chore: Adjust styles and animations

lib/pages/chat/chat.dart

@@ -462,21 +462,18 @@ class ChatController extends State<ChatPageWithRoom>
     scrollUpBannerEventId = eventId;
   });
 
+  bool firstUpdateReceived = false;
+
   void updateView() {
     if (!mounted) return;
     setReadMarker();
-    setState(() {});
+    setState(() {
+      firstUpdateReceived = true;
+    });
   }
 
   Future<void>? loadTimelineFuture;
 
-  int? animateInEventIndex;
-
-  void onInsert(int i) {
-    // setState will be called by updateView() anyway
-    if (timeline?.allowNewEvent == true) animateInEventIndex = i;
-  }
-
   Future<void> _getTimeline({String? eventContextId}) async {
     await Matrix.of(context).client.roomsLoading;
     await Matrix.of(context).client.accountDataLoading;
@@ -489,15 +486,11 @@ class ChatController extends State<ChatPageWithRoom>
       timeline = await room.getTimeline(
         onUpdate: updateView,
         eventContextId: eventContextId,
-        onInsert: onInsert,
       );
     } catch (e, s) {
       Logs().w('Unable to load timeline on event ID $eventContextId', e, s);
       if (!mounted) return;
-      timeline = await room.getTimeline(
-        onUpdate: updateView,
-        onInsert: onInsert,
-      );
+      timeline = await room.getTimeline(onUpdate: updateView);
       if (!mounted) return;
       if (e is TimeoutException || e is IOException) {
         _showScrollUpMaterialBanner(eventContextId!);

lib/pages/chat/chat_event_list.dart

@@ -35,7 +35,6 @@ class ChatEventList extends StatelessWidget {
     final events = timeline.events.filterByVisibleInGui(
       threadId: controller.activeThreadId,
     );
-    final animateInEventIndex = controller.animateInEventIndex;
 
     // create a map of eventId --> index to greatly improve performance of
     // ListView's findChildIndexCallback
@@ -120,10 +119,7 @@ class ChatEventList extends StatelessWidget {
 
             // The message at this index:
             final event = events[i];
-            final animateIn =
-                animateInEventIndex != null &&
-                timeline.events.length > animateInEventIndex &&
-                event == timeline.events[animateInEventIndex];
+            final animateIn = i == 0 && controller.firstUpdateReceived;
 
             final nextEvent = i + 1 < events.length ? events[i + 1] : null;
             final previousEvent = i > 0 ? events[i - 1] : null;
@@ -139,16 +135,13 @@ class ChatEventList extends StatelessWidget {
                 !controller.expandedEventIds.contains(event.eventId);
 
             return AutoScrollTag(
-              key: ValueKey(event.eventId),
+              key: ValueKey(event.transactionId ?? event.eventId),
               index: i,
               controller: controller.scrollController,
               child: Message(
                 event,
                 bigEmojis: controller.bigEmojis,
                 animateIn: animateIn,
-                resetAnimateIn: () {
-                  controller.animateInEventIndex = null;
-                },
                 onSwipe: () => controller.replyAction(replyTo: event),
                 onInfoTab: controller.showEventInfo,
                 onMention: () => controller.sendController.text +=