Hover effect in Gtk Image

hover_image.js

const GdkPixbuf = imports.gi.GdkPixbuf;
const Gtk = imports.gi.Gtk;
const Lang = imports.lang;
 
Gtk.init(null, 0);
 
 
let test_window = new Gtk.Window({
    default_width: 128,
    default_height: 128
});

let events = new Gtk.EventBox();
let layers = new Gtk.Overlay();
events.add(layers);

let original_pix = GdkPixbuf.Pixbuf.new_from_file_at_scale("image.jpg", 128, 128, false);

let bw_pix = original_pix.copy();
original_pix.saturate_and_pixelate(bw_pix, 0, 0);
layers.add(Gtk.Image.new_from_pixbuf(bw_pix));

let hover_image = Gtk.Image.new_from_pixbuf(original_pix);
hover_image.set_opacity(0);
hover_image.get_style_context().add_class('hover');
layers.add_overlay(hover_image);

events.connect('enter-notify-event', Lang.bind(this, function() {
    hover_image.set_opacity(1);
    hover_image.get_style_context().remove_class('hover');
}));

test_window.add(events);
test_window.show_all();
Gtk.main();