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/tracker.h

@@ -0,0 +1,139 @@
+/////////////////////////////////////////////////////////////////////////////
+// Name:        wx/tracker.h
+// Purpose:     Support class for object lifetime tracking (wxWeakRef<T>)
+// Author:      Arne Steinarson
+// Created:     2007-12-28
+// RCS-ID:      $Id:$
+// Copyright:   (c) 2007 Arne Steinarson
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_TRACKER_H_
+#define _WX_TRACKER_H_
+
+// This structure represents an object tracker and is stored in a linked list
+// in the tracked object. It is only used in one of its derived forms.
+struct wxTrackerNode
+{
+    wxTrackerNode() : m_next(NULL) { }
+    virtual ~wxTrackerNode() { }
+
+    virtual void OnObjectDestroy() = 0;
+
+    // This is to tell the difference between different tracker node types.
+    // It's a replacement of dynamic_cast<> for this class since dynamic_cast
+    // may be disabled (and we don't have wxDynamicCast since wxTrackerNode
+    // is not derived wxObject).
+    enum wxTrackerNodeType { WeakRef, EventConnectionRef };
+
+    virtual wxTrackerNodeType GetType() = 0;
+
+protected:
+    wxTrackerNode *m_next;
+
+    friend class wxTrackableBase;    // For list access
+    friend class wxEvtHandler;       // For list access
+};
+
+
+// Add-on base class for a trackable object.
+struct wxTrackableBase
+{
+    wxTrackableBase() : m_first(NULL) { }
+
+    ~wxTrackableBase()
+    {
+        // Notify all registered refs
+
+        // OnObjectDestroy has to remove the item from the link chain
+        while ( m_first )
+        {
+            wxTrackerNode *first = m_first;
+            first->OnObjectDestroy();
+            RemoveNode(first);
+        }
+    }
+
+    void AddNode(wxTrackerNode *node)
+    {
+        node->m_next = m_first;
+        m_first = node;
+    }
+
+    void RemoveNode(wxTrackerNode *node)
+    {
+        for ( wxTrackerNode **pn = &m_first; *pn; pn = &(*pn)->m_next )
+        {
+            if ( *pn == node )
+            {
+                *pn = node->m_next;
+                return;
+            }
+        }
+
+        wxFAIL_MSG( "node should be present" );
+    }
+
+    wxTrackerNode *GetFirst() { return m_first; }
+
+protected:
+    wxTrackerNode *m_first;
+};
+
+// The difference to wxTrackableBase is that this class adds
+// a VTable to enable dynamic_cast query for wxTrackable.
+struct wxTrackable : wxTrackableBase
+{
+    virtual ~wxTrackable() { }
+};
+
+
+// Helper to decide if an object has a base class or not
+// (strictly speaking, this test succeeds if a type is convertible
+//  to another type in some way.)
+template <class T, class B>
+struct wxHasBase
+{
+	static char Match(B *pb);
+	static int Match(...);
+
+	enum { value = sizeof(Match((T*)NULL)) == sizeof(char) };
+};
+
+// A structure to cast to wxTrackableBase, using either static_cast<> or
+// dynamic_cast<>.
+template <class T, bool is_static>
+struct wxTrackableCaster;
+
+template <class T>
+struct wxTrackableCaster<T, true>
+{
+    static wxTrackableBase* Cast(T* pt)
+    {
+        return static_cast<wxTrackableBase *>(pt);
+    }
+};
+
+#ifdef HAVE_DYNAMIC_CAST
+
+template <class T>
+struct wxTrackableCaster<T, false>
+{
+    static wxTrackableBase *Cast(T* pt)
+    {
+        return dynamic_cast<wxTrackableBase *>(pt);
+    }
+};
+
+#else // !HAVE_DYNAMIC_CAST
+
+template <class T>
+struct wxTrackableCaster<T, false>
+{
+    static wxTrackableBase *Cast(T* pt) { return NULL; }
+};
+
+#endif // HAVE_DYNAMIC_CAST/!HAVE_DYNAMIC_CAST
+
+#endif // _WX_TRACKER_H_
+