How to access NSWindow from @main App using only SwiftUI?

Question

At this answer the solution work for Scene plus swiftUI.

However using @main like:

@main
struct MyApp: App {
    @StateObject private var model = MyModel()
    
    var body: some Scene {
        WindowGroup {
            Router {
                AppContent()
            }.environmentObject(self.model)
        }
    }
}

I also tried to get the main window by using

var window: NSWindow? {
        let window = NSApplication.shared.mainWindow
        return window
    }

Nevertheless, the mainWindow always return nil

Update:

I need the NSWindow due to the need of conforming with ASWebAuthenticationPresentationContextProviding which obligates to return a NSWindow. Basically, I'm trying to do something like:

LoginView(store: AuthStore(window: window))

Where AuthStore uses the AuthenticationServices to perform an authentication.

Answer 1

Basically, I'm trying to do something like:

LoginView(store: AuthStore(window: window))

Here is a demo of possible approach (with some replicated entities)

class AuthStore {
    var window: NSWindow

    init(window: NSWindow) {
        self.window = window
    }
}

struct DemoWindowAccessor: View {
    @State private var window: NSWindow?   // << detected in run-time so optional
    var body: some View {
        VStack {
            if nil != window {
                LoginView(store: AuthStore(window: window!))    // << usage
            }
        }.background(WindowAccessor(window: $window))
    }
}

struct WindowAccessor: NSViewRepresentable {
    @Binding var window: NSWindow?

    func makeNSView(context: Context) -> NSView {
        let view = NSView()
        DispatchQueue.main.async {
            self.window = view.window   // << right after inserted in window
        }
        return view
    }

    func updateNSView(_ nsView: NSView, context: Context) {}
}

struct LoginView: View {
    let store: AuthStore

    var body: some View {
        Text("LoginView with Window: \(store.window)")
    }
}