Window Control Buttons Missing from New Window in SwiftUI App - swiftui

Question

Starting with a new SwiftUI macOS project in Xcode, I set up some very basic functionality.
#main
struct SwiftUIWindowTestApp: App {
var body: some Scene {
WindowGroup {
ContentView()
}
}
}
//ContentView
struct ContentView: View {
var body: some View {
//Button to open a new window
Button("Open Preferences"){
openPreferences()
}
.padding(100)
}
//Open the new window
func openPreferences(){
let preferencesWindow = NSWindow()
preferencesWindow.contentView = NSHostingView(rootView: PreferencesView())
let controller = NSWindowController(window: preferencesWindow)
controller.showWindow(nil)
}
}
//PreferencesView
struct PreferencesView: View {
var body: some View {
Text("Preferences")
.frame(width:300, height:200)
}
}
On app launch, I see what I expect:
But after I click Open Preferences, I see a new window appear like this:
Why are the control buttons (close, minimize, zoom) missing on that popup window?
I have tried explicitly setting the buttons to be visible (even though they should be by default) and nothing changes:
preferencesWindow.standardWindowButton(.closeButton)?.isHidden = false
preferencesWindow.standardWindowButton(.miniaturizeButton)?.isHidden = false
preferencesWindow.standardWindowButton(.zoomButton)?.isHidden = false
I have this same sample working fine in an AppKit app, so it appears to be something weird with SwiftUI. Any ideas?

Answer 1

Looks like NSWindow will create a window like that unless you set a hosting controller on it. This modified version of your code works for me:
func openPreferences(){
let preferencesWindow = NSWindow(contentViewController: NSHostingController(rootView: PreferencesView()))
let controller = NSWindowController(window: preferencesWindow)
controller.showWindow(nil)
}