react / react/react-native

Animated tracking using the native driver does not work as expected

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API: Animated Issue: Author Provided Repro Needs: Triage :mag:
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Description

Description

Tracking a dynamic animated value (such as scroll position) using the native driver doesn't work correctly. Instead of animating the pinned value simultaneously, the animation only starts once the dynamic value stops changing.

React Native Version

0.71.11

Output of npx react-native info
System:
    OS: macOS 13.2.1
    CPU: (10) arm64 Apple M1 Max
    Memory: 81.73 MB / 32.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 16.18.1 - ~/.nvm/versions/node/v16.18.1/bin/node
    Yarn: 1.22.19 - /opt/homebrew/bin/yarn
    npm: 8.19.2 - ~/.nvm/versions/node/v16.18.1/bin/npm
    Watchman: 2022.11.07.00 - /opt/homebrew/bin/watchman
  Managers:
    CocoaPods: 1.11.3 - /opt/homebrew/bin/pod
  SDKs:
    iOS SDK:
      Platforms: DriverKit 22.4, iOS 16.4, macOS 13.3, tvOS 16.4, watchOS 9.4
    Android SDK: Not Found
  IDEs:
    Android Studio: Not Found
    Xcode: 14.3.1/14E300c - /usr/bin/xcodebuild
  Languages:
    Java: Not Found
  npmPackages:
    @react-native-community/cli: Not Found
    react: 18.2.0 => 18.2.0 
    react-native: 0.71.11 => 0.71.11 
    react-native-macos: Not Found
  npmGlobalPackages:
    *react-native*: Not Found

Steps to reproduce

I have created an example app that illustrates the problem.

  1. Clone the repository from https://github.com/kolking/animated-tracking, install and run the app in the simulator.
  2. When the native driver is disabled, scroll the bottom part horizontally to see how red dots follow the scroll position with a stagger effect.
  3. Now, in the App.tsx change the NATIVE_DRIVER constant to true, reload the app and try scrolling the bottom part again.
Snack, code example, screenshot, or link to a repository

Also please take note that when the native driver is enabled, it ignores the initial contentOffset. As a result, the red dots are initially displayed on the left and will only move to the center after a manually triggered scroll event.

useNativeDriver: false useNativeDriver: true

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the behavior in the linked animated-tracking example, starting with App.tsx and the NATIVE_DRIVER toggle. Compare scrolling with the native driver disabled and enabled, including the initial contentOffset. Done means the animated dots track the changing scroll position with the stagger effect and begin at the initial offset when the native driver is enabled.

Written by the indexing model from the issue text.

Assessment

Tech stack
react-native, typescript
Domain
mobile
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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