Reimplementation of gtk::DropDown's default list factory

dropdown_list_factory.rs

let listfactory = gtk::SignalListItemFactory::new();
listfactory.connect_setup(|_, item| setup_handler(item, false));

let dropdown = self.outputdevice_dropdown.get();

listfactory.connect_bind(clone!(@weak dropdown => move |_factory, item| {
    let item: gtk::ListItem = item.downcast_ref().cloned().unwrap();

    fn selected_item_handler(dropdown: &gtk::DropDown, listitem: &gtk::ListItem) {
        if let Some (child) = listitem.child() {
            let box_: gtk::Box = child.downcast().unwrap();
            let icon = box_.last_child().unwrap();
            icon.set_opacity(
                if listitem.item() == dropdown.selected_item() {
                    1.0
                } else {
                    0.0
                }
            );
        }
    }
    
    let selected_item_closure = closure_local!(@watch dropdown as _dropdown, @strong item as listitem =>
        move |dropdown: &gtk::DropDown, _pspec: &glib::ParamSpec| {
            selected_item_handler(dropdown, &listitem);
    });
    dropdown.connect_closure("notify::selected-item", true, selected_item_closure);
    selected_item_handler(&dropdown, &item);

}));

self.outputdevice_dropdown.set_list_factory(Some(&listfactory));



// Or you know just do this which is much easier........

// Save the default factory implemenation
let default_dropdown_factory = self.outputdevice_dropdown.factory();
// Set out custom factory (which also impacts list-factory
self.outputdevice_dropdown.set_factory(Some(&factory));
// Reset list-factory to the default one after having set the main factory
self.outputdevice_dropdown.set_list_factory(default_dropdown_factory.as_ref());