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// -*- c++ -*-

/* $Id: dispatcher.h 4 2005-05-13 20:47:18Z taybin $ */

/* Copyright 2002 The gtkmm Development Team
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * Library General Public License for more details.
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

#include <sigc++/sigc++.h>
#include <glibmm/main.h>

namespace Glib

class DispatchNotifier;

/** Signal class for inter-thread communication.
 * @ingroup Threads
 * Glib::Dispatcher works similar to sigc::signal<void>.  But unlike normal
 * signals, the notification happens asynchronously through a pipe.  This is
 * a simple and efficient way of communicating between threads, and especially
 * useful in a thread model with a single GUI thread.
 * No mutex locking is involved, apart from the operating system's internal
 * I/O locking.  That implies some usage rules:
 * @li Only one thread may connect to the signal and receive notification, but
 * multiple senders are allowed even without locking.
 * @li The GLib main loop must run in the receiving thread (this will be the
 * GUI thread usually).
 * @li The Dispatcher object must be instantiated by the receiver thread.
 * @li The Dispatcher object should be instantiated before creating any of the
 * sender threads, if you want to avoid extra locking.
 * Notes about performance:
 * @li After instantiation, Glib::Dispatcher will never lock any mutexes on its
 * own.  The interaction with the GLib main loop might involve locking on the
 * @em receiver side.  The @em sender side, however, is guaranteed not to lock,
 * except for internal locking in the <tt>%write()</tt> system call.
 * @li All Dispatcher instances of a receiver thread share the same pipe.  That
 * is, if you use Glib::Dispatcher only to notify the GUI thread, only one pipe
 * is created no matter how many Dispatcher objects you have.
00063 class Dispatcher
  /** Create new Dispatcher instance using the default main context.
   * @throw Glib::FileError
  /** Create new Dispatcher instance using an arbitrary main context.
   * @throw Glib::FileError
  explicit Dispatcher(const Glib::RefPtr<MainContext>& context);

  void emit();
  void operator()();

  sigc::connection connect(const sigc::slot<void>& slot);

  sigc::signal<void> signal_;
  DispatchNotifier*   notifier_;

  // noncopyable
  Dispatcher(const Dispatcher&);
  Dispatcher& operator=(const Dispatcher&);

  friend class Glib::DispatchNotifier;

/*! A Glib::Dispatcher example.
 * @example thread/dispatcher.cc

} // namespace Glib


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