Add support for case-sensitive OpenType feature

[ashfurrow]

Summary:

This adds support for React Native to render text with the "case-sensitive forms" OpenType feature enabled. Similar to ligatures and tabular numbers, case sensitive forms modify how the font is rendered.

Normally, fonts vertically align their punctuation (eg + or -) with lowercase letters. Most letters are lower-case, so that makes sense. But for apps that use upper-case letters or numbers, the punctuation looks too low. Case-sensitive forms align these marks with uppercase letters and numbers, analogous to the CSS font-feature-settings: 'case' property. This is already supported by iOS and Android text rendering, I just exposed the functionality to the JS side.

I work on an app that displays financial data, with lots of numbers and stock symbols, and our punctuation looked too low. We are already using this patch in production, but I'd like to see it become part of React Native itself.

Changelog:

[GENERAL] [ADDED] - Add support for case-sensitive OpenType feature

Test Plan:

I added unit test coverage where I could and made sure everything compiled on both platforms.

I added a Demo for this to the iOS and Android Text demos, in rn-tester. There were some setbacks.

On iOS, I found a pre-installed font that supports the case feature but learned that the iOS simulator doesn't render the difference for this font. I installed on a device and it worked. I left the demo with a note. See the difference here, on the - character:

On Android, things were trickier because the in-built fonts on my device didn't support the OpenType feature. I installed the same font I used on iOS onto my Android device and got it working.

Since I couldn't get the demo to show the difference using the stock fonts on my device, I left the demo out of the Android rn-tester Text demos.

[github-actions]

Warning

JavaScript API change detected

This PR commits an update to ReactNativeApi.d.ts, indicating a change to React Native's public JavaScript API.

• Please include a clear changelog message.
• This change will be subject to additional review.

This change was flagged as: POTENTIALLY_BREAKING

[sidferreira]

@ashfurrow thanks... now I can't unsee it