PreferenceUIHostingController. Adds hiding home indicator and deferring system edge gestures to SwiftUI. (Don't work at the same time but I think that's normal?)

PreferenceUIHostingController.swift

extension View {
    /// Controls the application's preferred home indicator auto-hiding when this view is shown.
    func prefersHomeIndicatorAutoHidden(_ value: Bool) -> some View {
        preference(key: PreferenceUIHostingController.PrefersHomeIndicatorAutoHiddenPreferenceKey.self, value: value)
    }
    
    /// Controls the application's preferred screen edges deferring system gestures when this view is shown. Default is UIRectEdgeNone.
    func edgesDeferringSystemGestures(_ edge: UIRectEdge) -> some View {
        preference(key: PreferenceUIHostingController.PreferredScreenEdgesDeferringSystemGesturesPreferenceKey.self, value: edge)
    }
}

class PreferenceUIHostingController: UIHostingController<AnyView> {
    init<V: View>(wrappedView: V) {
        let box = Box()
        super.init(rootView: AnyView(wrappedView
            .onPreferenceChange(PrefersHomeIndicatorAutoHiddenPreferenceKey.self) {
                box.value?._prefersHomeIndicatorAutoHidden = $0
            }
            .onPreferenceChange(PreferredScreenEdgesDeferringSystemGesturesPreferenceKey.self) {
                box.value?._preferredScreenEdgesDeferringSystemGestures = $0
            }
        ))
        box.value = self
    }

    @objc required dynamic init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    private class Box {
        weak var value: PreferenceUIHostingController?
        init() {}
    }
    
    // MARK: Prefers Home Indicator Auto Hidden
    
    fileprivate struct PrefersHomeIndicatorAutoHiddenPreferenceKey: PreferenceKey {
        typealias Value = Bool
        
        static var defaultValue: Value = false
        
        static func reduce(value: inout Value, nextValue: () -> Value) {
            value = nextValue() || value
        }
    }
    
    private var _prefersHomeIndicatorAutoHidden = false {
        didSet { setNeedsUpdateOfHomeIndicatorAutoHidden() }
    }
    override var prefersHomeIndicatorAutoHidden: Bool {
        _prefersHomeIndicatorAutoHidden
    }
    
    // MARK: Preferred Screen Edges Deferring SystemGestures
    
    fileprivate struct PreferredScreenEdgesDeferringSystemGesturesPreferenceKey: PreferenceKey {
        typealias Value = UIRectEdge
        
        static var defaultValue: Value = []
        
        static func reduce(value: inout Value, nextValue: () -> Value) {
            value.formUnion(nextValue())
        }
    }
    
    private var _preferredScreenEdgesDeferringSystemGestures: UIRectEdge = [] {
        didSet { setNeedsUpdateOfScreenEdgesDeferringSystemGestures() }
    }
    override var preferredScreenEdgesDeferringSystemGestures: UIRectEdge {
        _preferredScreenEdgesDeferringSystemGestures
    }
}

PreferenceUIHostingControllerSwizzling.swift

/// If you are unable to access window.rootViewController this is a method using swizzling 
struct PreferenceUIHostingControllerView<Wrapped: View>: UIViewControllerRepresentable {
    init(@ViewBuilder wrappedView: @escaping () -> Wrapped) {
        _ = UIViewController.preferenceSwizzling
        self.wrappedView = wrappedView
    }
    
    var wrappedView: () -> Wrapped
    
    func makeUIViewController(context: Context) -> PreferenceUIHostingController {
        PreferenceUIHostingController(wrappedView: wrappedView())
    }
    
    func updateUIViewController(_ uiViewController: PreferenceUIHostingController, context: Context) {}
}

import SwizzleSwift // I have a fork of this for SPM (Amzd/SwizzleSwift)

extension UIViewController {
    static var preferenceSwizzling: Void = {
        Swizzle(UIViewController.self) {
            #selector(getter: childForScreenEdgesDeferringSystemGestures) <-> #selector(childForScreenEdgesDeferringSystemGestures_Amzd)
            #selector(getter: childForHomeIndicatorAutoHidden) <-> #selector(childForHomeIndicatorAutoHidden_Amzd)
        }
    }()
}

extension UIViewController {
    @objc func childForScreenEdgesDeferringSystemGestures_Amzd() -> UIViewController? {
        if self is PreferenceUIHostingController {
            // dont continue searching
            return nil
        } else {
            return search()
        }
    }
    @objc func childForHomeIndicatorAutoHidden_Amzd() -> UIViewController? {
        if self is PreferenceUIHostingController {
            // dont continue searching
            return nil
        } else {
            return search()
        }
    }
    
    private func search() -> PreferenceUIHostingController? {
        if let result = children.compactMap({ $0 as? PreferenceUIHostingController }).first {
            return result
        }
        
        for child in children {
            if let result = child.search() {
                return result
            }
        }
        
        return nil
    }
}

Has anybody had any luck adapting this to the iOS 16 life cycle? This no longer works for iOS 16 and while .persistentSystemOverlays(.hidden) is available, this is more preferential.

@LePips Do you have any more info on why this doesn't work on iOS 16? is there a new api for deferring system gestures in UIKit? as it should just use that right? or does the swizzle no longer work?

I do not have an idea why they don't work, the swizzled methods just aren't called. Most specifically, I am looking at the home indicator but I strongly assume this would also apply to all other methods.

Here is a minimal example that works for iOS 15 but not iOS 16:

Example

The commented out appDelegate is explained below.

@main
struct PreferenceHostingDevApp: App {
    
//    @UIApplicationDelegateAdaptor(MyAppDelegate.self)
//    var appDelegate
    
    var body: some Scene {
        WindowGroup {
            PreferenceUIHostingControllerView {
                ContentView()
            }
        }
    }
}

struct ContentView: View {
    
    @State
    private var showSecondView: Bool = false
    
    var body: some View {
        ZStack {
            
            VStack {
                Image(systemName: "globe")
                    .imageScale(.large)
                    .foregroundColor(.accentColor)
                Text("Hello, world!")
                
                Button {
                    showSecondView = true
                } label: {
                    Text("Present")
                }
            }
        }
        .ignoresSafeArea()
        .fullScreenCover(isPresented: $showSecondView) {
            SecondView(showSecondView: $showSecondView)
        }
    }
}

struct SecondView: View {
    
    @Binding
    var showSecondView: Bool
    
    var body: some View {
        VStack {
            Text("Hello There")
            
            Button {
                showSecondView = false
            } label: {
                Text("Dismiss")
            }
        }
        .prefersHomeIndicatorAutoHidden(true)
    }
}

Other things attempted:

• setting the scene window root view controller (via the appDelegate)
• create another solution that uses a proxy ObservableObject which will manually call the update method on the view controller
• wrapping SecondView in a PreferenceUIHostingControllerView

@LePips Hmm, is it possible that the preference key doesn’t forward from a presented view? Have you tried without the presented view?

If you mean trying to hide the home indicator on ContentView, that does work