include/wx/weakref.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        wx/weakref.h
   3 // Purpose:     wxWeakRef - Generic weak references for wxWidgets
   4 // Author:      Arne Steinarson
   5 // Created:     27 Dec 07
   6 // RCS-ID:      $Id$
   7 // Copyright:   (c) 2007 Arne Steinarson
   8 // Licence:     wxWindows licence
   9 /////////////////////////////////////////////////////////////////////////////
  10
  11 #ifndef _WX_WEAKREF_H_
  12 #define _WX_WEAKREF_H_
  13
  14 #include "wx/tracker.h"
  15
  16
  17 // Some compilers (VC6, Borland, otehrs?) have problem with template specialization.
  18 // However, this is only used for optimization purposes (a smaller wxWeakRef pointer)
  19 // (and the corner case of wxWeakRef<wxObject>). So for those compilers, we can fall
  20 // back to the non-optimal case, where we use a the same type of weak ref (static one)
  21 // in all cases. See defs.h for various setting these defines depending on compiler.
  22
  23 #if !defined(HAVE_PARTIAL_SPECIALIZATION) || !defined(HAVE_TEMPLATE_OVERLOAD_RESOLUTION)
  24     #define USE_ONLY_STATIC_WEAKREF
  25 #endif
  26
  27
  28 #ifndef USE_ONLY_STATIC_WEAKREF
  29
  30 // Avoid including this for simpler compilers
  31 #include "wx/meta/convertible.h"
  32 #include "wx/meta/int2type.h"
  33
  34 template <class T>
  35 struct wxIsStaticTrackable
  36 {
  37     enum { value = wxConvertibleTo<T, wxTrackable>::value };
  38 };
  39
  40 #endif // !USE_ONLY_STATIC_WEAKREF
  41
  42
  43 // Weak ref implementation when T has wxTrackable as a known base class
  44 template <class T>
  45 class wxWeakRefStatic : public wxTrackerNode
  46 {
  47 public:
  48     wxWeakRefStatic() : m_pobj(NULL) { }
  49
  50     void Release()
  51     {
  52         // Release old object if any
  53         if ( m_pobj )
  54         {
  55             // Remove ourselves from object tracker list
  56             wxTrackable *pt = static_cast<wxTrackable*>(m_pobj);
  57             pt->RemoveNode(this);
  58             m_pobj = NULL;
  59         }
  60     }
  61
  62 protected:
  63     void Assign(T* pobj)
  64     {
  65         if ( m_pobj == pobj )
  66             return;
  67
  68         Release();
  69
  70         // Now set new trackable object
  71         if ( pobj )
  72         {
  73             // Add ourselves to object tracker list
  74             wxTrackable *pt = static_cast<wxTrackable*>(pobj);
  75             pt->AddNode(this);
  76             m_pobj = pobj;
  77         }
  78     }
  79
  80     void AssignCopy(const wxWeakRefStatic& wr)
  81     {
  82         Assign( wr.m_pobj );
  83     }
  84
  85     virtual void OnObjectDestroy()
  86     {
  87         // Tracked object itself removes us from list of trackers
  88         wxASSERT( m_pobj!=NULL );
  89         m_pobj = NULL;
  90     }
  91
  92     T *m_pobj;
  93 };
  94
  95
  96
  97 #ifndef USE_ONLY_STATIC_WEAKREF
  98
  99 template<class T,bool use_static>
 100 struct wxWeakRefImpl;
 101
 102 // Intermediate class, to select the static case above.
 103 template <class T>
 104 struct wxWeakRefImpl<T, true> : public wxWeakRefStatic<T>
 105 {
 106     enum { value = 1 };
 107 };
 108
 109 // Weak ref implementation when T does not have wxTrackable as known base class
 110 template<class T>
 111 struct wxWeakRefImpl<T, false> : public wxTrackerNode
 112 {
 113     void Release()
 114     {
 115         // Release old object if any
 116         if ( m_pobj )
 117         {
 118             // Remove ourselves from object tracker list
 119             m_ptbase->RemoveNode(this);
 120             m_pobj = NULL;
 121             m_ptbase = NULL;
 122         }
 123     }
 124
 125 protected:
 126     wxWeakRefImpl() : m_pobj(NULL), m_ptbase(NULL) { }
 127
 128     // Assign receives most derived class here and can use that
 129     template <class TDerived>
 130     void Assign( TDerived* pobj )
 131     {
 132         AssignHelper( pobj, wxInt2Type<wxIsStaticTrackable<TDerived>::value>() );
 133     }
 134
 135     template <class TDerived>
 136     void AssignHelper(TDerived* pobj, wxInt2Type<true>)
 137     {
 138         wxTrackable *ptbase = static_cast<wxTrackable*>(pobj);
 139         DoAssign( pobj, ptbase );
 140     }
 141
 142 #ifdef HAVE_DYNAMIC_CAST
 143     void AssignHelper(T* pobj, wxInt2Type<false>)
 144     {
 145         // A last way to get a trackable pointer
 146         wxTrackable *ptbase = dynamic_cast<wxTrackable*>(pobj);
 147         if ( ptbase )
 148         {
 149             DoAssign( pobj, ptbase );
 150         }
 151         else
 152         {
 153             wxFAIL_MSG( "Tracked class should inherit from wxTrackable" );
 154
 155             Release();
 156         }
 157     }
 158 #endif // HAVE_DYNAMIC_CAST
 159
 160     void AssignCopy(const wxWeakRefImpl& wr)
 161     {
 162         DoAssign(wr.m_pobj, wr.m_ptbase);
 163     }
 164
 165     void DoAssign( T* pobj, wxTrackable *ptbase ) {
 166         if( m_pobj==pobj ) return;
 167         Release();
 168
 169         // Now set new trackable object
 170         if( pobj )
 171         {
 172             // Add ourselves to object tracker list
 173             wxASSERT( ptbase );
 174             ptbase->AddNode( this );
 175             m_pobj = pobj;
 176             m_ptbase = ptbase;
 177         }
 178     }
 179
 180     virtual void OnObjectDestroy()
 181     {
 182         // Tracked object itself removes us from list of trackers
 183         wxASSERT( m_pobj!=NULL );
 184         m_pobj = NULL;
 185         m_ptbase = NULL;
 186     }
 187
 188     T *m_pobj;
 189     wxTrackable *m_ptbase;
 190 };
 191
 192 #endif // #ifndef USE_ONLY_STATIC_WEAKREF
 193
 194
 195
 196 // A weak reference to an object of type T, where T has base wxTrackable
 197 // (usually statically but if not dynamic_cast<> is tried).
