Enable switching between navigation modes

Tusker/Screens/Main/MainSplitViewController.swift

@@ -7,6 +7,7 @@
 //
 
 import UIKit
+import Combine
 
 class MainSplitViewController: UISplitViewController {
 
@@ -20,10 +21,13 @@ class MainSplitViewController: UISplitViewController {
     
     private var tabBarViewController: MainTabBarViewController!
     
+    private var navigationMode: Preferences.WidescreenNavigationMode!
     private var secondaryNavController: NavigationControllerProtocol! {
         viewController(for: .secondary) as? NavigationControllerProtocol
     }
     
+    private var cancellables = Set<AnyCancellable>()
+    
     private var sidebarVisibile: Bool {
         get {
             (UserDefaults.standard.object(forKey: "MainSplitViewControllerSidebarVisible") as? Bool) ?? true
@@ -60,11 +64,18 @@ class MainSplitViewController: UISplitViewController {
             hide(.primary)
         }
         
-        let multiColumnNav = MultiColumnNavigationController()
-        setViewController(multiColumnNav, for: .secondary)
+        let nav: UIViewController
+        navigationMode = Preferences.shared.widescreenNavigationMode
+        switch navigationMode! {
+        case .stack:
+            nav = EnhancedNavigationViewController()
+        case .splitScreen:
+            nav = SplitNavigationController()
+        case .multiColumn:
+            nav = MultiColumnNavigationController()
+        }
+        setViewController(nav, for: .secondary)
         
-//        let splitNav = SplitNavigationController()
-//        setViewController(splitNav, for: .secondary)
         // don't unnecesarily construct a content VC unless the we're in actually split mode
         // when we change from compact -> split for the first time, the VC will be transferred anyways
         if traitCollection.horizontalSizeClass != .compact {
@@ -94,6 +105,37 @@ class MainSplitViewController: UISplitViewController {
         addKeyCommand(MenuController.composeCommand)
         
         MenuController.sidebarItemKeyCommands.forEach(addKeyCommand(_:))
+        
+        Preferences.shared.$widescreenNavigationMode
+            .sink { [unowned self] in
+                self.updateNavigationMode($0)
+            }
+            .store(in: &cancellables)
+    }
+    
+    private func updateNavigationMode(_ mode: Preferences.WidescreenNavigationMode) {
+        guard mode != navigationMode else {
+            return
+        }
+        let viewControllers = secondaryNavController.viewControllers
+        secondaryNavController.viewControllers = []
+        // Setting viewControllers = [] doesn't remove the VC views from their superviews immediately,
+        // so do that ourselves so we can re-parent the VCs to the new nav controller.
+        for viewController in viewControllers {
+            viewController.viewIfLoaded?.removeFromSuperview()
+        }
+        
+        let newNav: NavigationControllerProtocol
+        switch mode {
+        case .stack:
+            newNav = EnhancedNavigationViewController()
+        case .splitScreen:
+            newNav = SplitNavigationController()
+        case .multiColumn:
+            newNav = MultiColumnNavigationController()
+        }
+        newNav.viewControllers = viewControllers
+        self.setViewController(newNav, for: .secondary)
     }
     
     func select(item: MainSidebarViewController.Item) {

Tusker/Screens/Utilities/SplitNavigationController.swift

@@ -290,6 +290,9 @@ private class SplitSecondaryNavigationController: EnhancedNavigationViewControll
     
     override var viewControllers: [UIViewController] {
         didSet {
+            for vc in oldValue where vc.parent !== self {
+                removeSecondarySplitCloseButton(for: vc)
+            }
             if let first = viewControllers.first {
                 configureSecondarySplitCloseButton(for: first)
             }
@@ -324,6 +327,12 @@ private class SplitSecondaryNavigationController: EnhancedNavigationViewControll
         viewController.navigationItem.leftBarButtonItem = item
     }
     
+    private func removeSecondarySplitCloseButton(for viewController: UIViewController) {
+        if viewController.navigationItem.leftBarButtonItem?.tag == ViewTags.splitNavCloseSecondaryButton {
+            viewController.navigationItem.leftBarButtonItem = nil
+        }
+    }
+    
     @objc private func closeSecondary() {
         closeSecondaryImpl()
     }