[WIP] Fix issue where shadows may not appear on views

[lyahdav]

Credit goes to @appden. This isn't ready to commit because NSShadow.shadowBlurRadius is slightly different than CALayer.shadowRadius.

Fixes #824

[pull-bot]

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Generated by 🚫 dangerJS against 31c8034

[analysis-bot]

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

Base commit: 71e8921
Branch: main

[Saadnajmi]

Thanks! I didn't realize there was a shadowBlurRadius separate from shadowRadius :)

@mischreiber @lyahdav

[Saadnajmi]

@lyahdav a quick update from our side. We have a bug on our plate to to fix shadows on macOS, but the engineer that's assigned to is on vacation, so we'll revisit once they are back. When I locally tested this, it almost felt like they were two shadows showing up, one from the original iOS layer.shadow* setters, and one from the NSShadow property you added. As for NSShadow.shadowBlurRadius vs shadowRadius, Apple documentation has me thinking they both control the same thing :)

[Saadnajmi]

From local testing, it seems the shadow on the layer through the props in RCTViewManager is still showing up half the time, so it feels like we have 2 shadows:

• The one from the shadow override you introduced
• The one from layer, which only shows up half the time because of undefined behavior described here: Refactor to not modify view-backing layer properties which is documented as undefined behavior by Apple  #466

Could you instead change the RCTVIewManager macros to CUSTOM_VIEW_PROPERTY like we do here so we never set it directly on the layer? #1035

[lyahdav]

@Saadnajmi I wasn't planning on trying to land this anytime soon, I just made this PR to share WIP. You can make a new PR with your suggested change.

[christophpurrer]

It seems that issue was fixed in #1352

[Saadnajmi]

It seems that issue was fixed in #1352

Yep! We needed a little bit of extra code, so do give it a look.