Explore using UITableView for the scrolling list

Individual rows still use the new SwiftUI layout.

This makes scrolling feel smoother, since changes to row heights as content loads are animated in a way that makes sense rather than jumping the scroll.

Post interaction is broken, will need to be restored.

Contributes to IOS-409

Author: whattherestimefor

Mastodon.xcodeproj/project.pbxproj

@@ -1309,6 +1309,7 @@
 				Notifications/NotificationRowViewModel.swift,
 				Notifications/NotificationsCacheManager.swift,
 				Timeline/HomeTimelineListViewController.swift,
+				Timeline/HomeTimelineTableViewController.swift,
 				Timeline/TimelineFeedLoader.swift,
 			);
 			target = DB427DD125BAA00100D1B89D /* Mastodon */;

Mastodon/In Progress New Layout and Datamodel/Timeline/HomeTimelineListViewController.swift

@@ -336,7 +336,7 @@ enum MastodonTimelineOverlayView {
 }
 
 @MainActor
-private class HomeTimelineListViewModel: ObservableObject {
+class HomeTimelineListViewModel: ObservableObject {
     public var parentVcPresentScene: ((SceneCoordinator.Scene, SceneCoordinator.Transition) -> ())?
     private var authenticatedUser: MastodonAuthenticationBox?
     private var instanceConfiguration: MastodonAuthentication.InstanceConfiguration?
@@ -375,7 +375,7 @@ private class HomeTimelineListViewModel: ObservableObject {
     private var feedLoaderResultsSubscription: AnyCancellable?
     private var feedLoaderErrorSubscription: AnyCancellable?
 
-    var scrollManager: ScrollManager?
+    fileprivate var scrollManager: ScrollManager?
 
     private var tailItemIds = [String]()
     private let displayPrepBatchSize = 10
@@ -1049,8 +1049,8 @@ extension MastodonTimelineOverlayView {
     }
 }
 
-private struct HomeTimelinePostRowView: View {
-
+struct HomeTimelinePostRowView: View {
+    
     @Environment(MastodonPostViewModel.self) private var viewModel
     @ObservedObject var contentConcealModel: ContentConcealViewModel
     let contentWidth: CGFloat
@@ -1066,7 +1066,7 @@ private struct HomeTimelinePostRowView: View {
             viewModel.socialContextHeader
 
             HStack(alignment: .top) {
-            
+                
                 AvatarView(size: .large, authorAvatarUrl: author?.avatarURL ?? viewModel.initialDisplayInfo.actionableAuthorStaticAvatar, goToProfile: {
                     goToProfile(author)
                 })
@@ -1144,7 +1144,7 @@ private struct HomeTimelinePostRowView: View {
         }
     }
 
-    @ViewBuilder func componentView(_ component: PostViewComponent) -> some View {
+    @ViewBuilder fileprivate func componentView(_ component: PostViewComponent) -> some View {
         switch component {
         case .content(let string):
             PostContentView(text: string)

Mastodon/In Progress New Layout and Datamodel/Timeline/HomeTimelineTableViewController.swift

@@ -0,0 +1,106 @@
+// Copyright © 2025 Mastodon gGmbH. All rights reserved.
+
+import Combine
+import SwiftUI
+import UIKit
+
+private enum Section {
+    case main
+}
+
+private var avatarSize = AvatarSize.large
+
+@MainActor
+class HomeTimelineTableViewController: UITableViewController {
+
+    var viewModel = HomeTimelineListViewModel(timeline: .following)
+    fileprivate var datasource: TimelineDataSource?
+    fileprivate var viewModelSubscriptions = Set<AnyCancellable>()
+    
+    init() {
+        super.init(style: .plain)
+        
+        viewModel.$timelineItems.sink { [weak self] items in
+            guard let self else { return }
+            var replacementSnapshot = NSDiffableDataSourceSnapshot<Section, TimelineItem>()
+            replacementSnapshot.appendSections([.main])
+            replacementSnapshot.appendItems(items)
+            datasource?.apply(replacementSnapshot)
+            
+            if items.count > 10 {
+                DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(100)) {
+                    self.tableView.scrollToRow(at: IndexPath(row: items.count / 2, section: 0), at: .top, animated: false)
+                }
+            }
+        }.store(in: &viewModelSubscriptions)
+    }
+    
+    override func viewDidLoad() {
+        tableView.delegate = self
+        tableView.register(MastodonPostRowHostingCell.self, forCellReuseIdentifier: "cell")
+        datasource = TimelineDataSource(tableView: tableView, cellProvider: { [weak self] tableView, indexPath, itemIdentifier in
+            guard let self else { return UITableViewCell() }
+            let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! MastodonPostRowHostingCell
+            cell.contentWidth = self.postContentWidth(for: self.view.frame.size.width)
+            switch itemIdentifier {
+            case .loadingIndicator, .missingPosts:
+                cell.configureToShowSomething()
+            case .post(let viewModel):
+                cell.viewModel = viewModel
+            }
+            return cell
+        })
+        tableView.dataSource = datasource
+        
+        var snapshot = datasource?.snapshot()
+        snapshot?.appendSections([.main])
+        datasource?.apply(snapshot!)
+    }
+    
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+    
+    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
+        super.viewWillTransition(to: size, with: coordinator)
+        if let snapshot = datasource?.snapshot() {
+            datasource?.applySnapshotUsingReloadData(snapshot)
+        }
+    }
+    
+    func postContentWidth(for viewWidth: CGFloat) -> CGFloat {
+        let usableWidth = viewWidth
+        let contentWidth = max(1, usableWidth - (spacingBetweenGutterAndContent * 3) - avatarSize)
+        return contentWidth
+    }
+}
+
+class MastodonPostRowHostingCell: UITableViewCell {
+    var contentWidth: CGFloat = 10
+    var widthConstraint: NSLayoutConstraint?
+    
+    var viewModel: MastodonPostViewModel? {
+        didSet {
+            self.contentView.backgroundColor = .clear
+            self.contentConfiguration = UIHostingConfiguration(content: {
+                HomeTimelinePostRowView(contentConcealModel: .alwaysShow,
+                                        contentWidth: contentWidth)
+                .environment(viewModel)
+            })
+        }
+    }
+    
+    func configureToShowSomething() {
+        self.contentView.backgroundColor = .yellow
+        if self.widthConstraint == nil {
+            widthConstraint = widthAnchor.constraint(equalToConstant: contentWidth)
+            NSLayoutConstraint.activate([widthConstraint!])
+        }
+        widthConstraint?.constant = contentWidth
+        setNeedsUpdateConstraints()
+    }
+}
+
+fileprivate class TimelineDataSource: UITableViewDiffableDataSource<Section, TimelineItem> {
+    var contentWidth: CGFloat = 10
+}

Mastodon/Scene/Root/MainTab/MainTabBarController.swift

@@ -52,7 +52,8 @@ class MainTabBarController: UITabBarController {
         self.authenticationBox = authenticationBox
 
         if UserDefaults.standard.testNewHomeTimeline {
-            homeTimelineViewController = HomeTimelineListViewController()
+            homeTimelineViewController = HomeTimelineTableViewController()
+            // homeTimelineViewController = HomeTimelineListViewController()
         } else {
             homeTimelineViewController = HomeTimelineViewController()
         }