use fltk::{app, button::Button, frame::Frame, group::Flex, prelude::*, window::Window};
fn main() {
let app = app::App::default();
let mut wind = Window::default().with_size(400, 300);
let mut col = Flex::default_fill().column();
col.set_margins(120, 80, 120, 80);
let mut frame = Frame::default();
let mut but = Button::default().with_label("Click me!");
col.fixed(&but, 40);
col.end();
wind.end();
wind.show();
but.set_callback(move |_| frame.set_label("Hello world"));
app.run().unwrap();
}