timeline: Filter timeline start item if we have room create event

The code was removed when the SDK was updated recently, because the SDK
now provides the timeline start item, so the logic had to change. This
re-adds the old code and adapts it to filter the SDK items.

src/session/model/room/timeline/event/mod.rs

@@ -3,8 +3,9 @@ use std::sync::Arc;
 use gtk::{gio, glib, glib::closure_local, prelude::*, subclass::prelude::*};
 use indexmap::IndexMap;
 use matrix_sdk_ui::timeline::{
-    Error as TimelineError, EventSendState, EventTimelineItem, Message, MsgLikeKind,
-    RepliedToEvent, TimelineDetails, TimelineEventItemId, TimelineItemContent,
+    AnyOtherFullStateEventContent, Error as TimelineError, EventSendState, EventTimelineItem,
+    Message, MsgLikeKind, RepliedToEvent, TimelineDetails, TimelineEventItemId,
+    TimelineItemContent,
 };
 use ruma::{
     events::{receipt::Receipt, AnySyncTimelineEvent, TimelineEventType},
@@ -604,6 +605,19 @@ impl Event {
         }
     }
 
+    /// Whether this is the `m.room.create` event of the room.
+    pub(crate) fn is_room_create(&self) -> bool {
+        match self.item().content() {
+            TimelineItemContent::OtherState(other_state) => {
+                matches!(
+                    other_state.content(),
+                    AnyOtherFullStateEventContent::RoomCreate(_),
+                )
+            }
+            _ => false,
+        }
+    }
+
     /// The media message of this event, if any.
     pub(crate) fn media_message(&self) -> Option<MediaMessage> {
         match self.item().content() {

src/session/model/room/timeline/mod.rs

@@ -71,6 +71,10 @@ mod imp {
         start_items: OnceCell<SingleItemListModel>,
         /// Items provided by the SDK timeline.
         sdk_items: OnceCell<gio::ListStore>,
+        /// Filter for the list of items provided by the SDK timeline.
+        filter: gtk::CustomFilter,
+        /// Filtered list of items provided by the SDK timeline.
+        filtered_sdk_items: gtk::FilterListModel,
         /// Items added at the end of the timeline.
         ///
         /// Currently this can only contain one item at a time.
@@ -96,6 +100,9 @@ mod imp {
         /// Whether we have reached the start of the timeline.
         #[property(get)]
         has_reached_start: Cell<bool>,
+        /// Whether we have the `m.room.create` event in the timeline.
+        #[property(get)]
+        has_room_create: Cell<bool>,
         diff_handle: OnceCell<AbortHandle>,
         back_pagination_status_handle: OnceCell<AbortHandle>,
         read_receipts_changed_handle: OnceCell<AbortHandle>,
@@ -115,6 +122,25 @@ mod imp {
             SIGNALS.as_ref()
         }
 
+        fn constructed(&self) {
+            self.parent_constructed();
+
+            self.filter.set_filter_func(clone!(
+                #[weak(rename_to = imp)]
+                self,
+                #[upgrade_or]
+                true,
+                move |obj| {
+                    // Hide the timeline start item if we have the `m.room.create` event too.
+                    obj.downcast_ref::<VirtualItem>().is_none_or(|item| {
+                        !(imp.has_room_create.get()
+                            && item.kind() == VirtualItemKind::TimelineStart)
+                    })
+                }
+            ));
+            self.filtered_sdk_items.set_filter(Some(&self.filter));
+        }
+
         fn dispose(&self) {
             if let Some(handle) = self.diff_handle.get() {
                 handle.abort();
@@ -244,8 +270,11 @@ mod imp {
 
         /// Items provided by the SDK timeline.
         pub(super) fn sdk_items(&self) -> &gio::ListStore {
-            self.sdk_items
-                .get_or_init(gio::ListStore::new::<TimelineItem>)
+            self.sdk_items.get_or_init(|| {
+                let sdk_items = gio::ListStore::new::<TimelineItem>();
+                self.filtered_sdk_items.set_model(Some(&sdk_items));
+                sdk_items
+            })
         }
 
         /// Items added at the end of the timeline.
@@ -263,7 +292,7 @@ mod imp {
                 .get_or_init(|| {
                     let model_list = gio::ListStore::new::<gio::ListModel>();
                     model_list.append(self.start_items());
-                    model_list.append(self.sdk_items());
+                    model_list.append(&self.filtered_sdk_items);
                     model_list.append(self.end_items());
                     gtk::FlattenListModel::new(Some(model_list))
                 })
@@ -272,7 +301,7 @@ mod imp {
 
         /// Whether the timeline is empty.
         fn is_empty(&self) -> bool {
-            self.sdk_items().n_items() == 0
+            self.filtered_sdk_items.n_items() == 0
         }
 
         /// Set the loading state of the timeline.
@@ -322,6 +351,24 @@ mod imp {
             self.obj().notify_has_reached_start();
         }
 
+        /// Set whether the timeline has the `m.room.create` event of the room.
+        fn set_has_room_create(&self, has_room_create: bool) {
+            if self.has_room_create.get() == has_room_create {
+                return;
+            }
+
+            self.has_room_create.set(has_room_create);
+
+            let change = if has_room_create {
+                gtk::FilterChange::MoreStrict
+            } else {
+                gtk::FilterChange::LessStrict
+            };
+            self.filter.changed(change);
+
+            self.obj().notify_has_room_create();
+        }
+
         /// Clear the state of the timeline.
         ///
         /// This doesn't handle removing items in `sdk_items` because it can be
@@ -329,6 +376,7 @@ mod imp {
         fn clear(&self) {
             self.event_map.borrow_mut().clear();
             self.set_has_reached_start(false);
+            self.set_has_room_create(false);
         }
 
         /// Set whether the timeline should be pre-loaded when it is ready.
@@ -356,7 +404,7 @@ mod imp {
 
         /// Preload the timeline, if there are not enough items.
         async fn preload(&self) {
-            if self.sdk_items().n_items() < u32::from(MAX_BATCH_SIZE) {
+            if self.filtered_sdk_items.n_items() < u32::from(MAX_BATCH_SIZE) {
                 self.paginate_backwards(|| ControlFlow::Break(())).await;
             }
         }
@@ -550,6 +598,7 @@ mod imp {
         /// Remove the given item from this `Timeline`.
         fn remove_item(&self, item: &TimelineItem) {
             if let Some(event) = item.downcast_ref::<Event>() {
+                let mut removed_from_map = false;
                 let mut event_map = self.event_map.borrow_mut();
 
                 // We need to remove both the transaction ID and the event ID.
@@ -562,14 +611,19 @@ mod imp {
                 for id in identifiers {
                     // We check if we are removing the right event, in case we receive a diff that
                     // adds an existing event to another place, making us create a new event, before
-                    // another diff that removes it from its old place, making
-                    // us remove the old event.
+                    // another diff that removes it from its old place, making us remove the old
+                    // event.
                     let found = event_map.get(&id).is_some_and(|e| e == event);
 
                     if found {
                         event_map.remove(&id);
+                        removed_from_map = true;
                     }
                 }
+
+                if removed_from_map && event.is_room_create() {
+                    self.set_has_room_create(false);
+                }
             }
         }
 
@@ -712,6 +766,10 @@ mod imp {
                         member.set_latest_activity(u64::from(event.origin_server_ts().get()));
                     }
                 }
+
+                if event.is_room_create() {
+                    self.set_has_room_create(true);
+                }
             }
 
             item