Andy MatuschakandFacebook GitHub Bot
694e22de84
Summary: I noticed when porting my iOS app to macOS via Catalyst that the text rendering was somewhat different on the two platforms. Text looked blurry and over-weight on macOS, even when disabling the Catalyst scaling transform. I hazily remembered that I'd seen this problem before in my old Cocoa development days: this kind of blurring occurs when rendering text with sub-pixel anti-aliasing into an offscreen buffer which will then be traditionally composited, because when the SPAA algorithm attempts to blend with the underlying content (i.e. in the offscreen buffer), there isn't any. SPAA is disabled on iOS, so the issue wouldn't appear there. On macOS, typical approachs to displaying text (e.g. `CATextLayer`) normally disable SPAA, since it's been incompatible with the platform's compositing strategy since the transition to layer-backed views some years ago. But React Native uses `NSLayoutManager` to rasterize text (rather than relying on the system render server via `CATextLayer`), and that class doesn't touch the context's font smoothing bit before drawing. This change makes macOS/Catalyst text rendering consistent with iOS text rendering by disabling SPAA. It appears that the code I've modified is in the process of being refactored (for Fabric?). It looks like [this](https://github.com/facebook/react-native/blob/8d6b41e9bcede07fb627d57cf6c11050ae590d57/ReactCommon/react/renderer/textlayoutmanager/platform/ios/RCTTextLayoutManager.mm#L111) is the corresponding place in the new code (sammy-SC, is that right?). I'm happy to include a change to the new renderer in this patch if someone can point me at how to test that change. ## Changelog [iOS] [Fixed] - Improved text rendering on macOS Catalyst Pull Request resolved: https://github.com/facebook/react-native/pull/29609 Test Plan: 1. Prepare RNTester for running on macOS (or apply [this patch](https://gist.github.com/andymatuschak/d0f5b4fc1a28efc4f860801aa1deddcd) to handle parts 1 and 2, but you'll still need to do part 3): 1. Open the workspace, navigate to the `RNTester` target's configuration, and check the "Mac" checkbox under "Deployment Info. 2. Flipper doesn't yet compile for Catalyst (https://github.com/facebook/react-native/issues/27845), so you must disable it by: a) commenting out `use_flipper!` and `flipper_post_install` in the Podfile, then running `pod install`; and b) removing the `FB_SONARKIT_ENABLED` preprocessor flags in the Xcode project. 3. macOS has different signing rules from iOS; you must set a development team in the "Signing & Capabilities" tab of the `RNTester` target configuration pane. Unfortunately, you must also do this in the `Pods` project for the `React-Core-AccessibilityResources` target ([this is an issue which CocoaPods must fix](https://github.com/CocoaPods/CocoaPods/issues/8891)). 2. Run RNTester with and without the patch. You'll see that the font hinting is overweight without the patch; see screenshots below (incorrect rendering above, correct rendering below; note that fonts still remain slightly blurred because of Catalyst's window scaling transform, but that's removed on Big Sur).   Reviewed By: PeteTheHeat Differential Revision: D23344751 Pulled By: sammy-SC fbshipit-source-id: 1bbf682b681e381a8a90e152245d9b0df8ec7697
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 10.0 and Android 4.1 (API 16) 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 the React Native Community, @react-native-community/react-native-releases.
👏 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.