gistfile1.txt

const Gtk = imports.gi.Gtk;
const Gdk = imports.gi.Gdk;

Gtk.init(null);

let overlay = new Gtk.Overlay()

let button = new Gtk.Button({
    expand: true,
});

button.connect('clicked', function (widget) {
    print("hello")
})
button.set_size_request(200, 100)

button.get_style_context().add_class('shadow')

let css = ".shadow {background-color:red; border: 2px solid blue; box-shadow: 0px 1px 20px 0px alpha(black, 0.5); padding: 10px;}"

let provider = new Gtk.CssProvider();
provider.load_from_data(css);
let context = button.get_style_context();
context.add_provider(provider, Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION);


let mwindow = new Gtk.Window({
    default_width: 800,
    default_height: 600
});
overlay.add(button)
let stack = new Gtk.Stack({
    halign: Gtk.Align.START,
    hexpand: true,
})
stack.set_size_request(50, 50)
stack.get_style_context().add_class('shadow')

overlay.add_overlay(stack)
overlay.set_overlay_pass_through(stack, true)

mwindow.add(overlay);
mwindow.show_all();
mwindow.connect('destroy', function() { Gtk.main_quit() });

Gtk.main();