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<div class="titlepage"><div><div><h1 class="title">
<a name="chapter-combobox"></a>Chapter 10. Combo Boxes</h1></div></div></div>
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<p><b>Table of Contents</b></p>
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<li><span class="sect1"><a href="chapter-combobox.html#sec-combobox-model">The model</a></span></li>
<li><span class="sect1"><a href="sec-combobox-get.html">The chosen item</a></span></li>
<li><span class="sect1"><a href="sec-combobox-changes.html">Responding to changes</a></span></li>
<li><span class="sect1"><a href="combobox-example-full.html">Full Example</a></span></li>
<li><span class="sect1"><a href="combobox-example-simple.html">Simple Text Example</a></span></li>
<li><span class="sect1"><a href="sec-comboboxentry.html">ComboBox with an Entry</a></span></li>
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<p>The <code class="classname">ComboBox</code> widget offers a list (or tree) of choices in a dropdown menu. If appropriate, it can show extra information about each item, such as text, a picture, a checkbox, or a progress bar. The <code class="classname">ComboBox</code> widget usually restricts the user to the available choices, but it can optionally have an <code class="classname">Entry</code>, allowing the user to enter arbitrary text if none of the available choices are suitable.
</p>
<p>The list is provided via a <code class="classname">TreeModel</code>, and columns from this model are added to the ComboBox's view with the <code class="methodname">ComboBox::pack_start()</code> method. This provides flexibility and compile-time type-safety, but the <code class="classname">ComboBoxText</code> class provides a simpler text-based specialization in case that flexibility is not required.
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<p><a class="ulink" href="http://developer.gnome.org/gtkmm/3.24/classGtk_1_1ComboBox.html" target="_top">Reference</a></p>
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<a name="sec-combobox-model"></a>The model</h2></div></div></div>
<p>The model for a ComboBox can be defined and filled exactly as for a <code class="classname">TreeView</code>. For instance, you might derive a ComboBox class with one integer and one text column, like so:
</p>
<pre class="programlisting">ModelColumns()
{ add(m_col_id); add(m_col_name); }
Gtk::TreeModelColumn<int> m_col_id;
Gtk::TreeModelColumn<Glib::ustring> m_col_name;
};
ModelColumns m_columns;</pre>
<p>After appending rows to this model, you should provide the model to the <code class="classname">ComboBox</code> with the <code class="methodname">set_model()</code> method. Then use the <code class="methodname">pack_start()</code> or <code class="methodname">pack_end()</code> methods to specify what columns will be displayed in the ComboBox. As with the TreeView you may either use the default cell renderer by passing the <code class="classname">TreeModelColumn</code> to the pack methods, or you may instantiate a specific <code class="classname">CellRenderer</code> and specify a particular mapping with either <code class="methodname">add_attribute()</code> or <code class="methodname">set_cell_data_func()</code>. Note that these methods are in the <code class="classname">CellLayout</code> base class.</p>
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