# Hello World (JavaScript)

Susanna Huhtanen
ihmis.suski@gmail.com 2012
Tiffany Antopolski
tiffany.antopolski@gmail.com
Una aplicación «Hola mundo» básica

# Hola mundo

          This tutorial will demonstrate how to:

            create a small "Hello, World" application using JavaScript and GTK+
            make the .desktop file
            how to set up the build system

# Create the HelloWorld program

## Script para ejecutar la aplicación

This needs to be the first line of your script:

#!/usr/bin/gjs

It tells the script to use Gjs. Gjs is a JavaScript binding for GNOME.

## Bibliotecas que importar

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

In order for our script to work with GNOME, we need to import GNOME libraries via GObject Introspection. Here we import the language bindings and GTK+, the library which contains the graphical widgets used to make GNOME applications.

## Crear la ventana principal de la aplicación

const Application = new Lang.Class({ //A Class requires an explicit Name parameter. This is the Class Name. Name: 'Application',

//create the application _init: function() { this.application = new Gtk.Application();

//connect to 'activate' and 'startup' signals to handlers. this.application.connect('activate', Lang.bind(this, this._onActivate)); this.application.connect('startup', Lang.bind(this, this._onStartup)); },

//create the UI _buildUI: function() { this._window = new Gtk.ApplicationWindow({ application: this.application, title: "Hello World!" }); },

//handler for 'activate' signal _onActivate: function() { //show the window and all child widgets this._window.show_all(); },

//handler for 'startup' signal _onStartup: function() { this._buildUI(); } });

GtkApplication initializes Gtk+. It also connects the x button that's automatically generated along with the window to the "destroy" signal.

We can start building our first window. We do this by creating a variable called _window and assigning it a new Gtk.ApplicationWindow.

We give the window a property called title. The title can be any string you want it to be. To be on the safe side, it's best to stick to UTF-8 encoding.

Now we have a window which has a title and a working "close" button. Let's add the actual "Hello World" text.

## Etiqueta para la ventana

// Add a label widget to your window this.label = new Gtk.Label({ label: "Hello World" }); this._window.add(this.label); this._window.set_default_size(200, 200);

A text label is one of the GTK+ widgets we can use, on account of having imported the GTK+ library. To use it, we create a new variable called label, and assign it a new Gtk.Label. Then we give it properties inside the curly braces {}. In this case, we're setting the text that the label will hold. Finally, we create and run the application:

//run the application let app = new Application(); app.application.run(ARGV);

Gtk.ApplicationWindow can only hold one widget at a time. To construct more elaborate programs you need to create a holder widget like Gtk.Grid inside the window, and then add all the other widgets to it.

## helloWorld.js

The complete file:

## Running the application from terminal

To run this application, first save it as helloWorld.js. Then open Terminal, go to the folder where your application is stored and run:

    $ gjs helloWorld.js

# The .desktop.in file

Running applications from the Terminal is useful at the beginning of the application making process. To have fully working application integration in GNOME 3 requires a desktop launcher. For this you need to create a .desktop file. The .desktop file describes the application name, the used icon and various integration bits. A deeper insight into the .desktop file can be found here. The .desktop.in file will create the .desktop.

Before continuing, resave helloWorld.js as helloWorld. Then run this in the command line:

    $ chmod +x helloWorld

The example shows you the minimum requirements for a `.desktop.in` file.

Now let's go through some parts of the `.desktop.in` file.

## Nombre

The application name.

## Comment

A short description of the application.

## Exec

Specifies a command to execute when you choose the application from the menu. In this example exec just tells where to find the helloWorld file and the file takes care of the rest.

## Terminal

Specifies whether the command in the Exec key runs in a terminal window.

To put your application into the appropriate category, you need to add the necessary categories to the Categories line. More information on the different categories can be found in the menu specification.

In this example we use an existing icon. For a custom icon you need to have a .svg file of your icon, stored in /usr/share/icons/hicolor/scalable/apps. Write the name of your icon file to the .desktop.in file, on line 7. More information on icons in: Installing Icons for Themes , Installing Icons for Themes and on freedesktop.org: Specifications/icon-theme-spec.

# The build system

Para que su aplicación forme parte realmente del sistema GNOME 3 debe instalarla con la ayuda de autotools. La construcción autotools instalará todos los archivos necesarios en las ubicaciones correctas.

Para esto deberá tener los siguientes archivos:

## autogen.sh

After the autogen.sh file is ready and saved, run:

    $ chmod +x autogen.sh

## Makefile.am

## configure.ac

## README

Información que los usuarios deben leer primero. Este archivo puede estar vacío.

When you have the helloWorld, helloWorld.desktop.in, Makefile.am, configure.ac and autogen.sh files with correct information and rights, the README file can include the following instructions: