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<th width="60%" align="center">Chapter 8. The TreeView widget</th>
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<div class="sect1" title="The View">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-treeview"></a>The View</h2></div></div></div>
<p>
The View is the actual widget (<code class="classname">Gtk::TreeView</code>) that
displays the model (<code class="classname">Gtk::TreeModel</code>) data and allows the
user to interact with it. The View can show all of the model's columns, or just
some, and it can show them in various ways.
</p>
<p><a class="ulink" href="http://library.gnome.org/devel/gtkmm/unstable/classGtk_1_1TreeView.html" target="_top">Reference</a></p>
<div class="sect2" title="Using a Model">
<div class="titlepage"><div><div><h3 class="title">
<a name="sec-treeview-using-a-model"></a>Using a Model</h3></div></div></div>
<p>
You can specify a <code class="classname">Gtk::TreeModel</code> when constructing the
<code class="classname">Gtk::TreeView</code>, or you can use the
<code class="methodname">set_model()</code> method, like so:
</p>
<pre class="programlisting">m_TreeView.set_model(m_refListStore);</pre>
</div>
<div class="sect2" title="Adding View Columns">
<div class="titlepage"><div><div><h3 class="title">
<a name="treeview-adding-view-columns"></a>Adding View Columns</h3></div></div></div>
<p>
You can use the <code class="methodname">append_column()</code> method to tell the View
that it should display certain Model columns, in a certain order, with a
certain column title.
</p>
<pre class="programlisting">m_TreeView.append_column("Messages", m_Columns.m_col_text);</pre>
<p>
When using this simple <code class="methodname">append_column()</code> override, the
<code class="classname">TreeView</code> will display the model data with an appropriate
<code class="classname">CellRenderer</code>. For instance, strings and numbers are
shown in a simple <code class="classname">Gtk::Entry</code> widget, and booleans are
shown in a <code class="classname">Gtk::CheckButton</code>. This is usually what you
need. For other column types you must either connect a callback that converts
your type into a string representation, with
<code class="methodname">TreeViewColumn::set_cell_data_func()</code>, or derive a custom
<code class="classname">CellRenderer</code>. Note that (unsigned) short is not
supported by default - You could use (unsigned) int or (unsigned) long as the
column type instead.
</p>
</div>
<div class="sect2" title="More than one Model Column per View Column">
<div class="titlepage"><div><div><h3 class="title">
<a name="treeview-multiple-model-columns-per-view-column"></a>More than one Model Column per View Column</h3></div></div></div>
<p>
To render more than one model column in a view column, you need to create the
<code class="classname">TreeView::Column</code> widget manually, and use
<code class="methodname">pack_start()</code> to add the model columns to it.
</p>
<p>
Then use <code class="methodname">append_column()</code> to add the view Column to the
View. Notice that <code class="methodname">Gtk::View::append_column()</code> is overridden
to accept either a prebuilt <code class="classname">Gtk::View::Column</code> widget, or
just the <code class="classname">TreeModelColumn</code> from which it generates an
appropriate <code class="classname">Gtk::View::Column</code> widget.
</p>
<p>
Here is some example code from
<code class="filename">demos/gtk-demo/example_stockbrowser.cc</code>, which has a pixbuf
icon and a text name in the same column:
</p>
<pre class="programlisting">Gtk::TreeView::Column* pColumn =
Gtk::manage( new Gtk::TreeView::Column("Symbol") );
// m_columns.icon and m_columns.symbol are columns in the model.
// pColumn is the column in the TreeView:
pColumn->pack_start(m_columns.icon, false); //false = don't expand.
pColumn->pack_start(m_columns.symbol);
m_TreeView.append_column(*pColumn);</pre>
</div>
<div class="sect2" title="Specifying CellRenderer details">
<div class="titlepage"><div><div><h3 class="title">
<a name="treeview-cellrenderer-details"></a>Specifying CellRenderer details</h3></div></div></div>
<p>
The default <code class="classname">CellRenderers</code> and their default behaviour
will normally suffice, but you might occasionally need finer control. For
instance, this example code from
<code class="filename">demos/gtk-demo/example_treestore.cc</code>, manually constructs a
<code class="classname">Gtk::CellRenderer</code> widget and instructs it to render the
data from various model columns through various aspects of its appearance.
