i-am-legend/src/main.rs

use gtk::{
    Application,
    ApplicationWindow,
    Button,
    GtkWindowExt,
    WidgetExt,
    ContainerExt,
    ButtonExt,
    BoxExt,
};
use gio::prelude::{
    ApplicationExt,
    ApplicationExtManual,
};
use std::rc::Rc;
use std::cell::RefCell;


struct Legend {
    symbol: char,
    color: (f64, f64, f64),
}

impl Legend {
    fn draw_to_file(&self) {
        let f = std::fs::File::create("samp.svg").unwrap();
        let surf = cairo::SvgSurface::for_stream(
            100.0,
            100.0,
            f,
        ).unwrap();
        self.render(&cairo::Context::new(&surf));
        surf.finish_output_stream().unwrap();
    }

    fn render(&self, ctx: &cairo::Context) -> () {
        ctx.set_source_rgb(self.color.0, self.color.1, self.color.2);
        ctx.paint();

        ctx.set_source_rgb(0., 0., 0.);

        ctx.move_to(0.0, -23.0);
        let layout = pangocairo::functions::create_layout(&ctx).unwrap();
        layout.set_width(100 * 1024);
        layout.set_alignment(pango::Alignment::Center);
        let font = pango::FontDescription::from_string("Fira Sans 92");
        layout.set_font_description(Some(&font));

        layout.set_text(&self.symbol.to_string());
        pangocairo::functions::show_layout(&ctx, &layout);
    }
}

struct AppData {
    legend: Legend,
}

#[derive(Clone)]
struct App {
    data: Rc<RefCell<AppData>>,
}

impl App {
    fn new() -> App {
        let legend = Legend {
            symbol: 'X',
            color: (0.5, 0.5, 0.5),
        };
        let data = Rc::new(RefCell::new(AppData { legend }));
        App { data }
    }
}

fn mk_app(app: &gtk::Application) {
    let window = ApplicationWindow::new(app);

    let app = App::new();

    window.set_title("I Am Legend");
    let container = gtk::Box::new(gtk::Orientation::Vertical, 4);
    container.pack_start(&mk_icon_choice('A', app.clone()), false, true, 0);
    container.pack_start(&mk_icon_choice('B', app.clone()), false, true, 0);
    container.pack_start(&mk_icon_choice('C', app.clone()), false, true, 0);
    container.pack_start(&mk_icon_choice('D', app.clone()), false, true, 0);

    let flow = gtk::Box::new(gtk::Orientation::Horizontal, 2);
    flow.pack_start(&container, false, true, 0);
    let button = Button::with_label("Click me!");
    flow.pack_start(&button, false, true, 0);

    let canvas = gtk::DrawingArea::new();
    let copy = app.clone();
    canvas.connect_draw(move |cv, ctx| {
        copy.data.borrow_mut().legend.render(ctx);
        gtk::Inhibit(false)
    });
    flow.pack_start(&canvas, true, true, 0);

    button.connect_clicked(move |_| {
        app.data.borrow_mut().legend.draw_to_file();
    });

    window.add(&flow);
    window.show_all();
}

fn mk_icon_choice(choice: char, cell: App) -> gtk::Button {
    let button = gtk::Button::with_label(&choice.to_string());
    button.connect_clicked(move |_| {
        cell.data.borrow_mut().legend.symbol = choice;
        println!("Choosing '{}'", choice);
    });
    button
}

fn main() {
    let application = Application::new(
        Some("com.github.gtk-rs.examples.basic"),
        Default::default(),
    ).expect("failed to initialize GTK application");

    application.connect_activate(|app| {
        mk_app(app);
    });

    application.run(&[]);
}