fix historical event jumps

Fixes #118

lib/controllers/event.dart

@@ -18,26 +18,30 @@ class EventController(final GetEventRequest request)
 
     if (event != null) return event;
 
+    final link = ref.keepAlive();
     final fetchedEvent = await ref
         .read(ClientController.provider.notifier)
         .getEvent(request)
-        .onError((_, _) => null);
+        .onError((_, _) => null)
+        .whenComplete(link.close);
 
     if (fetchedEvent != null) {
-      ref
-          .read(RoomsController.provider.notifier)
-          .update(
+      // Storing the event invalidates this provider, as it watches the room.
+      // If nothing is listening, Riverpod won't rebuild it, and this build's
+      // result would be lost, so store it after returning.
+      final rooms = ref.read(RoomsController.provider.notifier);
+      Future.microtask(
+        () => rooms.update(
           .new({
             request.roomId: .new(
               events: .new({fetchedEvent.rowId: fetchedEvent}),
             ),
           }),
+        ),
       );
-
-      return fetchedEvent;
     }
 
-    return null;
+    return fetchedEvent;
   }
 
   static final provider = AsyncNotifierProvider.family

lib/helpers/hooks/chat_scroll.dart

@@ -127,10 +127,15 @@ final class ChatScroll({
           final isAtBottom = position.extentBefore <= 0;
           if (isAtBottom != atBottom.value) atBottom.value = isAtBottom;
 
+          // contextualEvent updates immediately when jumping, but
+          // controllerData is only for the historical timeline once it loads
+          final isHistorical =
+              contextualEvent.value != null &&
+              controllerData.value?.historicalData != null;
+
           if (position.extentAfter <= loadThreshold) {
             await paginate(.backward);
-          } else if (contextualEvent.value != null &&
-              position.extentBefore <= loadThreshold) {
+          } else if (isHistorical && position.extentBefore <= loadThreshold) {
             await paginate(.forward);
           } else if (position.extentBefore <= 0) {
             await markRead();
@@ -139,7 +144,7 @@ final class ChatScroll({
           if (controllerData.isLoading == false &&
               position.extentBefore <= 0 &&
               controllerData.value?.hasMoreForward == false &&
-              contextualEvent.value != null) {
+              isHistorical) {
             anchorId.value = null;
             contextualEvent.value = null;
           }