message-toolbar: Fix inserting mention before another mention

src/session/view/content/room_history/message_toolbar/composer_state.rs

@@ -236,18 +236,19 @@ mod imp {
 
         /// Add the given widget at the position of the given iter to this
         /// state.
-        pub(super) fn add_widget(&self, widget: impl IsA<gtk::Widget>, iter: &mut gtk::TextIter) {
-            let widget = widget.upcast();
-
-            let anchor = match iter.child_anchor() {
-                Some(anchor) => anchor,
-                None => self.buffer.create_child_anchor(iter),
+        pub(super) fn add_widget(&self, widget: gtk::Widget, iter: &mut gtk::TextIter) {
+            let Some(view) = self.view.upgrade() else {
+                return;
             };
 
-            if let Some(view) = self.view.upgrade() {
-                view.add_child_at_anchor(&widget, &anchor);
-            }
+            // Reuse the child anchor at the iter if it does not have a child widget,
+            // otherwise create a new one.
+            let anchor = iter
+                .child_anchor()
+                .filter(|anchor| self.widget_at_anchor(anchor).is_none())
+                .unwrap_or_else(|| self.buffer.create_child_anchor(iter));
 
+            view.add_child_at_anchor(&widget, &anchor);
             self.widgets.borrow_mut().push((widget, anchor));
         }
 
@@ -311,7 +312,7 @@ mod imp {
 
                 match DraftMention::new(&room, &text[content_start..content_end]) {
                     DraftMention::Source(source) => {
-                        self.add_widget(source.to_pill(), &mut end_iter);
+                        self.add_widget(source.to_pill().upcast(), &mut end_iter);
                     }
                     DraftMention::Text(s) => {
                         self.buffer.insert(&mut end_iter, s);
@@ -410,7 +411,7 @@ mod imp {
                         self.buffer.insert(&mut iter, &text[pos..start]);
                     }
 
-                    self.add_widget(pill, &mut iter);
+                    self.add_widget(pill.upcast(), &mut iter);
 
                     pos = end;
                 }
@@ -489,7 +490,7 @@ impl ComposerState {
 
     /// Add the given widget at the position of the given iter to this state.
     pub(crate) fn add_widget(&self, widget: impl IsA<gtk::Widget>, iter: &mut gtk::TextIter) {
-        self.imp().add_widget(widget, iter);
+        self.imp().add_widget(widget.upcast(), iter);
     }
 
     /// Get the widget at the given anchor, if any.