* Pulled `FinderBase` out of `Finder`
* `FinderBase` can be used for any object, not just elements
* Terminology was updated to be more "find" related
* Re-implemented `Finder` using `FinderBase<Element>`
* Backwards compatibility maintained with `_LegacyFinderMixin`
* Introduced base classes for SemanticsNode finders
* Introduced basic SemanticsNode finders through `find.semantics`
* Updated some relevant matchers to make use of the more generic `FinderBase`
Closes#123634Closes#115874
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")
The members which are currently hidden may get removed from `package:test_api` because they have no uses.
https://github.com/dart-lang/test/pull/2030
Switch to a `show` and list all the exported APIs. This is currently a no-op change, and is forward compatible with the breaking change when it lands.
A `show` is also safer than a `hide` when exporting across package boundaries. Adding a new member to a library _can be_ breaking, but is often treated as non-breaking. If a new member is added to `package:test_api/scaffolding.dart` it will need to be manually added to the list to be usable from `package:flutter_test`, but we anyways want to add a CHANGELOG entry for user facing changes.
In the multi view world, `RenderViews` are created by the `View` widget and no longer owned by the binding. Prior to this change, the `LiveTestWidgetsFlutterBinding` owned and managed a special subclass of `RenderView`, the `_LiveTestRenderView`. In the new world, where `RenderView`s can be created anywhere in the widget tree where a `View` widget is used, this setup is no longer feasible. This change removes this special `_LiveTestRenderView` and instead adds debug hocks to `RenderView` to allow the `LiveTestWidgetsFlutterBinding` to draw a debug overlay on top of the content of any `RenderView`.
Move imports of API available in `hooks.dart` or `scaffolding.dart` to use those more narrow libraries.
Move imports of APIs from `package:matcher` to import directly. The next major version of `test_api` will remove the exports of `matcher` APIs.
The latest version of `test_api` removed the deprecated annotation for a couple libraries. The deprecations had been a hack to avoid usage from inappropriate places, but they cause trouble and likely weren't effective for that goal.
Remove separate import for `registerException` since that was also moved to be available from the top level `scaffolding.dart` library.
Most of these imports were never appropriate. The `test_api` package was never intended for use in `_test.dart` files.
Where possible move imports to `matcher`, otherwise move them to `test` or `flutter_test`.
Leave uses of `test_api` from `flutter_test` library code.
* Reland "Inject current `FlutterView` into tree and make available via `View.of(context)` (#116924)"
This reverts commit 9102f2fe0b.
* remove window placeholder
* Use `curly_braces_in_flow_control_structures` for `packages/flutter_driver`
* Use `curly_braces_in_flow_control_structures` for `packages/flutter_goldens`
* Use `curly_braces_in_flow_control_structures` for `packages/flutter_goldens_client`
* Use `curly_braces_in_flow_control_structures` for `packages/flutter_localizations`
* Use `curly_braces_in_flow_control_structures` for `packages/flutter_test`
* Use `curly_braces_in_flow_control_structures` for `packages/flutter_web_plugins`
* fix comments
* Use `curly_braces_in_flow_control_structures` for `packages/integration_test`
* fix indentation
* Revert "Revert "Reland 2: Make LiveTestWidgetsFlutterBinding work with setSurfaceSize and live tests (#86912)" (#87233)"
This reverts commit 5b80d32a84.
* Record tap positions
