improved performance and battery usage on older devices

lib/view/pages/talk/chat_view.dart

@@ -14,6 +14,7 @@ import '../../../state/app/infrastructure/loadable_state/view/loadable_state_con
 import '../../../state/app/modules/chat/bloc/chat_bloc.dart';
 import '../../../state/app/modules/chat/bloc/chat_state.dart';
 import '../../../state/app/modules/chat_list/bloc/chat_list_bloc.dart';
+import '../../../utils/debouncer.dart';
 import '../../../widget/chat_background.dart';
 import '../../../widget/clickable_app_bar.dart';
 import '../../../widget/user_avatar.dart';
@@ -118,6 +119,7 @@ class _ChatViewState extends State<ChatView> with RouteAware {
     _markAsReadFinal();
     _chatBlocRef?.leaveChat(widget.room.token);
     _searchTextController.dispose();
+    Debouncer.cancel(_searchDebounceTag);
     super.dispose();
   }
 
@@ -150,6 +152,45 @@ class _ChatViewState extends State<ChatView> with RouteAware {
     context.read<ChatBloc>().setToken(widget.room.token);
   }
 
+  void _refetch({bool renew = false}) => _refresh();
+
+  // The built rows only depend on the chat data and the search state; the list
+  // itself rebuilds far more often (loading flips, keyboard, parent rebuilds),
+  // and re-sorting plus re-creating every bubble each time is wasted work.
+  Object? _itemsKey;
+  List<Widget> _items = const [];
+
+  List<Widget> _itemsFor(ChatState state) {
+    final key = (
+      state.chatResponse,
+      state.isLoadingOlder,
+      state.hasMoreOld,
+      _searchActive,
+      _searchQuery,
+      _activeMatchIndex,
+      widget.room,
+    );
+    if (key == _itemsKey) return _items;
+    _itemsKey = key;
+    final items = _buildMessages(state.chatResponse!).reversed.toList();
+    // reverse:true renders index 0 at the bottom, so the top marker
+    // (spinner / start-of-chat) goes at the end.
+    if (state.isLoadingOlder) {
+      items.add(const _LoadingOlderIndicator());
+    } else if (!state.hasMoreOld) {
+      items.add(
+        ChatBubble(
+          key: const ValueKey('chat-start'),
+          isSender: false,
+          bubbleData: GetChatResponseObject.getTextDummy('Anfang des Chats'),
+          chatData: widget.room,
+          refetch: _refetch,
+        ),
+      );
+    }
+    return _items = items;
+  }
+
   void _enterSearchMode() {
     setState(() {
       _searchActive = true;
@@ -163,6 +204,7 @@ class _ChatViewState extends State<ChatView> with RouteAware {
   }
 
   void _exitSearchMode() {
+    Debouncer.cancel(_searchDebounceTag);
     setState(() {
       _searchActive = false;
       _searchQuery = '';
@@ -175,7 +217,22 @@ class _ChatViewState extends State<ChatView> with RouteAware {
     });
   }
 
+  late final String _searchDebounceTag =
+      'chat-search-${identityHashCode(this)}';
+
+  /// Matching re-scans the whole history and rebuilds every row, so it runs
+  /// once typing pauses instead of per keystroke.
   void _onSearchChanged(String q) {
+    Debouncer.debounce(
+      _searchDebounceTag,
+      const Duration(milliseconds: 200),
+      () {
+        if (mounted) _applySearch(q);
+      },
+    );
+  }
+
+  void _applySearch(String q) {
     final chatResponse = context.read<ChatBloc>().state.data?.chatResponse;
     setState(() {
       _searchQuery = q;
@@ -268,9 +325,13 @@ class _ChatViewState extends State<ChatView> with RouteAware {
         messages.add(
           ChatBubble(
             isSender: false,
+            key: ValueKey(
+              'day-${elementDate.year}-${elementDate.month}-'
+              '${elementDate.day}',
+            ),
             bubbleData: GetChatResponseObject.getDateDummy(element.timestamp),
             chatData: widget.room,
-            refetch: ({bool renew = false}) => _refresh(),
+            refetch: _refetch,
           ),
         );
       }
@@ -286,6 +347,7 @@ class _ChatViewState extends State<ChatView> with RouteAware {
 
