Exposes tintColor in the dimmed state to SwiftUI. Use this to adapt any non-accentColor color to the dimmed state.

EnvironmentDimmedTintColorViewModifier.swift

//
//  EnvironmentDimmedTintColorViewModifier.swift
//  Learn
//
//  Created by Juan Arzola on 3/17/25.
//  Copyright © 2025 Juan Arzola. All rights reserved.
//
import SwiftUI
import UIKit

public extension View {

    /**
     * Exposes to the environment the tint color of the view at the "dimmed" state. While Color.accentColor automatically adapts
     * to this color, no other color does. This \.dimmedTintColor environment value helps you adapt any other color to the dimmed state when as well.
     */
    func environmentDimmedTintColor() -> some View {
        modifier(EnvironmentDimmedTintColorViewModifier())
    }
}

private struct EnvironmentDimmedTintColorViewModifier: ViewModifier {
    @State private var dimmedTintColor: Color? = nil

    func body(content: Content) -> some View {
        content
            .overlay(
                TintColorObserverRepresentable(
                    originalTint: UIColor(Color.accentColor),
                    dimmedTintColor: $dimmedTintColor
                )
                .frame(width: 0, height: 0)
                .accessibilityHidden(true)
                .allowsHitTesting(false)
            )
            .environment(\.dimmedTintColor, dimmedTintColor)
    }
}

private class TintColorObserver: UIView {
    var originalTint: UIColor? = nil
    var dimmedTintColor: Binding<Color?> = .constant(nil)
    override func tintColorDidChange() {
        super.tintColorDidChange()
        if let tintColor {
            if originalTint != tintColor {
                Task { @MainActor in
                    dimmedTintColor.wrappedValue = Color(tintColor)
                }
            }
        } else if dimmedTintColor.wrappedValue != nil {
            Task { @MainActor in
                dimmedTintColor.wrappedValue = nil
            }
        }
    }
}

private struct TintColorObserverRepresentable: UIViewRepresentable {
    var originalTint: UIColor?
    var dimmedTintColor: Binding<Color?>

    func makeUIView(context: Context) -> TintColorObserver {
        let view = TintColorObserver()
        view.originalTint = originalTint
        view.dimmedTintColor = dimmedTintColor.projectedValue
        return view
    }

    func updateUIView(_ uiView: TintColorObserver, context: Context) {
        uiView.originalTint = originalTint
    }
}

// MARK: - Environment

private struct DimmedTintColorKey: EnvironmentKey {
    static let defaultValue: Color? = nil
}

public extension EnvironmentValues {
    var dimmedTintColor: Color? {
        get { self[DimmedTintColorKey.self] }
        set { self[DimmedTintColorKey.self] = newValue }
    }
}