improved performance and battery usage on older devices

lib/view/pages/talk/widgets/chat_tile.dart

@@ -68,15 +68,25 @@ class _ChatTileState extends State<ChatTile> {
   /// One-line preview of the last message: rich-object placeholders resolved,
   /// newlines flattened and — for Markdown messages — formatting stripped so
   /// the list shows readable text rather than raw markers.
+  ///
+  /// Memoised per last message: the tile rebuilds on every chat-list emit and
+  /// the Markdown strip is a full parse. Keyed by content, since every refresh
+  /// delivers new message objects.
   String _lastMessagePreview() {
     final last = widget.data.lastMessage;
+    final key = (last.id, last.message, last.markdown);
+    if (key == _previewFor) return _preview;
     final text = RichObjectStringProcessor.parseToString(
       last.message.replaceAll('\n', ' '),
       last.messageParameters,
     );
-    return last.markdown ? markdownToPlainText(text) : text;
+    _previewFor = key;
+    return _preview = last.markdown ? markdownToPlainText(text) : text;
   }
 
+  Object? _previewFor;
+  String _preview = '';
+
   Future<void> _setCurrentAsRead() async {
     final token = widget.data.token;
     final lastId = widget.data.lastMessage.id;
@@ -89,7 +99,11 @@ class _ChatTileState extends State<ChatTile> {
 
   @override
   Widget build(BuildContext context) {
-    final chatBloc = context.watch<ChatBloc>();
+    // Only the open token matters here (split-view highlight); watching the
+    // whole bloc rebuilt every tile on each message of the open chat.
+    final currentToken = context.select(
+      (ChatBloc b) => b.state.data?.currentToken,
+    );
     final isGroup =
         widget.data.type != GetRoomResponseObjectConversationType.oneToOne;
     final circleAvatar = UserAvatar(
@@ -100,7 +114,7 @@ class _ChatTileState extends State<ChatTile> {
     return ListTile(
       style: ListTileStyle.list,
       tileColor:
-          chatBloc.state.data?.currentToken == widget.data.token &&
+          currentToken == widget.data.token &&
               TalkNavigator.isSecondaryVisible(context)
           ? Theme.of(context).primaryColor.withAlpha(100)
           : null,