Hide All Windows by Default in SwiftUI macOS App

I am working on a new SwiftUI-only menu bar application and stumbled into the following problem; Whenever I define either a Window or WindowGroup in SwiftUI, at least one window is always opened on app launch. Conditional rendering (like if x { Window() }) isn't supported either. The app should have an onboarding Window that is only shown depending on a user defaults setting. And there should be another window that can be manually opened via the menu bar item.

This is my SwiftUI App's class:

import SwiftUI

@main
struct ExampleApp: App {
	@Environment(\.openWindow) var openWindow
	@AppStorage("showIntroduction") private var showIntroduction = true

	init() {
		if showIntroduction {
			print("Show introduction")
			openWindow(id: "introduction")
		}
	}

	var body: some Scene {
		// How to hide this window by default?
		Window("Intro", id: "introduction") {
			WelcomeView()
		}
			.windowStyle(.hiddenTitleBar)
		Settings {
			SettingsView()
		}
		MenuBarExtra {
			MenuBarView()
		} label: {
			Text("Test")
		}
	}
}

Views have the .hidden() modifier - but this doesn't support Windows or WindowGroups. When my view is hidden but wrapped in a Window or WindowGroup an empty window is rendered instead.

Is there any way to achieve this with plain SwiftUI? Or is it necessary to programmatically create and open an NSWindow if it shouldn't be open by default?

Option 1: Declare your app as menu bar utility

put this in your info.plist or info tab in project settings:

Application is agent (UIElement) YES

Option 2: Switch activation policy programmatically

Normal app, opens window at launch, has menu, dock item:

NSApp.setActivationPolicy(.regular)

Agent, no window at launch, can be a menu bar app if a status item is set:

NSApp.setActivationPolicy(.accessory)

You could set up a @NSApplicationDelegateAdaptor and switch it in applicationWillFinishLaunching(_:).

Like this:

App.swift

import SwiftUI

@main
struct ExampleApp: App {
    
    @NSApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
   
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        Settings {
            SettingsView()
        }
    }
}

AppDelegate.swift

import AppKit

class AppDelegate: NSObject, NSApplicationDelegate {
    func applicationWillFinishLaunching(_ notification: Notification) {
        let isAgent = UserDefaults.standard.bool(forKey: "activationIsAgent")
        print("isAgent: \(isAgent)")
        if isAgent {
            NSApp.setActivationPolicy(.accessory)
        } else {
            NSApp.setActivationPolicy(.regular)
        }
    }
}

Then you'd still need a status bar item and put e.g. a toggling menu item for that UserDefaults key.

@AppStorage("activationIsAgent") private var activationIsAgent: Bool = false

I did not find a way to do this in pure SwiftUI.

However, here is a light weight approach with NSWindow:

import SwiftUI

var welcomeWindow: NSWindow?

@main
struct ExampleApp: App {
    @AppStorage("showIntroduction") private var showIntroduction = true
    
    init() {
        if showIntroduction {
            print("Show introduction")
            
            welcomeWindow = NSWindow()
            welcomeWindow?.contentView = NSHostingView(rootView: WelcomeView())
            welcomeWindow?.identifier = NSUserInterfaceItemIdentifier(rawValue: "introduction")
            welcomeWindow?.styleMask = [.closable, .titled]
            welcomeWindow?.isReleasedWhenClosed = true
            welcomeWindow?.center()
            welcomeWindow?.becomeFirstResponder()
            welcomeWindow?.orderFrontRegardless()
        }
    }
    
    var body: some Scene {        
        Settings {
            SettingsView()
                .navigationTitle("Settings")
        }
        MenuBarExtra {
            MenuBarView()
        } label: {
            Text("Test")
        }
    }
}

As you can see, there's no dedicated Window Scene.

If you don't like the titled, closable design, you can close the window with this function in your WelcomeView, e.g. on a Button:

Button("Done") {
    NSApp.windows.filter { $0.identifier?.rawValue == "introduction" }.first?.close()
}