#!/usr/bin/gjs

imports.gi.versions.Gtk = '3.0';

const Gio = imports.gi.Gio;

const GLib = imports.gi.GLib;

const Gtk = imports.gi.Gtk;

class GridExample {

    /* Create the application itself

       This boilerplate code is needed to build any GTK+ application. */

    constructor() {

        this.application = new Gtk.Application ({

            application_id: 'org.example.jsgrid',

            flags: Gio.ApplicationFlags.FLAGS_NONE

        });

        // Connect 'activate' and 'startup' signals to the callback functions

        this.application.connect('activate', this._onActivate.bind(this));

        this.application.connect('startup', this._onStartup.bind(this));

    }

    // Callback function for 'activate' signal presents windows when active

    _onActivate() {

        this._window.present();

    }

    // Callback function for 'startup' signal initializes menus and builds the UI

    _onStartup() {

        this._buildUI();

    }

    // Build the application's UI

    _buildUI() {

        // Create the application window

            this._window = new Gtk.ApplicationWindow  ({ application: this.application,

                                                         window_position: Gtk.WindowPosition.CENTER,

                                                         title: "Grid Example"});

        // Create the grid

        this.Grid = new Gtk.Grid ();

        // Create the widgets inside the grid

        this.progressBar = new Gtk.ProgressBar ();

        this.Button = new Gtk.Button ({ label: "Button" });

        this.Button.connect ("clicked", this._clickHandler.bind(this));

        // Assemble the grid

        this._window.add (this.Grid);

        this.Grid.attach (this.Button, 1, 1, 1, 1);

        this.Grid.attach_next_to (this.progressBar, this.Button, Gtk.PositionType.BOTTOM, 1, 1);

                // Show the window and all child widgets

                this._window.show_all();

    }

    // Here's the function that says what happens when the button is clicked

    _clickHandler() {

        this.progressBar.pulse ();

    }

};

// Run the application

let app = new GridExample ();

app.application.run (ARGV);