Example

#ifndef GTKMM_EXAMPLEWORKER_H
#define GTKMM_EXAMPLEWORKER_H

#include <gtkmm.h>

class ExampleWindow;

class ExampleWorker
{
public:
  ExampleWorker();

  // Thread function.
  void do_work(ExampleWindow* caller);

  void get_data(double* fraction_done, Glib::ustring* message) const;
  void stop_work();
  bool has_stopped() const;

private:
  // Synchronizes access to member data.
  mutable Glib::Threads::Mutex m_Mutex;

  // Data used by both GUI thread and worker thread.
  bool m_shall_stop;
  bool m_has_stopped;
  double m_fraction_done;
  Glib::ustring m_message;
};

#endif // GTKMM_EXAMPLEWORKER_H

#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H

#include <gtkmm.h>
#include "exampleworker.h"

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

  // Called from the worker thread.
  void notify();

private:
  // Signal handlers.
  void on_start_button_clicked();
  void on_stop_button_clicked();
  void on_quit_button_clicked();

  void update_start_stop_buttons();
  void update_widgets();

  // Dispatcher handler.
  void on_notification_from_worker_thread();

  // Member data.
  Gtk::Box m_VBox;
  Gtk::ButtonBox m_ButtonBox;
  Gtk::Button m_ButtonStart;
  Gtk::Button m_ButtonStop;
  Gtk::Button m_ButtonQuit;
  Gtk::ProgressBar m_ProgressBar;
  Gtk::ScrolledWindow m_ScrolledWindow;
  Gtk::TextView m_TextView;

  Glib::Dispatcher m_Dispatcher;
  ExampleWorker m_Worker;
  Glib::Threads::Thread* m_WorkerThread;
};

#endif // GTKMM_EXAMPLEWINDOW_H

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

ExampleWindow::ExampleWindow() :
  m_VBox(Gtk::ORIENTATION_VERTICAL, 5),
  m_ButtonBox(Gtk::ORIENTATION_HORIZONTAL),
  m_ButtonStart("Start work"),
  m_ButtonStop("Stop work"),
  m_ButtonQuit("_Quit", /* mnemonic= */ true),
  m_ProgressBar(),
  m_ScrolledWindow(),
  m_TextView(),
  m_Dispatcher(),
  m_Worker(),
  m_WorkerThread(0)
{
  set_title("Multi-threaded example");
  set_border_width(5);
  set_default_size(300, 300);

  add(m_VBox);

  // Add the ProgressBar.
  m_VBox.pack_start(m_ProgressBar, Gtk::PACK_SHRINK);

  m_ProgressBar.set_text("Fraction done");
  m_ProgressBar.set_show_text();

  // Add the TextView, inside a ScrolledWindow.
  m_ScrolledWindow.add(m_TextView);

  // Only show the scrollbars when they are necessary.
  m_ScrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);

  m_VBox.pack_start(m_ScrolledWindow);

  m_TextView.set_editable(false);

  // Add the buttons to the ButtonBox.
  m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);

  m_ButtonBox.pack_start(m_ButtonStart, Gtk::PACK_SHRINK);
  m_ButtonBox.pack_start(m_ButtonStop, Gtk::PACK_SHRINK);
  m_ButtonBox.pack_start(m_ButtonQuit, Gtk::PACK_SHRINK);
  m_ButtonBox.set_border_width(5);
  m_ButtonBox.set_spacing(5);
  m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);

  // Connect the signal handlers to the buttons.
  m_ButtonStart.signal_clicked().connect(sigc::mem_fun(*this, &ExampleWindow::on_start_button_clicked));
  m_ButtonStop.signal_clicked().connect(sigc::mem_fun(*this, &ExampleWindow::on_stop_button_clicked));
  m_ButtonQuit.signal_clicked().connect(sigc::mem_fun(*this, &ExampleWindow::on_quit_button_clicked));

  // Connect the handler to the dispatcher.
  m_Dispatcher.connect(sigc::mem_fun(*this, &ExampleWindow::on_notification_from_worker_thread));

