Initial tab bar/sidebar implementation

Tusker/Screens/Main/BaseMainTabBarViewController.swift

@@ -70,9 +70,12 @@ class BaseMainTabBarViewController: UITabBarController {
     }
     
     private func repositionFastSwitcherIndicator() {
-        guard let myProfileButton = findMyProfileTabBarButton() else {
+        guard let myProfileButton = findMyProfileTabBarButton(),
+              myProfileButton.window != nil else {
+            fastSwitcherIndicator?.isHidden = true
             return
         }
+        fastSwitcherIndicator?.isHidden = false
         NSLayoutConstraint.deactivate(fastSwitcherConstraints)
         let isPortrait = view.bounds.width < view.bounds.height
         if traitCollection.horizontalSizeClass == .compact && isPortrait {

Tusker/Screens/Main/NewMainTabBarViewController.swift

@@ -18,6 +18,7 @@ class NewMainTabBarViewController: BaseMainTabBarViewController {
         
         mode = .tabSidebar
         delegate = self
+        sidebar.delegate = self
         tabBar.isSpringLoaded = true
         view.backgroundColor = .appBackground
         
@@ -57,13 +58,33 @@ class NewMainTabBarViewController: BaseMainTabBarViewController {
         case .myProfile:
             root = MyProfileViewController(mastodonController: mastodonController)
         }
-        return EnhancedNavigationViewController(rootViewController: root)
+        let nav: any NavigationControllerProtocol
+        if UIDevice.current.userInterfaceIdiom == .phone {
+            nav = EnhancedNavigationViewController()
+        } else {
+            // TODO: need to figure out how to update the navigation controller if the pref changes
+            switch Preferences.shared.widescreenNavigationMode {
+            case .stack:
+                nav = EnhancedNavigationViewController()
+            case .splitScreen:
+                nav = SplitNavigationController()
+            case .multiColumn:
+                nav = MultiColumnNavigationController()
+            }
+        }
+        nav.viewControllers = [root]
+        return nav
     }
     
     @objc func handleComposeKeyCommand() {
         compose(editing: nil)
     }
     
+    fileprivate func updateViewControllerSafeAreaInsets(_ vc: MultiColumnNavigationController) {
+        // When in sidebar mode, for multi column mode, don't leave an inset for the floating tab bar, because it leaves a massive gap.
+        // The floating tab bar seems to always be 88pt tall, regardless of, e.g., Dynamic Type size.
+        vc.additionalSafeAreaInsets = UIEdgeInsets(top: sidebar.isHidden ? 0 : -88, left: 0, bottom: 0, right: 0)
+    }
 }
 
 @available(iOS 18.0, *)
@@ -112,12 +133,12 @@ extension NewMainTabBarViewController: UITabBarControllerDelegate {
     func tabBarController(_ tabBarController: UITabBarController, shouldSelectTab tab: UITab) -> Bool {
         if tab.identifier == Tab.compose.rawValue {
             let currentTab = selectedTab
-            compose(editing: nil) {
             // returning false for shouldSelectTab doesn't prevent the UITabBar from being updated (FB14857254)
             // but we need it to change to _something_ so that we can change back to the current tab
             self.selectedTab = tab
             self.selectedTab = currentTab
-            }
+            
+            compose(editing: nil)
             return false
         } else if let selectedTab,
                   selectedTab == tab,
@@ -130,6 +151,24 @@ extension NewMainTabBarViewController: UITabBarControllerDelegate {
             return true
         }
     }
+    
+    func tabBarController(_ tabBarController: UITabBarController, didSelectTab newTab: UITab, previousTab: UITab?) {
+        if let vc = newTab.viewController as? MultiColumnNavigationController {
+            self.updateViewControllerSafeAreaInsets(vc)
+        }
+    }
+}
+
+@available(iOS 18.0, *)
+extension NewMainTabBarViewController: UITabBarController.Sidebar.Delegate {
+    func tabBarController(_ tabBarController: UITabBarController, sidebarVisibilityWillChange sidebar: UITabBarController.Sidebar, animator: any UITabBarController.Sidebar.Animating) {
+        if let vc = selectedViewController as? MultiColumnNavigationController {
+            animator.addAnimations {
+                self.updateViewControllerSafeAreaInsets(vc)
+                vc.view.layoutIfNeeded()
+            }
+        }
+    }
 }
 
 @available(iOS 18.0, *)

Tusker/Screens/Utilities/MultiColumnNavigationController.swift

@@ -155,7 +155,7 @@ class MultiColumnNavigationController: UIViewController {
         if columnFrame.maxX < scrollView.bounds.width - scrollView.adjustedTrailingContentInset {
             offset = -scrollView.adjustedLeadingContentInset
         } else {
-            offset = columnFrame.minX + scrollView.adjustedLeadingContentInset - (scrollView.bounds.width - columnFrame.width)
+            offset = scrollView.contentSize.width - scrollView.bounds.width + scrollView.adjustedTrailingContentInset
         }
         scrollView.setContentOffset(CGPoint(x: offset, y: -scrollView.adjustedContentInset.top), animated: animated)
     }
@@ -185,6 +185,11 @@ class MultiColumnNavigationController: UIViewController {
         }
         animator.startAnimation()
     }
+    
+    // blergh, overriding private method on UIViewController
+    @objc func _shouldOverlayTabBar() -> Bool {
+        false
+    }
 }
 
 extension MultiColumnNavigationController: NavigationControllerProtocol {