<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" xml:lang="pt-BR">

  <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>

    <mal:credit xmlns:mal="http://projectmallard.org/1.0/" type="translator copyright">

      <mal:name>Rafael Ferreira</mal:name>

      <mal:email>rafael.f.f1@gmail.com</mal:email>

      <mal:years>2013</mal:years>

    </mal:credit>

  </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>

      
This tutorial will demonstrate how to:

      <list style="numbered">

        <item>
create a small "Hello, World" application using JavaScript and GTK+
</item>

        <item>
make the <file>.desktop</file> file
</item>

        <item>
how to set up the build system
</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>

      
This needs to be the first line of your script:

      
It tells the script to use <link href="https://live.gnome.org/Gjs/">Gjs</link>. Gjs is a JavaScript binding for GNOME.

    </section>

    <section id="imports"><title>Libraries to import</title>

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.  

    </section>

    <section id="mainwindow"><title>Creating the main window for the application</title>

    //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 <gui>x</gui> 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.

    </section>

    <section id="label"><title>Label for the window</title>

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:

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.

   </section>

    <section id="js"><title>hello-world.js</title>

      
The complete file:

      #!/usr/bin/gjs

imports.gi.versions.Gtk = '3.0'

const Gtk = imports.gi.Gtk;

class Application {

    //create the application

    constructor() {

        this.application = new Gtk.Application();

       //connect to 'activate' and 'startup' signals to handlers.

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

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

    }

    //create the UI

    _buildUI() {

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

                                                   title: "Hello World!" });

        this._window.set_default_size(200, 200);

        this.label = new Gtk.Label({ label: "Hello World" });

        this._window.add(this.label);

    }

    //handler for 'activate' signal

    _onActivate() {

        //show the window and all child widgets

        this._window.show_all();

    }

    //handler for 'startup' signal

    _onStartup() {

        this._buildUI();

    }

};

//run the application

let app = new Application();

app.application.run(ARGV);

    </section>

    <section id="terminal"><title>Running the application from terminal</title>

      
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:

      <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>

      
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>.

  <note>

       
Before continuing, resave <file>hello-world.js</file> as <file>hello-world</file>.  Then run this in the command line:

      <screen><output style="prompt">$ </output><input>chmod +x hello-world</input></screen>

  </note>

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

    [Desktop Entry]

Version=1.0

Encoding=UTF-8

Name=Hello World

Comment=Say Hello

Exec=@prefix@/bin/hello-world

Icon=application-default-icon

Terminal=false

Type=Application

StartupNotify=true

Categories=GNOME;GTK;Utility;

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

    <terms>

      <item><title>Name</title>
The application name.
</item>

      <item><title>Comment</title>
A short description of the application.
</item>

      <item><title>Exec</title>
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.
</item>

      <item><title>Terminal</title>
Specifies whether the command in the Exec key runs in a terminal window.
</item>

    </terms>

    
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>.

    
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://live.gnome.org/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>.

  </section>

  <section id="autotools"><title>The build system</title>

    
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. 

    
For this you need to have the following files:

    <links type="section"/>

      <section id="autogen"><title>autogen.sh</title>

        #!/bin/sh

set -e

test -n "$srcdir" || srcdir=`dirname "$0"`

test -n "$srcdir" || srcdir=.

olddir=`pwd`

cd "$srcdir"

# This will run autoconf, automake, etc. for us

autoreconf --force --install

cd "$olddir"

if test -z "$NOCONFIGURE"; then

  "$srcdir"/configure "$@"

fi

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

      <screen><output style="prompt">$ </output><input>chmod +x autogen.sh</input></screen>

    </section>

    <section id="makefile"><title>Makefile.am</title>

      # The actual runnable program is set to the SCRIPTS primitive.

# # Prefix bin_ tells where to copy this

bin_SCRIPTS = hello-world

# # List of files to be distributed

EXTRA_DIST =  \

	$(bin_SCRIPTS)

#

#     # The desktop files

desktopdir = $(datadir)/applications

desktop_DATA = \

	hello-world.desktop

    </section>

    <section id="configure"><title>configure.ac</title>

      # This file is processed by autoconf to create a configure script

AC_INIT([Hello World], 1.0)

AM_INIT_AUTOMAKE([1.10 no-define foreign dist-xz no-dist-gzip])

AC_CONFIG_FILES([Makefile hello-world.desktop])

AC_OUTPUT

    </section>

    <section id="readme"><title>README</title>

       
Information users should read first. This file can be blank.

       
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 rights, the <file>README</file> file can include the following instructions:

      To build and install this program:

./autogen.sh --prefix=/home/your_username/.local

make install

-------------

Running the first line above creates the following files:

aclocal.m4

autom4te.cache

config.log

config.status

configure

hello-world.desktop

install-sh

missing

Makefile.in

Makefile

Running "make install", installs the application in /home/your_username/.local/bin

and installs the hello-world.desktop file in /home/your_username/.local/share/applications

You can now run the application by typing "Hello World" in the Overview.

----------------

To uninstall, type:

make uninstall

----------------

To create a tarball type:

make distcheck

This will create hello-world-1.0.tar.xz

    </section>

  </section>

</page>