Paul Davis
e916ac2821
git-svn-id: svn://localhost/ardour2/branches/3.0@5303 d708f5d6-7413-0410-9779-e7cbd77b26cf
109 lines
3.7 KiB
C++
109 lines
3.7 KiB
C++
// -*- c++ -*-
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#ifndef _GLIBMM_DISPATCHER_H
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#define _GLIBMM_DISPATCHER_H
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/* $Id: dispatcher.h 779 2009-01-19 17:58:50Z murrayc $ */
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/* Copyright 2002 The gtkmm Development Team
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free
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* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <sigc++/sigc++.h>
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#include <glibmm/main.h>
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namespace Glib
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{
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#ifndef DOXYGEN_SHOULD_SKIP_THIS
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class DispatchNotifier;
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#endif
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/** Signal class for inter-thread communication.
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* @ingroup Threads
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* Glib::Dispatcher works similar to sigc::signal<void>. But unlike normal
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* signals, the notification happens asynchronously through a pipe. This is
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* a simple and efficient way of communicating between threads, and especially
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* useful in a thread model with a single GUI thread.
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*
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* No mutex locking is involved, apart from the operating system's internal
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* I/O locking. That implies some usage rules:
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*
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* @li Only one thread may connect to the signal and receive notification, but
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* multiple senders are allowed even without locking.
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* @li The GLib main loop must run in the receiving thread (this will be the
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* GUI thread usually).
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* @li The Dispatcher object must be instantiated by the receiver thread.
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* @li The Dispatcher object should be instantiated before creating any of the
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* sender threads, if you want to avoid extra locking.
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*
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* Notes about performance:
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*
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* @li After instantiation, Glib::Dispatcher will never lock any mutexes on its
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* own. The interaction with the GLib main loop might involve locking on the
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* @em receiver side. The @em sender side, however, is guaranteed not to lock,
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* except for internal locking in the <tt>%write()</tt> system call.
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* @li All Dispatcher instances of a receiver thread share the same pipe. That
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* is, if you use Glib::Dispatcher only to notify the GUI thread, only one pipe
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* is created no matter how many Dispatcher objects you have.
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*
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* Using Glib::Dispatcher on Windows:
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*
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* Glib::Dispatcher also works on win32-based systems. Unfortunately though,
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* the implementation cannot use a pipe on win32 and therefore does have to
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* lock a mutex on emission, too. However, the impact on performance is
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* likely minor and the notification still happens asynchronously. Apart
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* from the additional lock the behavior matches the Unix implementation.
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*/
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class Dispatcher
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{
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public:
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/** Create new Dispatcher instance using the default main context.
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* @throw Glib::FileError
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*/
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Dispatcher();
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/** Create new Dispatcher instance using an arbitrary main context.
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* @throw Glib::FileError
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*/
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explicit Dispatcher(const Glib::RefPtr<MainContext>& context);
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~Dispatcher();
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void emit();
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void operator()();
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sigc::connection connect(const sigc::slot<void>& slot);
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private:
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sigc::signal<void> signal_;
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DispatchNotifier* notifier_;
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// noncopyable
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Dispatcher(const Dispatcher&);
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Dispatcher& operator=(const Dispatcher&);
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#ifndef DOXYGEN_SHOULD_SKIP_THIS
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friend class Glib::DispatchNotifier;
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#endif
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};
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/*! A Glib::Dispatcher example.
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* @example thread/dispatcher.cc
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*/
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} // namespace Glib
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#endif /* _GLIBMM_DISPATCHER_H */
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