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