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<page xmlns="http://projectmallard.org/1.0/" xmlns:its="http://www.w3.org/2005/11/its" type="topic" style="task" id="tour-events" xml:lang="it">

  <info>
    <link type="next" xref="tour-get_object"/>
    <revision version="0.1" date="2013-06-17" status="stub"/>

    <credit type="author copyright">
      <name>Ekaterina Gerasimova</name>
      <email its:translate="no">kittykat3756@gmail.com</email>
      <years>2013</years>
    </credit>
    <credit type="author copyright">
      <name>Gordon Hill</name>
      <email its:translate="no">caseyweederman@gmail.com</email>
      <years>2013</years>
    </credit>

    <include xmlns="http://www.w3.org/2001/XInclude" href="cc-by-sa-3-0.xml"/>

    <desc>Bind functions to events using Lang.</desc>
  </info>

  <title>Actions and signals</title>

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  <links type="series" style="floatend">
    <title>Get started with GNOME</title>
  </links>

  <p>Gtk has a set of predefined events that you can use in your application.</p>
  <example>
    <p>Declare <code>HelloWorld</code> as a new <code>Lang</code> class.
    Gjs requires classes to have the Name property defined.</p>

    <code><![CDATA[
const HelloWorld = new Lang.Class({
    Name: 'HelloWorld',
]]></code>

    <p><code>_init</code> is called when a new instance is created. Create a
    <code>GtkApplication</code>, then connect <code>activate</code> to the
    existing Gtk event <code>_onActivate</code> and <code>startup</code> to
    <code>_onStartup</code>:</p>

    <code><![CDATA[
    _init: function() {
        this.application = new Gtk.Application();
        this.application.connect('activate', Lang.bind(this, this._onActivate));
        this.application.connect('startup', Lang.bind(this, this._onStartup));
    },
]]></code>

    <p>Show the window upon application activation:</p>
    <code><![CDATA[
    _onActivate: function(){
        this._window.show_all();
    },
]]></code>
  </example>
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