libs/pbd/pbd/shiva.h

   1 /*
   2     Copyright (C) 2000-2007 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_shiva_h__
  21 #define __pbd_shiva_h__
  22
  23 #include <sigc++/sigc++.h>
  24
  25 namespace PBD {
  26
  27 /* named after the Hindu god Shiva, The Destroyer */
  28
  29 template<typename ObjectWithGoingAway, typename ObjectToBeDestroyed>
  30 class Shiva {
  31   public:
  32         Shiva (ObjectWithGoingAway& emitter, ObjectToBeDestroyed& receiver) {
  33
  34                 /* if the emitter goes away, destroy the receiver */
  35
  36                 _connection = emitter.GoingAway.connect
  37                         (sigc::bind (sigc::mem_fun
  38                                      (*this, &Shiva<ObjectWithGoingAway,ObjectToBeDestroyed>::destroy),
  39                                      &receiver));
  40         }
  41
  42         ~Shiva() {
  43                 forget ();
  44         }
  45
  46   private:
  47         sigc::connection _connection;
  48
  49         void destroy (ObjectToBeDestroyed* obj) {
  50                 delete obj;
  51                 forget ();
  52         }
  53
  54         void forget () {
  55                 _connection.disconnect ();
  56         }
  57
  58 };
  59
  60 template<typename ObjectWithGoingAway, typename ObjectToBeDestroyed>
  61 class ProxyShiva {
  62   public:
  63         ProxyShiva (ObjectWithGoingAway& emitter, ObjectToBeDestroyed& receiver, void (*callback)(ObjectToBeDestroyed*, ObjectWithGoingAway*)) {
  64
  65                 /* if the emitter goes away, destroy the receiver */
  66
  67                 _callback = callback;
  68                 _callback_argument1 = &receiver;
  69                 _callback_argument2 = &emitter;
  70
  71                 _connection = emitter.GoingAway.connect
  72                         (sigc::bind (sigc::mem_fun
  73                                      (*this, &ProxyShiva<ObjectWithGoingAway,ObjectToBeDestroyed>::destroy),
  74                                      &receiver));
  75         }
  76
  77         ~ProxyShiva() {
  78                 forget ();
  79         }
  80
  81   private:
  82         sigc::connection _connection;
  83         void (*_callback) (ObjectToBeDestroyed*, ObjectWithGoingAway*);
  84         ObjectToBeDestroyed* _callback_argument1;
  85         ObjectWithGoingAway* _callback_argument2;
  86
  87         void destroy (ObjectToBeDestroyed* obj) {
  88                 /* callback must destroy obj if appropriate, not done here */
  89                 _callback (obj, _callback_argument2);
  90                 forget ();
  91         }
  92
  93         void forget () {
  94                 _connection.disconnect ();
  95         }
  96 };
  97
  98 template<typename ObjectWithGoingAway, typename ObjectToBeDestroyed>
  99 class PairedShiva {
 100   public:
 101         PairedShiva (ObjectWithGoingAway& emitter, ObjectToBeDestroyed& receiver) {
 102
 103                 /* if the emitter goes away, destroy the receiver */
 104
 105                 _connection1 = emitter.GoingAway.connect
 106                         (sigc::bind (sigc::mem_fun
 107                                      (*this, &PairedShiva<ObjectWithGoingAway,ObjectToBeDestroyed>::destroy),
 108                                      &receiver));
 109
 110                 /* if the receiver goes away, forget all this nonsense */
 111
 112                 _connection2 = receiver.GoingAway.connect
 113                         (sigc::mem_fun (*this, &PairedShiva<ObjectWithGoingAway,ObjectToBeDestroyed>::forget));
 114         }
 115
 116         ~PairedShiva() {
 117                 forget ();
 118         }
 119
 120   private:
 121         sigc::connection _connection1;
 122         sigc::connection _connection2;
 123
 124         void destroy (ObjectToBeDestroyed* obj) {
 125                 delete obj;
 126                 forget ();
 127         }
 128
 129         void forget () {
 130                 _connection1.disconnect ();
 131                 _connection2.disconnect ();
 132         }
 133
 134 };
 135
 136 }
 137
 138 #endif /* __pbd_shiva_h__ */