Nested Virtualized Lists in opposing directions firing all onViewableItemsChanged

[vincentvella]

Description

Nested Bidirectional FlatList onViewableItemsChanged Issue

App Image	Layout Image

The above images describe the layout where this problem has arisen. Essentially it's a 2D FlatList.

When the Vertical FlatList mounts and the onViewableItemsChanged prop callbacks fire for only the elements on the screen, the expected behavior is working.

However, once the nested FlatLists mount, instead of firing the onViewableItemsChanged callback for only the nested Horizontal FlatList items that are within the visible viewport, it fires for all rendered list items (including those that are out of the viewport). It seems that the correct viewability is determined on horizontal lists, however, the VirtualizedList doesn't check if those horizontal lists are vertically visible.

Below, I've illustrated the expected vs actual behavior with images/emojis

🎇 - Vertical FlatList onViewableItemsChanged callback fires 🔥 - Horizontal FlatList onViewableItemsChanged callback fires

Expected	Actual

I provided a minimum setup repo below you can clone. Only changed the App.tsx file to recreate the above steps.

React Native Version

0.71.0

Output of npx react-native info

System:
    OS: macOS 12.6
    CPU: (10) arm64 Apple M1 Max
    Memory: 204.02 MB / 32.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 16.18.0 - ~/.nvm/versions/node/v16.18.0/bin/node
    Yarn: 1.22.19 - ~/.nvm/versions/node/v16.18.0/bin/yarn
    npm: 8.19.2 - ~/.nvm/versions/node/v16.18.0/bin/npm
    Watchman: Not Found
  Managers:
    CocoaPods: Not Found
  SDKs:
    iOS SDK:
      Platforms: DriverKit 21.4, iOS 16.0, macOS 12.3, tvOS 16.0, watchOS 9.0
    Android SDK:
      API Levels: 29, 30, 31, 32, 33
      Build Tools: 29.0.3, 30.0.2, 30.0.3, 31.0.0, 32.0.0, 33.0.0, 33.0.0
      System Images: android-29 | Intel x86 Atom_64, android-29 | Google APIs Intel x86 Atom_64, android-29 | Google Play ARM 64 v8a, android-29 | Google Play Intel x86 Atom_64, android-31 | Google Play ARM 64 v8a, android-32 | Google APIs ARM 64 v8a, android-32 | Google Play ARM 64 v8a, android-33 | Google Play ARM 64 v8a
      Android NDK: Not Found
  IDEs:
    Android Studio: 2021.3 AI-213.7172.25.2113.9014738
    Xcode: 14.0.1/14A400 - /usr/bin/xcodebuild
  Languages:
    Java: 11.0.11 - /Users/vvella/.jenv/shims/javac
  npmPackages:
    @react-native-community/cli: Not Found
    react: 18.1.0 => 18.1.0
    react-native: 0.70.4 => 0.71.0
    react-native-macos: Not Found
  npmGlobalPackages:
    *react-native*: Not Found

Steps to reproduce

1. Create a vertical FlatList that contains a 2D data array with a length long enough to make the list run off of your screen and require scrolling
2. Create another FlatList (horizontal) to be rendered in the renderItem prop of the parent FlatList
3. Add an onViewableItemsChanged to the nested (horizontal) FlatList
4. Observe that all items rendered (regardless of vertical viewability) fire their onViewableItemsChanged callback

Snack, code example, screenshot, or link to a repository

Taken from the tester app See that InnerViewable shows "56,57,58" All of which are horizontally viewable but not vertically shown in the viewport

Snack: https://snack.expo.dev/@vincentvella/great-almond Repo: https://github.com/vincentvella/bidirectional-virtualized-list-issue

[github-actions[bot]]

:warning:

Newer Version of React Native is Available!

:information_source:

You are on a supported minor version, but it looks like there's a newer patch available - 0.71.10. Please upgrade to the highest patch for your minor or latest and verify if the issue persists (alternatively, create a new project and repro the issue in it). If it does not repro, please let us know so we can close out this issue. This helps us ensure we are looking at issues that still exist in the most recent releases.

[vincentvella]

Confirmed this is still an issue on the latest release.

[vincentvella]

Confirming issue is not fixed on 0.72.4

[vincentvella]

Commenting so this doesn't get marked as stale

[cortinico]

Commenting so this doesn't get marked as stale

@vincentvella FYI: Issues labelled with "Issue: Author Provided Repro" never get stale