[fractal] room-history: Don't loop when new messages are added

[Julian Sparber <jsparber src gnome org>]

commit b0274eaaf29a791f71e90dbc6132239474a781b1
Author: Kévin Commaille <zecakeh tedomum fr>
Date:   Mon Oct 10 14:58:41 2022 +0200

    room-history: Don't loop when new messages are added
    
    The scrollbar has not been updated when the `load()` method returns,
    so wait until we get notified of the change if new messages are added.

 src/session/content/room_history/mod.rs | 17 +----------------
 src/session/room/timeline/mod.rs        | 16 +++++++++-------
 2 files changed, 10 insertions(+), 23 deletions(-)
---
diff --git a/src/session/content/room_history/mod.rs b/src/session/content/room_history/mod.rs
index 665861bed..f75bf518f 100644
--- a/src/session/content/room_history/mod.rs
+++ b/src/session/content/room_history/mod.rs
@@ -842,22 +842,7 @@ impl RoomHistory {
             let obj_weak = self.downgrade();
             spawn!(async move {
                 loop {
-                    // We don't want to hold a strong ref to `obj` on `await`
-                    let need = if let Some(obj) = obj_weak.upgrade() {
-                        if obj.room().as_ref() == Some(&room) {
-                            obj.need_messages() || room.timeline().is_empty()
-                        } else {
-                            return;
-                        }
-                    } else {
-                        return;
-                    };
-
-                    if need {
-                        if !room.timeline().load().await {
-                            break;
-                        }
-                    } else {
+                    if !room.timeline().load().await {
                         break;
                     }
                 }
diff --git a/src/session/room/timeline/mod.rs b/src/session/room/timeline/mod.rs
index 1bdd5f79f..5c0fff5c4 100644
--- a/src/session/room/timeline/mod.rs
+++ b/src/session/room/timeline/mod.rs
@@ -507,9 +507,9 @@ impl Timeline {
         }
     }
 
-    /// Load the timeline
-    /// This function should also be called to load more events
-    /// Returns `true` when messages where successfully added
+    /// Load events at the start of the timeline.
+    ///
+    /// Returns `true` when no messages were added, but more can be loaded.
     pub async fn load(&self) -> bool {
         let priv_ = self.imp();
 
@@ -584,8 +584,7 @@ impl Timeline {
                 }
 
                 self.set_state(TimelineState::Ready);
-                self.prepend(events);
-                true
+                !self.prepend(events)
             }
             Ok(None) => {
                 self.remove_loading_spinner();
@@ -784,8 +783,10 @@ impl Timeline {
         }
     }
 
-    /// Prepends a batch of events
-    pub fn prepend(&self, batch: Vec<Event>) {
+    /// Prepends a batch of events.
+    ///
+    /// Returns `true` if new shown events where added to the timeline.
+    pub fn prepend(&self, batch: Vec<Event>) -> bool {
         let priv_ = self.imp();
         let mut added = batch.len();
 
@@ -831,6 +832,7 @@ impl Timeline {
         }
 
         self.items_changed(0, 0, added as u32);
+        added > 0
     }
 
     fn set_room(&self, room: Option<Room>) {