70fc00adae7/packages/flutter_markdown/lib/src/builder.dart#L829-L843, No Flutter Fix because of https://github.com/dart-lang/sdk/issues/52664 |
| `SelectableText.rich({ double? TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | The default constructor has an argument that can't be deprecated right away. No Flutter Fix because of https://github.com/dart-lang/sdk/issues/52664 |
| `SelectableText.textScaleFactor` getter | **To Be Deprecated** | A constructor argument can't be deprecated right away |

A lot of material widgets (`Slider`, `RangeSlider`, `TimePicker`, and different types of buttons) also change their layout based on `textScaleFactor`. These need to be handled in a case-by-case fashion and will be migrated in follow-up PRs.
      b2e22d35
    • Michael Goderbauer's avatar
      Stand-alone widget tree with multiple render trees to enable multi-view rendering (#125003) · 6f09064e
      Michael Goderbauer authored 
      This change enables Flutter to generate multiple Scenes to be rendered into separate FlutterViews from a single widget tree. Each Scene is described by a separate render tree, which are all associated with the single widget tree.

This PR implements the framework-side mechanisms to describe the content to be rendered into multiple views. Separate engine-side changes are necessary to provide these views to the framework and to draw the framework-generated Scene into them.

## Summary of changes

The details of this change are described in [flutter.dev/go/multiple-views](https://flutter.dev/go/multiple-views). Below is a high-level summary organized by layers.

### Rendering layer changes

* The `RendererBinding` no longer owns a single `renderView`. In fact, it doesn't OWN any `RenderView`s at all anymore. Instead, it offers an API (`addRenderView`/`removeRenderView`) to add and remove `RenderView`s that then will be MANAGED by the binding. The `RenderView` itself is now owned by a higher-level abstraction (e.g. the `RawView` Element of the widgets layer, see below), who is also in charge of adding it to the binding. When added, the binding will interact with the `RenderView` to produce a frame (e.g. by calling `compositeFrame` on it) and to perform hit tests for incoming pointer events. Multiple `RenderView`s can be added to the binding (typically one per `FlutterView`) to produce multiple Scenes.
* Instead of owning a single `pipelineOwner`, the `RendererBinding` now owns the root of the `PipelineOwner` tree (exposed as `rootPipelineOwner` on the binding). Each `PipelineOwner` in that tree (except for the root) typically manages its own render tree typically rooted in one of the `RenderView`s mentioned in the previous bullet. During frame production, the binding will instruct each `PipelineOwner` of that tree to flush layout, paint, semantics etc. A higher-level abstraction (e.g. the widgets layer, see below) is in charge of adding `PipelineOwner`s to this tree.
* Backwards compatibility: The old `renderView` and `pipelineOwner` properties of the `RendererBinding` are retained, but marked as deprecated. Care has been taken to keep their original behavior for the deprecation period, i.e. if you just call `runApp`, the render tree bootstrapped by this call is rooted in the deprecated `RendererBinding.renderView` and managed by the deprecated `RendererBinding.pipelineOwner`.

### Widgets layer changes

* The `WidgetsBinding` no longer attaches the widget tree to an existing render tree. Instead, it bootstraps a stand-alone widget tree that is not backed by a render tree. For this, `RenderObjectToWidgetAdapter` has been replaced by `RootWidget`.
* Multiple render trees can be bootstrapped and attached to the widget tree with the help of the `View` widget, which internally is backed by a `RawView` widget. Configured with a `FlutterView` to render into, the `RawView` creates a new `PipelineOwner` and a new `RenderView` for the new render tree. It adds the new `RenderView` to the `RendererBinding` and its `PipelineOwner` to the pipeline owner tree.
* The `View` widget can only appear in certain well-defined locations in the widget tree since it bootstraps a new render tree and does not insert a `RenderObject` into an ancestor. However, almost all Elements expect that their children insert `RenderObject`s, otherwise they will not function properly. To produce a good error message when the `View` widget is used in an illegal location, the `debugMustInsertRenderObjectIntoSlot` method has been added to Element, where a child can ask whether a given slot must insert a RenderObject into its ancestor or not. In practice, the `View` widget can be used as a child of the `RootWidget`, inside the `view` slot of the `ViewAnchor` (see below) and inside a `ViewCollection` (see below). In those locations, the `View` widget may be wrapped in other non-RenderObjectWidgets (e.g. InheritedWidgets).
* The new `ViewAnchor` can be used to create a side-view inside a parent `View`. The `child` of the `ViewAnchor` widget renders into the parent `View` as usual, but the `view` slot can take on another `View` widget, which has access to all inherited widgets above the `ViewAnchor`. Metaphorically speaking, the view is anchored to the location of the `ViewAnchor` in the widget tree.
* The new `ViewCollection` widget allows for multiple sibling views as it takes a list of `View`s as children. It can be used in all the places that accept a `View` widget.

## Google3

As of July 5, 2023 this change passed a TAP global presubmit (TGP) in google3: tap/OCL:544707016:BASE:545809771:1688597935864:e43dd651

## Note to reviewers

This change is big (sorry). I suggest focusing the initial review on the changes inside of `packages/flutter` first. The majority of the changes describe above are implemented in (listed in suggested review order):

* `rendering/binding.dart`
* `widgets/binding.dart`
* `widgets/view.dart`
* `widgets/framework.dart`

All other changes included in the PR are basically the fallout of what's implemented in those files. Also note that a lot of the lines added in this PR are documentation and tests.

I am also very happy to walk reviewers through the code in person or via video call, if that is helpful.

I appreciate any feedback.

## Feedback to address before submitting ("TODO")
      6f09064e
    • Reid Baker's avatar
      Update to valid build tools variant and update lockfiles (#125825) · 7a42ed7e
      Reid Baker authored 
      https://github.com/flutter/flutter/issues/125331
      7a42ed7e
  31. 15 Jul, 2023 1 commit

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