FullscreenOverlay.swift

extension View {
    func fullscreenOverlay<Overlay: View>(isPresented show: Binding<Bool>, @ViewBuilder overlay: () -> Overlay) -> some View {
        background {
            FullscreenOverlayPresenter(show: show, overlay: overlay())
        }
    }
}

struct FullscreenOverlayPresenter<Overlay: View>: UIViewControllerRepresentable {

    @Binding var show: Bool
    let overlay: Overlay

    @State private var presentedViewController: UIHostingController<Overlay>?

    private var isShowing: Bool { presentedViewController != nil }

    func makeUIViewController(context: Context) -> some UIViewController {
        UIViewController()
    }

    func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {

        if show && !isShowing {
            let toBePresented = UIHostingController(rootView: overlay)
            toBePresented.view.backgroundColor = UIColor(white: 0, alpha: 0.3)
            toBePresented.modalTransitionStyle = .crossDissolve
            toBePresented.modalPresentationStyle = .overFullScreen
            uiViewController.present(toBePresented, animated: true)

            DispatchQueue.main.async {
                presentedViewController = toBePresented
            }
        }

        if !show, let presented = presentedViewController {
            presented.dismiss(animated: true) {
                DispatchQueue.main.async {
                    presentedViewController = nil
                }
            }
        }
    }
}