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/***************************************************************************
UndoAction.h - Abstract base class for undo actions
-------------------
begin : Sat May 26 2001
copyright : (C) 2001 by Thomas Eschenbacher
email : Thomas Eschenbacher <Thomas.Eschenbacher@gmx.de>
***************************************************************************/
/***************************************************************************
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************/
#ifndef UNDO_ACTION_H
#define UNDO_ACTION_H
#include "config.h"
#include "libkwave_export.h"
#include <QtGlobal>
#include <QString>
#include "libkwave/String.h"
namespace Kwave
{
class SignalManager;
/**
* This is an abstract base class used for implementation of undo and redo.
* The constructor should take all information needed for storing the
* undo data and for being able to guess the amount of the needed memory.
* After construction, the caller can call size() for retaining the
* amount of needed memory and o provide enough space. The store() function
* can then save the data for further undo. Calling the undo() function
* also creates a new UndoAction object that is responsible for holding
* all information for undoing that undo (redo).
*/
class LIBKWAVE_EXPORT UndoAction
{
public:
/** Destructor */
virtual ~UndoAction()
{
}
/**
* Returns a verbose short description of the action.
*/
virtual QString description() = 0;
/**
* Returns the required amount of memory that is needed for storing
* undo data for the operation. This will be called to determine the
* free memory to be reserved.
* @note this is the first step (after the constructor)
*/
virtual qint64 undoSize() = 0;
/**
* Returns the difference of needed memory that is needed for
* redo.
*/
virtual qint64 redoSize() = 0;
/**
* Stores the data needed for undo.
* @param manager the SignalManager for modifying the signal
* @note this is the second step, after size() has been called
* @return true if successful, false if failed (e.g. out of memory)
*/
virtual bool store(Kwave::SignalManager &manager) = 0;
/**
* Takes back an action by creating a new undo action (for further
* redo) and restoring the previous state.
* @param manager the SignalManager for modifying the signal
* @param with_redo if true a UndoAction for redo will be created
* @note The return value is allowed to be the same object. This
* is useful for objects that can re-use their data for
* undo/redo. You have to check for this when deleting an
* UndoAction object after undo.
*/
virtual Kwave::UndoAction *undo(Kwave::SignalManager &manager,
bool with_redo) = 0;
/**
* Determines whether a undo action has to do with a modification
* of the signal or meta information and leads to a "modified"
* file. The default implementation returns "true". An example for
* a implementation that returns "false" is the UndoSelection class
* which contains only information about a change in selected samples.
* @return true if a modification is contained, false if not.
*/
virtual bool containsModification() const { return true; }
/** dump, for debugging purposes */
virtual void dump(const QString &indent) {
qDebug("%s%s", DBG(indent), DBG(description()));
}
};
}
#endif /* UNDO_ACTION_H */
//***************************************************************************
//***************************************************************************
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