// Define some model data
#[derive(Lens)]
pub struct AppData {
    count: i32,
}

// Define events to mutate the data
pub enum AppEvent {
    Increment,
}

// Describe how the data can be mutated
impl Model for AppData {
    fn event(&mut self, _: &mut Context, event: &mut Event) {
        event.map(|app_event, _| match app_event {
            AppEvent::Increment => {
                self.count += 1;
            }
        });
    }
}

Application::new(|cx| {
    // Build the model data into the tree
    AppData { count: 0 }.build(cx);

    HStack::new(cx, |cx| {
        // Declare a button which emits an event
        Button::new(cx, 
          |cx| cx.emit(AppEvent::Increment), 
          |cx| Label::new(cx, "Increment")
        );
        
        // Declare a label which is bound to part of the model, updating if it changes
        Label::new(cx, AppData::count)
            .width(Pixels(50.0));
    })
    .child_space(Stretch(1.0))
    .col_between(Pixels(50.0));
})
.title("Counter")
.inner_size((400, 100))
.run();