[Surface] `shadowColor` should follow the current theme by default

[fabriziocucci]

Current behaviour

It looks like the shadowColor of the Surface component has been hardcoded to pure black here.

That causes the shadow not to show up on other components that are backed by Surface (e.g. Card).

Expected behaviour

I'm not 100% sure of what the spec says but I believe the shadowColor should be set to something like theme.colors.onBackground by default to provide the necessary contrast.

How to reproduce?

1. set a dark theme (e.g. where theme.colors.background = 'black')
2. place a Card on the screen

Preview

• With the current shadowColor:

• With the shadowColor set to theme.colors.onBackground:

What have you tried so far?

I need to manually set shadowColor on each elevated component that requires a shadow.

Your Environment

software	version
ios	Unnecessary
android	Unnecessary
react-native	Unnecessary
react-native-paper	5.13.1
node	Unnecessary
npm or yarn	Unnecessary
expo sdk	Unnecessary

[raldred]

Seems as though the spec suggests it should always be #000000 (md.sys.color.shadow) regardless of theme or contrast options
https://m3.material.io/components/cards/specs#daab7734-3b3e-464c-a967-7c7fa14e6478

So I guess the question is should RNP provide a global override for shadowColor via the theme?