added wxWeakRef<T> (slightly modified patch 1860953)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@51042 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/weakref.h

@@ -0,0 +1,89 @@
+/////////////////////////////////////////////////////////////////////////////
+// Name:        wx/weakref.h
+// Purpose:     wxWeakRef - Generic weak references for wxWidgets
+// Author:      Arne Steinarson
+// Created:     2007-12-27
+// RCS-ID:      $Id:$
+// Copyright:   (c) 2007 Arne Steinarson
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_WEAKREF_H_
+#define _WX_WEAKREF_H_
+
+#include <wx/tracker.h>
+
+// A weak reference to an object of type T, where T has type wxTrackable
+// as one of its base classes (in a static or dynamic sense).
+template<class T>
+class wxWeakRef : public wxTrackerNode
+{
+public:
+    wxWeakRef(T *pobj = NULL) : m_pobj(NULL) { Assign(pobj); }
+
+    virtual ~wxWeakRef() { Assign(NULL); }
+
+    // Smart pointer functions
+    operator T*(){ return m_pobj; }
+    T* operator->(){ return m_pobj; }
+    T* operator=(T *pobj)
+    {
+        Assign(pobj);
+        return m_pobj;
+    }
+
+    virtual void OnObjectDestroy()
+    {
+        // Tracked object itself removes us from list of trackers
+        wxASSERT( m_pobj );
+        m_pobj = NULL;
+    }
+
+    virtual wxTrackerNodeType GetType() { return WeakRef; }
+
+protected:
+    wxTrackableBase *GetTrackable(T *pobj)
+    {
+        // this uses static_cast if possible or dynamic_cast otherwise
+        return wxTrackableCaster<T, wxHasBase<T, wxTrackableBase>::value>
+                ::Cast(pobj);
+    }
+
+    void Assign(T* pobj)
+    {
+        if ( m_pobj == pobj )
+            return;
+
+        // First release old object if any
+        if ( m_pobj )
+        {
+            // Remove ourselves from object tracker list
+            GetTrackable(m_pobj)->RemoveNode(this);
+            m_pobj = NULL;
+        }
+
+        // Now set new trackable object
+        if ( pobj )
+        {
+            wxTrackableBase * const pt = GetTrackable(pobj);
+            wxCHECK_RET( pt, "type must derive from wxTrackableBase" );
+
+            pt->AddNode(this);
+            m_pobj = pobj;
+        }
+    }
+
+    T *m_pobj;
+};
+
+// Provide some basic types of weak references
+class WXDLLIMPEXP_FWD_BASE wxObject;
+class WXDLLIMPEXP_FWD_BASE wxEvtHandler;
+class WXDLLIMPEXP_FWD_CORE wxWindow;
+
+typedef wxWeakRef<wxObject>      wxObjectRef;
+typedef wxWeakRef<wxEvtHandler>  wxEvtHandlerRef;
+typedef wxWeakRef<wxWindow>      wxWindowRef;
+
+#endif // _WX_WEAKREF_H_
+