use fltk::{app, button::Button, frame::Frame, prelude::*, window::Window};
fn main() {
let app = app::App::default();
let mut wind = Window::default().with_size(400, 300);
let mut frame = Frame::default().with_size(200, 100).center_of(&wind);
let mut but = Button::new(160, 210, 80, 40, "Click me!");
wind.end();
wind.show();
but.set_callback(move |_| frame.set_label("Hello world"));
app.run().unwrap();
}