300 lines
9.9 KiB
C++
300 lines
9.9 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_DATAENGINE_H
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#define PLASMA_DATAENGINE_H
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#include <QtCore/QAtomic>
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#include <QtCore/QHash>
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#include <QtCore/QObject>
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#include <QtCore/QStringList>
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#include <kgenericfactory.h>
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#include <plasma/plasma_export.h>
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namespace Plasma
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{
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class DataSource;
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/**
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* @class DataEngine
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* @brief Data provider for plasmoids (Plasma plugins)
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*
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* This is the base class for DataEngines, which provide access to bodies of
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* data via a common and consistent interface. The common use of a DataEngine
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* is to provide data to a widget for display. This allows a user interface
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* element to show all sorts of data: as long as there is a DataEngine, the
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* data is retrievable.
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*
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* DataEngines are loaded as plugins on demand and provide zero, one or more
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* data sources which are identified by name. For instance, a network
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* DataEngine might provide a data source for each network interface.
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**/
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class PLASMA_EXPORT DataEngine : public QObject
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{
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Q_OBJECT
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public:
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typedef QHash<QString, DataEngine*> Dict;
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typedef QHash<QString, QVariant> Data;
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typedef QHashIterator<QString, QVariant> DataIterator;
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typedef QHash<QString, DataSource*> SourceDict;
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/**
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* Default constructor.
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*
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* @param parent The parent object.
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**/
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explicit DataEngine(QObject* parent = 0);
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virtual ~DataEngine();
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/**
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* @return a list of all the data sources available via this DataEngine
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* Whether these sources are currently available (which is what
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* the default implementation provides) or not is up to the
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* DataEngine to decide.
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**/
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virtual QStringList sources() const;
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/**
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* Connects a source to an object for data updates. The object must
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* have a slot with the following signature:
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*
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* SLOT(updated(QString, Plasma::DataEngine::Data))
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*
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* The data is a QHash of QVariants keyed by QString names, allowing
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* one data source to provide sets of related data.
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*
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* @param source the name of the data source
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* @param visualization the object to connect the data source to
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**/
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void connectSource(const QString& source, QObject* visualization) const;
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/**
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* Disconnects a source to an object that was receiving data updates.
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*
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* @param source the name of the data source
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* @param visualization the object to connect the data source to
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**/
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void disconnectSource(const QString& source, QObject* visualization) const;
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/**
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* Connects all sources to an object for data updates. The object must
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* have a slot with the following signature:
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*
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* SLOT(updated(QString, Plasma::DataEngine::Data))
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*
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* The data is a QHash of QVariants keyed by QString names, allowing
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* one data source to provide sets of related data.
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*
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* @param visualization the object to connect the data source to
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**/
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void connectAllSources(QObject* viualization) const;
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/**
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* Gets the Data associated with a data source.
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*
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* The data is a QHash of QVariants keyed by QString names, allowing
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* one data source to provide sets of related data.
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*
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* @param source the data source to retrieve the data for
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* @return the Data associated with the source; if the source doesn't
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* exist an empty data set is returned
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**/
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Data query(const QString& source) const;
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/**
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* Reference counting method. Calling this method increases the count
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* by one.
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**/
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void ref();
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/**
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* Reference counting method. Calling this method decreases the count
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* by one.
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**/
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void deref();
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/**
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* Reference counting method. Used to determine if this DataEngine is
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* used.
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* @return true if the reference count is non-zero
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**/
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bool isUsed() const;
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/**
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* Returns true if this engine is valid, otherwise returns false
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**/
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bool isValid() const;
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/**
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* Sets the icon for this data engine
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**/
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void setIcon(const QString& icon);
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/**
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* @return the name of the icon for this data engine; and empty string
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* is returned if there is no associated icon.
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**/
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QString icon() const;
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Q_SIGNALS:
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/**
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* Emitted when a new data source is created
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* @param source the name of the new data source
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**/
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void newSource(const QString& source);
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/**
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* Emitted when a data source is removed.
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* @param source the name of the data source that was removed
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**/
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void sourceRemoved(const QString& source);
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protected:
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/**
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* This method is called when the DataEngine is started. When this
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* method is called the DataEngine is fully constructed and ready to be
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* used. This method should be reimplemented by DataEngine subclasses
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* which have the need to perform a startup routine.
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**/
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virtual void init();
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/**
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* When a source that does not currently exist is requested by the
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* consumer, this method is called to give the DataEngine the
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* opportunity to create one.
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*
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* The name of the data source (e.g. the source parameter passed into
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* setData) it must be the same as the name passed to sourceRequested
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* otherwise the requesting visualization may not receive notice of a
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* data update.
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*
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* @return true if a DataSource was set up, false otherwise
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*/
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virtual bool sourceRequested(const QString &name);
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/**
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* Sets a value for a data source. If the source
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* doesn't exist then it is created.
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*
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* @param source the name of the data source
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* @param value the data to associated with the source
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**/
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void setData(const QString &source, const QVariant &value);
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/**
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* Sets a value for a data source. If the source
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* doesn't exist then it is created.
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*
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* @param source the name of the data source
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* @param key the key to use for the data
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* @param value the data to associated with the source
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**/
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void setData(const QString& source, const QString& key, const QVariant& value);
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/**
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* Clears all the data associated with a data source.
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*
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* @param source the name of the data source
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**/
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void clearData(const QString& source);
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/**
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* Removes a data entry from a source
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*
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* @param source the name of the data source
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* @param key the data entry to remove
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**/
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void removeData(const QString& source, const QString& key);
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/**
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* Adds an already constructed data source. The DataEngine takes
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* ownership of the DataSource object.
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* @param source the DataSource to add to the DataEngine
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**/
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void addSource(DataSource* source);
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/**
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* Sets an upper limit on the number of data sources to keep in this engine.
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* If the limit is exceeded, then the oldest data source, as defined by last
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* update, is dropped.
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*
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* @param limit the maximum number of sources to keep active
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**/
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void setSourceLimit(uint limit);
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/* DataSource* domain(const QString &domain);
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void createDataSource(const QString& source,
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const QString& domain = QString());*/
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/**
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* Removes all data sources
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**/
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void clearSources();
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/**
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* Sets whether or not this engine is valid, e.g. can be used.
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* In practice, only the internal fall-back engine, the NullEngine
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* should have need for this.
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*
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* @param valid whether or not the engine is valid
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**/
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void setValid(bool valid);
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/**
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* @return the list of active DataSources.
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*/
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SourceDict sourceDict() const;
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protected Q_SLOTS:
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/**
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* Call this method when you call setData directly on a DataSource instead
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* of using the DataEngine::setData methods.
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* If this method is not called, no updated(..) signals will be emitted!
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*/
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void checkForUpdates();
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/**
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* Removes a data source.
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* @param source the name of the data source to remove
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**/
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void removeSource(const QString& source);
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/**
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* @internal
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**/
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void startInit();
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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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} // Plasma namespace
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#define K_EXPORT_PLASMA_DATAENGINE(libname, classname) \
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K_EXPORT_COMPONENT_FACTORY( \
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plasma_engine_##libname, \
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KGenericFactory<classname>("plasma_engine_" #libname))
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#endif // multiple inclusion guard
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