Fix deletion of new message divider

Before, when a new message divider was deleted after 5 seconds of its
creation, only its corresponding widget in the field listbox of List
got erased. With this commit, its corresponding element in the field
list of List gets erased as well.

fractal-gtk/src/widgets/divider.rs

@@ -9,7 +9,7 @@ pub struct NewMessageDivider {
 }
 
 impl NewMessageDivider {
-    pub fn new(text: &str) -> NewMessageDivider {
+    pub fn new<F: Fn() + 'static>(text: &str, remove_divider: F) -> NewMessageDivider {
         let row = gtk::ListBoxRow::new();
         row.set_selectable(false);
 
@@ -43,30 +43,25 @@ impl NewMessageDivider {
          * destroy the NewMessageDivider after it's added to the History with a couple of
          * secounds delay */
         let revealer_weak = revealer.downgrade();
-        row.connect_parent_set(move |w, _| {
-            || -> Option<()> {
-                let revealer = revealer_weak.upgrade()?;
+        row.connect_parent_set(move |_, _| {
+            revealer_weak.upgrade().map(|revealer| {
                 let revealer_weak = revealer.downgrade();
                 gtk::timeout_add(5000, move || {
                     /* when the user closes the room the divider gets destroyed and this tiemout
                      * does nothing, but that's fine */
-                    || -> Option<()> {
-                        let r = revealer_weak.upgrade()?;
+                    revealer_weak.upgrade().map(|r| {
                         r.set_reveal_child(false);
-                        None
-                    }();
+                    });
                     glib::Continue(false)
                 });
-                let row_weak = w.downgrade();
-                revealer.connect_property_child_revealed_notify(move |_| {
-                    || -> Option<()> {
-                        let r = row_weak.upgrade()?;
-                        r.destroy();
-                        None
-                    }();
-                });
-                None
-            }();
+            });
+        });
+        let row_weak = row.downgrade();
+        revealer.connect_property_child_revealed_notify(move |_| {
+            row_weak.upgrade().map(|r| {
+                r.destroy();
+                remove_divider();
+            });
         });
         NewMessageDivider {
             revealer: revealer,

fractal-gtk/src/widgets/room_history.rs

@@ -24,6 +24,7 @@ use url::Url;
 
 struct List {
     list: VecDeque<Element>,
+    new_divider_index: Option<usize>,
     listbox: gtk::ListBox,
     view: widgets::ScrollWidget,
 }
@@ -32,6 +33,7 @@ impl List {
     pub fn new(view: widgets::ScrollWidget, listbox: gtk::ListBox) -> List {
         List {
             list: VecDeque::new(),
+            new_divider_index: None,
             listbox,
             view,
         }
@@ -72,9 +74,27 @@ impl List {
                 self.listbox.insert(divider, -1);
             }
         }
+        if let Some(index) = self.new_divider_index {
+            self.new_divider_index = Some(index + 1);
+        }
         self.list.push_front(element);
         None
     }
+
+    fn create_new_message_divider(rows: Rc<RefCell<Self>>) -> widgets::NewMessageDivider {
+        let rows_weak = Rc::downgrade(&rows);
+        let remove_divider = move || {
+            rows_weak.upgrade().map(|rows| {
+                let new_divider_index = rows
+                    .borrow_mut()
+                    .new_divider_index
+                    .take()
+                    .expect("The new divider index must exist, since there is a new divider");
+                rows.borrow_mut().list.remove(new_divider_index);
+            });
+        };
+        widgets::NewMessageDivider::new(i18n("New Messages").as_str(), remove_divider)
+    }
 }
 
 /* These Enum contains all differnet types of rows the room history can have, e.g room message, new
@@ -190,8 +210,11 @@ impl RoomHistory {
                         rows.borrow_mut().add_top(prev_day_divider);
                     }
                     if item.last_viewed && !rows.borrow().list.is_empty() {
-                        let divider = Element::NewDivider(create_new_message_divider());
+                        let divider =
+                            Element::NewDivider(List::create_new_message_divider(rows.clone()));
                         rows.borrow_mut().add_top(divider);
+                        let new_divider_index = rows.borrow().list.len() - 1;
+                        rows.borrow_mut().new_divider_index = Some(new_divider_index);
                     }
                     item.widget = Some(create_row(
                         item.clone(),
@@ -249,8 +272,10 @@ impl RoomHistory {
         };
 
         if item.last_viewed {
-            let divider = Element::NewDivider(create_new_message_divider());
+            let divider = Element::NewDivider(List::create_new_message_divider(self.rows.clone()));
             rows.add_bottom(divider);
+            let new_divider_index = rows.list.len() - 1;
+            rows.new_divider_index = Some(new_divider_index);
         }
         if let Some(day_divider) = day_divider {
             rows.add_bottom(day_divider);
@@ -411,7 +436,3 @@ fn create_day_divider(date: DateTime<Local>) -> gtk::ListBoxRow {
     row.show_all();
     row
 }
-
-fn create_new_message_divider() -> widgets::NewMessageDivider {
-    widgets::NewMessageDivider::new(i18n("New Messages").as_str())
-}