Rust gtk4 hello world

main.rs

use gtk4::prelude::*;
use gtk4::{
    Application, ApplicationWindow, Button, DrawingArea, EventControllerKey, EventControllerMotion,
    Inhibit,
};

fn main() {
    let app = Application::builder()
        .application_id("org.example.HelloWorld")
        .build();

    app.connect_activate(|app| {
        // We create the main window.
        let window = ApplicationWindow::builder()
            .application(app)
            .default_width(320)
            .default_height(200)
            .title("Hello, World!")
            .build();
        let button = Button::with_label("Click me!");
        let mouse = EventControllerMotion::new();
        let keys = EventControllerKey::new();
        let canvas = DrawingArea::new();
        canvas.add_controller(&mouse);
        canvas.add_controller(&keys);
        keys.connect_key_pressed(move |_, a, b, c| {
            eprintln!("keyval {}", a);
            eprintln!("keycode {}", b);
            eprintln!("state {}", c);
            Inhibit(false)
        });

        mouse.connect_motion(|_, x, y| {
            eprintln!("x:{}, y:{}", x, y);
        });
        button.connect_clicked(|_| {
            eprintln!("Clicked!");
        });

        window.set_child(Some(&canvas));
        // Show the window.
        window.show();
    });

    app.run();
}