diff --git a/ReactAndroid/src/main/java/com/facebook/react/flat/README.md b/ReactAndroid/src/main/java/com/facebook/react/flat/README.md new file mode 100644 index 00000000000..f9fc580c021 --- /dev/null +++ b/ReactAndroid/src/main/java/com/facebook/react/flat/README.md @@ -0,0 +1,49 @@ +# Nodes + +Nodes is an experimental, alternate version of +[UIImplementation](https://github.com/facebook/react-native/blob/master/ReactAndroid/src/main/java/com/facebook/react/uimanager/UIImplementation.java) for ReactNative on Android. It has two main advantages over the existing `UIImplementation`: + +1. Support for `overflow:visible` on Android. +2. More efficient generation of view hierarchies. + +The intention is to ultimately replace the existing `UIImplementation` on +Android with Nodes (after all the issues are ironed out). + +## How to test + +In a subclass of `ReactNativeHost`, add this: + +```java +@Override +protected UIImplementationProvider getUIImplementationProvider() { + return new FlatUIImplementationProvider(); +} +``` + +## How it Works + +The existing +[UIImplementation](https://github.com/facebook/react-native/blob/master/ReactAndroid/src/main/java/com/facebook/react/uimanager/UIImplementation.java) maps all non-layout tags to `View`s (resulting in an almost 1:1 mapping of tags +to Views, with the exception of some optimizations for layout only tags that +don't draw content). Nodes, on the other hand, maps react tags to a set of +`DrawCommand`s. In other words, an `` tag will often be mapped to a +`Drawable` instead of an `ImageView` and a `` tag will be mapped to a +`Layout` instead of a `TextView`. This helps flatten the resulting `View` +hierarchy. + +There are situations where `DrawCommand`s are promoted to `View`s: + +1. Existing Android components that are wrapped by React Native (for example, +`ViewPager`, `ScrollView`, etc). +2. When using a `View` is more optimal (for example, `opacity`, to avoid +unnecessary invalidations). +3. To facilitate the implementation of certain features (accessibility, +transforms, etc). + +This means that existing custom `ViewManager`s should continue to work as they +did with the existing `UIImplementation`. + +## Limitations and Known Issues + +- `LayoutAnimation`s are not yet supported +- `zIndex` is not yet supported