Jumping to an unread message did not keep scroll location (#534)

* Jumping to an unread message did not set the scroll location to the first unread message

* Wait for channel to load before allowing reading messages

* Show scroll to last message button after jumping. Disable animations when paginating messages

* Mark as read when scrolling to the last message

Author: laevandus

CHANGELOG.md

@@ -8,6 +8,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### 🐞 Fixed
 - Smoother and more performant view updates in channel and message lists [#522](https://github.com/GetStream/stream-chat-swiftui/pull/522)
+- Fix scrolling location when jumping to a message not in the currently loaded message list [#533](https://github.com/GetStream/stream-chat-swiftui/pull/533)
 
 # [4.58.0](https://github.com/GetStream/stream-chat-swiftui/releases/tag/4.58.0)
 _June 27, 2024_

Sources/StreamChatSwiftUI/ChatChannel/ChatChannelViewModel.swift

@@ -35,7 +35,8 @@ open class ChatChannelViewModel: ObservableObject, MessagesDataSource {
 
     private var isActive = true
     private var readsString = ""
-    private var canMarkRead = true
+    private var canMarkRead = false
+    private var hasSetInitialCanMarkRead = false
 
     private let messageListDateOverlay: DateFormatter = DateFormatter.messageListDateOverlay
 
@@ -44,7 +45,7 @@ open class ChatChannelViewModel: ObservableObject, MessagesDataSource {
 
     private var loadingPreviousMessages: Bool = false
     private var loadingMessagesAround: Bool = false
-    private var lastMessageRead: String?
+    private var scrollsToUnreadAfterJumpToMessage = false
     private var disableDateIndicator = false
     private var channelName = ""
     private var onlineIndicatorShown = false
@@ -245,25 +246,21 @@ open class ChatChannelViewModel: ObservableObject, MessagesDataSource {
             updateScrolledIdToNewestMessage()
         } else {
             channelDataSource.loadFirstPage { [weak self] _ in
-                self?.scrolledId = self?.messages.first?.messageId
+                DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
+                    self?.scrolledId = self?.messages.first?.messageId
+                    self?.showScrollToLatestButton = false
+                }
             }
         }
     }
 
     public func jumpToMessage(messageId: String) -> Bool {
         if messageId == .unknownMessageId {
             if firstUnreadMessageId == nil, let lastReadMessageId {
-                channelDataSource.loadPageAroundMessageId(lastReadMessageId) { [weak self] error in
+                scrollsToUnreadAfterJumpToMessage = true
+                channelDataSource.loadPageAroundMessageId(lastReadMessageId) { error in
                     if error != nil {
                         log.error("Error loading messages around message \(messageId)")
-                        return
-                    }
-                    if let firstUnread = self?.channelDataSource.firstUnreadMessageId,
-                       let message = self?.channelController.dataStore.message(id: firstUnread) {
-                        self?.firstUnreadMessageId = message.messageId
-                        DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
-                            self?.scrolledId = message.messageId
-                        }
                     }
                 }
             }
@@ -338,13 +335,13 @@ open class ChatChannelViewModel: ObservableObject, MessagesDataSource {
         } else {
             checkForNewerMessages(index: index)
         }
-        if let firstUnreadMessageId, firstUnreadMessageId.contains(message.id) {
+        if let firstUnreadMessageId, firstUnreadMessageId.contains(message.id), hasSetInitialCanMarkRead {
             canMarkRead = true
         }
         if utils.messageListConfig.dateIndicatorPlacement == .overlay {
             save(lastDate: message.createdAt)
         }
-        if index == 0 {
+        if index == 0, channelDataSource.hasLoadedAllNextMessages {
             let isActive = UIApplication.shared.applicationState == .active
             if isActive && canMarkRead {
                 sendReadEventIfNeeded(for: message)
@@ -427,6 +424,17 @@ open class ChatChannelViewModel: ObservableObject, MessagesDataSource {
 
         refreshMessageListIfNeeded()
 
