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/home/tetron/hack/vos/libs/vos/vos/listener.hh

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/*
    This file is part of the Virtual Object System of
    the Interreality project (http://interreality.org).

    Copyright (C) 2001-2003 Peter Amstutz

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA

    Peter Amstutz <http://www.interreality.org>
*/
#ifndef _LISTENER_HH_
#define _LISTENER_HH_

/** @file
    Defines ChildChangeListener, ParentChangeListener, and TypeChangeListener.
*/

#include <vos/vos/vosdefs.hh>
#include <vos/vutil/listener.hh>
#include <vos/vos/vobject.hh>
#include <vos/vos/vobjectevent.hh>
#include <vos/vutil/taskqueue.hh>

#include <string>

namespace VOS
{
/** @class ChildChangeListener listener.hh vos/vos/listener.hh
    @ingroup libvos

    Interface to be called when a listened-to object has some change
    to its child list.
*/
class VOS_API ChildChangeListener
{
public:
    /** Destructor */
    virtual ~ChildChangeListener() { };

    /** Called when a child has been inserted into the listened-to children list */
    virtual void notifyChildInserted(VobjectEvent& e) = 0;

    /** Called when a child has replaced another child in the listened-to children list */
    virtual void notifyChildReplaced(VobjectEvent& e) = 0;

    /** Called when a child has been deleted in the listened-to children list */
    virtual void notifyChildRemoved(VobjectEvent& e) = 0;
};

/** @class ParentChangeListener listener.hh vos/vos/listener.hh
    @ingroup libvos

    Interface to be called when a listened-to object has some change
    to its parent set.
*/
class VOS_API ParentChangeListener
{
public:
    virtual ~ParentChangeListener() { }

    /** Called when an object has aquired a new parent. */
    virtual void notifyParentInserted(VobjectEvent& e) = 0;

    /** Called when an object has lost a parent. */
    virtual void notifyParentRemoved(VobjectEvent& e) = 0;
};

/** @class TypeChangeListener listener.hh vos/vos/listener.hh
    @ingroup libvos

    Interface to be called when a listened-to object has some change
    to its type set.
*/
class VOS_API TypeChangeListener
{
public:
    virtual ~TypeChangeListener() { }

    /** Called when an object has gained a type. */
    virtual void notifyTypeInserted(VobjectEvent& e) = 0;

    /** Called when an object has lost a type. */
    virtual void notifyTypeRemoved(VobjectEvent& e) = 0;
};

/** @class DoNothingListener listener.hh vos/vos/listener.hh
    @ingroup libvos

    Trivial listener implementation that does nothing.  It can be
    useful, however, to force the local cache of remote objects to be
    kept up to date.  This is because RemoteVobject only keeps the
    cache "fresh" so long as there some part of the application is
    registered as a listener -- if there are no listeners, then it
    tells the remote site to stop pushing updates.
*/

class VOS_API DoNothingListener : public ChildChangeListener,
                          public ParentChangeListener,
                          public TypeChangeListener
{
public:
    static DoNothingListener static_;

    virtual void notifyChildInserted(VobjectEvent& /*e*/) { }
    virtual void notifyChildReplaced(VobjectEvent& /*e*/) { }
    virtual void notifyChildRemoved(VobjectEvent& /*e*/) { }
    virtual void notifyParentInserted(VobjectEvent& /*e*/) { }
    virtual void notifyParentRemoved(VobjectEvent& /*e*/) { }
    virtual void notifyTypeInserted(VobjectEvent& /*e*/) { }
    virtual void notifyTypeRemoved(VobjectEvent& /*e*/) { }
};
}

#endif