Bugfix FXIOS-10756 App hangs while opening Tab Tray when there are many tabs open

firefox-ios/Client/Frontend/Browser/SwipeAnimator.swift

@@ -75,13 +75,15 @@ extension SwipeAnimator {
         // Calculate the edge to calculate distance from
         let translation = velocity.x >= 0 ? animatingView.frame.width : -animatingView.frame.width
         let timeStep = TimeInterval(abs(translation) / speed)
-        self.delegate?.swipeAnimator(self)
         UIView.animate(
             withDuration: timeStep,
             animations: {
                 animatingView.transform = self.transformForTranslation(translation)
                 animatingView.alpha = self.alphaForDistanceFromCenter(abs(translation))
-            }, completion: { finished in
+            }, completion: { [weak self] finished in
+                if let self {
+                    delegate?.swipeAnimator(self)
+                }
                 if finished {
                     animatingView.alpha = 0
                 }

firefox-ios/Client/Frontend/Browser/Tabs/Views/TabCell.swift

@@ -40,7 +40,7 @@ class TabCell: UICollectionViewCell, ThemeApplicable, ReusableCell {
 
     private lazy var smallFaviconView: FaviconImageView = .build()
     private lazy var favicon: FaviconImageView = .build()
-    private var headerView = UIVisualEffectView(effect: UIBlurEffect(style: .dark))
+    private lazy var headerView = UIVisualEffectView(effect: UIBlurEffect(style: .dark))
 
     // MARK: - UI
 
@@ -82,8 +82,8 @@ class TabCell: UICollectionViewCell, ThemeApplicable, ReusableCell {
 
     override init(frame: CGRect) {
         super.init(frame: frame)
-        self.animator = SwipeAnimator(animatingView: self)
-        self.closeButton.addTarget(self, action: #selector(close), for: .touchUpInside)
+        animator = SwipeAnimator(animatingView: self)
+        closeButton.addTarget(self, action: #selector(close), for: .touchUpInside)
 
         contentView.addSubview(backgroundHolder)
 
@@ -92,14 +92,14 @@ class TabCell: UICollectionViewCell, ThemeApplicable, ReusableCell {
 
         accessibilityCustomActions = [
             UIAccessibilityCustomAction(name: .TabTrayCloseAccessibilityCustomAction,
-                                        target: self.animator,
+                                        target: animator,
                                         selector: #selector(SwipeAnimator.closeWithoutGesture))
         ]
 
         headerView.translatesAutoresizingMaskIntoConstraints = false
-        headerView.contentView.addSubview(self.closeButton)
-        headerView.contentView.addSubview(self.titleText)
-        headerView.contentView.addSubview(self.favicon)
+        headerView.contentView.addSubview(closeButton)
+        headerView.contentView.addSubview(titleText)
+        headerView.contentView.addSubview(favicon)
 
         setupConstraints()
     }
@@ -112,7 +112,7 @@ class TabCell: UICollectionViewCell, ThemeApplicable, ReusableCell {
         self.delegate = delegate
 
         if let swipeAnimatorDelegate = delegate as? SwipeAnimatorDelegate {
-            self.animator?.delegate = swipeAnimatorDelegate
+            animator?.delegate = swipeAnimatorDelegate
         }
 
         animator?.animateBackToCenter()

firefox-ios/Client/Frontend/Browser/Tabs/Views/TabDisplayPanelViewController.swift

@@ -72,7 +72,6 @@ class TabDisplayPanelViewController: UIViewController,
         super.viewWillAppear(animated)
 
         if !viewHasAppeared {
-            tabDisplayView.layoutIfNeeded()
             store.dispatch(TabPanelViewAction(panelType: panelType,
                                               windowUUID: windowUUID,
                                               actionType: TabPanelViewActionType.tabPanelWillAppear))
@@ -162,6 +161,8 @@ class TabDisplayPanelViewController: UIViewController,
     }
 
     func newState(state: TabsPanelState) {
+        guard state != tabsState else { return }
+
         tabsState = state
         tabDisplayView.newState(state: tabsState)
         shouldShowEmptyView(tabsState.isPrivateTabsEmpty)

firefox-ios/Client/Frontend/Browser/Tabs/Views/TabDisplayView.swift

@@ -127,19 +127,14 @@ class TabDisplayView: UIView,
     private func scrollToTab(_ scrollState: TabsPanelState.ScrollState) {
         let section: Int = scrollState.isInactiveTabSection ? 0 : 1
         let indexPath = IndexPath(row: scrollState.toIndex, section: section)
-
-        // We cannot get the visible cells unless all layout operations have finished finished (e.g. after `reloadData()`)
-        collectionView.layoutIfNeeded()
-
-        // Only scroll to the view if it is not visible.
-        guard !collectionView.indexPathsForFullyVisibleItems.contains(indexPath) else { return }
-
-        // Scrolling to an invalid cell will crash the app, so check indexPath first
-        guard collectionView.isValid(indexPath: indexPath) else { return }
-
-        collectionView.scrollToItem(at: indexPath,
-                                    at: .centeredVertically,
-                                    animated: scrollState.withAnimation)
+        // Piping this into main thread let the collection view finish its layout process
+        DispatchQueue.main.async {
+            guard !self.collectionView.indexPathsForFullyVisibleItems.contains(indexPath) else { return }
+            guard self.collectionView.isValid(indexPath: indexPath) else { return }
+            self.collectionView.scrollToItem(at: indexPath,
+                                             at: .centeredVertically,
+                                             animated: scrollState.withAnimation)
+        }
     }
 
     private func configureDataSource() {

firefox-ios/Client/Frontend/Browser/Tabs/Views/TabTrayViewController.swift

@@ -291,9 +291,12 @@ class TabTrayViewController: UIViewController,
     }
 
     func newState(state: TabTrayState) {
+        guard state != tabTrayState else { return }
+
         tabTrayState = state
-        updateTabCountImage(count: state.normalTabsCount)
-        segmentedControl.selectedSegmentIndex = state.selectedPanel.rawValue
+
+        updateTabCountImage(count: tabTrayState.normalTabsCount)
+        segmentedControl.selectedSegmentIndex = tabTrayState.selectedPanel.rawValue
 
         if tabTrayState.shouldDismiss {
             delegate?.didFinish()
@@ -303,7 +306,7 @@ class TabTrayViewController: UIViewController,
             showCloseAllConfirmation()
         }
 
-        if let toastType = state.toastType {
+        if let toastType = tabTrayState.toastType {
             presentToast(toastType: toastType) { [weak self] undoClose in
                 guard let self else { return }