iOS: border width and color renders incorrectly on iOS for particular values

Environment

  React Native Environment Info:
    System:
      OS: macOS Sierra 10.12.6
      CPU: x64 Intel(R) Core(TM) i5-4278U CPU @ 2.60GHz
      Memory: 38.27 MB / 16.00 GB
      Shell: 3.2.57 - /bin/bash
    Binaries:
      Node: 8.11.3 - /usr/local/opt/node@8/bin/node
      Yarn: yarn install v0.27.5
[1/4] Resolving packages...
[2/4] Fetching packages...
[3/4] Linking dependencies...
[4/4] Building fresh packages...
Done in 31.83s. - /usr/local/bin/yarn
      npm: 5.6.0 - /usr/local/opt/node@8/bin/npm
      Watchman: 4.7.0 - /usr/local/bin/watchman
    SDKs:
      iOS SDK:
        Platforms: iOS 11.2, macOS 10.13, tvOS 11.2, watchOS 4.2
      Android SDK:
        Build Tools: 23.0.1, 25.0.2, 25.0.3, 26.0.1, 26.0.2, 27.0.3
        API Levels: 23, 25, 26, 27, 28
    IDEs:
      Android Studio: 3.1 AI-173.4907809
      Xcode: 9.2/9C40b - /usr/bin/xcodebuild
    npmPackages:
      react: 16.6.0-alpha.8af6728 => 16.6.0-alpha.8af6728 
      react-native: 0.57.3 => 0.57.3 
    npmGlobalPackages:
      create-react-native-app: 1.0.0
      react-native-cli: 2.0.1
      react-native-git-upgrade: 0.2.7

Description

I have a triangle build with View and styles only. It renders incorrectly depending on the width/height values on iOS. The problem occurred after upgrading to react-native 0.57.3 (from 0.55.x).

Actual:

Expected:

Reproducible Demo

The following snippet is not working (tested with iPhone 6 Plus and iPhone X):

<View style={{
                width: 0,
                height: 0,
                backgroundColor: 'transparent',
                borderStyle: 'solid',
                borderTopWidth: 0,
                borderRightWidth: 82.4,
                borderBottomWidth: 82.4,
                borderLeftWidth: 0,
                borderTopColor: 'transparent',
                borderRightColor: 'red',
                borderBottomColor: 'transparent',
                borderLeftColor: 'transparent',
            }}
            />

The following snippet is working:

<View style={{
                width: 0,
                height: 0,
                backgroundColor: 'transparent',
                borderStyle: 'solid',
                borderTopWidth: 0,
                borderRightWidth: 82.5,
                borderBottomWidth: 82.5,
                borderLeftWidth: 0,
                borderTopColor: 'transparent',
                borderRightColor: 'red',
                borderBottomColor: 'transparent',
                borderLeftColor: 'transparent',
            }}
            />

It’s just an example, there are much more values showing the problem!

[johman10]

I have found a fix for the triangle issue. Adding a border radius of any value bigger than 0 seems to fix the issue for now without reverting any commit.

Complete styles that work for me:

borderTopWidth: 0,
borderRightWidth: 50,
borderBottomWidth: 50,
borderLeftWidth: 0,
borderTopColor: 'transparent',
borderRightColor: 'red',
borderBottomColor: 'transparent',
borderLeftColor: 'transparent',
width: 0,
height: 0,
backgroundColor: 'transparent',
borderStyle: 'solid',
borderRadius: 0.000001,

without borderRadius	with borderRadius

Hope this helps some of you!

[mezod]

After having fixed the issue using borderRadius: 0.000001, the error started appearing again randomly (some triangles would appear cut while some others not) setting a bigger borderRadius made the trick, so borderRadius: 1, works better