如何在Gtk-rs中创建一个建议的圆角按钮？

extern crate gtk;
use gtk::prelude::*;
use gtk::{Button, Window, WindowType};

fn main() {
    gtk::init().expect("Failed to initialize GTK.");

    let window = Window::new(WindowType::Toplevel);
    window.set_title("圆角按钮示例");
    window.set_default_size(200, 100);

    let button = Button::new_with_label("按钮");
    button.set_border_width(10);
    button.set_border_radius(10);
    button.set_size_request(100, 50);

    window.add(&button);

    window.show_all();

    gtk::main();
}

$ cargo build
$ cargo run