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