       messages.add(
         ChatBubble(
+          key: ValueKey(element.id),
           isSender:
               element.actorId == widget.selfId &&
               (element.messageType ==
@@ -294,7 +356,7 @@ class _ChatViewState extends State<ChatView> with RouteAware {
                       GetRoomResponseObjectMessageType.deletedComment),
           bubbleData: element,
           chatData: widget.room,
-          refetch: ({bool renew = false}) => _refresh(),
+          refetch: _refetch,
           isRead: element.id <= commonRead,
           selfId: widget.selfId,
           highlightQuery: highlightQuery,
@@ -317,17 +379,7 @@ class _ChatViewState extends State<ChatView> with RouteAware {
 
   @override
   Widget build(BuildContext context) {
-    // Swallow the first back gesture while the keyboard is visible so it
-    // dismisses the IME instead of popping the chat — matches platform UX
-    // expectations (e.g. WhatsApp/Telegram) and prevents accidental exits
-    // mid-typing.
-    final keyboardOpen = MediaQuery.viewInsetsOf(context).bottom > 0;
-    return PopScope(
-      canPop: !keyboardOpen,
-      onPopInvokedWithResult: (didPop, _) {
-        if (didPop) return;
-        FocusManager.instance.primaryFocus?.unfocus();
-      },
+    return _KeyboardDismissPopScope(
       child: Scaffold(
         backgroundColor: const Color(0xffefeae2),
         appBar: _searchActive
@@ -376,25 +428,7 @@ class _ChatViewState extends State<ChatView> with RouteAware {
                       state.currentToken == widget.room.token,
                   enablePullToRefresh: false,
                   child: (state, _) {
-                    final items = _buildMessages(
-                      state.chatResponse!,
-                    ).reversed.toList();
-                    // reverse:true renders index 0 at the bottom, so the top
-                    // marker (spinner / start-of-chat) goes at the end.
-                    if (state.isLoadingOlder) {
-                      items.add(const _LoadingOlderIndicator());
-                    } else if (!state.hasMoreOld) {
-                      items.add(
-                        ChatBubble(
-                          isSender: false,
-                          bubbleData: GetChatResponseObject.getTextDummy(
-                            'Anfang des Chats',
-                          ),
-                          chatData: widget.room,
-                          refetch: ({bool renew = false}) => _refresh(),
-                        ),
-                      );
-                    }
+                    final items = _itemsFor(state);
                     _itemCount = items.length;
                     return ScrollablePositionedList.builder(
                       reverse: true,
@@ -448,3 +482,27 @@ class _LoadingOlderIndicator extends StatelessWidget {
     ),
   );
 }
+
+/// Swallows the first back gesture while the keyboard is visible so it
+/// dismisses the IME instead of popping the chat — matches platform UX
+/// expectations (e.g. WhatsApp/Telegram) and prevents accidental exits
+/// mid-typing. A separate widget so the per-frame inset changes during the
+/// keyboard animation only rebuild this scope, not the whole chat.
+class _KeyboardDismissPopScope extends StatelessWidget {
+  final Widget child;
+
+  const _KeyboardDismissPopScope({required this.child});
+
+  @override
+  Widget build(BuildContext context) {
+    final keyboardOpen = MediaQuery.viewInsetsOf(context).bottom > 0;
+    return PopScope(
+      canPop: !keyboardOpen,
+      onPopInvokedWithResult: (didPop, _) {
+        if (didPop) return;
+        FocusManager.instance.primaryFocus?.unfocus();
+      },
+      child: child,
+    );
+  }
+}