Line height is distributed unevenly when lineHeight <= fontSize

Description

When lineHeight is less than the fontSize, Text shrinks the line’s bounding box only by removing space from above the text, rather than distributing the space evenly above and below, as is done with extra line height. Actually, the issue manifests when lineHeight is less than fontSize plus some small amount (perhaps the font bounding box height?)—e.g. <= 45px for 40px Helvetica.

This leads to clipped glyphs and produces differences in text rendering between react-native-web and react-native (https://github.com/necolas/react-native-web/issues/1687). After some discussion with @necolas, my inclination is that RNW’s behavior is the more reasonable one, so I thought I’d open an issue here.

This issue reproduces across a variety of fonts.

Unfortunately,I worry that fixing this issue will create subtle and surprising source compatibility issues for existing clients.

React Native version:

System:
    OS: macOS 10.15.5
    CPU: (16) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 337.02 MB / 32.00 GB
    Shell: 3.2.57 - /bin/bash
  Binaries:
    Node: 10.21.0 - ~/.nvm/versions/node/v10.21.0/bin/node
    Yarn: 1.19.1 - /usr/local/bin/yarn
    npm: 6.14.4 - ~/.nvm/versions/node/v10.21.0/bin/npm
    Watchman: 4.9.0 - /usr/local/bin/watchman
  Managers:
    CocoaPods: 1.9.3 - /usr/local/bin/pod
  SDKs:
    iOS SDK:
      Platforms: iOS 13.6, DriverKit 19.0, macOS 10.15, tvOS 13.4, watchOS 6.2
    Android SDK: Not Found
  IDEs:
    Android Studio: 3.5 AI-191.8026.42.35.5900203
    Xcode: 11.6/11E708 - /usr/bin/xcodebuild
  Languages:
    Java: 11.0.2 - /usr/bin/javac
    Python: 2.7.16 - /usr/bin/python
  npmPackages:
    @react-native-community/cli: Not Found
    react: Not Found
    react-native: 0.63.2 => 0.63.2 
  npmGlobalPackages:
    *react-native*: Not Found

Steps To Reproduce

Run example app here: https://snack.expo.io/W51F2OAqD

Expected Results

The extra line spacing should be removed evenly from both above and below the type.

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

https://snack.expo.io/W51F2OAqD

[Dinkelborg]

I can confirm that this is still an issue

Thanks for the tip with the workaround @andymatuschak

[andymatuschak]

A workaround for readers who stumble on this issue: if you’d like to use smaller line heights without glyph clipping, you’ll need to add top padding to the Text element, which you must then compensate for by shifting the element up (e.g. via top plus relative positioning, or a negative marginTop).