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#ifndef _GLIBMM_DISPATCHER_H
#define _GLIBMM_DISPATCHER_H
/* 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 Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 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
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*/
#include <sigc++/sigc++.h>
#include <glibmm/main.h>
namespace Glib
{
/** 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.
* @li The Dispatcher object must be deleted by the receiver thread.
* @li All Dispatcher objects instantiated by the same receiver thread must
* use the same main context.
*
* 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.
*
* Using Glib::Dispatcher on Windows:
*
* Glib::Dispatcher also works on win32-based systems. Unfortunately though,
* the implementation cannot use a pipe on win32 and therefore does have to
* lock a mutex on emission, too. However, the impact on performance is
* likely minor and the notification still happens asynchronously. Apart
* from the additional lock the behavior matches the Unix implementation.
*/
class GLIBMM_API Dispatcher
{
public:
/** Create new Dispatcher instance using the default main context.
* @throw Glib::FileError
*/
Dispatcher();
// noncopyable
Dispatcher(const Dispatcher&) = delete;
Dispatcher& operator=(const Dispatcher&) = delete;
/** Create new Dispatcher instance using an arbitrary main context.
* @throw Glib::FileError
*/
explicit Dispatcher(const Glib::RefPtr<MainContext>& context);
~Dispatcher() noexcept;
void emit();
void operator()();
sigc::connection connect(const sigc::slot<void()>& slot);
/** @newin{2,48}
*/
sigc::connection connect(sigc::slot<void()>&& slot);
#ifndef DOXYGEN_SHOULD_SKIP_THIS
struct Impl;
#endif
private:
Impl* impl_; // hidden implementation
};
/*! A Glib::Dispatcher example.
* @example thread/dispatcher.cc
*/
} // namespace Glib
#endif /* _GLIBMM_DISPATCHER_H */
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