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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-dnd-example"></a>Example</h2></div></div></div>
<p>Here is a very simple example, demonstrating a drag and drop <code class="literal">Copy</code> operation:</p>
<div class="figure">
<a name="figure-drag-and-drop"></a><p class="title"><b>Figure 18.1. Drag and Drop</b></p>
<div class="figure-contents"><div class="screenshot"><div><img src="figures/drag_and_drop.png" alt="Drag and Drop"></div></div></div>
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<br class="figure-break"><p><a class="ulink" href="http://git.gnome.org/browse/gtkmm-documentation/tree/examples/book/drag_and_drop?h=gtkmm-3-24" target="_top">Source Code</a></p>
<p>File: <code class="filename">dndwindow.h</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#ifndef GTKMM_EXAMPLE_DNDWINDOW_H
#define GTKMM_EXAMPLE_DNDWINDOW_H
#include <gtkmm/box.h>
#include <gtkmm/label.h>
#include <gtkmm/window.h>
#include <gtkmm/button.h>
class DnDWindow : public Gtk::Window
{
public:
DnDWindow();
virtual ~DnDWindow();
protected:
//Signal handlers:
void on_button_drag_data_get(
const Glib::RefPtr<Gdk::DragContext>& context,
Gtk::SelectionData& selection_data, guint info, guint time);
void on_label_drop_drag_data_received(
const Glib::RefPtr<Gdk::DragContext>& context, int x, int y,
const Gtk::SelectionData& selection_data, guint info, guint time);
//Member widgets:
Gtk::Box m_HBox;
Gtk::Button m_Button_Drag;
Gtk::Label m_Label_Drop;
};
#endif // GTKMM_EXAMPLE_DNDWINDOW_H
</pre>
<p>File: <code class="filename">dndwindow.cc</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#include "dndwindow.h"
#include <iostream>
DnDWindow::DnDWindow()
: m_Button_Drag("Drag Here\n"),
m_Label_Drop("Drop here\n")
{
set_title("DnD example");
add(m_HBox);
//Targets:
std::vector<Gtk::TargetEntry> listTargets;
listTargets.push_back( Gtk::TargetEntry("STRING") );
listTargets.push_back( Gtk::TargetEntry("text/plain") );
//Drag site:
//Make m_Button_Drag a DnD drag source:
m_Button_Drag.drag_source_set(listTargets);
//Connect signals:
m_Button_Drag.signal_drag_data_get().connect(sigc::mem_fun(*this,
&DnDWindow::on_button_drag_data_get));
m_HBox.pack_start(m_Button_Drag);
//Drop site:
//Make m_Label_Drop a DnD drop destination:
m_Label_Drop.drag_dest_set(listTargets);
//Connect signals:
m_Label_Drop.signal_drag_data_received().connect(sigc::mem_fun(*this,
&DnDWindow::on_label_drop_drag_data_received) );
m_HBox.pack_start(m_Label_Drop);
show_all();
}
DnDWindow::~DnDWindow()
{
}
void DnDWindow::on_button_drag_data_get(
const Glib::RefPtr<Gdk::DragContext>&,
Gtk::SelectionData& selection_data, guint, guint)
{
selection_data.set(selection_data.get_target(), 8 /* 8 bits format */,
(const guchar*)"I'm Data!",
9 /* the length of I'm Data! in bytes */);
}
void DnDWindow::on_label_drop_drag_data_received(
const Glib::RefPtr<Gdk::DragContext>& context, int, int,
const Gtk::SelectionData& selection_data, guint, guint time)
{
const int length = selection_data.get_length();
if((length >= 0) && (selection_data.get_format() == 8))
{
std::cout << "Received \"" << selection_data.get_data_as_string()
<< "\" in label " << std::endl;
}
context->drag_finish(false, false, time);
}
</pre>
<p>File: <code class="filename">main.cc</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#include "dndwindow.h"
#include <gtkmm/application.h>
int main (int argc, char *argv[])
{
auto app = Gtk::Application::create(argc, argv, "org.gtkmm.example");
DnDWindow dndWindow;
//Shows the window and returns when it is closed.
return app->run(dndWindow);
}
</pre>
<p>
There is a more complex example in examples/others/dnd.
</p>
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