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, g++ < 3.3) 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) || \
  24     !defined(HAVE_TEMPLATE_OVERLOAD_RESOLUTION) || \
  25     (defined(__GNUC__) && !wxCHECK_GCC_VERSION(3, 3))
  26     #define USE_ONLY_STATIC_WEAKREF
  27 #endif
  28
  29
  30 #ifndef USE_ONLY_STATIC_WEAKREF
  31
  32 // Avoid including this for simpler compilers
  33 #include "wx/meta/convertible.h"
  34 #include "wx/meta/int2type.h"
  35
  36 template <class T>
  37 struct wxIsStaticTrackable
  38 {
  39     enum { value = wxConvertibleTo<T, wxTrackable>::value };
  40 };
  41
  42 #endif // !USE_ONLY_STATIC_WEAKREF
  43
  44
  45 // Weak ref implementation when T has wxTrackable as a known base class
  46 template <class T>
  47 class wxWeakRefStatic : public wxTrackerNode
  48 {
  49 public:
  50     wxWeakRefStatic() : m_pobj(NULL) { }
  51
  52     void Release()
  53     {
  54         // Release old object if any
  55         if ( m_pobj )
  56         {
  57             // Remove ourselves from object tracker list
  58             wxTrackable *pt = static_cast<wxTrackable*>(m_pobj);
  59             pt->RemoveNode(this);
  60             m_pobj = NULL;
  61         }
  62     }
  63
  64     virtual void OnObjectDestroy()
  65     {
  66         // Tracked object itself removes us from list of trackers
  67         wxASSERT(m_pobj != NULL);
  68         m_pobj = NULL;
  69     }
  70
  71 protected:
  72     void Assign(T* pobj)
  73     {
  74         if ( m_pobj == pobj )
  75             return;
  76
  77         Release();
  78
  79         // Now set new trackable object
  80         if ( pobj )
  81         {
  82             // Add ourselves to object tracker list
  83             wxTrackable *pt = static_cast<wxTrackable*>(pobj);
  84             pt->AddNode(this);
  85             m_pobj = pobj;
  86         }
  87     }
  88
  89     void AssignCopy(const wxWeakRefStatic& wr)
  90     {
  91         Assign( wr.m_pobj );
  92     }
  93
  94     T *m_pobj;
  95 };
  96
  97
  98
  99 #ifndef USE_ONLY_STATIC_WEAKREF
 100
 101 template<class T,bool use_static>
 102 struct wxWeakRefImpl;
 103
 104 // Intermediate class, to select the static case above.
 105 template <class T>
 106 struct wxWeakRefImpl<T, true> : public wxWeakRefStatic<T>
 107 {
 108     enum { value = 1 };
 109 };
 110
 111 // Weak ref implementation when T does not have wxTrackable as known base class
 112 template<class T>
 113 struct wxWeakRefImpl<T, false> : public wxTrackerNode
 114 {
 115     void Release()
 116     {
 117         // Release old object if any
 118         if ( m_pobj )
 119         {
 120             // Remove ourselves from object tracker list
 121             m_ptbase->RemoveNode(this);
 122             m_pobj = NULL;
 123             m_ptbase = NULL;
 124         }
 125     }
 126
 127     virtual void OnObjectDestroy()
 128     {
 129         // Tracked object itself removes us from list of trackers
 130         wxASSERT(m_pobj != NULL);
 131         m_pobj = NULL;
 132         m_ptbase = NULL;
 133     }
 134
 135 protected:
 136     wxWeakRefImpl() : m_pobj(NULL), m_ptbase(NULL) { }
 137
 138     // Assign receives most derived class here and can use that
 139     template <class TDerived>
 140     void Assign( TDerived* pobj )
 141     {
 142         AssignHelper( pobj, wxInt2Type<wxIsStaticTrackable<TDerived>::value>() );
 143     }
 144
 145     template <class TDerived>
 146     void AssignHelper(TDerived* pobj, wxInt2Type<true>)
 147     {
 148         wxTrackable *ptbase = static_cast<wxTrackable*>(pobj);
 149         DoAssign( pobj, ptbase );
 150     }
 151
 152 #ifdef HAVE_DYNAMIC_CAST
 153     void AssignHelper(T* pobj, wxInt2Type<false>)
 154     {
 155         // A last way to get a trackable pointer
 156         wxTrackable *ptbase = dynamic_cast<wxTrackable*>(pobj);
 157         if ( ptbase )
 158         {
 159             DoAssign( pobj, ptbase );
 160         }
 161         else
 162         {
 163             wxFAIL_MSG( "Tracked class should inherit from wxTrackable" );
 164
 165             Release();
 166         }
 167     }
 168 #endif // HAVE_DYNAMIC_CAST
 169
 170     void AssignCopy(const wxWeakRefImpl& wr)
 171     {
 172         DoAssign(wr.m_pobj, wr.m_ptbase);
 173     }
 174
 175     void DoAssign( T* pobj, wxTrackable *ptbase ) {
 176         if( m_pobj==pobj ) return;
 177         Release();
 178
 179         // Now set new trackable object
 180         if( pobj )
 181         {
 182             // Add ourselves to object tracker list
 183             wxASSERT( ptbase );
 184             ptbase->AddNode( this );
 185             m_pobj = pobj;
 186             m_ptbase = ptbase;
 187         }
 188     }
 189
 190     T *m_pobj;
 191     wxTrackable *m_ptbase;
 192 };
 193
 194 #endif // #ifndef USE_ONLY_STATIC_WEAKREF
 195
 196
 197
 198 // A weak reference to an object of type T, where T has base wxTrackable
 199 // (usually statically but if not dynamic_cast<> is tried).
