From a “controller” window, I want to dynamically change the default size of a secondary window. Environment Objects do not work, because they aren’t instantiated when the App class is called:

import SwiftUI

@main
struct WindowSizeTestApp: App {
    @Environment(.dismissWindow) private var dismissWindow
    
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        .defaultSize(CGSize(width: 300, height: 300))
        
        WindowGroup ("Second", id: "second") {
            SecondView()
        }
        .defaultSize(CGSize(width: Singleton.shared.windowWidth, height: 300))
    }
}

So my work-around was to create a singleton, such as this:

import Foundation

class Singleton: ObservableObject {
    static let shared = Singleton()
    
    @Published var windowWidth: Double = 800.0
    
    func setWidth (width: Double) {
        windowWidth = width
    }
}

This works for getting the initial value (800) but doesn’t work when the value is modified.

import SwiftUI

struct ContentView: View {
    @Environment(.supportsMultipleWindows) private var supportsMultipleWindows
    @Environment(.openWindow) private var openWindow
    @Environment(.dismissWindow) private var dismissWindow
    
    @State private var width: Double = 100.0
    
    var body: some View {
        VStack {
            Text("Width: (Int(width))")
                .padding()
            
            Slider(value: $width, in: 100...500, step: 1)
                .padding()
                .onChange(of: width) { newValue, oldValue in
                    Singleton.shared.setWidth(width: newValue)
                }
            
            Button(action: {
                dismissWindow(id: "second")
                openWindow(id: "second")
            }) {
                VStack {
                    Text("Open Window")
                        .font(.caption)
                }
            }
            .padding()
            .buttonStyle(PlainButtonStyle())
        }
        .padding()
    }
}

The second window I have is just some default text like this:

import SwiftUI

struct SecondView: View {
    var body: some View {
        Text("Ere I am JH")
    }
}

Is there a way to update a value and “redraw” or force a re-rendering of the windowgroups in an App class?