  // Create a text buffer mark for use in update_widgets().
  Glib::RefPtr<Gtk::TextBuffer> buffer = m_TextView.get_buffer();
  buffer->create_mark("last_line", buffer->end(), /* left_gravity= */ true);

  update_start_stop_buttons();

  show_all_children();
}

void ExampleWindow::on_start_button_clicked()
{
  if (m_WorkerThread)
  {
    std::cout << "Can't start a worker thread while another one is running." << std::endl;
  }
  else
  {
    // Start a new worker thread.
    m_WorkerThread = Glib::Threads::Thread::create(
      sigc::bind(sigc::mem_fun(m_Worker, &ExampleWorker::do_work), this));
  }
  update_start_stop_buttons();
}

void ExampleWindow::on_stop_button_clicked()
{
  if (!m_WorkerThread)
  {
    std::cout << "Can't stop a worker thread. None is running." << std::endl;
  }
  else
  {
   // Order the worker thread to stop.
    m_Worker.stop_work();
    m_ButtonStop.set_sensitive(false);
  }
}

void ExampleWindow::update_start_stop_buttons()
{
  const bool thread_is_running = m_WorkerThread != 0;

  m_ButtonStart.set_sensitive(!thread_is_running);
  m_ButtonStop.set_sensitive(thread_is_running);
}

void ExampleWindow::update_widgets()
{
  double fraction_done;
  Glib::ustring message_from_worker_thread;
  m_Worker.get_data(&fraction_done, &message_from_worker_thread);

  m_ProgressBar.set_fraction(fraction_done);

  if (message_from_worker_thread != m_TextView.get_buffer()->get_text())
  {
    Glib::RefPtr<Gtk::TextBuffer> buffer = m_TextView.get_buffer();
    buffer->set_text(message_from_worker_thread);

    // Scroll the last inserted line into view. That's somewhat complicated.
    Gtk::TextIter iter = buffer->end();
    iter.set_line_offset(0); // Beginning of last line
    Glib::RefPtr<Gtk::TextMark> mark = buffer->get_mark("last_line");
    buffer->move_mark(mark, iter);
    m_TextView.scroll_to(mark);
    // TextView::scroll_to(iter) is not perfect.
    // We do need a TextMark to always get the last line into view.
  }
}

void ExampleWindow::on_quit_button_clicked()
{
  if (m_WorkerThread)
  {
    // Order the worker thread to stop and wait for it to stop.
    m_Worker.stop_work();
    m_WorkerThread->join();
  }
  hide();
}

// notify() is called from ExampleWorker::do_work(). It is executed in the worker
// thread. It triggers a call to on_notification_from_worker_thread(), which is
// executed in the GUI thread.
void ExampleWindow::notify()
{
  m_Dispatcher.emit();
}

void ExampleWindow::on_notification_from_worker_thread()
{
  if (m_WorkerThread && m_Worker.has_stopped())
  {
    // Work is done.
    m_WorkerThread->join();
    m_WorkerThread = 0;
    update_start_stop_buttons();
  }
  update_widgets();
}

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

int main (int argc, char* argv[])
{
  Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

  ExampleWindow window;

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

#include "exampleworker.h"
#include "examplewindow.h"
#include <sstream>

ExampleWorker::ExampleWorker() :
  m_Mutex(),
  m_shall_stop(false),
  m_has_stopped(false),
  m_fraction_done(0.0),
  m_message()
{
}

// Accesses to these data are synchronized by a mutex.
// Some microseconds can be saved by getting all data at once, instead of having
// separate get_fraction_done() and get_message() methods.
void ExampleWorker::get_data(double* fraction_done, Glib::ustring* message) const
{
  Glib::Threads::Mutex::Lock lock(m_Mutex);

  if (fraction_done)
    *fraction_done = m_fraction_done;

  if (message)
    *message = m_message;
}

void ExampleWorker::stop_work()
{
  Glib::Threads::Mutex::Lock lock(m_Mutex);
  m_shall_stop = true;
}

bool ExampleWorker::has_stopped() const
{
  Glib::Threads::Mutex::Lock lock(m_Mutex);
  return m_has_stopped;
}

void ExampleWorker::do_work(ExampleWindow* caller)
{
  {
    Glib::Threads::Mutex::Lock lock(m_Mutex);
    m_has_stopped = false;
    m_fraction_done = 0.0;
    m_message = "";
  } // The mutex is unlocked here by lock's destructor.

  // Simulate a long calculation.
  for (int i = 0; ; ++i) // do until break
  {
    Glib::usleep(250000); // microseconds

    Glib::Threads::Mutex::Lock lock(m_Mutex);

    m_fraction_done += 0.01;

    if (i % 4 == 3)
    {
      std::ostringstream ostr;
      ostr << (m_fraction_done * 100.0) << "% done\n";
      m_message += ostr.str();
    }

    if (m_fraction_done >= 1.0)
    {
      m_message += "Finished";
      break;
    }
    if (m_shall_stop)
    {
      m_message += "Stopped";
      break;
    }
    lock.release();
    caller->notify();
  }

  Glib::Threads::Mutex::Lock lock(m_Mutex);
  m_shall_stop = false;
  m_has_stopped = true;
  lock.release();
  caller->notify();
}