signals.h

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/*
    Copyright (C) 2009-2012 Paul Davis 
    
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/

#ifndef __pbd_signals_h__
#define __pbd_signals_h__

#include <list>
#include <map>

#ifdef nil
#undef nil
#endif

#include <glibmm/threads.h>

#include <boost/noncopyable.hpp>
#include <boost/bind.hpp>
#include <boost/bind/protect.hpp>
#include <boost/function.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/optional.hpp>

#include "pbd/libpbd_visibility.h"
#include "pbd/event_loop.h"

#ifndef NDEBUG
#define DEBUG_PBD_SIGNAL_CONNECTIONS
#endif

#ifdef DEBUG_PBD_SIGNAL_CONNECTIONS
#include "pbd/stacktrace.h"
#include <iostream>
#endif

namespace PBD {

class LIBPBD_API Connection;

class LIBPBD_API SignalBase
{
public:
        SignalBase ()
#ifdef DEBUG_PBD_SIGNAL_CONNECTIONS
        : _debug_connection (false)
#endif
        {}
        virtual ~SignalBase () {}
        virtual void disconnect (boost::shared_ptr<Connection>) = 0;
#ifdef DEBUG_PBD_SIGNAL_CONNECTIONS
        void set_debug_connection (bool yn) { _debug_connection = yn; }
#endif

protected:
        Glib::Threads::Mutex _mutex;
#ifdef DEBUG_PBD_SIGNAL_CONNECTIONS
        bool _debug_connection;
#endif
};

class LIBPBD_API Connection : public boost::enable_shared_from_this<Connection>
{
public:
        Connection (SignalBase* b) : _signal (b) {}

        void disconnect ()
        {
                Glib::Threads::Mutex::Lock lm (_mutex);
                if (_signal) {
                        _signal->disconnect (shared_from_this ());
                        _signal = 0;
                }
        }

        void signal_going_away ()
        {
                Glib::Threads::Mutex::Lock lm (_mutex);
                _signal = 0;
        }

private:
        Glib::Threads::Mutex _mutex;
        SignalBase* _signal;
};

template<typename R>
class /*LIBPBD_API*/ OptionalLastValue
{
public:
        typedef boost::optional<R> result_type;

        template <typename Iter>
        result_type operator() (Iter first, Iter last) const {
                result_type r;
                while (first != last) {
                        r = *first;
                        ++first;
                }

                return r;
        }
};
        
typedef boost::shared_ptr<Connection> UnscopedConnection;
        
class LIBPBD_API ScopedConnection
{
public:
        ScopedConnection () {}
        ScopedConnection (UnscopedConnection c) : _c (c) {}
        ~ScopedConnection () {
                disconnect ();
        }

        void disconnect ()
        {
                if (_c) {
                        _c->disconnect ();
                }
        }

        ScopedConnection& operator= (UnscopedConnection const & o)
        {
                if (_c == o) {
                        return *this;
                }
                
                disconnect ();
                _c = o;
                return *this;
        }

private:
        UnscopedConnection _c;
};
        
class LIBPBD_API ScopedConnectionList  : public boost::noncopyable
{
  public:
        ScopedConnectionList();
        virtual ~ScopedConnectionList ();
        
        void add_connection (const UnscopedConnection& c);
        void drop_connections ();

  private:
        /* this class is not copyable */
        ScopedConnectionList(const ScopedConnectionList&);

        /* Even though our signals code is thread-safe, this additional list of
           scoped connections needs to be protected in 2 cases:

           (1) (unlikely) we make a connection involving a callback on the
               same object from 2 threads. (wouldn't that just be appalling 
               programming style?)
             
           (2) where we are dropping connections in one thread and adding
               one from another.
         */

        Glib::Threads::Mutex _lock;

        typedef std::list<ScopedConnection*> ConnectionList;
        ConnectionList _list;
};

#include "pbd/signals_generated.h"      
        
} /* namespace */

#endif /* __pbd_signals_h__ */