Bypass scroll handling for GtkScale (gtk-rs)

bypass_gtkscale_scroll_handler.rs

    impl WidgetImpl for PwVolumeBox {

        fn map(&self) {
            self.parent_map();

            // Hack until I have a better way of getting at the scrolled window
            //                         ListBox           Box               Viewport          Scrolled window
            let p = self.obj().parent().unwrap().parent().unwrap().parent().unwrap().parent().unwrap();
            let scrolledwindow: gtk::ScrolledWindow = p.downcast().expect("downcast to scrolled window");

            let ecs = gtk::EventControllerScroll::new(gtk::EventControllerScrollFlags::BOTH_AXES);
            ecs.set_propagation_phase(gtk::PropagationPhase::Capture);
            ecs.set_propagation_limit(gtk::PropagationLimit::SameNative);

            // Need to actually handle the scroll event in order to block propagation to the GtkScale widget
            ecs.connect_local("scroll", false, clone!(@weak scrolledwindow => @default-return None, move |v| {
                let y: f64 = v.get(2).unwrap().get().unwrap();
                dbg!(&y);

                // No way to redirect this event to underlying widget so we need to reimplement the scroll handling
                let adjustment = scrolledwindow.vadjustment();
                adjustment.set_value(adjustment.value() + y*adjustment.step_increment());
                
                Some(true.to_value())
            }));
            self.volume_scale.parent().unwrap().add_controller(ecs);
        }
    }