border-color opacity level is not visible when a background-color without opacity is set on the same view (iOS)

[flo-sch]

Description

On a given <View />, when applying a background color without opacity, together with a border-color having an opacity level, the border-color appears opaque on iOS, while it appears as expected on Android.

<View
  style={{
    width: 20,
    height: 20,
    borderRadius: 10,
    backgroundColor: 'rgb(208, 12, 123)',
    borderStyle: 'solid',
    borderWidth: 2,
    borderColor: 'rgba(208, 12, 123, 0.2)',
  }}
/>

As shown on the screenshots below, the border-color has a visual opacity value on Android, but is rendered "opaque" on iOS, as if the opacity of the background-color takes over the opacity of the border-color.

It is possible to workaround that for my case by adding the opaque background on a child View, but I am interested to know whether this is intentional behaviour or not.

React Native Version

0.71.11

Output of npx react-native info

info Fetching system and libraries information...
System:
    OS: macOS 13.5.1
    CPU: (16) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 22.72 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 18.17.1 - ~/.nvm/versions/node/v18.17.1/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 9.6.7 - ~/.nvm/versions/node/v18.17.1/bin/npm
    Watchman: Not Found
  Managers:
    CocoaPods: 1.12.0 - /[...]/.rbenv/shims/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: 2022.3 AI-223.8836.35.2231.10671973
    Xcode: 14.3.1/14E300c - /usr/bin/xcodebuild
  Languages:
    Java: 20.0.1 - /usr/local/opt/openjdk/bin/javac
  npmPackages:
    @react-native-community/cli: 10.1.3 => 10.1.3 
    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

• Implement a View of any dimension
• Give it an opaque background-color (ex rgb(255, 0, 0))
• Give it a border of style solid, a width, and an non-opaque background-color (ex: rgba(255, 0, 0, 0.2))
• Compare how it visually differs between Android and iOS

Snack, screenshot, or link to a repository

https://snack.expo.dev/@flo-sch/react-native-background-vs-border-color-opacity

[github-actions]

⚠️

Newer Version of React Native is Available!

ℹ️

You are on a supported minor version, but it looks like there's a newer patch available - 0.71.13. 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.

[flo-sch]

Potentially related to #34722, without certitude?

[github-actions]

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[github-actions]

This issue was closed because it has been stalled for 7 days with no activity.

[dani-mp]

I can repro this as well.

[AlixH]

Up

[mattaningram]

This is how borders behave on the web (they are rendered inside the element) and I thought generally the same in React Native so the opacity is not being ignored, it just is showing the background through it and the background is the same color so it looks identical. Not sure why the Android version is behaving differently.