Here is a very simple example, demonstrating a drag and drop Copy operation:
File: dndwindow.h (For use with gtkmm 4)
#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::Drag>& drag,
Gtk::SelectionData& selection_data);
void on_label_drop_drag_data_received(
const Glib::RefPtr<Gdk::Drop>& drop,
const Gtk::SelectionData& selection_data);
//Member widgets:
Gtk::Box m_HBox;
Gtk::Button m_Button_Drag;
Gtk::Label m_Label_Drop;
};
#endif // GTKMM_EXAMPLE_DNDWINDOW_H
File: main.cc (For use with gtkmm 4)
#include "dndwindow.h"
#include <gtkmm/application.h>
int main (int argc, char *argv[])
{
auto app = Gtk::Application::create("org.gtkmm.example");
DnDWindow dndWindow;
//Shows the window and returns when it is closed.
return app->run(dndWindow, argc, argv);
}
File: dndwindow.cc (For use with gtkmm 4)
#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);
//Drag site:
//Make m_Button_Drag a DnD drag source:
m_Button_Drag.drag_source_set(Glib::RefPtr<Gdk::ContentFormats>());
m_Button_Drag.drag_source_add_text_targets();
//Connect signals:
m_Button_Drag.signal_drag_data_get().connect(sigc::mem_fun(*this,
&DnDWindow::on_button_drag_data_get));
m_HBox.add(m_Button_Drag);
m_Button_Drag.set_expand(true);
//Drop site:
//Make m_Label_Drop a DnD drop destination:
// Don't do this: m_Label_Drop.drag_dest_set({}).
// It would call the wrong overload of drag_dest_set() with the wrong
// default values of flags and actions (wrong in this simple example).
m_Label_Drop.drag_dest_set(Glib::RefPtr<Gdk::ContentFormats>());
m_Label_Drop.drag_dest_add_text_targets();
//Connect signals:
m_Label_Drop.signal_drag_data_received().connect(sigc::mem_fun(*this,
&DnDWindow::on_label_drop_drag_data_received) );
m_HBox.add(m_Label_Drop);
m_Label_Drop.set_expand(true);
}
DnDWindow::~DnDWindow()
{
}
void DnDWindow::on_button_drag_data_get(
const Glib::RefPtr<Gdk::Drag>&,
Gtk::SelectionData& selection_data)
{
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::Drop>& drop,
const Gtk::SelectionData& selection_data)
{
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;
}
drop->failed();
}
There is a more complex example in examples/others/dnd.