Fix a bunch of cases where the read marker wasn't being updated

lib/pages/chat/chat.dart

@@ -596,8 +596,14 @@ class ChatController extends State<ChatPageWithRoom>
     // We are already setting a read marker
     if (_setReadMarkerFuture != null) return;
 
-    // We only set read marker if we are at the bottom
-    if (_scrolledUp) return;
+    // We only set read marker if we are at the bottom. Prefer the live
+    // scroll position, but fall back to the cached flag when no client is
+    // attached yet.
+    if (scrollController.hasClients
+        ? scrollController.position.pixels > 0
+        : _scrolledUp) {
+      return;
+    }
 
     // We do not set read marker if we offer user the scroll up banner
     if (scrollUpBannerEventId != null) return;
@@ -614,16 +620,21 @@ class ChatController extends State<ChatPageWithRoom>
     }
 
     final setOnLatestEvent = eventId == null;
+    // When we are viewing a context slice of older events, do not treat
+    // the newest loaded event as the room's latest event.
+    if (setOnLatestEvent && timeline.allowNewEvent == false) return;
+    // Target the latest message-like event. Do not gate this on push rule
+    // evaluation: read markers track what the user has seen, not what
+    // notifies them.
     eventId ??= timeline.events
         .firstWhereOrNull(
-          (event) => room.pushRuleState == PushRuleState.notify
-              ? room.client.pushruleEvaluator.match(event).notify
-              : {
-                      EventTypes.Message,
-                      EventTypes.Encrypted,
-                      EventTypes.Sticker,
-                    }.contains(event.type) &&
-                    event.eventId.isValidMatrixIdStrict(),
+          (event) =>
+              {
+                EventTypes.Message,
+                EventTypes.Encrypted,
+                EventTypes.Sticker,
+              }.contains(event.type) &&
+              event.eventId.isValidMatrixIdStrict(),
         )
         ?.eventId;
 
@@ -633,8 +644,10 @@ class ChatController extends State<ChatPageWithRoom>
     // This is a sending event, we do not set a readmarker yet
     if (eventId.isValidMatrixIdStrict() == false) return;
 
-    // Already set a read marker on this event
-    if (room.fullyRead == eventId) return;
+    // Already set a read marker on this event, unless the room still shows
+    // new messages: re-posting refreshes the receipts' timestamps, which the
+    // unread indicator depends on.
+    if (room.fullyRead == eventId && !room.hasNewMessages) return;
 
     // Set a readmarker on a specific event, not latest, but room is not unread
     // at all.
@@ -651,7 +664,11 @@ class ChatController extends State<ChatPageWithRoom>
           eventId: eventId,
           public: AppSettings.sendPublicReadReceipts.value,
         )
-        .then((_) {
+        .catchError((Object e, StackTrace s) {
+          Logs().w('Failed to set read marker', e, s);
+        })
+        .whenComplete(() {
+          // Always release the latch, even when the request fails.
           _setReadMarkerFuture = null;
         });
   }