As of 2022/03 - SwiftUI's macOS built in Window management via the WindowGroups and Scenes mechanism is very limited. Many basic window operations on macOS are not available and require dropping to AppKit to achieve.

This application demonstrates how this can be achieved.

1. Creating and maintaining a single, unclosable main window.

   • Non-closable, ever present across restarts.
   • Restores on restart.
   • Close button removed from window chrome.
   • Menu close window items respond to window selection appropriately.

2. Singleton windows.

   • Closable.
   • Restore on restart if left open
   • Only ever a single instance.
   • If existing instance, attempts to create new then raises existing instead.
   • Menu items to create and close windows respond appropriately.

3. Generic window creation with remote raising and closing.

   • Closable
   • Instances restore on restart.
   • Windows given identifiable titles.
   • Menu items to create and close windows respond correctly.
   • If existing window has same title, then opening raises that instance rather than creating a new window.

4. App menu creation and entry validation along with keyboard shortcuts operates as would be expected for each window type.

5. App URI scheme and routing

   • Open or raise a singleton window - swiftuiWindowFun://singleton
   • Open and route to a generic window - swiftuiWindowFun://generic?title=Spock

6. Maintaining a list of windows, programatic raising and closing as needed.

This project has been built using Xcode 13.2 targeting macOS 12.1 Monterey and hand tested with version 12.3.

It should build and run successfully on any macOS 12. Monterey installation.

App attempts to use SwiftUI to maximum extent possible but goes under the covers to get hold of a NSWindow reference to enable it to add missing macOS standard control and customisation functionallity.

Specifically ...

• Uses openURL to spawn new windows in conjunction with .handlesExternalEvents(preferring: allowing:) where necessary to provide singleton windows. Window opening and routing is done in AppModel.

• The underlying AppKit NSWindow is obtained by using SwiftUI's NSViewRepresentable to add a hidden diagnostic probe NSView to the window's render tree and pull the information from the that. See HostingWindowFinder for implementation, and PermanentView, SingletonView and GenericView for how it has been incorporated.

• References to individual windows and control over what can be closed and post close cleaning operations is done via NSWindow delegation. See AppModel and its extension NSWindow+NSWindowDelegate for more on that.

• Menu options are set out in FileMenuCommands which uses functionallity from AppModel to manage windows and control available menu options.

More details and notes in code.