feat(sdk,ui): Automatically subscribe to LatestEvents if EventCache has subscribed.

crates/matrix-sdk-ui/src/room_list_service/mod.rs

@@ -465,13 +465,15 @@ impl RoomListService {
 
         // Before subscribing, let's listen these rooms to calculate their latest
         // events.
-        let latest_events = self.client.latest_events().await;
+        if self.client.event_cache().has_subscribed() {
+            let latest_events = self.client.latest_events().await;
 
-        for room_id in room_ids {
-            if let Err(error) = latest_events.listen_to_room(room_id).await {
-                // Let's not fail the room subscription. Instead, emit a log because it's very
-                // unlikely to happen.
-                error!(?error, ?room_id, "Failed to listen to the latest event for this room");
+            for room_id in room_ids {
+                if let Err(error) = latest_events.listen_to_room(room_id).await {
+                    // Let's not fail the room subscription. Instead, emit a log because it's very
+                    // unlikely to happen.
+                    error!(?error, ?room_id, "Failed to listen to the latest event for this room");
+                }
             }
         }
 

crates/matrix-sdk/src/event_cache/mod.rs

@@ -408,6 +408,11 @@ impl EventCache {
         info!("Auto-shrink linked chunk task has been closed, exiting");
     }
 
+    /// Check whether [`EventCache::subscribe`] has been called.
+    pub fn has_subscribed(&self) -> bool {
+        self.inner.drop_handles.get().is_some()
+    }
+
     /// Return a room-specific view over the [`EventCache`].
     pub(crate) async fn for_room(
         &self,

crates/matrix-sdk/src/sync.rs

@@ -359,6 +359,10 @@ pub(crate) async fn subscribe_to_room_latest_events<'a, R>(client: &'a Client, r
 where
     R: Iterator<Item = &'a OwnedRoomId>,
 {
+    if !client.event_cache().has_subscribed() {
+        return;
+    }
+
     let latest_events = client.latest_events().await;
 
     for room_id in room_ids {