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<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-builder-using-derived-widgets"></a>Using derived widgets</h2></div></div></div>
<p>
You can use <span class="application">Glade</span> to layout your own custom widgets
derived from <span class="application">gtkmm</span> widget classes. This keeps your code organized and
encapsulated. Of course you won't see the exact appearance and properties of
your derived widget in <span class="application">Glade</span>, but you can specify
its location and child widgets and the properties of its <span class="application">gtkmm</span> base class.
</p>
<p>Use <code class="methodname">Gtk::Builder::get_widget_derived()</code> like so:
</p>
<pre class="programlisting">
DerivedDialog* pDialog = nullptr;
builder->get_widget_derived("DialogBasic", pDialog);
</pre>
<p>
</p>
<p>
Your derived class must have a constructor that takes a pointer to the
underlying C type, and the <code class="classname">Gtk::Builder</code> instance.
All relevant classes of <span class="application">gtkmm</span> typedef their underlying C type as
<code class="classname">BaseObjectType</code> (<code class="classname">Gtk::Dialog</code>
typedefs <code class="classname">BaseObjectType</code> as <span class="type">GtkDialog</span>, for instance).
</p>
<p>
You must call the base class's constructor in the initialization list, providing the C pointer. For
instance,
</p>
<pre class="programlisting">
DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& builder)
: Gtk::Dialog(cobject)
{
}
</pre>
<p>
</p>
<p>
You could then encapsulate the manipulation of the child widgets in the
constructor of the derived class, maybe using <code class="methodname">get_widget()</code>
or <code class="methodname">get_widget_derived()</code> again. For instance,
</p>
<pre class="programlisting">
DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& builder)
: Gtk::Dialog(cobject),
m_builder(builder),
m_pButton(nullptr)
{
//Get the Glade-instantiated Button, and connect a signal handler:
m_builder->get_widget("quit_button", m_pButton);
if(m_pButton)
{
m_pButton->signal_clicked().connect( sigc::mem_fun(*this, &DerivedDialog::on_button_quit) );
}
}
</pre>
<p>
</p>
<p>
Starting with <span class="application">gtkmm</span> 3.19.7, it's possible to pass additional arguments from
<code class="methodname">get_widget_derived()</code> to the constructor of the derived
widget. For instance, this call to <code class="methodname">get_widget_derived()</code>
</p>
<pre class="programlisting">
DerivedDialog* pDialog = nullptr;
builder->get_widget_derived("DialogBasic", pDialog, true);
</pre>
<p>
can invoke this constructor
</p>
<pre class="programlisting">
DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& builder, bool warning)
: Gtk::Dialog(cobject),
m_builder(builder),
m_pButton(nullptr)
{
// ....
}
</pre>
<p>
</p>
<div class="sect2">
<div class="titlepage"><div><div><h3 class="title">
<a name="builder-example-accessing"></a>Example</h3></div></div></div>
<p>
This example shows how to load a <span class="application">Glade</span> file at runtime and access the widgets via a derived class.
</p>
<p><a class="ulink" href="http://git.gnome.org/browse/gtkmm-documentation/tree/examples/book/builder/derived?h=gtkmm-3-24" target="_top">Source Code</a></p>
<p>File: <code class="filename">deriveddialog.h</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#ifndef GTKMM_EXAMPLE_DERIVED_DIALOG_H
#define GTKMM_EXAMPLE_DERIVED_DIALOG_H
#include <gtkmm.h>
class DerivedDialog : public Gtk::Dialog
{
public:
DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& refGlade);
DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& refGlade,
bool is_glad);
virtual ~DerivedDialog();
protected:
//Signal handlers:
void on_button_quit();
Glib::RefPtr<Gtk::Builder> m_refGlade;
Gtk::Button* m_pButton;
};
#endif //GTKMM_EXAMPLE_DERIVED_WINDOW_H
</pre>
<p>File: <code class="filename">main.cc</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#include "deriveddialog.h"
#include <iostream>
#include <cstring>
int main (int argc, char **argv)
{
bool show_icon = false;
bool is_glad = true;
int argc1 = argc;
if (argc > 1)
{
if (std::strcmp(argv[1], "--glad") == 0)
{
show_icon = true;
is_glad = true;
argc1 = 1; // Don't give the command line arguments to Gtk::Application.
}
else if (std::strcmp(argv[1], "--sad") == 0)
{
show_icon = true;
is_glad = false;
argc1 = 1; // Don't give the command line arguments to Gtk::Application.
}
}
auto app = Gtk::Application::create(argc1, argv, "org.gtkmm.example");
//Load the Glade file and instantiate its widgets:
auto refBuilder = Gtk::Builder::create();
try
{
refBuilder->add_from_file("derived.glade");
}
catch(const Glib::FileError& ex)
{
std::cerr << "FileError: " << ex.what() << std::endl;
return 1;
}
catch(const Glib::MarkupError& ex)
{
std::cerr << "MarkupError: " << ex.what() << std::endl;
return 1;
}
catch(const Gtk::BuilderError& ex)
{
std::cerr << "BuilderError: " << ex.what() << std::endl;
return 1;
}
//Get the GtkBuilder-instantiated dialog:
DerivedDialog* pDialog = nullptr;
if (show_icon)
// This call to get_widget_derived() requires gtkmm 3.19.7 or higher.
refBuilder->get_widget_derived("DialogDerived", pDialog, is_glad);
else
refBuilder->get_widget_derived("DialogDerived", pDialog);
if(pDialog)
{
//Start:
app->run(*pDialog);
}
delete pDialog;
return 0;
}
</pre>
<p>File: <code class="filename">deriveddialog.cc</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#include "deriveddialog.h"
DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& refGlade)
: Gtk::Dialog(cobject),
m_refGlade(refGlade),
m_pButton(nullptr)
{
//Get the Glade-instantiated Button, and connect a signal handler:
m_refGlade->get_widget("quit_button", m_pButton);
if(m_pButton)
{
m_pButton->signal_clicked().connect( sigc::mem_fun(*this, &DerivedDialog::on_button_quit) );
}
}
// The first two parameters are mandatory in a constructor that will be called
// from Gtk::Builder::get_widget_derived().
// Additional parameters, if any, correspond to additional arguments in the call
// to Gtk::Builder::get_widget_derived().
DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& refGlade,
bool is_glad)
: DerivedDialog(cobject, refGlade) // Delegate to the other constructor
{
// Show an icon.
auto pImage = Gtk::make_managed<Gtk::Image>();
pImage->set_from_icon_name(is_glad ? "face-smile" : "face-sad", Gtk::ICON_SIZE_DIALOG);
pImage->show_all();
get_content_area()->pack_start(*pImage);
}
DerivedDialog::~DerivedDialog()
{
}
void DerivedDialog::on_button_quit()
{
hide(); //hide() will cause Gtk::Application::run() to end.
}
</pre>
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