How to open a windowcontroller on top of a maximised windowcontroller - swift

Question

I have a osx (MacOS) application with a mainwindowController and the user can maximise the view. The app also has a preferences window that opens as a childwindowcontroller.
However if the main window is maximised the child window also tries to be maximised which ends up with a black screen with the child window display in the middle.
Is there anyway to make the child window not be displayed based on the main window maximised state and the child window always not be maximised.
Here is some code of how the preferences window is displayed.
let currentWindowController = self.view.window?.windowController as! MainWindowViewController
let childWindowControllers = windowControllers[currentWindowController]
if let subPreferencesWindowController: SubPreferenceWindowViewController? = {
for windowController in childWindowControllers! {
if windowController is SubPreferenceWindowViewController {
return windowController as? SubPreferenceWindowViewController
}
}
return nil
}(){
let subPreferencesController = subPreferencesWindowController?.contentViewController as! SubPreferenceViewController
subPreferencesController.appStateJSON = self.appStateJSON!
subPreferencesController.preferences = self.preferencesJSON!
subPreferencesController.setUpSubPreferences()
}

Answer 1

SOLVED IT - When I create the window I add a styling mask to set the new window to not be resizable. (Last line of code)
if let subPreferenceViewController = storyboard.instantiateController(withIdentifier: NSStoryboard.SceneIdentifier(rawValue: "sub-preferences")) as? SubPreferenceViewController {
let subPreferenceWindow = NSWindow(contentViewController: subPreferenceViewController)
let subPreferenceWindowController = SubPreferenceWindowViewController(window: subPreferenceWindow)
var windowControllersForCurrent = windowControllers[currentWindowController]
windowControllersForCurrent?.append(subPreferenceWindowController)
windowControllers[currentWindowController] = windowControllersForCurrent
newWindowController = subPreferenceWindowController
newWindow = subPreferenceWindow
newWindow.standardWindowButton(.zoomButton)!.isHidden = true
width = 400
height = 607
newWindow.maxSize = NSSize(width: width, height: height)
newWindow.styleMask.remove(.resizable)
}