Luna Wei

This commit **improves error handling** within the **`react-native`** package by elevating a previous warning to a critical error. Specifically, it modifies `packages/react-native/src/private/webapis/intersectionobserver/internals/IntersectionObserverManager.js` to **throw an error** if the native `IntersectionObserver` TurboModule is null when its `observe` or `unobserve` methods are invoked. This **maintenance** change ensures that developers are immediately aware of a missing native implementation, preventing silent failures and making integration issues with the **`IntersectionObserver`** Web API polyfill more explicit and easier to debug.

This commit **enhances the testing infrastructure** for the **`IntersectionObserver`** API by introducing new **End-to-End (E2E) tests**. It also **refactors existing `IntersectionObserver` examples** within the project to make them more suitable and "friendlier" for automated E2E assertions. This **maintenance and testing improvement** ensures the correct behavior and **reliability** of the `IntersectionObserver` functionality, providing better coverage for future changes.

This commit performs an **internal refactoring** within the **`rn-tester` package** of **`react-native-github`**. It **migrates** 8 files from manually instantiating `Animated.Value` using `useRef(new Animated.Value(x))` to leveraging the more idiomatic `useAnimatedValue(x)` hook. This change streamlines the management of animated values, enhancing code readability and consistency across the affected test components.

This commit introduces the **IntersectionObserver Web API** to React Native, initially gating its availability behind a new **feature flag** named `enableIntersectionObserverByDefault`. This **new capability** is specifically enabled for **Canary builds** (both Android and OSS) to facilitate early testing and feedback. The changes involve extensive modifications to the **React Native feature flag system** across Kotlin, C++, and JavaScript, alongside updates to **native module integration** (Podspecs, `Package.swift`, JNI) to conditionally include the `IntersectionObserver` module. This controlled rollout ensures the API can be thoroughly validated before a wider release, with an example added to the **RNTester app** for demonstration.

This commit **enhances the robustness and clarity of the `IntersectionObserver` Web API implementation** within React Native. It introduces **error handling** to the `IntersectionObserver` constructor, causing it to explicitly throw an error when unsupported options are provided. Furthermore, it implements error-throwing getters for the `delay`, `scrollMargin`, and `trackVisibility` properties, ensuring that attempts to access these **unavailable properties** result in an immediate runtime error. This **maintenance fix** prevents silent failures and provides clearer feedback to developers, improving the overall developer experience by enforcing the API's supported capabilities.

This commit introduces a **new feature flag**, `enableVirtualViewClippingWithoutScrollViewClipping`, to **refine the rendering behavior** of **ReactVirtualView** components on Android. It **modifies how virtual views determine their clipping region**, allowing them to **ignore the parent ScrollView's subview clipping status** and instead consistently use their own drawing rectangle for clipping. This **feature enhancement** effectively **decouples virtual view clipping from ScrollView's explicit clipping property**, aiming for more predictable rendering. The flag is integrated across the **Android and C++ feature flag infrastructure** and applied within `ReactVirtualView.kt` and `ReactVirtualViewExperimental.kt`, impacting the **rendering pipeline for virtualized lists and complex views**.

This commit introduces **support for the `rootMargin` option** within React Native's **`IntersectionObserver` API**, allowing developers to define a margin around the root element for intersection calculations. This **new capability** involves comprehensive updates across both the **JavaScript `IntersectionObserver` implementation** for validation and passing, and the **native C++ modules** (`IntersectionObserver.cpp`, `IntersectionObserverManager.cpp`) for parsing, storing, and applying `rootMargin` to accurately compute intersections. The change enhances the flexibility of observing element visibility, impacting features like lazy loading and infinite scrolling by providing more control over when elements are considered "intersecting." New integration and benchmark tests were also added to ensure correctness and performance of the `rootMargin` functionality.

This commit **fixes a bug** in the **IntersectionObserver** implementation, specifically addressing an issue where **edge-adjacent intersections** were not correctly recognized. The core logic within `ReactCommon/react/renderer/observers/intersection/IntersectionObserver.cpp` is updated to ensure that elements precisely aligned with observer boundaries are properly considered intersecting, even if their `intersectionRatio` is zero. This **enhances the accuracy and reliability** of the **IntersectionObserver API** for React Native applications by modifying `computeIntersection` and `updateIntersectionObservation` and introducing a new helper `intersectOrNull`. New test cases have been added in `IntersectionObserver-itest.js` to validate this corrected behavior for edge-adjacent scenarios.

This commit performs an **internal terminology refactoring** within the **React Native renderer's IntersectionObserver** implementation to align with the W3C specification. Specifically, it renames the term "custom root" to "explicit root," affecting parameters and local variables like `hasCustomRoot` in functions such as `computeIntersection` and `updateIntersectionObservation` within `IntersectionObserver.cpp`. Additionally, the associated **integration tests** in `IntersectionObserver-itest.js` have been updated to reflect this new terminology in descriptions and comments. This **maintenance** change improves internal consistency and adherence to web standards without altering any functional behavior of the IntersectionObserver.

This commit performs a **refactoring** within the **React Native Android virtual view experimental implementation**. It **removes an unnecessary null-safe call operator (`?.`)** from the `updateClippingRect` function in `ReactVirtualViewExperimental.kt`. This **code cleanup** improves the **readability and maintainability** of the **virtual view clipping logic** by eliminating a redundant null check. The change is internal to the `com.facebook.react.views.virtual.viewexperimental` package, optimizing the existing code without altering external behavior.

