<?xml version='1.0' encoding='UTF-8'?>
<page xmlns="http://projectmallard.org/1.0/"
      xmlns:its="http://www.w3.org/2005/11/its"
      xmlns:xi="http://www.w3.org/2001/XInclude"
      type="guide" style="task"
      id="hello-world.js">

  <info>
  <title type="text">Hello World (JavaScript)</title>
    <link type="guide" xref="beginner.js#tutorials" group="#first"/>

    <revision version="0.1" date="2013-06-17" status="review"/>

    <credit type="author copyright">
      <name>Susanna Huhtanen</name>
      <email its:translate="no">ihmis.suski@gmail.com</email>
      <years>2012</years>
    </credit>
    <credit type="editor">
      <name>Tiffany Antopolski</name>
      <email its:translate="no">tiffany.antopolski@gmail.com</email>
    </credit>

    <desc>A basic "hello, world" application</desc>
  </info>

  <title>How to build, install and create a <file>tar.xz</file> of a Hello World program</title>
    <media type="image" mime="image/png" style="floatend" src="media/hello-world.png"/>
    <synopsis>
      <p>This tutorial will demonstrate how to:</p>
      <list style="numbered">
        <item><p>create a small "Hello, World" application using JavaScript and GTK+</p></item>
        <item><p>make the <file>.desktop</file> file</p></item>
        <item><p>how to set up the build system</p></item>
      </list>
    </synopsis>



  <links type="section" />

  <section id="HelloWorld"><title>Create the program</title>

    <links type="section" />

    <section id="script"><title>Script for running the application</title>
      <p>This needs to be the first line of your script:</p>
      <code mime="application/javascript"><![CDATA[#!/usr/bin/gjs]]></code>
      <p>It tells the script to use <link href="https://live.gnome.org/Gjs/">Gjs</link>. Gjs is a JavaScript binding for GNOME.</p>
    </section>


    <section id="imports"><title>Libraries to import</title>
      <code mime="application/javascript"><![CDATA[const Lang = imports.lang;

imports.gi.versions.Gtk = '3.0'
const Gtk = imports.gi.Gtk;]]></code>
      <p>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.  </p>
    </section>

    <section id="mainwindow"><title>Creating the main window for the application</title>
      <code mime="application/javascript"><![CDATA[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();
    }
});
]]></code>

    <p>GtkApplication initializes GTK+. It also connects the <gui>x</gui> button that's automatically generated along with the window to the "destroy" signal.</p>
    <p>We can start building our first window. We do this by creating a variable called <var>_window</var> and assigning it a new Gtk.ApplicationWindow.</p>
    <p>We give the window a property called <var>title</var>. 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.</p>
    <p>Now we have a window which has a title and a working "close" button. Let's add the actual "Hello World" text.</p>
    </section>

    <section id="label"><title>Label for the window</title>
      <code mime="application/javascript"><![CDATA[// 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);]]></code>

      <p>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:</p>

      <code mime="application/javascript"><![CDATA[//run the application
let app = new Application();
app.application.run(ARGV);]]></code>

      <p>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.</p>
   </section>


    <section id="js"><title>hello-world.js</title>
      <p>The complete file:</p>
      <code mime="application/javascript" style="numbered"><xi:include href="samples/hello-in-js/hello-world" parse="text"><xi:fallback/></xi:include></code>
    </section>

    <section id="terminal"><title>Running the application from terminal</title>
      <p>To run this application, first save it as hello-world.js. Then open Terminal, go to the folder where your application is stored and run:</p>
      <screen><output style="prompt">$ </output><input>gjs hello-world.js</input></screen>
    </section>
  </section>



