This example allows copy and pasting of application-specific data, using the standard text target. Although this is simple, it's not ideal because it does not identify the Clipboard data as being of a particular type.

Source Code

File: examplewindow.h (For use with gtkmm 3, not gtkmm 2)

#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H

#include <gtkmm.h>

class ExampleWindow : public Gtk::Window
{
public:
  ExampleWindow();
  virtual ~ExampleWindow();

protected:
  //Signal handlers:
  void on_button_copy();
  void on_button_paste();
  void on_clipboard_text_received(const Glib::ustring& text);

  //Child widgets:
  Gtk::Box m_VBox;

  Gtk::Label m_Label;

  Gtk::Grid m_Grid;
  Gtk::ToggleButton m_ButtonA1, m_ButtonA2, m_ButtonB1, m_ButtonB2;

  Gtk::ButtonBox m_ButtonBox;
  Gtk::Button m_Button_Copy, m_Button_Paste;
};

#endif //GTKMM_EXAMPLEWINDOW_H

File: main.cc (For use with gtkmm 3, not gtkmm 2)

#include "examplewindow.h"
#include <gtkmm/application.h>

int main(int argc, char *argv[])
{
  //APPLICATION_NON_UNIQUE because it shall be possible to run several
  //instances of this application simultaneously.
  auto app = Gtk::Application::create(
    argc, argv, "org.gtkmm.example", Gio::APPLICATION_NON_UNIQUE);

  ExampleWindow window;

  //Shows the window and returns when it is closed.
  return app->run(window);
}

File: examplewindow.cc (For use with gtkmm 3, not gtkmm 2)

#include "examplewindow.h"

ExampleWindow::ExampleWindow()
: m_VBox(Gtk::ORIENTATION_VERTICAL),
  m_Label("Select cells in the grid, click Copy, then open a second "
        "instance of this example to try pasting the copied data."),
  m_ButtonA1("A1"), m_ButtonA2("A2"), m_ButtonB1("B1"), m_ButtonB2("B2"),
  m_Button_Copy("_Copy", /* mnemonic= */ true), m_Button_Paste("_Paste", true)
{
  set_title("Gtk::Clipboard example");
  set_border_width(12);

  add(m_VBox);

  m_VBox.pack_start(m_Label, Gtk::PACK_SHRINK);

  //Fill Grid:
  m_VBox.pack_start(m_Grid);
  m_Grid.set_row_homogeneous(true);
  m_Grid.set_column_homogeneous(true);
  m_Grid.attach(m_ButtonA1, 0, 0, 1, 1);
  m_Grid.attach(m_ButtonA2, 1, 0, 1, 1);
  m_Grid.attach(m_ButtonB1, 0, 1, 1, 1);
  m_Grid.attach(m_ButtonB2, 1, 1, 1, 1);

  //Add ButtonBox to bottom:
  m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);
  m_VBox.set_spacing(6);

  //Fill ButtonBox:
  m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
  m_ButtonBox.pack_start(m_Button_Copy, Gtk::PACK_SHRINK);
  m_Button_Copy.signal_clicked().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_button_copy) );
  m_ButtonBox.pack_start(m_Button_Paste, Gtk::PACK_SHRINK);
  m_Button_Paste.signal_clicked().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_button_paste) );

  show_all_children();
}

ExampleWindow::~ExampleWindow()
{
}

void ExampleWindow::on_button_copy()
{
  //Build a string representation of the stuff to be copied:
  //Ideally you would use XML, with an XML parser here:
  Glib::ustring strData;
  strData += m_ButtonA1.get_active() ? "1" : "0";
  strData += m_ButtonA2.get_active() ? "1" : "0";
  strData += m_ButtonB1.get_active() ? "1" : "0";
  strData += m_ButtonB2.get_active() ? "1" : "0";

  auto refClipboard = Gtk::Clipboard::get();
  refClipboard->set_text(strData);
}

void ExampleWindow::on_button_paste()
{
  //Tell the clipboard to call our method when it is ready:
  auto refClipboard = Gtk::Clipboard::get();
  refClipboard->request_text(sigc::mem_fun(*this,
              &ExampleWindow::on_clipboard_text_received) );
}

void ExampleWindow::on_clipboard_text_received(const Glib::ustring& text)
{
  //See comment in on_button_copy() about this silly clipboard format.
  if(text.size() >= 4)
  {
    m_ButtonA1.set_active( text[0] == '1' );
    m_ButtonA2.set_active( text[1] == '1' );
    m_ButtonB1.set_active( text[2] == '1' );
    m_ButtonB2.set_active( text[3] == '1' );
  }
}