 198 template <class T>
 199 class wxWeakRef : public
 200 #ifdef USE_ONLY_STATIC_WEAKREF
 201                   wxWeakRefStatic<T>
 202 #else
 203                   wxWeakRefImpl<T, wxIsStaticTrackable<T>::value>
 204 #endif
 205 {
 206 public:
 207     // Default ctor
 208     wxWeakRef() { }
 209
 210     // When we have the full type here, static_cast<> will always work
 211     // (or give a straight compiler error).
 212     template <class TDerived>
 213     wxWeakRef(TDerived* pobj)
 214     {
 215         Assign(pobj);
 216     }
 217
 218     // We need this copy ctor, since otherwise a default compiler (binary) copy
 219     // happens (if embedded as an object member).
 220     wxWeakRef(const wxWeakRef<T>& wr)
 221     {
 222         Assign(wr.get());
 223     }
 224
 225     template <class TDerived>
 226     wxWeakRef<T>& operator=(TDerived* pobj)
 227     {
 228         Assign(pobj);
 229         return *this;
 230     }
 231
 232     wxWeakRef<T>& operator=(const wxWeakRef<T>& wr)
 233     {
 234         AssignCopy(wr);
 235         return *this;
 236     }
 237
 238     virtual ~wxWeakRef() { this->Release(); }
 239
 240     // Smart pointer functions
 241     T& operator*() const    { return *this->m_pobj; }
 242     T* operator->() const   { return this->m_pobj; }
 243
 244     T* get() const          { return this->m_pobj; }
 245     operator T*() const     { return this->m_pobj; }
 246 };
 247
 248
 249 #ifdef HAVE_DYNAMIC_CAST
 250
 251 // Weak ref implementation assign objects are queried for wxTrackable
 252 // using dynamic_cast<>
 253 template <class T>
 254 class wxWeakRefDynamic : public wxTrackerNode
 255 {
 256 public:
 257     wxWeakRefDynamic() : m_pobj(NULL) { }
 258
 259     wxWeakRefDynamic(T* pobj) : m_pobj(pobj)
 260     {
 261         Assign(pobj);
 262     }
 263
 264     wxWeakRefDynamic(const wxWeakRef<T>& wr)
 265     {
 266         Assign(wr.get());
 267     }
 268
 269     virtual ~wxWeakRefDynamic() { Release(); }
 270
 271     // Smart pointer functions
 272     T& operator*() const    { wxASSERT(m_pobj); return *m_pobj; }
 273     T* operator->() const   { wxASSERT(m_pobj); return m_pobj; }
 274
 275     T* get() const          { return m_pobj; }
 276     operator T* () const    { return m_pobj; }
 277
 278     T* operator = (T* pobj) { Assign(pobj); return m_pobj; }
 279
 280     // Assign from another weak ref, point to same object
 281     T* operator = (const wxWeakRef<T> &wr) { Assign( wr.get() ); return m_pobj; }
 282
 283     void Release()
 284     {
 285         // Release old object if any
 286         if( m_pobj )
 287         {
 288             // Remove ourselves from object tracker list
 289             wxTrackable *pt = dynamic_cast<wxTrackable*>(m_pobj);
 290             wxASSERT(pt);
 291             pt->RemoveNode(this);
 292             m_pobj = NULL;
 293         }
 294     }
 295
 296 protected:
 297     void Assign(T *pobj)
 298     {
 299         if ( m_pobj == pobj )
 300             return;
 301
 302         Release();
 303
 304         // Now set new trackable object
 305         if ( pobj )
 306         {
 307             // Add ourselves to object tracker list
 308             wxTrackable *pt = dynamic_cast<wxTrackable*>(pobj);
 309             if ( pt )
 310             {
 311                 pt->AddNode(this);
 312                 m_pobj = pobj;
 313             }
 314             else
 315             {
 316                 // If the object we want to track does not support wxTackable, then
 317                 // log a message and keep the NULL object pointer.
 318                 wxFAIL_MSG( "Tracked class should inherit from wxTrackable" );
 319             }
 320         }
 321     }
 322
 323     virtual void OnObjectDestroy()
 324     {
 325         wxASSERT_MSG( m_pobj, "tracked object should have removed us itself" );
 326
 327         m_pobj = NULL;
 328     }
 329
 330     T *m_pobj;
 331 };
 332
 333 #endif // #ifdef HAVE_DYNAMIC_CAST
 334
 335
 336 // Provide some basic types of weak references
 337 class WXDLLIMPEXP_FWD_BASE wxEvtHandler;
 338 class WXDLLIMPEXP_FWD_CORE wxWindow;
 339
 340
 341 typedef wxWeakRef<wxEvtHandler>  wxEvtHandlerRef;
 342 typedef wxWeakRef<wxWindow>      wxWindowRef;
 343
 344 #endif // _WX_WEAKREF_H_
 345