  <section id="desktop.in"><title>The <file>.desktop.in</file> file</title>
      <p>Running applications from the Terminal is useful at the beginning of the application making process. To have fully working <link href= "https://developer.gnome.org/integration-guide/stable/mime.html.en">application integration</link> in GNOME 3 requires a desktop launcher. For this you need to create a  <file>.desktop</file> file. The <file>.desktop</file> file describes the application name, the used icon and various integration bits. A deeper insight into the <file>.desktop</file> file can be found <link href= "http://developer.gnome.org/desktop-entry-spec/">here</link>. The <file>.desktop.in</file> file will create the <file>.desktop</file>.</p>

  <note>
       <p>Before continuing, resave <file>hello-world.js</file> as <file>hello-world</file>.  Then run this in the command line:</p>
      <screen><output style="prompt">$ </output><input>chmod +x hello-world</input></screen>
  </note>

    <p>The example shows you the minimum requirements for a <code>.desktop.in</code> file.</p>
    <code mime="text/desktop" style="numbered"><xi:include href="samples/hello-in-js/hello-world.desktop.in" parse="text"><xi:fallback/></xi:include></code>

    <p>Save this as <file>hello-world.desktop.in</file>. Now let's go through some parts of the <code>.desktop.in</code> file.</p>
    <terms>
      <item><title>Name</title><p>The application name.</p></item>
      <item><title>Comment</title><p>A short description of the application.</p></item>
      <item><title>Exec</title><p>Specifies a command to execute when you choose the application from the menu. In this example exec just tells where to find the <file>hello-world</file> file and the file takes care of the rest.</p></item>
      <item><title>Terminal</title><p>Specifies whether the command in the Exec key runs in a terminal window.</p></item>
    </terms>

    <p>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 <link href = "http://standards.freedesktop.org/menu-spec/latest/apa.html">menu specification</link>.</p>
    <p>In this example we use an existing icon. For a custom icon you need to have a .svg file of your icon, stored in <file>/usr/share/icons/hicolor/scalable/apps</file>. Write the name of your icon file to the .desktop.in file, on line 7. More information on icons in: <link href="https://wiki.gnome.org/Initiatives/GnomeGoals/AppIcon">Installing Icons for Themes</link> and <link href="http://freedesktop.org/wiki/Specifications/icon-theme-spec">on freedesktop.org: Specifications/icon-theme-spec</link>.</p>
  </section>

  <section id="autotools"><title>The build system</title>
    <p>To make your application truly a part of the GNOME 3 system you need to install it with the help of autotools. The autotools build will install all the necessary files to all the right places. </p>
    <p>For this you need to have the following files:</p>
    <links type="section"/>

      <section id="autogen"><title>autogen.sh</title>
        <code mime="application/x-shellscript" style="numbered"><xi:include href="samples/hello-in-js/autogen.sh" parse="text"><xi:fallback/></xi:include></code>

      <p>After the <file>autogen.sh</file> file is ready and saved, run:</p>
      <screen><output style="prompt">$ </output><input>chmod +x autogen.sh</input></screen>
    </section>


    <section id="makefile"><title>Makefile.am</title>
      <code mime="application/x-shellscript" style="numbered"><xi:include href="samples/hello-in-js/Makefile.am" parse="text"><xi:fallback/></xi:include></code>
    </section>


    <section id="configure"><title>configure.ac</title>
      <code mime="application/x-shellscript" style="numbered"><xi:include href="samples/hello-in-js/configure.ac" parse="text"><xi:fallback/></xi:include></code>
    </section>


    <section id="readme"><title>README</title>
       <p>Information users should read first. This file can be blank.</p>

       <p>When you have the <file>hello-world</file>, <file>hello-world.desktop.in</file>, <file>Makefile.am</file>, <file>configure.ac</file> and <file>autogen.sh</file> files with correct information and permissions, create a <file>README</file> file with installation instructions. Below is a sample of what suitable README instructions may look like:</p>
      <code mime="text/readme" style="numbered"><xi:include href="samples/hello-in-js/README" parse="text"><xi:fallback/></xi:include></code>
    </section>

    <!-- TODO: How to make a custom icon with autotools -->

  </section>
</page>