This commit introduces **subview clipping** for the **experimental `VirtualView` component** on **Android**, significantly enhancing rendering performance. It updates the `ReactAndroid` API to reflect `ReactVirtualViewExperimentalManager` inheriting from `ReactClippingViewManager` and adds the `setRemoveClippedSubviews` method. The core clipping logic, including `updateClippingRect`, is implemented within `ReactVirtualViewExperimental.kt` and integrated with mode changes. This **new capability** is exposed to developers via a `removeClippedSubviews` prop in the `VirtualViewExperimentalNativeComponent.js` interface, allowing for optimized rendering of large lists or complex UIs.

This commit introduces a **hysteresis window** as a **feature enhancement** for the **`VirtualViewExperimental`** system in **React Native's Android implementation**. It integrates a hysteresis ratio and logic within the `updateModes` function of `VirtualViewContainer.kt` to **prevent rapid and unnecessary mode changes** for virtual views. This mechanism significantly improves the stability and performance of experimental virtual views by reducing "flapping" between states, thereby providing a smoother and more consistent user experience. A minor refactor also adds a `debugLog` import to `ReactVirtualViewExperimental.kt` to support this functionality.

This commit performs **maintenance** by **removing** the `enableEagerAlternateStateNodeCleanup` parameter from the **React Native internal rendering system**. This flag is now redundant because the eager alternate state node cleanup behavior it controlled is now **default true**. The change simplifies the codebase by eliminating an unnecessary configuration option, ensuring that the optimized cleanup process is always active. This streamlines the internal rendering process by enforcing eager alternate state node cleanup, removing a configurable flag that is no longer necessary.

This commit introduces **enhancements** to **React Native's Android virtual view system** by ensuring `ReactVirtualViewExperimental` and `ReactScrollView` properly react to size changes. It now listens to `onSizeChanged` events to update the `VirtualViewContainer`'s state and relative rects, which is crucial for maintaining **accurate layout and rendering**. Additionally, this work significantly improves **debuggability** by adding more detailed logs and consistently formatting the `virtualViewID` for easier grepping and issue diagnosis. This is a **maintenance** change that refines existing behavior and observability within the **virtual view components**.

This commit **fixes an alignment issue** within the **`VirtualViewExperimental` component** by refining how it handles empty view states, particularly for `ScrollView` instances. It **removes unnecessary empty rectangle checks** and introduces **early returns for empty visible rectangles** in the `updateModes` logic for both **iOS (Fabric)** and **Android** virtual view containers. Additionally, null checks are added in the `onModeChange` method of the **Android `ReactVirtualViewExperimental`** to prevent errors when emitters or scroll views are uninitialized. This **bug fix** ensures more robust and consistent behavior for virtualized lists, aligning the implementation with the expected v1 behavior of `VirtualView`.

This commit introduces a **hysteresis window** for `VirtualView`s, a **new capability** designed to stabilize their rendering mode transitions within **React Native's Fabric (iOS) and Android rendering pipelines**. By defining a buffer zone between the prerender and hidden window sizes, the system now prevents frequent and unnecessary mode changes, such as those triggered by minor view movements like overscroll. This **performance optimization** and **stability enhancement** is controlled by a new `virtualViewHysteresisRatio` **feature flag**, allowing for configurable behavior. The core logic is implemented in `RCTVirtualViewComponentView.mm` and `ReactVirtualView.kt`'s `updateMode` methods, ensuring a smoother user experience by reducing visual "flicker" and excessive re-renders.

This commit introduces **support for subview clipping** within the **`VirtualView` component** on Android, enhancing rendering performance. It exposes new API methods like `setRemoveClippedSubviews` and `updateClippingRect` via `ReactAndroid.api` and implements the core clipping logic in `ReactVirtualView.kt`. This **new capability** allows developers to optimize rendering by enabling the `removeClippedSubviews` prop on `VirtualView` instances, preventing off-screen subviews from being drawn. The change also involves internal refactoring in `ReactViewGroup.kt` and `ReactVirtualViewManager.kt` to integrate this functionality, making clipping-related fields and methods accessible.

This commit **enhances the `ReactVirtualView` component** within **React Native's Android implementation** by overriding the `onSizeChanged` method. It introduces the capability to **dispatch mode changes** whenever the virtual view's size is altered, ensuring proper state propagation. This **internal improvement** addresses scenarios where `onSizeChanged` might be called independently of `onLayoutChange`, making the view's size handling more robust. Specifically, the `onSizeChanged` method in `packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/virtual/view/ReactVirtualView.kt` is updated to trigger these dispatches. While currently not impacting visible `VirtualViews` due to their default visibility, this change proactively improves the reliability of size-dependent logic for future use cases.

This commit introduces a **performance optimization** to the **`VirtualViewExperimental`** component within **React Native's Android implementation**. It prevents unnecessary updates to the `VirtualViewContainer` by adding a check to ensure that the container is only updated if its rectangle dimensions have actually changed. This **refactoring**, specifically in `ReactVirtualViewExperimental.kt`, aims to reduce redundant rendering cycles, thereby improving the efficiency and responsiveness of views utilizing this experimental virtual view system. The change also involves renaming the reporting function for clarity, affecting methods like `onDropViewInstance` and `reportRectChangeToContainer`.

This commit introduces a **new capability** and **refactoring** for **iOS Fabric's VirtualViewExperimental** by centralizing scroll interaction logic within the `ScrollView`. It moves the responsibility of determining virtual view visibility and prerender states from individual `VirtualViewExperimental` instances to the containing `ScrollView`, significantly reducing the number of scroll listeners from N to 1 for improved **performance**. This is achieved by introducing `RCTVirtualViewContainerProtocol` and `RCTVirtualViewProtocol`, with `RCTScrollViewComponentView` adopting the container role via `RCTVirtualViewContainerState` to manage `RCTVirtualViewExperimentalComponentView` instances. The change streamlines how virtual views react to scroll events, leading to a more efficient and scalable rendering system.