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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id-1.2.3.11"></a>Building user interfaces</h2></div></div></div>
<p>When construcing a more complicated user interface, with dozens
    or hundreds of widgets, doing all the setup work in C code is
    cumbersome, and making changes becomes next to impossible.</p>
<p>Thankfully, GTK+ supports the separation of user interface
    layout from your business logic, by using UI descriptions in an
    XML format that can be parsed by the <a class="link" href="GtkBuilder.html" title="GtkBuilder"><span class="type">GtkBuilder</span></a> class.</p>
<div class="example">
<a name="id-1.2.3.11.4"></a><p class="title"><b>Example 3. Packing buttons with GtkBuilder</b></p>
<div class="example-contents">
<p>Create a new file with the following content named example-3.c.</p>
<pre class="programlisting">#include &lt;gtk/gtk.h&gt;

static void
print_hello (GtkWidget *widget,
             gpointer   data)
{
  g_print ("Hello World\n");
}

int
main (int   argc,
      char *argv[])
{
  GtkBuilder *builder;
  GObject *window;
  GObject *button;
  GError *error = NULL;

  gtk_init (&amp;argc, &amp;argv);

  /* Construct a GtkBuilder instance and load our UI description */
  builder = gtk_builder_new ();
  if (gtk_builder_add_from_file (builder, "builder.ui", &amp;error) == 0)
    {
      g_printerr ("Error loading file: %s\n", error-&gt;message);
      g_clear_error (&amp;error);
      return 1;
    }

  /* Connect signal handlers to the constructed widgets. */
  window = gtk_builder_get_object (builder, "window");
  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);

  button = gtk_builder_get_object (builder, "button1");
  g_signal_connect (button, "clicked", G_CALLBACK (print_hello), NULL);

  button = gtk_builder_get_object (builder, "button2");
  g_signal_connect (button, "clicked", G_CALLBACK (print_hello), NULL);

  button = gtk_builder_get_object (builder, "quit");
  g_signal_connect (button, "clicked", G_CALLBACK (gtk_main_quit), NULL);

  gtk_main ();

  return 0;
}
</pre>
<p>Create a new file with the following content named builder.ui.</p>
<pre class="programlisting">&lt;interface&gt;
  &lt;object id="window" class="GtkWindow"&gt;
    &lt;property name="visible"&gt;True&lt;/property&gt;
    &lt;property name="title"&gt;Grid&lt;/property&gt;
    &lt;property name="border-width"&gt;10&lt;/property&gt;
    &lt;child&gt;
      &lt;object id="grid" class="GtkGrid"&gt;
        &lt;property name="visible"&gt;True&lt;/property&gt;
        &lt;child&gt;
          &lt;object id="button1" class="GtkButton"&gt;
            &lt;property name="visible"&gt;True&lt;/property&gt;
            &lt;property name="label"&gt;Button 1&lt;/property&gt;
          &lt;/object&gt;
          &lt;packing&gt;
            &lt;property name="left-attach"&gt;0&lt;/property&gt;
            &lt;property name="top-attach"&gt;0&lt;/property&gt;
          &lt;/packing&gt;
        &lt;/child&gt;
        &lt;child&gt;
          &lt;object id="button2" class="GtkButton"&gt;
            &lt;property name="visible"&gt;True&lt;/property&gt;
            &lt;property name="label"&gt;Button 2&lt;/property&gt;
          &lt;/object&gt;
          &lt;packing&gt;
            &lt;property name="left-attach"&gt;1&lt;/property&gt;
            &lt;property name="top-attach"&gt;0&lt;/property&gt;
          &lt;/packing&gt;
        &lt;/child&gt;
        &lt;child&gt;
          &lt;object id="quit" class="GtkButton"&gt;
            &lt;property name="visible"&gt;True&lt;/property&gt;
            &lt;property name="label"&gt;Quit&lt;/property&gt;
          &lt;/object&gt;
          &lt;packing&gt;
            &lt;property name="left-attach"&gt;0&lt;/property&gt;
            &lt;property name="top-attach"&gt;1&lt;/property&gt;
            &lt;property name="width"&gt;2&lt;/property&gt;
          &lt;/packing&gt;
        &lt;/child&gt;
      &lt;/object&gt;
      &lt;packing&gt;
      &lt;/packing&gt;
    &lt;/child&gt;
  &lt;/object&gt;
&lt;/interface&gt;
</pre>
</div>
</div>
<br class="example-break"><p>
      You can compile the program above with GCC using:
      </p>
<div class="literallayout"><p><br>
        <code class="literal">gcc `pkg-config --cflags gtk+-3.0` -o example-3 example-3.c `pkg-config --libs gtk+-3.0`</code><br>
      </p></div>
<p>
    </p>
<p>Note that GtkBuilder can also be used to construct objects
    that are not widgets, such as tree models, adjustments, etc.
    That is the reason the method we use here is called
    <a class="link" href="GtkBuilder.html#gtk-builder-get-object" title="gtk_builder_get_object ()"><code class="function">gtk_builder_get_object()</code></a> and returns a GObject* instead of a
    GtkWidget*.</p>
<p>Normally, you would pass a full path to
    <a class="link" href="GtkBuilder.html#gtk-builder-add-from-file" title="gtk_builder_add_from_file ()"><code class="function">gtk_builder_add_from_file()</code></a> to make the execution of your program
    independent of the current directory. A common location to install
    UI descriptions and similar data is
    <code class="filename">/usr/share/<em class="replaceable"><code>appname</code></em></code>.
    </p>
<p>It is also possible to embed the UI description in the source
    code as a string and use <a class="link" href="GtkBuilder.html#gtk-builder-add-from-string" title="gtk_builder_add_from_string ()"><code class="function">gtk_builder_add_from_string()</code></a> to load it.
    But keeping the UI description in a separate file has several
    advantages: It is then possible to make minor adjustments to the UI
    without recompiling your program, and, more importantly, graphical
    UI editors such as <a class="ulink" href="http://glade.gnome.org" target="_top">glade</a>
    can load the file and allow you to create and modify your UI by
    point-and-click.</p>
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