Transparent background window with SwiftUI on macOS

ContentView.swift

import SwiftUI

class WindowBackedHelperView: NSView {
    var didMoveToWindow: (NSWindow) -> Void
    
    init(didMoveToWindow: @escaping (NSWindow) -> Void) {
        self.didMoveToWindow = didMoveToWindow
        super.init(frame: .zero)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidMoveToWindow() {
        super.viewDidMoveToWindow()
        guard let window else {
            return
        }
        didMoveToWindow(window)
    }
}

struct WindowBackedView: NSViewRepresentable {
    typealias NSViewType = WindowBackedHelperView
    
    var didMoveToWindow: (NSWindow) -> Void
    
    func makeNSView(context: Context) -> WindowBackedHelperView {
        WindowBackedHelperView {
            didMoveToWindow($0)
        }
    }
    
    func updateNSView(_ nsView: WindowBackedHelperView, context: Context) {
        
    }
}

struct DidMoveToWindowModifier: ViewModifier {
    var didMoveToWindow: (NSWindow) -> Void
    
    func body(content: Content) -> some View {
        content
            .background(
                WindowBackedView {
                    didMoveToWindow($0)
                }
            )
    }
}

extension View {
    func didMoveToWindow(_ completion: @convention(block) @escaping (NSWindow) -> Void) -> some View {
        self.modifier(DidMoveToWindowModifier(didMoveToWindow: completion))
    }
}

struct ContentView: View {
    var body: some View {
        VStack {
            Image(systemName: "globe")
                .imageScale(.large)
                .foregroundStyle(.tint)
            Text("Hello, world!")
        }
        .padding()
        .didMoveToWindow { window in
            window.isOpaque = false
            window.backgroundColor = .clear
        }
    }
}

Thank you for this!