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Victoria Ashworth 825e901e00
Set cacheExtent for SliverFillRemaining widget (#143612) 
When a Sliver with items is outside of the Viewport, but within the Viewport's `cacheExtent`, the framework should create SemanticNodes for the items even though they are out of view. However, for this to work, the Sliver's geometry must have a `cacheExtent` (how much space the sliver took up of the Viewport's `cacheExtent`) greater than 0, otherwise it is [excluded](f01ce9f4cb/packages/flutter/lib/src/rendering/viewport.dart (L311-L315)).

`SliverFillRemaining` widgets that fall outside the viewport did not have this set and therefore were being excluded when SemanticNodes were created, even if they were within the Viewport's `cacheExtent`. This PR sets the `cacheExtent` for `SliverFillRemaining` widgets.

In addition, `RenderSliverFillRemainingWithScrollable` would get dropped from the semantic tree because it's child had a size of 0 when outside the remaining paint extent. To fix, we give the child a `maxExtent` of the sliver's `cacheExtent` if it's outside the remaining paint extent but within the viewport's cacheExtent.

Fixes https://github.com/flutter/flutter/issues/142065.

Definitions:
* `RenderViewport.cacheExtent`:
  ```dart
  /// The viewport has an area before and after the visible area to cache items
  /// that are about to become visible when the user scrolls.
  ///
  /// Items that fall in this cache area are laid out even though they are not
  /// (yet) visible on screen. The [cacheExtent] describes how many pixels
  /// the cache area extends before the leading edge and after the trailing edge
  /// of the viewport.
  ///
  /// The total extent, which the viewport will try to cover with children, is
  /// [cacheExtent] before the leading edge + extent of the main axis +
  /// [cacheExtent] after the trailing edge.
  ///
  /// The cache area is also used to implement implicit accessibility scrolling
  /// on iOS: When the accessibility focus moves from an item in the visible
  /// viewport to an invisible item in the cache area, the framework will bring
  /// that item into view with an (implicit) scroll action.
  ```
* `SliverGeometry.cacheExtent`:
  ```dart
  /// How many pixels the sliver has consumed in the
  /// [SliverConstraints.remainingCacheExtent].
  ```
* `SliverContraints.remainingCacheExtent`:
  ```dart
  /// Describes how much content the sliver should provide starting from the
  /// [cacheOrigin].
  ///
  /// Not all content in the [remainingCacheExtent] will be visible as some
  /// of it might fall into the cache area of the viewport.
  ///
  /// Each sliver should start laying out content at the [cacheOrigin] and
  /// try to provide as much content as the [remainingCacheExtent] allows.
  ```
2024-03-13 16:34:25 +00:00
.github Bump actions/checkout from 4.1.1 to 4.1.2 (#145032) 2024-03-12 22:35:56 +00:00
.vscode Adjust repo config for VS Code formatting (#122758) 2023-04-14 12:35:42 +02:00
bin Roll Flutter Engine from 285b9fb287a3 to 2871c2601135 (2 revisions) (#145067) 2024-03-13 16:14:26 +00:00
dev Reland "Add a microbenchmark for text intrinsic height layout (#145007)" (#145037) 2024-03-13 00:52:24 +00:00
examples Manually roll pub packages (#145005) 2024-03-12 19:53:57 +00:00
packages Set cacheExtent for SliverFillRemaining widget (#143612) 2024-03-13 16:34:25 +00:00
.ci.yaml Revert "Remove unused drone_dimension field" (#145024) 2024-03-12 22:24:06 +00:00
.gitattributes Add pre-stable support for create on Windows (#51895) 2020-03-23 10:42:26 -07:00
.gitignore add .pub-cache back to .gitignore (#128894) 2023-06-15 19:21:05 +00:00
analysis_options.yaml Allow deprecated members from the Dart SDK and Flutter Engine to roll in (#143347) 2024-02-13 10:41:46 -08:00
AUTHORS Added newline at end of .gitignore files (#141270) 2024-01-12 23:22:11 +00:00
CODE_OF_CONDUCT.md Update list of CoC contacts. (#130630) 2023-07-16 23:39:20 +00:00
CODEOWNERS Reverts "Refactor external_ui → external_textures" (#142173) 2024-01-24 21:41:17 +00:00
CONTRIBUTING.md Add a DevTools section to CONTRIBUTING.md (#137193) 2023-11-13 21:51:07 +00:00
dartdoc_options.yaml Enable missing-code-block-language (#144443) 2024-03-01 01:06:53 +00:00
flutter_console.bat License update (#45373) 2019-11-27 15:04:02 -08:00
LICENSE License update (#45373) 2019-11-27 15:04:02 -08:00
PATENT_GRANT Rename patent file (#38686) 2019-08-16 16:54:58 +01:00
README.md Add Flutter CI status to README (#140513) 2024-01-04 18:26:48 +00:00
TESTOWNERS Remove force Xcode debug workflow (#144185) 2024-02-27 18:18:07 +00:00

README.md

Flutter

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Flutter is Google's SDK for crafting beautiful, fast user experiences for mobile, web, and desktop from a single codebase. Flutter works with existing code, is used by developers and organizations around the world, and is free and open source.

Documentation

For announcements about new releases, follow the flutter-announce@googlegroups.com mailing list. Our documentation also tracks breaking changes across releases.

Terms of service

The Flutter tool may occasionally download resources from Google servers. By downloading or using the Flutter SDK, you agree to the Google Terms of Service: https://policies.google.com/terms

For example, when installed from GitHub (as opposed to from a prepackaged archive), the Flutter tool will download the Dart SDK from Google servers immediately when first run, as it is used to execute the flutter tool itself. This will also occur when Flutter is upgraded (e.g. by running the flutter upgrade command).

About Flutter

We think Flutter will help you create beautiful, fast apps, with a productive, extensible and open development model, whether you're targeting iOS or Android, web, Windows, macOS, Linux or embedding it as the UI toolkit for a platform of your choice.

Beautiful user experiences

We want to enable designers to deliver their full creative vision without being forced to water it down due to limitations of the underlying framework. Flutter's layered architecture gives you control over every pixel on the screen and its powerful compositing capabilities let you overlay and animate graphics, video, text, and controls without limitation. Flutter includes a full set of widgets that deliver pixel-perfect experiences whether you're building for iOS (Cupertino) or other platforms (Material), along with support for customizing or creating entirely new visual components.

Reflectly hero image

Fast results

Flutter is fast. It's powered by hardware-accelerated 2D graphics libraries like Skia (that underpins Chrome and Android) and Impeller. We architected Flutter to support glitch-free, jank-free graphics at the native speed of your device.

Flutter code is powered by the world-class Dart platform, which enables compilation to 32-bit and 64-bit ARM machine code for iOS and Android, JavaScript and WebAssembly for the web, as well as Intel x64 and ARM for desktop devices.

Dart diagram

Productive development

Flutter offers stateful hot reload, allowing you to make changes to your code and see the results instantly without restarting your app or losing its state.

Hot reload animation

Extensible and open model

Flutter works with any development tool (or none at all), and also includes editor plug-ins for both Visual Studio Code and IntelliJ / Android Studio. Flutter provides tens of thousands of packages to speed your development, regardless of your target platform. And accessing other native code is easy, with support for both FFI (on Android, on iOS, on macOS, and on Windows) as well as platform-specific APIs.

Flutter is a fully open-source project, and we welcome contributions. Information on how to get started can be found in our contributor guide.