Override FLTK's resizing defaults

resize_override.rs

#![allow(unused_variables)]

use fltk::{
    app::App,
    button::Button,
    enums::Event,
    group::Group,
    prelude::{GroupExt, WidgetBase, WidgetExt, WindowExt},
    window::Window,
};

fn main() {
    let app = App::default();
    let mut win = Window::default().with_size(400, 300);

    // but1 is automatically resized by FLTK
    let but1 = Button::new(80, 200, 80, 40, "but1");

    // We'll override but2's resizing in the win event handler
    let mut but2 = Button::new(180, 200, 80, 40, "but2");

    // We put but3 in a group to disable its resizing
    let mut grp = Group::new(280, 200, 80, 40, "");
    let but3 = Button::new(280, 200, 80, 40, "but3");
    grp.end();
    // This makes but3 unresizable
    grp.make_resizable(false);

    win.end();
    win.make_resizable(true);
    win.show();

    // This limits the window's size range to a minimun of (400, 300) and max (800, 600)
    // To remove the upper limit, pass zeroes: `win.size_range(400, 300, 0, 0);`
    win.size_range(400, 300, 800, 600);

    win.handle(move |w, ev| match ev {
        Event::Resize => {
            but2.resize(but2.x(), but2.y(), w.w() / 5 - 20, w.h() / 5 - 20);
            true
        }
        _ => false,
    });

    app.run().unwrap();
}