Examples
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Examples

Simple

This example allows copy and pasting of application-specific data, using the standard text target. Although this is simple, it's not ideal because


Google

it does not identify the clipboard data as being of a particular type.

Figure 16.1. Clipboard - Simple

Source Code

File: examplewindow.h 

#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H

#include <gtkmm.h>

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

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

  //Child widgets:
  Gtk::VBox m_VBox;

  Gtk::Label m_Label;
  
  Gtk::Table m_Table;
  Gtk::ToggleButton m_ButtonA1, m_ButtonA2, m_ButtonB1, m_ButtonB2;

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

#endif //GTKMM_EXAMPLEWINDOW_H

File: examplewindow.cc 

#include "examplewindow.h"

ExampleWindow::ExampleWindow()
: m_Label("Select cells in the table, click Copy, then open a second instance of this example to try pasting the copied data."),
  m_Table(2, 2, true),
  m_ButtonA1("A1"), m_ButtonA2("A2"), m_ButtonB1("B1"), m_ButtonB2("B2"),
  m_Button_Copy(Gtk::Stock::COPY), m_Button_Paste(Gtk::Stock::PASTE)
{                                                                                                
  set_title("Gtk::Clipboard example");
  set_border_width(12);                         

  add(m_VBox);

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

  //Fill Table:
  m_VBox.pack_start(m_Table);
  m_Table.attach(m_ButtonA1, 0, 1, 0, 1);
  m_Table.attach(m_ButtonA2, 1, 2, 0, 1);
  m_Table.attach(m_ButtonB1, 0, 1, 1, 2);
  m_Table.attach(m_ButtonB2, 1, 2, 1, 2);

  //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::slot(*this, &ExampleWindow::on_button_copy) );
  m_ButtonBox.pack_start(m_Button_Paste, Gtk::PACK_SHRINK);
  m_Button_Paste.signal_clicked().connect( SigC::slot(*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";
   
  Glib::RefPtr<Gtk::Clipboard> refClipboard = Gtk::Clipboard::get();
  refClipboard->set_text(strData);
}

void ExampleWindow::on_button_paste()
{        
  //Tell the clipboard to call our method when it is ready:
  Glib::RefPtr<Gtk::Clipboard> refClipboard = Gtk::Clipboard::get();
  refClipboard->request_text( SigC::slot(*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' );
  }
}

File: main.cc 

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

int main(int argc, char *argv[])
{
  Gtk::Main kit(argc, argv);

  ExampleWindow window;
  Gtk::Main::run(window); //Shows the window and returns when it is closed.

  return 0;
}

Ideal

This is like the simple example, but it

  1. Defines a custom clipboard target, though the format of that target is still text.
  2. It supports pasting of 2 targets - both the custom one and a text one that creates an arbitrary text representation of the custom data.
  3. It uses request_targets() and disables the Paste button if it can't use anything on the clipboard

Figure 16.2. Clipboard - Ideal

Source Code

File: examplewindow.h 

#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H

#include <gtkmm.h>

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

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

  virtual void on_clipboard_get(Gtk::SelectionData& selection_data, guint info);
  virtual void on_clipboard_clear();

  virtual void on_clipboard_received(const Gtk::SelectionData& selection_data);
  virtual void on_clipboard_received_targets(const Gtk::SelectionData& selection_data);
   
  virtual void update_paste_status(); //Disable the paste button if there is nothing to paste.

  //Child widgets:
  Gtk::VBox m_VBox;

  Gtk::Label m_Label;
  
  Gtk::Table m_Table;
  Gtk::ToggleButton m_ButtonA1, m_ButtonA2, m_ButtonB1, m_ButtonB2;

  Gtk::HButtonBox 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: examplewindow.cc 

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


namespace
{

const char example_target_custom[] = "gtkmmclipboardexample";
const char example_target_text[]   = "UTF8_STRING";

} // anonymous namespace


ExampleWindow::ExampleWindow()
: m_Label("Select cells in the table, 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_Table(2, 2, true),
  m_ButtonA1("A1"), m_ButtonA2("A2"), m_ButtonB1("B1"), m_ButtonB2("B2"),
  m_Button_Copy(Gtk::Stock::COPY), m_Button_Paste(Gtk::Stock::PASTE)
{                                                                                                
  set_title("Gtk::Clipboard example");
  set_border_width(12);                         

  add(m_VBox);

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

  //Fill Table:
  m_VBox.pack_start(m_Table);
  m_Table.attach(m_ButtonA1, 0, 1, 0, 1);
  m_Table.attach(m_ButtonA2, 1, 2, 0, 1);
  m_Table.attach(m_ButtonB1, 0, 1, 1, 2);
  m_Table.attach(m_ButtonB2, 1, 2, 1, 2);

  //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::slot(*this, &ExampleWindow::on_button_copy) );
  m_ButtonBox.pack_start(m_Button_Paste, Gtk::PACK_SHRINK);
  m_Button_Paste.signal_clicked().connect( SigC::slot(*this, &ExampleWindow::on_button_paste) );
    
  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";

  //Store the copied data until it is pasted:
  m_ClipboardStore = strData;
   
  Glib::RefPtr<Gtk::Clipboard> refClipboard = Gtk::Clipboard::get();

  //Targets:
  std::list<Gtk::TargetEntry> listTargets;

  listTargets.push_back( Gtk::TargetEntry(example_target_custom) );
  listTargets.push_back( Gtk::TargetEntry(example_target_text) );
  
  refClipboard->set( listTargets, SigC::slot(*this, &ExampleWindow::on_clipboard_get), SigC::slot(*this, &ExampleWindow::on_clipboard_clear) );

  update_paste_status();
}

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

  refClipboard->request_contents(example_target_custom,  SigC::slot(*this, &ExampleWindow::on_clipboard_received) );

  update_paste_status();
}

void ExampleWindow::on_clipboard_get(Gtk::SelectionData& selection_data, guint)
{
  //info is meant to indicate the target, but it seems to be always 0,
  //so we use the 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();

  if(target == example_target_custom) //It should always be this, because that' what we asked for when calling request_contents().
  {
    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.
  
  Glib::RefPtr<Gtk::Clipboard> refClipboard = Gtk::Clipboard::get();

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

void ExampleWindow::on_clipboard_received_targets(const Gtk::SelectionData& selection_data)
{
  // Get the list of available clipboard targets:
  const std::list<std::string> targets (selection_data.get_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);
}

File: main.cc 

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

int main(int argc, char *argv[])
{
  Gtk::Main kit(argc, argv);

  ExampleWindow window;
  Gtk::Main::run(window); //Shows the window and returns when it is closed.

  return 0;
}