window: Drop AdwFlap for Headerbar

Redo everything headerbar related with new Adw widgets
when there is a working concept.

Closes #112

Part-of: <https://gitlab.gnome.org/Incubator/loupe/-/merge_requests/192>

src/window.rs

@@ -68,8 +68,6 @@ mod imp {
         // TemplateChild<T> wrapper, where T is the
         // object type of the template child.
         #[template_child]
-        pub(super) flap: TemplateChild<adw::Flap>,
-        #[template_child]
         pub(super) headerbar: TemplateChild<gtk::HeaderBar>,
         #[template_child]
         pub(super) properties_button: TemplateChild<gtk::ToggleButton>,
@@ -783,18 +781,6 @@ impl LpWindow {
         }
     }
 
-    // We also have a closure that returns `adw::FlapFoldPolicy`.
-    // if we aren't fullscreened, or if the properties are revealed,
-    // we unfold the main flap. Otherwise we're always folded.
-    #[template_callback]
-    fn fold_policy(&self, fullscreened: bool, properties_revealed: bool) -> adw::FlapFoldPolicy {
-        if !fullscreened || properties_revealed {
-            adw::FlapFoldPolicy::Never
-        } else {
-            adw::FlapFoldPolicy::Always
-        }
-    }
-
     #[template_callback]
     fn on_motion_cb(&self) {
         let controller = &self.imp().motion_controller;