This is like the simple example, but it

Source Code

File: examplewindow.h (For use with gtkmm 3, not gtkmm 2)

#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H

#include <gtkmm.h>

class ExampleWindow : public Gtk::Window
{
public:
  ExampleWindow();
  virtual ~ExampleWindow();

protected:
  //Signal handlers:
  void on_button_copy();
  void on_button_paste();

  void on_clipboard_owner_change(GdkEventOwnerChange* event);
  void on_clipboard_get(Gtk::SelectionData& selection_data, guint info);
  void on_clipboard_clear();

  void on_clipboard_received(const Gtk::SelectionData& selection_data);
  void on_clipboard_received_targets(const std::vector<Glib::ustring>& targets);

  void update_paste_status(); //Disable the paste button if there is nothing to paste.

  //Child widgets:
  Gtk::Box m_VBox;

  Gtk::Label m_Label;

  Gtk::Grid m_Grid;
  Gtk::ToggleButton m_ButtonA1, m_ButtonA2, m_ButtonB1, m_ButtonB2;

  Gtk::ButtonBox m_ButtonBox;
  Gtk::Button m_Button_Copy, m_Button_Paste;

  Glib::ustring m_ClipboardStore; //Keep copied stuff here, until it is pasted. This could be a big complex data structure.
};

#endif //GTKMM_EXAMPLEWINDOW_H

File: main.cc (For use with gtkmm 3, not gtkmm 2)

#include "examplewindow.h"
#include <gtkmm/application.h>

int main(int argc, char *argv[])
{
  //APPLICATION_NON_UNIQUE because it shall be possible to run several
  //instances of this application simultaneously.
  auto app = Gtk::Application::create(
    argc, argv, "org.gtkmm.example", Gio::APPLICATION_NON_UNIQUE);

  ExampleWindow window;

  //Shows the window and returns when it is closed.
  return app->run(window);
}

File: examplewindow.cc (For use with gtkmm 3, not gtkmm 2)

#include "examplewindow.h"
#include <algorithm>

namespace
{

//These should usually be MIME types.
const char example_target_custom[] = "gtkmmclipboardexample";
const char example_target_text[]   = "UTF8_STRING";

} // anonymous namespace


ExampleWindow::ExampleWindow()
: m_VBox(Gtk::ORIENTATION_VERTICAL),
  m_Label("Select cells in the grid, click Copy, then open a second instance "
          "of this example to try pasting the copied data.\nOr try pasting the "
          "text representation into gedit."),
  m_ButtonA1("A1"), m_ButtonA2("A2"), m_ButtonB1("B1"), m_ButtonB2("B2"),
  m_Button_Copy("_Copy", /* mnemonic= */ true), m_Button_Paste("_Paste", true)
{
  set_title("Gtk::Clipboard example");
  set_border_width(12);

  add(m_VBox);

  m_VBox.pack_start(m_Label, Gtk::PACK_SHRINK);

  //Fill Grid:
  m_VBox.pack_start(m_Grid);
  m_Grid.set_row_homogeneous(true);
  m_Grid.set_column_homogeneous(true);
  m_Grid.attach(m_ButtonA1, 0, 0, 1, 1);
  m_Grid.attach(m_ButtonA2, 1, 0, 1, 1);
  m_Grid.attach(m_ButtonB1, 0, 1, 1, 1);
  m_Grid.attach(m_ButtonB2, 1, 1, 1, 1);

  //Add ButtonBox to bottom:
  m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);
  m_VBox.set_spacing(6);

  //Fill ButtonBox:
  m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
  m_ButtonBox.pack_start(m_Button_Copy, Gtk::PACK_SHRINK);
  m_Button_Copy.signal_clicked().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_button_copy) );
  m_ButtonBox.pack_start(m_Button_Paste, Gtk::PACK_SHRINK);
  m_Button_Paste.signal_clicked().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_button_paste) );

