A mouse test program written in gjs (Gtk+ JavaScript)

mousetest.js

#!/usr/bin/gjs

const GObject = imports.gi.GObject;
const Gdk = imports.gi.Gdk;
const Gtk = imports.gi.Gtk;
const Lang = imports.lang;

const MouseTest = new Lang.Class({

    Name: "Mouse Test",
    
    _init : function() {
        this.application = new Gtk.Application({
            application_id: "org.example.mousetest"
        });
        this.application.connect("activate", Lang.bind(this, this._onActivate));
        this.application.connect("startup", Lang.bind(this, this._onStartup));
    },

    _onActivate: function() {
        this.window.present();
    },

    _onStartup: function() {
        this._buildUI();
    },

    _buildUI: function () {
        this.window = new Gtk.ApplicationWindow({
            application: this.application,
            window_position: Gtk.WindowPosition.CENTER,
            title: "Mouse Test",
            default_width: 640,
            default_height: 480
        });
        this.window.set_events(
            Gdk.EventMask.POINTER_MOTION_MASK |
            Gdk.EventMask.BUTTON_MOTION_MASK
        );
        this.window.connect("destroy", function() {
            Gtk.main_quit();
        });
        this.window.connect("motion_notify_event", this._onMouseEvent);
        this.window.connect("button_press_event", this._onMouseEvent);
        this.window.show();
    },
    
    _onMouseEvent: function(stage, event) {
        const coords = event.get_coords();
        let res = "";
        if(coords[0])
            res += "(" + coords[1] + ", " + coords[2] + ")";
        const buttons = event.get_button();
        if(buttons[0])
            res += " Button: " + buttons[1];
        if(res)
            print(res);
    }


});

let app = new MouseTest();
app.application.run(ARGV);