Rubén NorteandFacebook GitHub Bot
220dcdec3a
Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/40944 ## Summary This creates a new version of `RuntimeScheduler` that's intended to be backwards compatible but with a few notable changes: 1. `scheduleTask` is now thread-safe. 2. `scheduleWork` is now just an alias of `scheduleTask` with immediate priority (to preserve the yielding semantics it had over other tasks). 3. Yielding mechanism has changed, to make lower priority tasks to yield to higher priority tasks, instead of just yielding to `scheduleWork` and `executeNowOnTheSameThread`. We don't expect this to have any impact in performance or user perceivable behavior, so we consider it a short-lived refactor. When we validate this assumptions in a complex application we'll delete the old version and only keep the fork. ## Motivation The main motivation for this refactor is to reduce the amount of unnecessary interruptions of running tasks (via `shouldYield`) that are only used to schedule asynchronous tasks from native. The `scheduleWork` method is the only available mechanism exposed to native APIs to schedule work in the JS thread (as the existing version of `scheduleTask` is only meant to be called from JS). This mechanism **always** asks for any running tasks in the scheduler to yield, so these tasks are always considered to have the highest priority. This makes sense for discrete user events, but not for many other use cases coming from native (e.g.: notifying network responses could be UserBlocking, Normal or Low depending on the use case). We need a way to schedule tasks from native with other kinds of priorities, so we don't always have to interrupt what's currently executing if it has a higher priority than what we're scheduling. ## Changes **General APIs:** This centralizes scheduling in only 2 APIs in `RuntimeScheduler` (which already exist in the legacy version): * `scheduleTask`, which is non-blocking for the caller and can be used from any thread. This always uses the task queue in the scheduler and a new yielding mechanism. * `executeNowOnTheSameThread`, which is blocking for the caller and asks any task executing in the scheduler to yield. These tasks don't go through the task queue and instead queue through the existing synchronization mechanism in `RuntimeExecutor`. The yielding mechanism for these tasks is preserved. `scheduleWork` will be deprecated and it's just an alias for `scheduleTask` with an immediate priority (to preserve a similar behavior). **Yielding behavior:** Before, tasks would only yield to tasks scheduled via `scheduleWork` and `executeNowOnTheSameThread` (those tasks didn't go through the task queue). With this implementation, tasks would now yield to any task that has a higher position in the task queue. That means we reuse the existing mechanism to avoid lower priority tasks to never execute because higher priority tasks never stop coming. All tasks would yield to requests for synchronous access (via `executeNowOnTheSameThread`) as did the current implementation. Changelog: [internal] Reviewed By: javache, sammy-SC Differential Revision: D49316881 fbshipit-source-id: 046afc8b6f510a8608ef3da6e27b2663d861f1b8
React Native
Learn once, write anywhere:
Build mobile apps with React.
Getting Started · Learn the Basics · Showcase · Contribute · Community · Support
React Native brings React's declarative UI framework to iOS and Android. With React Native, you use native UI controls and have full access to the native platform.
- Declarative. React makes it painless to create interactive UIs. Declarative views make your code more predictable and easier to debug.
- Component-Based. Build encapsulated components that manage their state, then compose them to make complex UIs.
- Developer Velocity. See local changes in seconds. Changes to JavaScript code can be live reloaded without rebuilding the native app.
- Portability. Reuse code across iOS, Android, and other platforms.
React Native is developed and supported by many companies and individual core contributors. Find out more in our ecosystem overview.
Contents
- Requirements
- Building your first React Native app
- Documentation
- Upgrading
- How to Contribute
- Code of Conduct
- License
📋 Requirements
React Native apps may target iOS 13.4 and Android 5.0 (API 21) or newer. You may use Windows, macOS, or Linux as your development operating system, though building and running iOS apps is limited to macOS. Tools like Expo can be used to work around this.
🎉 Building your first React Native app
Follow the Getting Started guide. The recommended way to install React Native depends on your project. Here you can find short guides for the most common scenarios:
📖 Documentation
The full documentation for React Native can be found on our website.
The React Native documentation discusses components, APIs, and topics that are specific to React Native. For further documentation on the React API that is shared between React Native and React DOM, refer to the React documentation.
The source for the React Native documentation and website is hosted on a separate repo, @facebook/react-native-website.
🚀 Upgrading
Upgrading to new versions of React Native may give you access to more APIs, views, developer tools, and other goodies. See the Upgrading Guide for instructions.
React Native releases are discussed in this discussion repo.
👏 How to Contribute
The main purpose of this repository is to continue evolving React Native core. We want to make contributing to this project as easy and transparent as possible, and we are grateful to the community for contributing bug fixes and improvements. Read below to learn how you can take part in improving React Native.
Code of Conduct
Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read the full text so that you can understand what actions will and will not be tolerated.
Contributing Guide
Read our Contributing Guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to React Native.
Open Source Roadmap
You can learn more about our vision for React Native in the Roadmap.
Good First Issues
We have a list of good first issues that contain bugs which have a relatively limited scope. This is a great place to get started, gain experience, and get familiar with our contribution process.
Discussions
Larger discussions and proposals are discussed in @react-native-community/discussions-and-proposals.
📄 License
React Native is MIT licensed, as found in the LICENSE file.
React Native documentation is Creative Commons licensed, as found in the LICENSE-docs file.