wxWidgets/include/wx/persist.h

///////////////////////////////////////////////////////////////////////////////
// Name:        wx/persist.h
// Purpose:     common classes for persistence support
// Author:      Vadim Zeitlin
// Created:     2009-01-18
// RCS-ID:      $Id: wxhead.h,v 1.10 2008-04-15 23:34:19 zeitlin Exp $
// Copyright:   (c) 2009 Vadim Zeitlin <vadim@wxwidgets.org>
// Licence:     wxWindows licence
///////////////////////////////////////////////////////////////////////////////

#ifndef _WX_PERSIST_H_
#define _WX_PERSIST_H_

#include "wx/string.h"
#include "wx/hashmap.h"
#include "wx/confbase.h"

class wxPersistentObject;

WX_DECLARE_VOIDPTR_HASH_MAP(wxPersistentObject *, wxPersistentObjectsMap);

// ----------------------------------------------------------------------------
// global functions
// ----------------------------------------------------------------------------

/*
   We do _not_ declare this function as doing this would force us to specialize
   it for the user classes deriving from the standard persistent classes.
   However we do define overloads of wxCreatePersistentObject() for all the wx
   classes which means that template wxPersistentObject::Restore() picks up the
   right overload to use provided that the header defining the correct overload
   is included before calling it. And a compilation error happens if this is
   not done.

template <class T>
wxPersistentObject *wxCreatePersistentObject(T *obj);

 */

// ----------------------------------------------------------------------------
// wxPersistenceManager: global aspects of persistent windows
// ----------------------------------------------------------------------------

class WXDLLIMPEXP_CORE wxPersistenceManager
{
public:
    // accessor to the unique persistence manager object
    static wxPersistenceManager& Get();


    // globally disable restoring or saving the persistent properties (both are
    // enabled by default)
    void DisableSaving() { m_doSave = false; }
    void DisableRestoring() { m_doRestore = false; }


    // register an object with the manager: when using the first overload,
    // wxCreatePersistentObject() must be specialized for this object class;
    // with the second one the persistent adapter is created by the caller
    //
    // the object shouldn't be already registered with us
    template <class T>
    wxPersistentObject *Register(T *obj)
    {
        return Register(obj, wxCreatePersistentObject(obj));
    }

    wxPersistentObject *Register(void *obj, wxPersistentObject *po);

    // check if the object is registered and return the associated
    // wxPersistentObject if it is or NULL otherwise
    wxPersistentObject *Find(void *obj) const;

    // unregister the object, this is called by wxPersistentObject itself so
    // there is usually no need to do it explicitly
    //
    // deletes the associated wxPersistentObject
    void Unregister(void *obj);

    
    // save/restore the state of an object
    //
    // these methods do nothing if DisableSaving/Restoring() was called
    //
    // Restore() returns true if the object state was really restored
    void Save(void *obj);
    bool Restore(void *obj);

    // combines both Save() and Unregister() calls
    void SaveAndUnregister(void *obj)
    {
        Save(obj);
        Unregister(obj);
    }

    // combines both Register() and Restore() calls
    template <class T>
    bool RegisterAndRestore(T *obj)
    {
        return Register(obj) && Restore(obj);
    }

    bool RegisterAndRestore(void *obj, wxPersistentObject *po)
    {
        return Register(obj, po) && Restore(obj);
    }


    // methods used by the persistent objects to save and restore the data
    //
    // currently these methods simply use wxConfig::Get()
    //
    // TODO: make this customizable by allowing
    //          (a) specifying custom wxConfig object to use
    //          (b) allowing to use something else entirely
    template <typename T>
    bool
    SaveValue(const wxPersistentObject& who, const wxString& name, T value)
    {
        wxConfigBase * const conf = GetConfig();
        if ( !conf )
            return false;

        return conf->Write(GetKey(who, name), value);
    }

    template <typename T>
    bool
    RestoreValue(const wxPersistentObject& who, const wxString& name, T *value)
    {
        wxConfigBase * const conf = GetConfig();
        if ( !conf )
            return false;

        return conf->Read(GetKey(who, name), value);
    }

private:
    // ctor is private, use Get()
    wxPersistenceManager()
    {
        m_doSave =
        m_doRestore = true;
    }

    // helpers of Save/Restore(), will be customized later
    wxConfigBase *GetConfig() const { return wxConfigBase::Get(); }
    wxString GetKey(const wxPersistentObject& who, const wxString& name) const;


    // map with the registered objects as keys and associated
    // wxPersistentObjects as values
    wxPersistentObjectsMap m_persistentObjects;

    // true if we should restore/save the settings (it doesn't make much sense
    // to use this class when both of them are false but setting one of them to
    // false may make sense in some situations)
    bool m_doSave,
         m_doRestore;

    DECLARE_NO_COPY_CLASS(wxPersistenceManager);
};

// ----------------------------------------------------------------------------
// wxPersistentObject: ABC for anything persistent
// ----------------------------------------------------------------------------

class wxPersistentObject
{
public:
    // ctor associates us with the object whose options we save/restore
    wxPersistentObject(void *obj) : m_obj(obj) { }

    // trivial but virtual dtor
    virtual ~wxPersistentObject() { }


    // methods used by wxPersistenceManager
    // ------------------------------------

    // save/restore the corresponding objects settings
    //
    // these methods shouldn't be used directly as they don't respect the
    // global wxPersistenceManager::DisableSaving/Restoring() settings, use
    // wxPersistenceManager methods with the same name instead
    virtual void Save() const = 0;
    virtual bool Restore() = 0;


    // get the kind of the objects we correspond to, e.g. "Frame"
    virtual wxString GetKind() const = 0;

    // get the name of the object we correspond to, e.g. "Main"
    virtual wxString GetName() const = 0;


    // return the associated object
    void *GetObject() const { return m_obj; }

protected:
    // wrappers for wxPersistenceManager methods which don't require passing
    // "this" as the first parameter all the time
    template <typename T>
    bool SaveValue(const wxString& name, T value) const
    {
        return wxPersistenceManager::Get().SaveValue(*this, name, value);
    }

    template <typename T>
    bool RestoreValue(const wxString& name, T *value)
    {
        return wxPersistenceManager::Get().RestoreValue(*this, name, value);
    }

private:
    void * const m_obj;

    DECLARE_NO_COPY_CLASS(wxPersistentObject)
};

#endif // _WX_PERSIST_H_