Samuel Susla
cf75d032d0
Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/44169 ## Changelog: [General][Changed] Disable new event loop behavior when bridgeless (new architecture) is enabled. # What is the problem With event loop, specifically with `batchRenderingUpdatesInEventLoop`, prop change is not delivered to Android mounting layer if the prop change was initiated from state update inside of `useLayoutEffect`, `componentDidMount` or `componentDidUpdate`. Note this has to be a prop change affecting mounting layer directly, not something consumed by Yoga, e.g. background colour or border colour. This affects android only. Minimal repro : ``` import React, {useLayoutEffect, useState} from 'react'; import {Button, SafeAreaView, View} from 'react-native'; function Foo() { const [bgColor, setBgColor] = React.useState('red'); useLayoutEffect(() => { console.log('useLayoutEffect'); setBgColor('blue'); }, []); return ( <View style={{ backgroundColor: bgColor, width: '100%', height: '100%', }} /> ); } function RNTesterApp() { const [show, setShow] = useState(false); return ( <SafeAreaView> <Button title="Toggle" onPress={() => setShow(!show)} /> {show && <Foo />} </SafeAreaView> ); } export default RNTesterApp; ``` # The underlaying problem The problem is in batched rendering updates and how props are delivered to Android mounting layer. Here is a step by step what happens in the repro above: 1. React issues asks Fabric to create new shadow node A with background colour **red**. 2. Fabric asks Android to allocate a view for shadow node A with background colour **red**. 3. React commits tree **T1** and calls layout effects. Meanwhile Fabric waits, without trying to mount the tree **T1**, to prevent painting state that is about to be updated and prevent flickering. 4. React clones node A, changing the background colour to **blue** and commits the new tree **T2**. 5. Fabric, will now go ahead and mount the latest tree **T2**. While creating mount instructions, it will drop prop updates because it believes prop updates where delivered already as part of step 2. At first this might appear as a problem with view preallocation. But the underlaying trouble is that on Android, we currently have no way of knowing how to combine changesets from React into single folly::dynamic. Reviewed By: javache, cortinico Differential Revision: D56355863 fbshipit-source-id: f8616ee48e10fc10e129bb632c5d398842220d24
React Native
Learn once, write anywhere:
Build mobile apps with React.
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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 6.0 (API 23) 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.