  //Connect a signal handler that will be called when the contents of
  //the clipboard change.
  Gtk::Clipboard::get()->signal_owner_change().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_clipboard_owner_change) );

  show_all_children();

  update_paste_status();
}

ExampleWindow::~ExampleWindow()
{
}

void ExampleWindow::on_button_copy()
{
  //Build a string representation of the stuff to be copied:
  //Ideally you would use XML, with an XML parser here:
  Glib::ustring strData;
  strData += m_ButtonA1.get_active() ? "1" : "0";
  strData += m_ButtonA2.get_active() ? "1" : "0";
  strData += m_ButtonB1.get_active() ? "1" : "0";
  strData += m_ButtonB2.get_active() ? "1" : "0";

  auto refClipboard = Gtk::Clipboard::get();

  //Targets:
  std::vector<Gtk::TargetEntry> targets;

  targets.push_back( Gtk::TargetEntry(example_target_custom) );
  targets.push_back( Gtk::TargetEntry(example_target_text) );

  refClipboard->set(targets,
    sigc::mem_fun(*this, &ExampleWindow::on_clipboard_get),
    sigc::mem_fun(*this, &ExampleWindow::on_clipboard_clear) );

  //Store the copied data until it is pasted:
  //(Must be done after the call to refClipboard->set(), because that call
  //may trigger a call to on_clipboard_clear.)
  m_ClipboardStore = strData;

  update_paste_status();
}

void ExampleWindow::on_button_paste()
{
  //Tell the clipboard to call our method when it is ready:
  auto refClipboard = Gtk::Clipboard::get();

  refClipboard->request_contents(example_target_custom,
    sigc::mem_fun(*this, &ExampleWindow::on_clipboard_received) );

  update_paste_status();
}

void ExampleWindow::on_clipboard_owner_change(GdkEventOwnerChange*)
{
  update_paste_status();
}

void ExampleWindow::on_clipboard_get(Gtk::SelectionData& selection_data,
  guint /* info */)
{
  // info corresponds to the optional info parameter in Gtk::TargetEntry's
  // constructor. We don't use that, so we use selection_data's target instead.

  const std::string target = selection_data.get_target();

  if(target == example_target_custom)
  {
    // This set() override uses an 8-bit text format for the data.
    selection_data.set(example_target_custom, m_ClipboardStore);
  }
  else if(target == example_target_text)
  {
    //Build some arbitrary text representation of the data,
    //so that people see something when they paste into a text editor:
    Glib::ustring text_representation;

    text_representation += m_ButtonA1.get_active() ? "A1, " : "";
    text_representation += m_ButtonA2.get_active() ? "A2, " : "";
    text_representation += m_ButtonB1.get_active() ? "B1, " : "";
    text_representation += m_ButtonB2.get_active() ? "B2, " : "";

    selection_data.set_text(text_representation);
  }
  else
  {
    g_warning("ExampleWindow::on_clipboard_get(): "
            "Unexpected clipboard target format.");
  }
}

void ExampleWindow::on_clipboard_clear()
{
  //This isn't really necessary. I guess it might save memory.
  m_ClipboardStore.clear();
}

void ExampleWindow::on_clipboard_received(
        const Gtk::SelectionData& selection_data)
{
  const std::string target = selection_data.get_target();

  //It should always be this, because that's what we asked for when calling
  //request_contents().
  if(target == example_target_custom)
  {
    Glib::ustring clipboard_data = selection_data.get_data_as_string();

    //See comment in on_button_copy() about this silly clipboard format.
    if(clipboard_data.size() >= 4)
    {
      m_ButtonA1.set_active( clipboard_data[0] == '1' );
      m_ButtonA2.set_active( clipboard_data[1] == '1' );
      m_ButtonB1.set_active( clipboard_data[2] == '1' );
      m_ButtonB2.set_active( clipboard_data[3] == '1' );
    }
  }
}

void ExampleWindow::update_paste_status()
{
  //Disable the paste button if there is nothing to paste.

  auto refClipboard = Gtk::Clipboard::get();

  //Discover what targets are available:
  refClipboard->request_targets(sigc::mem_fun(*this,
              &ExampleWindow::on_clipboard_received_targets) );
}

void ExampleWindow::on_clipboard_received_targets(
  const std::vector<Glib::ustring>& targets)
{
  const bool bPasteIsPossible =
    std::find(targets.begin(), targets.end(),
      example_target_custom) != targets.end();

  // Enable/Disable the Paste button appropriately:
  m_Button_Paste.set_sensitive(bPasteIsPossible);
}