Platforms Impacted

• iOS
• visionOS
• macOS

Description of changes

We were running into a very rare crash when simultaneously accessing the same Fluent color on multiple threads. There appears to be some cacheing issue when creating a UIColor that wraps a dynamic SwiftUI Color when the resolver is a class instead of a struct.

In the meantime, a quick fix is to change it back to a struct (I don't even remember why it was a class in the first place).

This does do away with Objective-C support for DynamicColor, but that was pretty short lived anyway :)

Binary change

(how is our binary size impacted -- see https://github.com/microsoft/fluentui-apple/wiki/Size-Comparison)

Verification

Verified that we can create 100,000 Fluent colors simultaneously without crashing (before this change, it would crash 100% at that scale).

Pull request checklist

This PR has considered:

• Light and Dark appearances
• iOS supported versions (all major versions greater than or equal current target deployment version)
• VoiceOver and Keyboard Accessibility
• Internationalization and Right to Left layouts
• Different resolutions (1x, 2x, 3x)
• Size classes and window sizes (iPhone vs iPad, notched devices, multitasking, different window sizes, etc)
• iPad Pointer interaction
• SwiftUI consumption (validation or new demo scenarios needed)
• Objective-C exposure (provide it only if needed)

Microsoft Reviewers: Open in CodeFlow