Fix inconsistent shadows

[Lynn Zhang (lyzhan7)]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native-macos 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native-macos 👍
• I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

Summary

Pull request #1227 mostly fixed the consistency issue but had a problem with the shadow opacity. There isn't a shadowOpacity property on NSShadow, the shadow opacity from the layer needed to be passed into the alpha channel of the NSShadow shadowColor property.

Fixes#824

Test Plan

This fix was tested with the fluentui-react-native tester app.

Before:

before.mov

After:

afteropacityfix.mov

[Lynn Zhang (lyzhan7)]

Note: We tried an additional approach to fix this, since the root issue behind this bug is that modifying certain layer props (including shadow related ones) on a layer owned by an NSView is undefined behavior, and we are still doing this in RCTViewManager with RCT_REMAP_VIEW_PROPERTY

RCT_REMAP_VIEW_PROPERTY(shadowColor, layer.shadowColor, CGColor)
RCT_REMAP_VIEW_PROPERTY(shadowOffset, layer.shadowOffset, CGSize)
RCT_REMAP_VIEW_PROPERTY(shadowOpacity, layer.shadowOpacity, float)
RCT_REMAP_VIEW_PROPERTY(shadowRadius, layer.shadowRadius, CGFloat)

In the second approach, rather than modifying RCTView.m, we changed RCTViewManager.m to use RCT_CUSTOM_VIEW_PROPERTY instead of RCT_REMAP_VIEW_PROPERTY, and set the view.shadow there.

We decided to keep the original approach since the result is the same, it's simpler and there will be less diffs between React Native macOS and React Native Core. If there are further issues with shadow rendering consistency this could be something we revisit.

[Pull Request Analyser (pull-bot)]

Messages

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[Code Analyser (analysis-bot)]

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

Base commit: e532f86
Branch: main