+        // Jump to a message but we were already scrolled to the bottom
+        if !channelDataSource.hasLoadedAllNextMessages {
+            showScrollToLatestButton = true
+        }
+        
+        // Set scroll id after the message id has changed
+        if scrollsToUnreadAfterJumpToMessage, let firstUnreadMessageId {
+            scrollsToUnreadAfterJumpToMessage = false
+            scrolledId = firstUnreadMessageId
+        }
+        
         if !showScrollToLatestButton && scrolledId == nil && !loadingNextMessages {
             updateScrolledIdToNewestMessage()
         }
@@ -441,6 +449,7 @@ open class ChatChannelViewModel: ObservableObject, MessagesDataSource {
         checkTypingIndicator()
         checkHeaderType()
         checkOnlineIndicator()
+        checkUnreadCount()
     }
 
     public func showReactionOverlay(for view: AnyView) {
@@ -472,31 +481,29 @@ open class ChatChannelViewModel: ObservableObject, MessagesDataSource {
     // MARK: - private
 
     private func checkForOlderMessages(index: Int) {
-        if index < channelDataSource.messages.count - 25 {
-            return
-        }
-
+        guard index >= channelDataSource.messages.count - 25 else { return }
+        guard !loadingPreviousMessages else { return }
+        guard !channelController.hasLoadedAllPreviousMessages else { return }
+        
         log.debug("Loading previous messages")
-        if !loadingPreviousMessages {
-            loadingPreviousMessages = true
-            channelDataSource.loadPreviousMessages(
-                before: nil,
-                limit: utils.messageListConfig.pageSize,
-                completion: { [weak self] _ in
-                    guard let self = self else { return }
+        loadingPreviousMessages = true
+        channelDataSource.loadPreviousMessages(
+            before: nil,
+            limit: utils.messageListConfig.pageSize,
+            completion: { [weak self] _ in
+                guard let self = self else { return }
+                DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
                     self.loadingPreviousMessages = false
                 }
-            )
-        }
+            }
+        )
     }
 
     private func checkForNewerMessages(index: Int) {
-        if channelDataSource.hasLoadedAllNextMessages {
-            return
-        }
-        if loadingNextMessages || (index > 5) {
-            return
-        }
+        guard index <= 5 else { return }
+        guard !loadingNextMessages else { return }
+        guard !channelController.hasLoadedAllNextMessages else { return }
+        
         loadingNextMessages = true
 
         if scrollPosition != messages.first?.messageId {
@@ -529,13 +536,11 @@ open class ChatChannelViewModel: ObservableObject, MessagesDataSource {
     }
 
     private func sendReadEventIfNeeded(for message: ChatMessage) {
-        if message.id != lastMessageRead {
-            lastMessageRead = message.id
-            throttler.throttle { [weak self] in
-                self?.channelController.markRead()
-                DispatchQueue.main.async {
-                    self?.firstUnreadMessageId = nil
-                }
+        guard let channel, channel.unreadCount.messages > 0 else { return }
+        throttler.throttle { [weak self] in
+            self?.channelController.markRead()
+            DispatchQueue.main.async {
+                self?.firstUnreadMessageId = nil
             }
         }
     }
@@ -633,7 +638,14 @@ open class ChatChannelViewModel: ObservableObject, MessagesDataSource {
 
     private func checkUnreadCount() {
         guard !isMessageThread else { return }
-        if channelController.channel?.unreadCount.messages ?? 0 > 0 {
+        
+        guard let channel = channelController.channel else { return }
+        // Delay marking any messages as read until channel has loaded for the first time (slow internet + observer delay)
+        guard !hasSetInitialCanMarkRead else { return }
+        hasSetInitialCanMarkRead = true
+        canMarkRead = true
+        
+        if channel.unreadCount.messages > 0 {
             if channelController.firstUnreadMessageId != nil {
                 firstUnreadMessageId = channelController.firstUnreadMessageId
                 canMarkRead = false
@@ -657,7 +669,13 @@ open class ChatChannelViewModel: ObservableObject, MessagesDataSource {
     }
 
     private func shouldAnimate(changes: [ListChange<ChatMessage>]) -> Bool {
-        if !utils.messageListConfig.messageDisplayOptions.animateChanges || loadingNextMessages {
+        if !utils.messageListConfig.messageDisplayOptions.animateChanges {
+            return false
+        }
+        if loadingMessagesAround || loadingPreviousMessages || loadingNextMessages {
+            return false
+        }
+        if channelController.channel == nil {
             return false
         }
 

Sources/StreamChatSwiftUI/ChatChannel/MessageList/MessageListView.swift

@@ -230,8 +230,8 @@ public struct MessageListView<Factory: ViewFactory>: View, KeyboardReadable {
                             } else if diff < 0 && scrollDirection == .down {
                                 scrollDirection = .up
                             }
+                            utils.messageCachingUtils.scrollOffset = offsetValue
                         }
-                        utils.messageCachingUtils.scrollOffset = offsetValue
                         let scrollButtonShown = offsetValue < -20
                         if scrollButtonShown != showScrollToLatestButton {
                             showScrollToLatestButton = scrollButtonShown