Fix multi-column nav not animating scroll position when replacing subsequent columns

Closes #500

Tusker/Screens/Utilities/MultiColumnNavigationController.swift

@@ -11,14 +11,18 @@ import UIKit
 class MultiColumnNavigationController: UIViewController {
     
     private var isManuallyUpdating = false
-    var viewControllers: [UIViewController]  = [] {
-        didSet {
-            guard isViewLoaded,
-                  !isManuallyUpdating else {
-                return
+    private var _viewControllers: [UIViewController] = []
+    var viewControllers: [UIViewController] {
+        get {
+            _viewControllers
+        }
+        set {
+            _viewControllers = newValue
+            if isViewLoaded,
+               !isManuallyUpdating {
+                updateViews()
+                scrollToEnd(animated: false)
             }
-            updateViews()
-            scrollToEnd(animated: false)
         }
     }
     
@@ -68,13 +72,13 @@ class MultiColumnNavigationController: UIViewController {
     
     private func updateViews() {
         var i = 0
-        while i < viewControllers.count {
+        while i < _viewControllers.count {
             let needsCloseButton = i > 0
             if i <= stackView.arrangedSubviews.count - 1 {
                 let existing = stackView.arrangedSubviews[i] as! ColumnView
-                existing.setContent(viewControllers[i], needsCloseButton: needsCloseButton)
+                existing.setContent(_viewControllers[i], needsCloseButton: needsCloseButton)
             } else {
-                let new = ColumnView(owner: self, contentViewController: viewControllers[i], needsCloseButton: needsCloseButton)
+                let new = ColumnView(owner: self, contentViewController: _viewControllers[i], needsCloseButton: needsCloseButton)
                 stackView.addArrangedSubview(new)
             }
             i += 1
@@ -92,7 +96,7 @@ class MultiColumnNavigationController: UIViewController {
             var index: Int? = nil
             var current: UIViewController? = sender
             while let c = current {
-                index = viewControllers.firstIndex(of: c)
+                index = _viewControllers.firstIndex(of: c)
                 if index != nil {
                     break
                 } else {
@@ -112,19 +116,20 @@ class MultiColumnNavigationController: UIViewController {
     }
     
     func replaceViewControllers(_ vcs: [UIViewController], after afterIndex: Int, animated: Bool) {
-        if afterIndex == viewControllers.count - 1 && vcs.count == 1 {
+        if afterIndex == _viewControllers.count - 1 && vcs.count == 1 {
             pushViewController(vcs[0], animated: animated)
         } else {
-            viewControllers = Array(viewControllers[...afterIndex]) + vcs
+            _viewControllers = Array(_viewControllers[...afterIndex]) + vcs
+            updateViews()
             scrollToEnd(animated: animated)
         }
     }
     
     private func scrollToEnd(animated: Bool) {
-        if viewControllers.isEmpty {
+        if _viewControllers.isEmpty {
             scrollView.setContentOffset(.init(x: -scrollView.adjustedLeadingContentInset, y: -scrollView.adjustedContentInset.top), animated: false)
         } else {
-            scrollColumnToEnd(columnIndex: viewControllers.count - 1, animated: animated)
+            scrollColumnToEnd(columnIndex: _viewControllers.count - 1, animated: animated)
         }
     }
     
@@ -142,14 +147,12 @@ class MultiColumnNavigationController: UIViewController {
     }
     
     fileprivate func closeColumn(_ vc: UIViewController) {
-        guard let index = viewControllers.firstIndex(of: vc),
+        guard let index = _viewControllers.firstIndex(of: vc),
               index > 0 else {
             // Can't close the last column
             return
         }
-        isManuallyUpdating = true
-        defer { isManuallyUpdating = false }
-        viewControllers.removeSubrange(index...)
+        _viewControllers.removeSubrange(index...)
         animateChanges {
             for column in self.stackView.arrangedSubviews[index...] {
                 column.layer.opacity = 0
@@ -158,7 +161,6 @@ class MultiColumnNavigationController: UIViewController {
         } completion: {
             self.updateViews()
         }
-
     }
     
     private func animateChanges(_ animations: @escaping () -> Void, completion: (() -> Void)? = nil) {
@@ -173,19 +175,22 @@ class MultiColumnNavigationController: UIViewController {
 
 extension MultiColumnNavigationController: NavigationControllerProtocol {
     var topViewController: UIViewController? {
-        viewControllers.last
+        _viewControllers.last
     }
     
     func popToRootViewController(animated: Bool) -> [UIViewController]? {
-        let removed = Array(viewControllers.dropFirst())
-        viewControllers = [viewControllers.first!]
+        guard !_viewControllers.isEmpty else {
+            return nil
+        }
+        let removed = Array(_viewControllers.dropFirst())
+        _viewControllers = [_viewControllers.first!]
+        updateViews()
+        scrollToEnd(animated: animated)
         return removed
     }
     
     func pushViewController(_ vc: UIViewController, animated: Bool) {
-        isManuallyUpdating = true
-        defer { isManuallyUpdating = false }
-        viewControllers.append(vc)
+        _viewControllers.append(vc)
         updateViews()
         scrollToEnd(animated: animated)
         if animated {