fix(ui): Reduce number of updates in the room list.

This patch fixes a “bug” in the Room List. It's updated by
`RoomInfoNotableUpdateReasons`. However, 1 reason is creating
unnecessary updates: `RECENCY_STAMP`. The Room List is already updated
by the Latest Event. One usage of the Latest Event is to sort the Room
List by recency. Thus, since the Room List is updated by `LATEST_EVENT`,
we can ignore `RECENCY_STAMP`.

Author: Hywan

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

@@ -25,7 +25,7 @@ use matrix_sdk::{
     Client, Room, RoomRecencyStamp, RoomState, SlidingSync, SlidingSyncList,
     executor::{JoinHandle, spawn},
 };
-use matrix_sdk_base::RoomInfoNotableUpdate;
+use matrix_sdk_base::{RoomInfoNotableUpdate, RoomInfoNotableUpdateReasons};
 use ruma::MilliSecondsSinceUnixEpoch;
 use tokio::{
     select,
@@ -257,6 +257,22 @@ fn merge_stream_and_receiver(
                 update = room_info_notable_update_receiver.recv() => {
                     match update {
                         Ok(update) => {
+                            // Filter which _reason_ can trigger an update of
+                            // the room list.
+                            //
+                            // If the update is strictly about the
+                            // `RECENCY_STAMP`, let's ignore it, because the
+                            // Latest Event type is used to sort the room list
+                            // by recency already. We don't want to trigger an
+                            // update because of `RECENCY_STAMP`.
+                            //
+                            // If the update contains more reasons than
+                            // `RECENCY_STAMP`, then it's fine. That's why we
+                            // are using `==` instead of `contains`.
+                            if update.reasons == RoomInfoNotableUpdateReasons::RECENCY_STAMP {
+                                continue;
+                            }
+
                             // Emit a `VectorDiff::Set` for the specific rooms.
                             if let Some(index) = current_values.iter().position(|room| room.room_id() == update.room_id) {
                                 let mut room = current_values[index].clone();