Joshua Gross
00751f64c7
Summary: See also D36889794. This is a very similar idea, except the core problem is that BaseTextProps is accessing the same props as ViewProps; and for ParagraphProps parsing, it first defers to ViewProps' parser and then BaseTextProps. RawPropsParser is optimized to access the same props in the same order, *exactly once*, so if we access a prop out-of-order, or for a second time, that access and the next access are deoptimized. Paragraph/Text, in particular, were quite bad because we did this several times, and each out-of-order access requires scanning /all/ props. This fixes the issue, at least partially, by (1) pulling all the duplicate accesses to the beginning of BaseTextProps, and (2) accessing them all in the same order as ViewProps, relatively (some props are skipped, but that matters less). Practically what this means is that now, all of Props' accesses have a cost of O(1) for lookup, or a total of O(n) for all of them; each access is at the n+1 position in the internal RawPropsParser array, so each access is cheap. BaseTextProps' duplicate accesses, even though there are only 4 of them: (1) the first one scans the entire array until we reach the prop in question; (2) the next accesses require scans, but not whole-array scans, since they're in order. (3) The BaseTextProps accesses /after/ the duplicate accesses are all O(1). tl;dr is that before we had something like O(n*6) cost for BaseTextProps parsing and now it is O(n*2). Similar to my summary in the last diff: we may want to revisit the RawPropsParser API... but I want to tread gently there, and this gets us a large improvement without major, risky changes. Empirically, based on a couple of systraces, average time for a single UIManager::createNode called from JS thread, before this stack: 17us. After: 667ns (3% as long). On average, for every 60 createNode calls, we will save 1ms on the UI thread. The savings will be greater for certain screens that use many Views or Text nodes, and lesser for screens that use fewer of these components. Changelog: [Internal] Reviewed By: mdvacca Differential Revision: D36890072 fbshipit-source-id: 5d24b986c391d7bb158ed2f43d130a71960837d1
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 11.0 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.