iPad: when creating a new window, take over and close the previous one

Author: zydeco

Mini vMac/DefaultSceneDelegate.swift

@@ -9,7 +9,7 @@
 import UIKit
 
 class DefaultSceneDelegate: UIResponder, UIWindowSceneDelegate {
-    var window: UIWindow?
+    var window: UIWindow? // keep window reference to be able to set background colour before destroying
 
     func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
         guard let windowScene = scene as? UIWindowScene else {
@@ -24,17 +24,32 @@ class DefaultSceneDelegate: UIResponder, UIWindowSceneDelegate {
         windowScene.sizeRestrictions?.maximumSize = size
 
         window = UIWindow(windowScene: windowScene)
-        let rootViewController = appDelegate.window?.rootViewController ?? UIStoryboard(name: "Main", bundle: .main).instantiateInitialViewController()
-
         if let window {
             appDelegate.window = window
-            window.rootViewController = rootViewController
+            window.rootViewController = UIStoryboard(name: "Main", bundle: .main).instantiateInitialViewController()
             window.makeKeyAndVisible()
         }
+        self.destroyOtherSessions(not: session)
+    }
+
+    private func destroyOtherSessions(not session: UISceneSession) {
+        let app = UIApplication.shared
+        let options = UIWindowSceneDestructionRequestOptions()
+        options.windowDismissalAnimation = .decline
+        for otherSession in app.openSessions.filter({ $0 != session && $0.configuration.name == "Default"}) {
+            if let window = (otherSession.scene as? UIWindowScene)?.windows.first {
+                window.rootViewController?.view.removeFromSuperview()
+                window.backgroundColor = .darkGray
+                app.requestSceneSessionRefresh(otherSession)
+            }
+            app.requestSceneSessionDestruction(otherSession, options: options)
+            // window will remain visible until window switcher is dismissed!
+        }
     }
 
     func sceneDidEnterBackground(_ scene: UIScene) {
-        if UserDefaults.standard.bool(forKey: "runInBackground") == false {
+        let app = UIApplication.shared
+        if UserDefaults.standard.bool(forKey: "runInBackground") == false && app.connectedScenes.filter({ $0 != scene && $0.session.configuration.name == "Default"}).isEmpty {
             AppDelegate.emulator.isRunning = false
         }
     }