/////////////////////////////////////////////////////////////////////////////

// Name:        wx/tracker.h

// Purpose:     Support class for object lifetime tracking (wxWeakRef<T>)

// Author:      Arne Steinarson

// Created:     28 Dec 07

// Copyright:   (c) 2007 Arne Steinarson

// Licence:     wxWindows licence

/////////////////////////////////////////////////////////////////////////////

#ifndef _WX_TRACKER_H_

#define _WX_TRACKER_H_

#include "wx/defs.h"

class wxEventConnectionRef;

// This class 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.

class WXDLLIMPEXP_BASE wxTrackerNode

{

public:

    wxTrackerNode() : m_nxt(nullptr) { }

    virtual ~wxTrackerNode() = default;

    virtual void OnObjectDestroy() = 0;

    virtual wxEventConnectionRef *ToEventConnection() { return nullptr; }

private:

    wxTrackerNode *m_nxt;

    friend class wxTrackable;        // For list access

    friend class wxEvtHandler;       // For list access

};

// Add-on base class for a trackable object.

class WXDLLIMPEXP_BASE wxTrackable

{

public:

    void AddNode(wxTrackerNode *prn)

    {

        prn->m_nxt = m_first;

        m_first = prn;

    }

    void RemoveNode(wxTrackerNode *prn)

    {

        for ( wxTrackerNode **pprn = &m_first; *pprn; pprn = &(*pprn)->m_nxt )

        {

            if ( *pprn == prn )

            {

                *pprn = prn->m_nxt;

                return;

            }

        }

        wxFAIL_MSG( "removing invalid tracker node" );

    }

    wxTrackerNode *GetFirst() const { return m_first; }

protected:

    // this class is only supposed to be used as a base class but never be

    // created nor destroyed directly so all ctors and dtor are protected

    wxTrackable() : m_first(nullptr) { }

    // copy ctor and assignment operator intentionally do not copy m_first: the

    // objects which track the original trackable shouldn't track the new copy

    wxTrackable(const wxTrackable& WXUNUSED(other)) : m_first(nullptr) { }

    wxTrackable& operator=(const wxTrackable& WXUNUSED(other)) { return *this; }

    // dtor is not virtual: this class is not supposed to be used

    // polymorphically and adding a virtual table to it would add unwanted

    // overhead

    ~wxTrackable()

    {

        // Notify all registered refs

        while ( m_first )

        {

            wxTrackerNode * const first = m_first;

            m_first = first->m_nxt;

            first->OnObjectDestroy();

        }

    }

    wxTrackerNode *m_first;

};

#endif // _WX_TRACKER_H_