libs/pbd/pbd/signals.h

   1 /*
   2     Copyright (C) 2009-2012 Paul Davis
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12     GNU General Public License for more details.
  13
  14     You should have received a copy of the GNU General Public License
  15     along with this program; if not, write to the Free Software
  16     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17
  18 */
  19
  20 #ifndef __pbd_signals_h__
  21 #define __pbd_signals_h__
  22
  23 #include <list>
  24 #include <map>
  25
  26 #ifdef nil
  27 #undef nil
  28 #endif
  29
  30 #include <glibmm/threads.h>
  31
  32 #include <boost/noncopyable.hpp>
  33 #include <boost/bind.hpp>
  34 #include <boost/bind/protect.hpp>
  35 #include <boost/function.hpp>
  36 #include <boost/enable_shared_from_this.hpp>
  37 #include <boost/optional.hpp>
  38
  39 #include "pbd/libpbd_visibility.h"
  40 #include "pbd/event_loop.h"
  41
  42 #ifndef NDEBUG
  43 #define DEBUG_PBD_SIGNAL_CONNECTIONS
  44 #endif
  45
  46 #ifdef DEBUG_PBD_SIGNAL_CONNECTIONS
  47 #include "pbd/stacktrace.h"
  48 #include <iostream>
  49 #endif
  50
  51 namespace PBD {
  52
  53 class LIBPBD_API Connection;
  54
  55 class LIBPBD_API SignalBase
  56 {
  57 public:
  58         SignalBase ()
  59 #ifdef DEBUG_PBD_SIGNAL_CONNECTIONS
  60         : _debug_connection (false)
  61 #endif
  62         {}
  63         virtual ~SignalBase () {}
  64         virtual void disconnect (boost::shared_ptr<Connection>) = 0;
  65 #ifdef DEBUG_PBD_SIGNAL_CONNECTIONS
  66         void set_debug_connection (bool yn) { _debug_connection = yn; }
  67 #endif
  68
  69 protected:
  70         Glib::Threads::Mutex _mutex;
  71 #ifdef DEBUG_PBD_SIGNAL_CONNECTIONS
  72         bool _debug_connection;
  73 #endif
  74 };
  75
  76 class LIBPBD_API Connection : public boost::enable_shared_from_this<Connection>
  77 {
  78 public:
  79         Connection (SignalBase* b) : _signal (b) {}
  80
  81         void disconnect ()
  82         {
  83                 Glib::Threads::Mutex::Lock lm (_mutex);
  84                 if (_signal) {
  85                         _signal->disconnect (shared_from_this ());
  86                         _signal = 0;
  87                 }
  88         }
  89
  90         void signal_going_away ()
  91         {
  92                 Glib::Threads::Mutex::Lock lm (_mutex);
  93                 _signal = 0;
  94         }
  95
  96 private:
  97         Glib::Threads::Mutex _mutex;
  98         SignalBase* _signal;
  99 };
 100
 101 template<typename R>
 102 class /*LIBPBD_API*/ OptionalLastValue
 103 {
 104 public:
 105         typedef boost::optional<R> result_type;
 106
 107         template <typename Iter>
 108         result_type operator() (Iter first, Iter last) const {
 109                 result_type r;
 110                 while (first != last) {
 111                         r = *first;
 112                         ++first;
 113                 }
 114
 115                 return r;
 116         }
 117 };
 118
 119 typedef boost::shared_ptr<Connection> UnscopedConnection;
 120
 121 class LIBPBD_API ScopedConnection
 122 {
 123 public:
 124         ScopedConnection () {}
 125         ScopedConnection (UnscopedConnection c) : _c (c) {}
 126         ~ScopedConnection () {
 127                 disconnect ();
 128         }
 129
 130         void disconnect ()
 131         {
 132                 if (_c) {
 133                         _c->disconnect ();
 134                 }
 135         }
 136
 137         ScopedConnection& operator= (UnscopedConnection const & o)
 138         {
 139                 if (_c == o) {
 140                         return *this;
 141                 }
 142
 143                 disconnect ();
 144                 _c = o;
 145                 return *this;
 146         }
 147
 148 private:
 149         UnscopedConnection _c;
 150 };
 151
 152 class LIBPBD_API ScopedConnectionList  : public boost::noncopyable
 153 {
 154   public:
 155         ScopedConnectionList();
 156         virtual ~ScopedConnectionList ();
 157
 158         void add_connection (const UnscopedConnection& c);
 159         void drop_connections ();
 160
 161   private:
 162         /* this class is not copyable */
 163         ScopedConnectionList(const ScopedConnectionList&);
 164
 165         /* Even though our signals code is thread-safe, this additional list of
 166            scoped connections needs to be protected in 2 cases:
 167
 168            (1) (unlikely) we make a connection involving a callback on the
 169                same object from 2 threads. (wouldn't that just be appalling
 170                programming style?)
 171
 172            (2) where we are dropping connections in one thread and adding
 173                one from another.
 174          */
 175
 176         Glib::Threads::Mutex _lock;
 177
 178         typedef std::list<ScopedConnection*> ConnectionList;
 179         ConnectionList _list;
 180 };
 181
 182 #include "pbd/signals_generated.h"
 183
 184 } /* namespace */
 185
 186 #endif /* __pbd_signals_h__ */