perf(llc, core): guard channel list event handlers against unnecessary re-sorts

packages/stream_chat/CHANGELOG.md

@@ -3,6 +3,7 @@
 ✅ Added
 
 - Added an `upsert` flag to `ChannelClientState.updateMessage` (defaults to `true`). Pass `false` to update a message only if it's already loaded in the state, skipping unknown messages instead of adding them.
+- Added `EventType.userPresenceChanged` (`user.presence.changed`) constant.
 
 🔄 Changed
 

packages/stream_chat/lib/src/event_type.dart

@@ -72,6 +72,9 @@ class EventType {
   /// Event sent when a user is updated
   static const String userUpdated = 'user.updated';
 
+  /// Event sent when a user's presence changes
+  static const String userPresenceChanged = 'user.presence.changed';
+
   /// Event sent when a member is added to a channel
   static const String memberAdded = 'member.added';
 

packages/stream_chat_flutter_core/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - Fixed `StreamChannelListController` not handling `notification.channel_deleted` event.
 - Fixed backwards pagination not working if channel was never opened.
+- Guarded `StreamChannelListController`'s `channel.updated`, `member.updated`, and `user.presence.changed`/`user.updated` event handlers to skip the full list re-sort when the event doesn't affect any listed channel.
 
 ## 10.1.0
 

packages/stream_chat_flutter_core/lib/src/stream_channel_list_controller.dart

@@ -332,7 +332,7 @@ class StreamChannelListController extends PagedValueNotifier<int, Channel> {
         _eventHandler.onNotificationMessageNew(event, this);
       } else if (eventType == EventType.notificationRemovedFromChannel) {
         _eventHandler.onNotificationRemovedFromChannel(event, this);
-      } else if (eventType == 'user.presence.changed' || eventType == EventType.userUpdated) {
+      } else if (eventType == EventType.userPresenceChanged || eventType == EventType.userUpdated) {
         _eventHandler.onUserPresenceChanged(event, this);
       } else if (eventType == EventType.memberUpdated) {
         _eventHandler.onMemberUpdated(event, this);

packages/stream_chat_flutter_core/lib/src/stream_channel_list_event_handler.dart

@@ -48,19 +48,27 @@ mixin class StreamChannelListEventHandler {
   ///
   /// This event is fired when a channel is updated.
   ///
-  /// By default, this updates the channel received in the event.
+  /// By default, this re-sorts the list when the updated channel is present in
+  /// it, and does nothing otherwise.
   void onChannelUpdated(Event event, StreamChannelListController controller) {
-    controller.channels = [...controller.currentItems];
+    final cid = event.cid ?? event.channel?.cid;
+    final channels = controller.currentItems;
+    if (!channels.any((it) => it.cid == cid)) return;
+    controller.channels = [...channels];
   }
 
   /// Function which gets called for the event
   /// [EventType.memberUpdated].
   ///
   /// This event is fired when a member is updated.
   ///
-  /// By default, this sorts the channels.
+  /// By default, this re-sorts the list when the member's channel is present in
+  /// it, and does nothing otherwise.
   void onMemberUpdated(Event event, StreamChannelListController controller) {
-    controller.channels = [...controller.currentItems];
+    final cid = event.cid ?? event.channel?.cid;
+    final channels = controller.currentItems;
+    if (!channels.any((it) => it.cid == cid)) return;
+    controller.channels = [...channels];
   }
 
   /// Function which gets called for the event
@@ -180,11 +188,14 @@ mixin class StreamChannelListEventHandler {
   }
 
   /// Function which gets called for the event
-  /// 'user.presence.changed' and [EventType.userUpdated].
+  /// [EventType.userPresenceChanged] and [EventType.userUpdated].
   ///
   /// This event is fired when a user's presence changes or gets updated.
   ///
-  /// By default, this updates the channel member with the event user.
+  /// By default, this updates the event user in every listed channel where they
+  /// appear — either among the loaded members, or, when the event is about the
+  /// current user, as the channel membership — then re-sorts the list.
+  /// Does nothing when no listed channel references the user.
   void onUserPresenceChanged(
     Event event,
     StreamChannelListController controller,
@@ -194,12 +205,14 @@ mixin class StreamChannelListEventHandler {
 
     final channels = [...controller.currentItems];
 
-    final updatedChannels = channels.map((channel) {
+    var updated = false;
+    for (final channel in channels) {
       final existingMembership = channel.membership;
       final existingMembers = [...channel.state!.members];
 
-      // Return if the user is not a existing member of the channel.
-      if (!existingMembers.any((m) => m.userId == user.id)) return channel;
+      // Leave channels untouched where the user is not an existing member.
+      final containsUser = existingMembership?.userId == user.id || existingMembers.any((m) => m.userId == user.id);
+      if (!containsUser) continue;
 
       Member? maybeUpdateMemberUser(Member? existingMember) {
         if (existingMember == null) return null;
@@ -216,9 +229,12 @@ mixin class StreamChannelListEventHandler {
         ),
       );
 
-      return channel;
-    });
+      updated = true;
+    }
+
+    // Skip the re-sort when no listed channel contained the user.
+    if (!updated) return;
 
-    controller.channels = [...updatedChannels];
+    controller.channels = [...channels];
   }
 }

packages/stream_chat_flutter_core/test/mocks.dart

@@ -1,8 +1,14 @@
 import 'package:mocktail/mocktail.dart';
 import 'package:stream_chat/stream_chat.dart';
+import 'package:stream_chat_flutter_core/src/stream_channel_list_controller.dart';
+import 'package:stream_chat_flutter_core/src/stream_channel_list_event_handler.dart';
 
 class MockLogger extends Mock implements Logger {}
 
+class MockStreamChannelListController extends Mock implements StreamChannelListController {}
+
+class MockStreamChannelListEventHandler extends Mock implements StreamChannelListEventHandler {}
+
 class MockClient extends Mock implements StreamChatClient {
   MockClient() {
     when(() => wsConnectionStatus).thenReturn(ConnectionStatus.connected);