This PR contains a series of minor changes to address issues that I happened to run into: - Pretty-print errors triggered when handling events that are pending because of having locked event handling. Previously these were just dumped to the console. - Add more documentation for `debugPaintPadding`. - Add documentation to `Tween` saying how to implement it. - Slight formatting changes in the scrollbar code to align some expressions. - Since we convert ScrollMetricsNotifications to ScrollNotifications in various places, provide an explicit API to do this. This will make the behaviour consistent throughout, and makes the code easier to understand. Added a test for this. - Clarifications to some of the BindingBase and SchedulerBinding documentation. - Clarified some documentation in `flutter_test`'s `Finder` class.
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.

Fast results
Flutter is fast. It's powered by the same hardware-accelerated 2D graphics library that underpins Chrome and Android: Skia. 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, as well as JavaScript for the web and Intel x64 for desktop devices.

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.
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.
