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<div class="titlepage"><div><div><h1 class="title">
<a name="chapter-builder"></a>Chapter 26. Gtk::Builder</h1></div></div></div>
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<p><b>Table of Contents</b></p>
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<li><span class="section"><a href="chapter-builder.html#sec-builder-loading-ui-file">Loading the .ui file</a></span></li>
<li><span class="section"><a href="sec-builder-accessing-widgets.html">Accessing widgets</a></span></li>
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<p>
Although you can use C++ code to instantiate and arrange widgets, this can soon
become tedious and repetitive. And it requires a recompilation to show changes.
The <a class="ulink" href="https://gitlab.gnome.org/jpu/cambalache" target="_top">Cambalache</a>
application allows you to layout widgets on screen and then save an XML description
of the arrangement. Your application can then use the <span class="application">Gtk::Builder</span>
API to load that XML file at runtime and obtain a pointer to specifically named
widget instances.
</p>
<p>
This has the following advantages:
</p>
<div class="orderedlist"><ol class="orderedlist" type="1">
<li class="listitem">Less C++ code is required.</li>
<li class="listitem">UI changes can be seen more quickly, so UIs are able to improve.</li>
<li class="listitem">Designers without programming skills can create and edit UIs.</li>
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You still need C++ code to deal with User Interface changes triggered by user
actions, but using <span class="application">Gtk::Builder</span> for the widget
layout allows you to focus on implementing that functionality.
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<p>
<span class="application">Cambalache</span> replaces the <span class="application">Glade</span>
application. <span class="application">Glade</span> can generate XML files to be used
with gtk3/<span class="application">gtkmm</span>3, but it does not support gtk4/<span class="application">gtkmm</span>4.
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<a name="sec-builder-loading-ui-file"></a>Loading the .ui file</h2></div></div></div>
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<code class="classname">Gtk::Builder</code> must be used via a
<code class="classname">Glib::RefPtr</code>. Like all such classes, you need to use a
<code class="methodname">create()</code> method to instantiate it. For instance,</p>
<pre class="programlisting"><code class="code">auto builder = Gtk::Builder::create_from_file("basic.ui");
</code></pre>
<p>This will instantiate the windows defined in the <code class="filename">.ui</code> file.
</p>
<p>To instantiate just one window, or just one of the child widgets, you can specify the name of a widget as the second parameter. For instance,
</p>
<pre class="programlisting"><code class="code">auto builder = Gtk::Builder::create_from_file("basic.ui", "treeview_products");
</code></pre>
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