Demonstrates how to respect a UIViewController's preferredContentSize while hosted in a UIViewControllerRepresentable

UIViewControllerRepresentable and preferredContentSize

import UIKit
import SwiftUI
import Combine
import PlaygroundSupport

let image1 = #imageLiteral(resourceName: "FKCLjJCWQAsnvY0.jpeg")
let image2 = #imageLiteral(resourceName: "tim-cook-apple-11 (dragged).jpg")

struct TestView: View {
    var body: some View {
        ScrollView {
            VStack(alignment: .center) {
                Spacer()
                Text("This view's size hugs, as expected.")
                    .background(Color.blue)
                Spacer()
                HostView(image: image1)
                Spacer()
                HostView(image: image2)
                Spacer()
            }
            .background(Color.gray)
        }
    }
}

struct HostView: View {
    let image: UIImage
    
    @State private var preferredContentSize: CGSize? = nil
    
    var body: some View {
        HostingView(image: image) { size in
            preferredContentSize = size
        }
        .frame(width: preferredContentSize?.width, height: preferredContentSize?.height)
    }
}

struct HostingView: UIViewControllerRepresentable {
    let image: UIImage
    let preferredContentSizeDidChange: (CGSize) -> Void
    
    func makeUIViewController(context: Context) -> HostingViewController {
        let vc = HostingViewController(image: image)
        vc
            .publisher(for: \.preferredContentSize)
            .removeDuplicates()
            .sink(receiveValue: preferredContentSizeDidChange)
            .store(in: &context.coordinator.cancellables)
        return vc
    }
    
    func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {
        
    }
    
    final class Coordinator {
        var cancellables = Set<AnyCancellable>()
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator()
    }
}

class HostingViewController: UIViewController {
    let image: UIImage
    
    init(image: UIImage) {
        self.image = image
        super.init(nibName: nil, bundle: nil)
    }
    
    required init?(coder: NSCoder) {
        fatalError()
    }
    
    override func loadView() {
        let container = UIView()
        container.backgroundColor = .orange
        
        let imageView = UIImageView(image: image)

        container.addSubview(imageView)
        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        imageView.setContentHuggingPriority(.required, for: .horizontal)
        
        NSLayoutConstraint.activate([
            imageView.widthAnchor.constraint(lessThanOrEqualTo: container.widthAnchor, multiplier: 1),
            imageView.leadingAnchor.constraint(equalTo: container.leadingAnchor),
            imageView.trailingAnchor.constraint(equalTo: container.trailingAnchor),
            imageView.topAnchor.constraint(equalTo: container.topAnchor),
            imageView.bottomAnchor.constraint(equalTo: container.bottomAnchor),
            imageView.heightAnchor.constraint(equalTo: imageView.widthAnchor, multiplier: image.size.height / image.size.width)
        ])
        
        view = container
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        
        print("Bounds: \(view.bounds)")
        preferredContentSize = view.systemLayoutSizeFitting(view.bounds.size, withHorizontalFittingPriority: .defaultHigh, verticalFittingPriority: .fittingSizeLevel)
        
        print("\(preferredContentSize)")
    }
}

PlaygroundPage.current.setLiveView(TestView().frame(width: 400, height: 700))

Image files