A theoretical boxflight double-button example

two_buttons.rs

pub fn main() {
    let mut ctx = Context::new();
    let mut rng = thread_rng(); 
    ctx.add_element(ButtonsModel {
        color_a: random_color(&mut rng),
        color_b: random_color(&mut rng),
    });
    ctx.launch();
}

enum ButtonsMessage {
    ChangeColor {
        button: usize, 
        to: [f32; 3],
        ids: IdSource::new(),
    },
    NoOp,
}

// so we don't have to ButtonsMessage::ChangeColor { ... }
use ButtonsMessage::*;

impl Message for ButtonsMessage {
    fn noop() -> Self { NoOp }
}

// our model
struct ButtonsModel {
    color_a: [f32; 3],
    color_b: [f32; 3],
    ids: IdSource,
}

// generate a random color
fn random_color<R: Rng>(&mut rng) -> [f32; 3] {
    [rng.next_f32(), rng.next_f32(), rng.next_f32()]
}

// create a button of a given color `color`, that changes the color of #`other`
fn make_button(other: usize, color: [f32; 3], id: ElementId) -> objects::Button {
    let rng = thread_rng(); // new rng
    objects::Button { // make button view
        // allows for in-progress animations to carry over
        element_id: id,
        // send change color event
        on_press: ChangeColor { button: other, to: random_color(&mut rng) },
        style: styles::NiceButton { // our own styler, from some other module
            primary_color: color,
            Default::default(),
        },
        Default::default() // all other events/params empty
    }
}

impl Model<ButtonsMessage> for ButtonsModel {
    // on message
    fn message(&mut self, event: ButtonsMessage, cont: Controller) {
        match event {
            ChangeColor { button: 0, to } => { self.color_a = to; cont.invalidate(); },
            ChangeColor { button: 1, to } => { self.color_b = to; cont.invalidate(); },
            _ => (),
        }
    }

    // builds the view
    fn view(&self) -> View { 
        let mut conn = layouts::Connected::new();

        // the root element is a button that changes the color of #1
        let root = conn.root(make_button(1, self.color_a, self.ids.by_int(0)));
        // 0.2cm below that is a button that changes the color of #0
        conn.below(root, make_button(0, self.color_b, self.ids.by_hash("another way to id")), 0.2);
        // export the item
        conn.build()
    }
}