</p>
<pre class="programlisting">Gtk::CellRendererToggle* pRenderer =
Gtk::manage( new Gtk::CellRendererToggle() );
int cols_count = m_TreeView.append_column("Alex", *pRenderer);
Gtk::TreeViewColumn* pColumn = m_TreeView.get_column(cols_count-1);
if(pColumn)
{
pColumn->add_attribute(pRenderer->property_active(),
m_columns.alex);
pColumn->add_attribute(pRenderer->property_visible(),
m_columns.visible);
pColumn->add_attribute(pRenderer->property_activatable(),
m_columns.world);</pre>
<p>
You can also connect to <code class="classname">CellRenderer</code> signals to detect user
actions. For instance:
</p>
<pre class="programlisting">Gtk::CellRendererToggle* pRenderer =
Gtk::manage( new Gtk::CellRendererToggle() );
pRenderer->signal_toggled().connect(
sigc::bind( sigc::mem_fun(*this,
&Example_TreeView_TreeStore::on_cell_toggled), m_columns.dave)
);</pre>
</div>
<div class="sect2" title="Editable Cells">
<div class="titlepage"><div><div><h3 class="title">
<a name="treeview-editable-cells"></a>Editable Cells</h3></div></div></div>
<div class="sect3" title="Automatically-stored editable cells.">
<div class="titlepage"><div><div><h4 class="title">
<a name="treeview-editable-cells-automatic"></a>Automatically-stored editable cells.</h4></div></div></div>
<p>
Cells in a <code class="classname">TreeView</code> can be edited in-place by the user.
To allow this, use the <code class="classname">Gtk::TreeView</code>
<code class="methodname">insert_column_editable()</code> and
<code class="methodname">append_column_editable()</code> methods instead of
<code class="methodname">insert_column()</code> and <code class="methodname">append_column()</code>.
When these cells are edited the new values will be stored immediately in the
Model. Note that these methods are templates which can only be instantiated for
simple column types such as <code class="classname">Glib::ustring</code>, int, and
long.
</p>
</div>
<div class="sect3" title="Implementing custom logic for editable cells.">
<div class="titlepage"><div><div><h4 class="title">
<a name="treeview-editable-cells-custom"></a>Implementing custom logic for editable cells.</h4></div></div></div>
<p>
However, you might not want the new values to be stored
immediately. For instance, maybe you want to restrict the input to
certain characters or ranges of values.
</p>
<p>
To achieve this, you should use the normal <code class="classname">Gtk::TreeView</code>
<code class="methodname">insert_column()</code> and <code class="methodname">append_column()</code>
methods, then use <code class="methodname">get_column_cell_renderer()</code> to get the
<code class="classname">Gtk::CellRenderer</code> used by that column.
</p>
<p>
You should then cast that <code class="classname">Gtk::CellRenderer*</code> to the
specific <code class="classname">CellRenderer</code> that you expect, so you can use specific API.
</p>
<p>For instance, for a CellRendererText, you would set the cell's <span class="emphasis"><em>editable</em></span> property to true, like
so:
</p>
<pre class="programlisting">cell.property_editable() = true;</pre>
<p>
For a CellRendererToggle, you would set the <span class="emphasis"><em>activatable</em></span>
property instead.
</p>
<p>You can then connect
to the appropriate "edited" signal. For instance, connect to
<code class="methodname">Gtk::CellRendererText::signal_edited()</code>, or
<code class="methodname">Gtk::CellRendererToggle::signal_toggled()</code>. If the column
contains more than one <code class="classname">CellRenderer</code> then you will need
to use <code class="methodname">Gtk::TreeView::get_column()</code> and then call
<code class="methodname">get_cell_renderers()</code> on that view Column.
</p>
<p>
In your signal handler, you should examine the new value and then
store it in the Model if that is appropriate for your application.
</p>
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