feat: Enhanced timeline

lib/pages/chat/chat.dart

@@ -184,28 +184,21 @@ class ChatController extends State<Chat> {
     setState(() {});
   }
 
-  Future<bool> getTimeline() async {
+  Future<bool> getTimeline({String? eventContextId}) async {
     if (timeline == null) {
+      eventContextId ??= room!.fullyRead;
       await Matrix.of(context).client.roomsLoading;
       await Matrix.of(context).client.accountDataLoading;
-      timeline = await room!.getTimeline(onUpdate: updateView);
+      timeline = await room!.getTimeline(
+        onUpdate: updateView,
+        eventContextId: eventContextId,
+      );
       if (timeline!.events.isNotEmpty) {
         if (room!.markedUnread) room!.markUnread(false);
         setReadMarker();
       }
 
-      // when the scroll controller is attached we want to scroll to an event id, if specified
-      // and update the scroll controller...which will trigger a request history, if the
-      // "load more" button is visible on the screen
-      SchedulerBinding.instance.addPostFrameCallback((_) async {
-        if (mounted) {
-          final event = VRouter.of(context).queryParameters['event'];
-          if (event != null) {
-            scrollToEventId(event);
-          }
-          _updateScrollController();
-        }
-      });
+      if (eventContextId.isNotEmpty) scrollToEventId(eventContextId);
     }
     timeline!.requestKeys(onlineKeyBackupOnly: false);
     return true;
@@ -636,59 +629,42 @@ class ChatController extends State<Chat> {
     inputFocus.requestFocus();
   }
 
-  void scrollToEventId(String eventId) async {
-    var eventIndex = timeline!.events.indexWhere((e) => e.eventId == eventId);
-    if (eventIndex == -1) {
-      // event id not found...maybe we can fetch it?
-      // the try...finally is here to start and close the loading dialog reliably
-      await showFutureLoadingDialog(
-          context: context,
-          future: () async {
-            // okay, we first have to fetch if the event is in the room
-            try {
-              final event = await timeline!.getEventById(eventId);
-              if (event == null) {
-                // event is null...meaning something is off
-                return;
-              }
-            } catch (err) {
-              if (err is MatrixException && err.errcode == 'M_NOT_FOUND') {
-                // event wasn't found, as the server gave a 404 or something
-                return;
-              }
-              rethrow;
-            }
-            // okay, we know that the event *is* in the room
-            while (eventIndex == -1) {
-              if (!canLoadMore) {
-                // we can't load any more events but still haven't found ours yet...better stop here
-                return;
-              }
-              try {
-                await timeline!.requestHistory(historyCount: _loadHistoryCount);
-              } catch (err) {
-                if (err is TimeoutException) {
-                  // loading the history timed out...so let's do nothing
-                  return;
-                }
-                rethrow;
-              }
-              eventIndex =
-                  timeline!.events.indexWhere((e) => e.eventId == eventId);
-            }
-          });
-    }
-    if (!mounted) {
-      return;
-    }
-    await scrollController.scrollToIndex(
-      eventIndex,
-      preferPosition: AutoScrollPosition.middle,
-    );
-    _updateScrollController();
+  void openTimelineAtEventId(String eventId) async {
+    setState(() {
+      timeline = null;
+    });
+    await getTimeline(eventContextId: eventId);
+    scrollToEventId(eventId);
   }
 
-  void scrollDown() => scrollController.jumpTo(0);
+  /// when the scroll controller is attached we want to scroll to an event id, if specified
+  /// and update the scroll controller...which will trigger a request history, if the
+  /// "load more" button is visible on the screen
+  void scrollToEventId(String eventId) async {
+    SchedulerBinding.instance.addPostFrameCallback((_) async {
+      if (!mounted) return;
+      final eventIndex =
+          timeline!.events.indexWhere((e) => e.eventId == eventId);
+      if (eventIndex == -1) return;
+      if (!mounted) return;
+      await scrollController.scrollToIndex(
+        eventIndex,
+        preferPosition: AutoScrollPosition.middle,
+      );
+      _updateScrollController();
+    });
+  }
+
+  void scrollDown() {
+    if (timeline!.isFragmentedTimeline) {
+      setState(() {
+        timeline = null;
+      });
+      getTimeline();
+    } else {
+      scrollController.jumpTo(0);
+    }
+  }
 
   void onEmojiSelected(_, Emoji? emoji) {
     switch (emojiPickerType) {

lib/pages/chat/chat_event_list.dart

@@ -55,16 +55,17 @@ class ChatEventList extends StatelessWidget {
               ],
             );
           }
+          i--;
 
           // Request history button or progress indicator:
-          if (i == controller.timeline!.events.length + 1) {
+          if (i == controller.timeline!.events.length) {
             if (controller.timeline!.isRequestingHistory) {
               return const Center(
                 child: CircularProgressIndicator.adaptive(strokeWidth: 2),
               );
             }
             if (controller.canLoadMore) {
-              Center(
+              return Center(
                 child: OutlinedButton(
                   style: OutlinedButton.styleFrom(
                     backgroundColor: Theme.of(context).scaffoldBackgroundColor,
@@ -78,7 +79,10 @@ class ChatEventList extends StatelessWidget {
           }
 
           // The message at this index:
-          final event = controller.timeline!.events[i - 1];
+          if (i >= controller.timeline!.events.length) {
+            return Container();
+          }
+          final event = controller.timeline!.events[i];
 
           return AutoScrollTag(
             key: ValueKey(event.eventId),

lib/pages/chat/events/message.dart

@@ -219,9 +219,7 @@ class Message extends StatelessWidget {
                                         );
                                   return InkWell(
                                     onTap: () {
-                                      if (scrollToEventId != null) {
-                                        scrollToEventId!(replyEvent.eventId);
-                                      }
+                                      scrollToEventId?.call(replyEvent.eventId);
                                     },
                                     child: AbsorbPointer(
                                       child: Container(

lib/pages/chat/pinned_events.dart

@@ -35,7 +35,7 @@ class PinnedEvents extends StatelessWidget {
                     ))
                 .toList());
 
-    if (eventId != null) controller.scrollToEventId(eventId);
+    if (eventId != null) controller.openTimelineAtEventId(eventId);
   }
 
   @override