Compose Multiplatformでテーマに同期してStatusBarのアイコン色を変更する

@Composable
internal fun App(onChangeDarkMode: (Boolean) -> Unit) {
    var isDark by remember { mutableStateOf(false) }
    MaterialTheme(colorScheme = if (isDark) darkColorScheme() else lightColorScheme()) {
        Surface {
            Box(
                modifier = Modifier.fillMaxSize(),
                contentAlignment = Alignment.Center
            ) {
                IconButton(
                    onClick = {
                        isDark = !isDark
                        onChangeDarkMode(isDark)
                    }
                ) {
                    Icon(
                        modifier = Modifier.size(64.dp),
                        imageVector = if (isDark) Icons.Default.LightMode else Icons.Default.DarkMode,
                        contentDescription = null
                    )
                }
            }
        }
    }
}

class AppActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            App(onChangeDarkMode = { /** StatusBarの色を変更する処理 */ })
        }
    }
}

fun MainViewController(): UIViewController = ComposeUIViewController {
    App(onChangeDarkMode = {  /** StatusBarの色を変更する処理 */ })
}

class AppActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            App(onChangeDarkMode = { changeStatusBarColor(it) })
        }
    }

    private fun changeStatusBarColor(isDark: Boolean) {
        val window = this.window
        val systemBarColor = if (isDark) Color.BLACK else Color.WHITE
        window.statusBarColor = systemBarColor
        window.navigationBarColor = systemBarColor
        WindowCompat.getInsetsController(window, window.decorView).apply {
            isAppearanceLightStatusBars = !isDark
            isAppearanceLightNavigationBars = !isDark
        }
    }
}

fun MainViewController(): UIViewController  = ComposeUIViewController { App() }

@main
struct iosApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

struct ContentView: View {
    var body: some View {
        ComposeView().ignoresSafeArea(.all)
    }
}

struct ComposeView: UIViewControllerRepresentable {
    func makeUIViewController(context: Context) -> UIViewController {
        MainKt.MainViewController()
    }

    func updateUIViewController(_ uiViewController: UIViewController, context: Context) {}
}

class CustomUIViewController : ComposeUIViewController {
    override fun preferredStatusBarStyle(): UIStatusBarStyle {
        // UIStatusBarStyleDarkContentやUIStatusBarStyleLightContentを指定して、StatusBarの表示をどっちのテーマにするか決める
        return UIStatusBarStyleDarkContent
    }
}

fun MainViewController(): UIViewController = MainUIViewController()

class MainUIViewController : UIViewController {
    @OverrideInit
    constructor() : super(nibName = null, bundle = null)

    @OverrideInit
    constructor(coder: NSCoder) : super(coder)

    /**
     * isDarkの状態を変更したら、StatusBarのアップデートを要求する
     */
    private var isDark: Boolean = false
        set(value) {
            field = value
            setNeedsStatusBarAppearanceUpdate()
        }

    /**
     * Appkから通知された、isDarkを内部に保存し、その時にStatusBarをアップデートする
     */
    private val childComposeViewController = ComposeUIViewController {
        App(onChangeDarkMode = { isDark -> this.isDark = isDark })
    }

    /**
     * isDarkの状態によって、StatusBarStyleが変化するようにする
     */
    override fun preferredStatusBarStyle(): UIStatusBarStyle {
        return if (isDark)  UIStatusBarStyleLightContent else UIStatusBarStyleDarkContent
    }

    override fun loadView() {
        super.loadView()

        // RootのUIViewControllerのViewをセットする
        view = UIView().apply {
            // SubViewとしてComposeのUIViewControlerのViewをセットする
            addSubview(
                childComposeViewController.view.apply {
                    // AutoresizingMaskを利用し、RootのViewに合わせてリサイズするようにする
                    setAutoresizingMask(
                        UIViewAutoresizingFlexibleWidth or UIViewAutoresizingFlexibleHeight
                    )
                }
            )
        }

        // RootのUIViewControllerの子にComposeのUIViewControllerを追加する
        addChildViewController(childComposeViewController)
        childComposeViewController.didMoveToParentViewController(this)
    }
}