Animate portrait to landscape transitions in three panel mode

iOS/RootSplitViewController.swift

@@ -13,6 +13,12 @@ class RootSplitViewController: UISplitViewController {
 	
 	var coordinator: SceneCoordinator!
 	
+	override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
+		coordinator.animate(alongsideTransition: { [weak self] context in
+			self?.coordinator.configureThreePanelMode(for: size)
+		})
+	}
+	
 	// MARK: Keyboard Shortcuts
 	
 	@objc func scrollOrGoToNextUnread(_ sender: Any?) {

iOS/SceneCoordinator.swift

@@ -83,12 +83,6 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 	}
 	
 	var isThreePanelMode: Bool {
-		return rootSplitViewController.traitCollection.userInterfaceIdiom == .pad &&
-			!rootSplitViewController.isCollapsed &&
-			UIDevice.current.orientation.isLandscape
-	}
-	
-	var isThreePanelModeConfigured: Bool {
 		return rootSplitViewController.children.last?.children.first is UISplitViewController
 	}
 	
@@ -274,7 +268,6 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 		NotificationCenter.default.addObserver(self, selector: #selector(userDidAddAccount(_:)), name: .UserDidAddAccount, object: nil)
 		NotificationCenter.default.addObserver(self, selector: #selector(userDidDeleteAccount(_:)), name: .UserDidDeleteAccount, object: nil)
 
-		NotificationCenter.default.addObserver(self, selector: #selector(orientationDidChange(_:)), name: UIDevice.orientationDidChangeNotification, object: nil)
 		NotificationCenter.default.addObserver(self, selector: #selector(userDefaultsDidChange(_:)), name: UserDefaults.didChangeNotification, object: nil)
 		NotificationCenter.default.addObserver(self, selector: #selector(accountDidDownloadArticles(_:)), name: .AccountDidDownloadArticles, object: nil)
 		
@@ -282,7 +275,7 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 		let _ = DetailViewControllerWebViewProvider.shared
 	}
 	
-	func start() -> UIViewController {
+	func start(for size: CGSize) -> UIViewController {
 		rootSplitViewController = RootSplitViewController()
 		rootSplitViewController.coordinator = self
 		rootSplitViewController.preferredDisplayMode = .automatic
@@ -302,6 +295,8 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 		shimController.replaceChildAndPinView(detailNavController)
 		rootSplitViewController.showDetailViewController(shimController, sender: self)
 
+		configureThreePanelMode(for: size)
+		
 		return rootSplitViewController
 	}
 	
@@ -327,6 +322,21 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 		}
 	}
 	
+	func configureThreePanelMode(for size: CGSize) {
+		guard rootSplitViewController.traitCollection.userInterfaceIdiom == .pad && !rootSplitViewController.isCollapsed else {
+			return
+		}
+		if size.width > size.height {
+			if !isThreePanelMode {
+				transitionToThreePanelMode()
+			}
+		} else {
+			if isThreePanelMode {
+				transitionFromThreePanelMode()
+			}
+		}
+	}
+	
 	func selectFirstUnreadInAllUnread() {
 		selectFeed(IndexPath(row: 1, section: 0))
 		selectFirstUnreadArticleInTimeline()
@@ -415,10 +425,6 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 		}
 	}
 
-	@objc func orientationDidChange(_ note: Notification) {
-		configureThreePanelMode()
-	}
-	
 	@objc func userDefaultsDidChange(_ note: Notification) {
 		self.sortDirection = AppDefaults.timelineSortDirection
 	}
@@ -1589,21 +1595,6 @@ private extension SceneCoordinator {
 		return shimController
 	}
 	
-	func configureThreePanelMode() {
-		guard rootSplitViewController.traitCollection.userInterfaceIdiom == .pad && !rootSplitViewController.isCollapsed else {
-			return
-		}
-		if UIDevice.current.orientation.isLandscape {
-			if !isThreePanelModeConfigured {
-				transitionToThreePanelMode()
-			}
-		} else {
-			if isThreePanelModeConfigured {
-				transitionFromThreePanelMode()
-			}
-		}
-	}
-	
 	@discardableResult
 	func transitionToThreePanelMode() -> UIViewController {
 		
@@ -1611,13 +1602,7 @@ private extension SceneCoordinator {
 			masterNavigationController.viewControllers = [masterFeedViewController]
 		}
 		
-		if currentFeedIndexPath == nil && currentArticleIndexPath == nil {
+		installTimelineControllerIfNecessary(animated: false)
-			
-			let wrappedSystemMessageController = fullyWrappedSystemMesssageController(showButton: false)
-			rootSplitViewController.showDetailViewController(wrappedSystemMessageController, sender: self)
-			return wrappedSystemMessageController
-			
-		} else {
 		
 		let controller: UIViewController = {
 			if let result = detailViewController {
@@ -1638,7 +1623,7 @@ private extension SceneCoordinator {
 		subSplit.showDetailViewController(navController, sender: self)
 		
 		return shimController
-		}
+
 	}
 	
 	func transitionFromThreePanelMode() {

iOS/SceneDelegate.swift

@@ -20,7 +20,7 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate {
 		
 		window = UIWindow(windowScene: scene as! UIWindowScene)
 		window!.tintColor = AppAssets.netNewsWireBlueColor
-		window!.rootViewController = coordinator.start()
+		window!.rootViewController = coordinator.start(for: window!.frame.size)
 
 		if let shortcutItem = connectionOptions.shortcutItem {
 			window!.makeKeyAndVisible()