BackgroundColor animates for no reason

[bartlomiejbloniarz]

Description

When changing the backgroundColor of a FlatList item, there is an animation between these colors. The bug is reproducible both on the 0.76 RCs and main.

Steps to reproduce

1. paste the snack App.js code to RNTester
2. click toggle theme

React Native Version

0.76.0-rc.4, main

Affected Platforms

Runtime - iOS

Output of npx react-native info

System:
  OS: macOS 14.6.1
  CPU: (8) arm64 Apple M1 Pro
  Memory: 97.02 MB / 16.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 22.9.0
    path: /opt/homebrew/bin/node
  Yarn:
    version: 1.22.19
    path: /opt/homebrew/bin/yarn
  npm:
    version: 10.8.3
    path: /opt/homebrew/bin/npm
  Watchman:
    version: 2024.10.07.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.15.2
    path: /Users/bartlomiejbloniarz/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.0
      - iOS 18.0
      - macOS 15.0
      - tvOS 18.0
      - visionOS 2.0
      - watchOS 11.0
  Android SDK: Not Found
IDEs:
  Android Studio: 2024.2 AI-242.21829.142.2421.12409432
  Xcode:
    version: 16.0/16A242d
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.12
    path: /opt/homebrew/opt/openjdk@17/bin/javac
  Ruby:
    version: 3.2.2
    path: /Users/bartlomiejbloniarz/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli": Not Found
  react: Not Found
  react-native: Not Found
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: false
  newArchEnabled: false
iOS:
  hermesEnabled: true
  newArchEnabled: true

Stacktrace or Logs

-

Reproducer

https://snack.expo.dev/Tg8ResSSqSuiNHOg3iCq5

Screenshots and Videos

Screen.Recording.2024-10-14.at.13.11.00.mov

[shubhamguptadream11]

@bartlomiejbloniarz What according to you should be an expected behaviour? It changes colour smoothly.

[bartlomiejbloniarz]

@shubhamguptadream11 It should change instantaneously, as there is no animation being used.

[cortinico]

The bug is reproducible both on the 0.76 RCs and main.

Has this regressed since 0.75? Asking as there has been ongoing work on Backgrounds recently (cc @NickGerleman )

Also does this reproduces on both Android & iOS?

[bartlomiejbloniarz]

Yes, it worked fine on the previous version (I think this bug was also present in some older version, but was quickly fixed).

It only reproduces on iOS in both debug and production builds on the New Architecture.

[cortinico]

It only reproduces on iOS in both debug and production builds on the New Architecture.

So is this New Architecture only?

Yes, it worked fine on the previous version

Do you confirm that this regresses in 0.76 so that it was working in 0.75 iOS NewArch?

[bartlomiejbloniarz]

So is this New Architecture only?

yes

Do you confirm that this regresses in 0.76 so that it was working in 0.75 iOS NewArch?

yes

[zhongwuzw]

@bartlomiejbloniarz @cortinico Hi, I made a PR #47064 to fix this issue.