2638b6031b
* 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
88 lines
2.7 KiB
C++
88 lines
2.7 KiB
C++
/*
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* Copyright (C) 2006 Aaron Seigo <aseigo@kde.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Library General Public License version 2 as
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* published by the Free Software Foundation
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#ifndef PLASMA_ENGINE_MANAGER_H
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#define PLASMA_ENGINE_MANAGER_H
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#include <QtCore/QHash>
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#include "plasma/dataengine.h"
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namespace Plasma
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{
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/**
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* @brief DataEngine loader and life time manager
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*
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* Plasma::DataEngineManager provides facilities for listing, loading and
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* according to reference count unloading of DataEngines.
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**/
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class PLASMA_EXPORT DataEngineManager
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{
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public:
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/**
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* Singleton pattern accessor.
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*/
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static DataEngineManager* self();
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/**
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* Default constructor. Usually the singleton method self() is the
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* preferred access mechanism.
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*/
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DataEngineManager();
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~DataEngineManager();
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/**
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* Returns a data engine object if one is loaded and available.
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* On failure, the fallback NullEngine (which does nothing and
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* !isValid()) is returned.
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*
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* @param name the name of the engine
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*/
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Plasma::DataEngine* dataEngine(const QString& name) const;
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/**
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* Loads a data engine and increases the reference count on it.
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* This should be called once per object (or set of objects) using the
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* DataEngine. Afterwards, dataEngine should be used or the return
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* value cached. Call unloadDataEngine when finished with the engine.
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*
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* @param name the name of the engine
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* @return the data engine that was loaded, or the NullEngine on failure.
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*/
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Plasma::DataEngine* loadDataEngine(const QString& name);
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/**
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* Decreases the reference count on the engine. If the count reaches
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* zero, then the engine is deleted to save resources.
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*/
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void unloadDataEngine(const QString& name);
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/**
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* Returns a listing of all known engines by name
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*/
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static QStringList knownEngines();
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private:
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class Private;
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Private* const d;
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};
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} // namespace Plasma
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#endif // multiple inclusion guard
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