Support user-defined PlatformColors on iOS

[oblador]

Summary

This is a continuation of #29683. I've talked to @danilobuerger who does not intend on continue work on it and is OK with me picking up where he left. This PR is identical besides adding a test case in the RN Tester app as requested in the original PR.

In summary it gives iOS feature parity with Android in the sense that one can use user-defined native colors, something even the docs claim is possible. It's useful as it enables accessibility features such as high contrast colors and makes implementing dark mode simple. For an example on how it can be used, see https://github.com/klarna-incubator/platform-colors

Changelog

[iOS] [Added] - Allow PlatformColor to return user-defined named asset color

Test Plan

Test case added to RN Tester.

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: 66173e1

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	9,247,877	-58
android	hermes	armeabi-v7a	8,765,593	-70
android	hermes	x86	9,709,493	-53
android	hermes	x86_64	9,675,466	-66
android	jsc	arm64-v8a	10,866,445	+16
android	jsc	armeabi-v7a	10,377,208	+14
android	jsc	x86	10,894,788	+22
android	jsc	x86_64	11,502,679	+13

Base commit: 66173e1

[facebook-github-bot]

@p-sun has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[p-sun]

Is there an example of how custom colors can be defined similarly for Android in RN Tester?

[oblador]

@p-sun: In the linked repo there's this for example: https://github.com/klarna-incubator/platform-colors/blob/master/examples/ColorViewerApp/ios/ColorViewerApp/Images.xcassets/accent.colorset/Contents.json Is that what you're asking for?

[p-sun]

In summary it gives iOS feature parity with Android in the sense that one can use user-defined native colors

I wondering how this similar feature works in Android and whether there's an usage example.

[oblador]

The main use case for me is supporting dark mode without having to re-implement that logic in JavaScript. Additionally it adds accessibility features such as high contrast color support.

[oblador]

The documentation for PlatformColor can be found here if that helps: https://reactnative.dev/docs/platformcolor

[p-sun]

Would this PR cause a different color to appear if the defined in RCTSemanticColorsMap in RCTConvert.m doesn't match the one defined in Apple's UI Element Colors. i.e. Could this PR cause Apple's UI Element Colors to override the one in RCTSemanticColorsMap? Just wondering out loud - I haven't looked deeply into the color logic.

This feature this PR adds is similar to custom colors in Android, but hasn't been documented for iOS, since this custom color is neither a "UIColor Standard Colors" or "UIColor UI Element Colors", from the React Native docs.

[oblador]

If you have a custom color defined with a name conflicting with one defined in RCTSemanticColorsMap it would prefer the custom color.

Re docs: yep that's fair, I'll make a PR updating the docs explicitly stating that custom colors are supported on iOS if this one lands.

[p-sun]

I edited my previous comment with a different question. ^

[oblador]

Do you mean this one?

Is there an example of how custom colors can be defined similarly for Android in RN Tester?

If so it doesn't seem that way aside from textColor, here's an example on how that can look like. Do you want me to add an example for Android too as a part of this PR?

[p-sun]

I meant this question.

Would this PR cause a different color to appear if the defined in RCTSemanticColorsMap in RCTConvert.m doesn't match the one defined in Apple's UI Element Colors. i.e. Could this PR cause Apple's UI Element Colors to override the one in RCTSemanticColorsMap?

You don't need to add an example to Android as part of this PR, unless you want too.

[oblador]

To my understanding it would only use RCTSemanticColorsMap if the color doesn't exist on that particular version of iOS. I can change is so that RCTSemanticColorsMap is preferred, but don't think that should matter as the purpose of it is providing fallbacks.

[oblador]

@p-sun: To keep this PR moving, are there any changes you want?

[facebook-github-bot]

@p-sun merged this pull request in 36c0a7d.