xmlns:its="http://www.w3.org/2005/11/its"

      xmlns:xi="http://www.w3.org/2001/XInclude"

      type="guide" style="task"

      id="hello-world.vala">

  <info>

  <title type="text">Hello World (Vala)</title>

    <link type="guide" xref="beginner.vala#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>

      
This tutorial will demonstrate how to:

      <list style="numbered">

        <item>
create a small "Hello, World" application using 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="hello-world"><title>Create the program</title>

    <links type="section" />

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

        protected override void activate () {

                var window = new Gtk.ApplicationWindow (this);

                window.set_title ("Welcome to GNOME");

                window.set_default_size (200, 100);

                window.show_all ();

        }

}]]>

    
Gtk.Application 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 title using set_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>

                window.add (label);

]]>

      
Finally, we create and run the application:

        return new MyApplication ().run (args);

}]]>

      
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="vala"><title>hello-world.vala</title>

      
The complete file:

      <xi:include href="samples/hello-in-vala/hello-world.vala" parse="text"><xi:fallback/></xi:include>

    </section>

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

      
To run this application, first save it as hello-world.vala. Then open Terminal, go to the folder where your application is stored.

      
Compile the program:

           <screen>valac --pkg gtk+-3.0 <file>hello-world.vala</file></screen>

      
Run the program:

           <screen>./hello-world</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>.

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

    <xi:include href="samples/hello-in-vala/hello-world.desktop.in" parse="text"><xi:fallback/></xi:include>

    
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>

        <xi:include href="samples/hello-in-vala/autogen.sh" parse="text"><xi:fallback/></xi:include>

      
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>

      <xi:include href="samples/hello-in-vala/Makefile.am" parse="text"><xi:fallback/></xi:include>

    </section>

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

      <xi:include href="samples/hello-in-vala/configure.ac" parse="text"><xi:fallback/></xi:include>

    </section>

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

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

       
When you have the <file>hello-world.c</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:

      <xi:include href="samples/hello-in-vala/README" parse="text"><xi:fallback/></xi:include>

    </section>

  </section>

</page>