 200 template <class T>
 201 class wxWeakRef : public
 202 #ifdef USE_ONLY_STATIC_WEAKREF
 203                   wxWeakRefStatic<T>
 204 #else
 205                   wxWeakRefImpl<T, wxIsStaticTrackable<T>::value != 0>
 206 #endif
 207 {
 208 public:
 209     // Default ctor
 210     wxWeakRef() { }
 211
 212     // When we have the full type here, static_cast<> will always work
 213     // (or give a straight compiler error).
 214     template <class TDerived>
 215     wxWeakRef(TDerived* pobj)
 216     {
 217         Assign(pobj);
 218     }
 219
 220     // We need this copy ctor, since otherwise a default compiler (binary) copy
 221     // happens (if embedded as an object member).
 222     wxWeakRef(const wxWeakRef<T>& wr)
 223     {
 224         Assign(wr.get());
 225     }
 226
 227     template <class TDerived>
 228     wxWeakRef<T>& operator=(TDerived* pobj)
 229     {
 230         this->Assign(pobj);
 231         return *this;
 232     }
 233
 234     wxWeakRef<T>& operator=(const wxWeakRef<T>& wr)
 235     {
 236         AssignCopy(wr);
 237         return *this;
 238     }
 239
 240     virtual ~wxWeakRef() { this->Release(); }
 241
 242     // Smart pointer functions
 243     T& operator*() const    { return *this->m_pobj; }
 244     T* operator->() const   { return this->m_pobj; }
 245
 246     T* get() const          { return this->m_pobj; }
 247     operator T*() const     { return this->m_pobj; }
 248 };
 249
 250
 251 #ifdef HAVE_DYNAMIC_CAST
 252
 253 // Weak ref implementation assign objects are queried for wxTrackable
 254 // using dynamic_cast<>
 255 template <class T>
 256 class wxWeakRefDynamic : public wxTrackerNode
 257 {
 258 public:
 259     wxWeakRefDynamic() : m_pobj(NULL) { }
 260
 261     wxWeakRefDynamic(T* pobj) : m_pobj(pobj)
 262     {
 263         Assign(pobj);
 264     }
 265
 266     wxWeakRefDynamic(const wxWeakRef<T>& wr)
 267     {
 268         Assign(wr.get());
 269     }
 270
 271     virtual ~wxWeakRefDynamic() { Release(); }
 272
 273     // Smart pointer functions
 274     T& operator*() const    { wxASSERT(m_pobj); return *m_pobj; }
 275     T* operator->() const   { wxASSERT(m_pobj); return m_pobj; }
 276
 277     T* get() const          { return m_pobj; }
 278     operator T* () const    { return m_pobj; }
 279
 280     T* operator = (T* pobj) { Assign(pobj); return m_pobj; }
 281
 282     // Assign from another weak ref, point to same object
 283     T* operator = (const wxWeakRef<T> &wr) { Assign( wr.get() ); return m_pobj; }
 284
 285     void Release()
 286     {
 287         // Release old object if any
 288         if( m_pobj )
 289         {
 290             // Remove ourselves from object tracker list
 291             wxTrackable *pt = dynamic_cast<wxTrackable*>(m_pobj);
 292             wxASSERT(pt);
 293             pt->RemoveNode(this);
 294             m_pobj = NULL;
 295         }
 296     }
 297
 298     virtual void OnObjectDestroy()
 299     {
 300         wxASSERT_MSG(m_pobj, "tracked object should have removed us itself");
 301
 302         m_pobj = NULL;
 303     }
 304
 305 protected:
 306     void Assign(T *pobj)
 307     {
 308         if ( m_pobj == pobj )
 309             return;
 310
 311         Release();
 312
 313         // Now set new trackable object
 314         if ( pobj )
 315         {
 316             // Add ourselves to object tracker list
 317             wxTrackable *pt = dynamic_cast<wxTrackable*>(pobj);
 318             if ( pt )
 319             {
 320                 pt->AddNode(this);
 321                 m_pobj = pobj;
 322             }
 323             else
 324             {
 325                 // If the object we want to track does not support wxTackable, then
 326                 // log a message and keep the NULL object pointer.
 327                 wxFAIL_MSG( "Tracked class should inherit from wxTrackable" );
 328             }
 329         }
 330     }
 331
 332     T *m_pobj;
 333 };
 334
 335 #endif // #ifdef HAVE_DYNAMIC_CAST
 336
 337
 338 // Provide some basic types of weak references
 339 class WXDLLIMPEXP_FWD_BASE wxEvtHandler;
 340 class WXDLLIMPEXP_FWD_CORE wxWindow;
 341
 342
 343 typedef wxWeakRef<wxEvtHandler>  wxEvtHandlerRef;
 344 typedef wxWeakRef<wxWindow>      wxWindowRef;
 345
 346 #endif // _WX_WEAKREF_H_
 347