include/wx/tracker.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        wx/tracker.h
   3 // Purpose:     Support class for object lifetime tracking (wxWeakRef<T>)
   4 // Author:      Arne Steinarson
   5 // Created:     28 Dec 07
   6 // RCS-ID:      $Id$
   7 // Copyright:   (c) 2007 Arne Steinarson
   8 // Licence:     wxWindows licence
   9 /////////////////////////////////////////////////////////////////////////////
  10
  11 #ifndef _WX_TRACKER_H_
  12 #define _WX_TRACKER_H_
  13
  14 #include "wx/defs.h"
  15
  16 class wxEventConnectionRef;
  17
  18 // This class represents an object tracker and is stored in a linked list
  19 // in the tracked object. It is only used in one of its derived forms.
  20 class WXDLLIMPEXP_BASE wxTrackerNode
  21 {
  22 public:
  23     wxTrackerNode() : m_nxt(NULL) { }
  24     virtual ~wxTrackerNode() { }
  25
  26     virtual void OnObjectDestroy() = 0;
  27
  28     virtual wxEventConnectionRef *ToEventConnection() { return NULL; }
  29
  30 private:
  31     wxTrackerNode *m_nxt;
  32
  33     friend class wxTrackable;        // For list access
  34     friend class wxEvtHandler;       // For list access
  35 };
  36
  37 // Add-on base class for a trackable object.
  38 class wxTrackable
  39 {
  40 public:
  41     void AddNode(wxTrackerNode *prn)
  42     {
  43         prn->m_nxt = m_first;
  44         m_first = prn;
  45     }
  46
  47     void RemoveNode(wxTrackerNode *prn)
  48     {
  49         for ( wxTrackerNode **pprn = &m_first; *pprn; pprn = &(*pprn)->m_nxt )
  50         {
  51             if ( *pprn == prn )
  52             {
  53                 *pprn = prn->m_nxt;
  54                 return;
  55             }
  56         }
  57
  58         wxFAIL_MSG( "removing invalid tracker node" );
  59     }
  60
  61     wxTrackerNode *GetFirst() const { return m_first; }
  62
  63 protected:
  64     // this class is only supposed to be used as a base class but never be
  65     // created nor destroyed directly so all ctors and dtor are protected
  66
  67     wxTrackable() : m_first(NULL) { }
  68
  69     // copy ctor and assignment operator intentionally do not copy m_first: the
  70     // objects which track the original trackable shouldn't track the new copy
  71     wxTrackable(const wxTrackable& WXUNUSED(other)) : m_first(NULL) { }
  72     wxTrackable& operator=(const wxTrackable& WXUNUSED(other)) { return *this; }
  73
  74     // dtor is not virtual: this class is not supposed to be used
  75     // polymorphically and adding a virtual table to it would add unwanted
  76     // overhead
  77     ~wxTrackable()
  78     {
  79         // Notify all registered refs
  80         while ( m_first )
  81         {
  82             wxTrackerNode * const first = m_first;
  83             m_first = first->m_nxt;
  84             first->OnObjectDestroy();
  85         }
  86     }
  87
  88     wxTrackerNode *m_first;
  89 };
  90
  91 #endif // _WX_TRACKER_H_
  92