plasma-framework/dataenginemanager.h
Aaron J. Seigo 2638b6031b * introduce a NullEngine
* return an instance of the NullEngine on engine loading failure; this way applets don't have to test for engine existence and can just assume something gets returned
* DataEngine::isValid() in case someone really cares to know whether they have a non-functional engine (e.g. the NullEngine)

svn path=/trunk/KDE/kdebase/workspace/lib/plasma/; revision=670900
2007-06-02 22:23:26 +00:00

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2.7 KiB
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/*
* Copyright (C) 2006 Aaron Seigo <aseigo@kde.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Library General Public License version 2 as
* published by the Free Software Foundation
*
* This program 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 General Public License for more details
*
* You should have received a copy of the GNU Library General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#ifndef PLASMA_ENGINE_MANAGER_H
#define PLASMA_ENGINE_MANAGER_H
#include <QtCore/QHash>
#include "plasma/dataengine.h"
namespace Plasma
{
/**
* @brief DataEngine loader and life time manager
*
* Plasma::DataEngineManager provides facilities for listing, loading and
* according to reference count unloading of DataEngines.
**/
class PLASMA_EXPORT DataEngineManager
{
public:
/**
* Singleton pattern accessor.
*/
static DataEngineManager* self();
/**
* Default constructor. Usually the singleton method self() is the
* preferred access mechanism.
*/
DataEngineManager();
~DataEngineManager();
/**
* Returns a data engine object if one is loaded and available.
* On failure, the fallback NullEngine (which does nothing and
* !isValid()) is returned.
*
* @param name the name of the engine
*/
Plasma::DataEngine* dataEngine(const QString& name) const;
/**
* Loads a data engine and increases the reference count on it.
* This should be called once per object (or set of objects) using the
* DataEngine. Afterwards, dataEngine should be used or the return
* value cached. Call unloadDataEngine when finished with the engine.
*
* @param name the name of the engine
* @return the data engine that was loaded, or the NullEngine on failure.
*/
Plasma::DataEngine* loadDataEngine(const QString& name);
/**
* Decreases the reference count on the engine. If the count reaches
* zero, then the engine is deleted to save resources.
*/
void unloadDataEngine(const QString& name);
/**
* Returns a listing of all known engines by name
*/
static QStringList knownEngines();
private:
class Private;
Private* const d;
};
} // namespace Plasma
#endif // multiple inclusion guard