60c898d864
Summary:
This is meant to show a possible route format for a persistent form of Yoga. Where previous layouts can remain intact while still taking advantage of incremental layout by reusing previous subtrees.
```c
YGNodeRef YGNodeClone(const YGNodeRef node);
```
The core of this functionality is a new API to clone an existing node. This makes a new detached node with all the same values as the previous one. Conceptually this makes the original node "frozen" from that point on. It's now immutable. (This is not yet enforced at runtime in this PR but something we should add.)
Since the original is frozen, we reuse the children set from the original node. Their parent pointers still point back to the original tree though.
The cloned node is still mutable. It can have its styles updated, and nodes can be inserted or deleted. If an insertion/deletion happens on a cloned node whose children were reused, it'll first shallow clone its children automatically.
As a convenience I also added an API to clear all children:
```c
void YGNodeRemoveAllChildren(const YGNodeRef node);
```
During insert/delete, or as a result of layout a set of reused children may need to be first cloned. A kind of copy-on-write. When that happens, the host may want to respond. E.g. by updating the `context` such as by cloning any wrapper objects and attaching them to the new node.
```c
typedef void (*YGNodeClonedFunc)(YGNodeRef oldNode,
YGNodeRef newNode,
YGNodeRef parent,
int childIndex);
void YGConfigSetNodeClonedFunc(YGConfigRef config,
YGNodeClonedFunc callback);
```
This PR doesn't change any existing semantics for trees that are not first cloned.
It's possible for a single node to exist in two trees at once and be used by multiple threads. Therefore it's not safe to recursively free a whole tree when you use persistence. To solve this, any user of the library has to manually manage ref counting or tracing GC. E.g. by replicating the tree structure in a wrapper.
In a follow up we could consider moving ref counting into Yoga.
Closes https://github.com/facebook/yoga/pull/636
Reviewed By: emilsjolander
Differential Revision: D5941921
Pulled By: sebmarkbage
fbshipit-source-id: c8e93421824c112d09c4773bed4e3141b6491ccf
React Native · 
Learn once, write anywhere: Build mobile apps with React.
- Build native mobile apps using JavaScript and React: React Native lets you build mobile apps using only JavaScript. It uses the same design as React, letting you compose a rich mobile UI from declarative components.
- A React Native app is a real mobile app: With React Native, you don't build a "mobile web app", an "HTML5 app", or a "hybrid app". You build a real mobile app that's indistinguishable from an app built using Objective-C, Java, or Swift. React Native uses the same fundamental UI building blocks as regular iOS and Android apps. You just put those building blocks together using JavaScript and React.
- Don't waste time recompiling: React Native lets you build your app faster. Instead of recompiling, you can reload your app instantly. With hot reloading, you can even run new code while retaining your application state. Give it a try - it's a magical experience.
- Use native code when you need to: React Native combines smoothly with components written in Objective-C, Java, or Swift. It's simple to drop down to native code if you need to optimize a few aspects of your application. It's also easy to build part of your app in React Native, and part of your app using native code directly - that's how the Facebook app works.
The focus of React Native is on developer efficiency across all the platforms you care about - learn once, write anywhere. Facebook uses React Native in multiple production apps and will continue investing in React Native.
See the official React Native website for an introduction to React Native.
Supported operating systems are >= Android 4.1 (API 16) and >= iOS 8.0.
Getting Started
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 website’s documentation is divided into multiple sections.
- There are Guides that discuss topics like debugging, integrating with existing apps, and the gesture responder system.
- The Components section covers React components such as
ViewandButton. - The APIs section covers other libraries like Animated and StyleSheet that aren’t React components themselves.
- Finally, React Native provides a small number of Polyfills that offer web-like APIs.
Another great way to learn more about the components and APIs included with React Native is to read their source. Look under the Libraries/Components directory for components like ScrollView and TextInput, for example. The RNTester example is also here to demonstrate some of the ways to use these components. From the source you can get an accurate understanding of each component’s behavior and API.
The React Native documentation only discusses the components, APIs and topics specific to React Native (React on iOS and Android). For further documentation on the React API that is shared between React Native and React DOM, refer to the React documentation.
Upgrading
React Native is under active development. See the guide on upgrading React Native to keep your project up-to-date.
Contributing
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 bug fixes and improvements, and how to build and test your changes to React Native.
Beginner Friendly Bugs
We have a list of beginner friendly issues to help you get your feet wet in the React Native codebase and familiar with our contribution process. This is a great place to get started.
License
React Native is BSD licensed. We also provide an additional patent grant.
React documentation is Creative Commons licensed.