fix: preserve content when rebuilding appearance drawer

cosmic-settings/src/pages/desktop/appearance/drawer.rs

@@ -153,6 +153,16 @@ impl Content {
         }
     }
 
+    pub fn preserve_from(&mut self, previous: &mut Content) {
+        self.font_config
+            .take_families_from(&mut previous.font_config);
+
+        self.icons_fetched = previous.icons_fetched;
+        self.icon_theme_active = previous.icon_theme_active;
+        self.icon_themes = std::mem::take(&mut previous.icon_themes);
+        self.icon_handles = std::mem::take(&mut previous.icon_handles);
+    }
+
     pub fn update_font(
         &mut self,
         message: FontMessage,

cosmic-settings/src/pages/desktop/appearance/font_config.rs

@@ -94,6 +94,11 @@ impl Model {
         self.font_filter.clear();
     }
 
+    pub fn take_families_from(&mut self, other: &mut Model) {
+        self.interface_font_families = std::mem::take(&mut other.interface_font_families);
+        self.monospace_font_families = std::mem::take(&mut other.monospace_font_families);
+    }
+
     pub fn font_loaded(
         &mut self,
         mono: Vec<Arc<str>>,

cosmic-settings/src/pages/desktop/appearance/mod.rs

@@ -200,7 +200,9 @@ impl Page {
 
             Message::DrawerOpen(context_view) => {
                 self.context_view = Some(context_view);
-                self.drawer = drawer::Content::from(&self.theme_manager);
+                let mut previous =
+                    std::mem::replace(&mut self.drawer, drawer::Content::from(&self.theme_manager));
+                self.drawer.preserve_from(&mut previous);
                 tasks.push(cosmic::task::message(
                     crate::app::Message::OpenContextDrawer(self.entity),
                 ));