440 lines
17 KiB
C++
440 lines
17 KiB
C++
/*
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* Copyright 2006-2007 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 as
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* published by the Free Software Foundation; either version 2, or
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* (at your option) any later version.
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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/QHash>
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#include <QtCore/QObject>
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#include <QtCore/QStringList>
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#include <KDE/KGenericFactory>
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#include <KDE/KService>
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#include <plasma/plasma_export.h>
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#include <plasma/plasma.h>
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namespace Plasma
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{
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class DataContainer;
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class DataEngineScript;
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class Package;
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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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friend class DataEngineScript;
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friend class DataEngineManager;
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friend class NullEngine;
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Q_OBJECT
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Q_PROPERTY( QStringList sources READ sources )
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Q_PROPERTY( bool valid READ isValid )
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Q_PROPERTY( QString icon READ icon WRITE setIcon )
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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, DataContainer*> SourceDict;
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/**
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* Constructor.
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*
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* @param parent The parent object.
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* @param service pointer to the service that describes the engine
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**/
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explicit DataEngine(QObject* parent = 0, KService::Ptr service = KService::Ptr(0));
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DataEngine(QObject* parent, const QVariantList& args);
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virtual ~DataEngine();
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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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* @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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* Returns the engine name for the DataEngine
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*/
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QString name() 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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* dataUpdated(const QString &sourceName, const Plasma::DataEngine::Data &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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* @param pollingInterval the frequency, in milliseconds, with which to check for updates;
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* a value of 0 (the default) means to update only
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* when there is new data spontaneously generated
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* (e.g. by the engine); any other value results in
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* periodic updates from this source. This value is
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* per-visualization and can be handy for items that require
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* constant updates such as scrolling graphs or clocks.
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* If the data has not changed, no update will be sent.
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* @param intervalAlignment the number of ms to align the interval to
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**/
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Q_INVOKABLE void connectSource(const QString& source, QObject* visualization,
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uint pollingInterval = 0,
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Plasma::IntervalAlignment intervalAlignment = NoAlignment) const;
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/**
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* Connects all currently existing sources to an object for data updates.
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* The object must have a slot with the following signature:
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*
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* SLOT(dataUpdated(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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* This method may be called multiple times for the same visualization
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* without side-effects. This can be useful to change the pollingInterval.
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*
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* Note that this method does not automatically connect sources that
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* may appear later on. Connecting and responding to the sourceAdded sigal
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* is still required to achieve that.
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*
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* @param visualization the object to connect the data source to
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* @param pollingInterval the frequency, in milliseconds, with which to check for updates;
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* a value of 0 (the default) means to update only
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* when there is new data spontaneously generated
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* (e.g. by the engine); any other value results in
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* periodic updates from this source. This value is
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* per-visualization and can be handy for items that require
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* constant updates such as scrolling graphs or clocks.
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* If the data has not changed, no update will be sent.
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* @param intervalAlignment the number of ms to align the interval to
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**/
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Q_INVOKABLE void connectAllSources(QObject* visualization, uint pollingInterval = 0,
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Plasma::IntervalAlignment intervalAlignment = NoAlignment) 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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Q_INVOKABLE void disconnectSource(const QString& source, QObject* visualization) const;
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/**
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* Retrevies a pointer to the DataContainer for a given source. This method
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* should not be used if possible. An exception is for script engines that
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* can not provide a QMetaObject as required by connectSource for the initial
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* call to dataUpdated. Using this method, such engines can provide their own
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* connectSource API.
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*
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* @param source the name of the source.
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* @return pointer to a DataContainer, or zero on failure
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**/
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Q_INVOKABLE DataContainer* containerForSource(const QString &source);
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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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Q_INVOKABLE DataEngine::Data query(const QString& source) 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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* Returns true if the data engine is empty, which is to say that it has no
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* data sources currently.
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*/
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bool isEmpty() const;
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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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/**
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* Accessor for the associated Package object if any.
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*
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* @return the Package object, or 0 if none
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**/
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const Package* package() 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 sourceAdded(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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* 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) 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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* If the source can not be populated with data immediately (e.g. due to
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* an asynchronous data acquisition method such as an HTTP request)
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* the source must still be created, even if it is empty. This can
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* be accomplished in these cases with the follow line:
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*
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* setData(name, DataEngine::Data());
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*
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* @param source the name of the source that has been requested
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* @return true if a DataContainer was set up, false otherwise
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*/
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virtual bool sourceRequested(const QString &source);
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/**
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* Called by internal updating mechanisms to trigger the engine
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* to refresh the data contained in a given source. Reimplement this
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* method when using facilities such as setPollingInterval.
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* @see setPollingInterval
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*
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* @param source the name of the source that should be updated
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* @return true if the data was changed, or false if there was no
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* change or if the change will occur later
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**/
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virtual bool updateSource(const QString& source);
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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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* Adds a set of data to 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 data the data to add to the source
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**/
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void setData(const QString &source, const Data &data);
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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 DataContainer object.
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* @param source the DataContainer to add to the DataEngine
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**/
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void addSource(DataContainer* 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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/**
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* Sets the minimum amount of time, in milliseconds, that must pass between
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* successive updates of data. This can help prevent too many updates happening
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* due to multiple update requests coming in, which can be useful for
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* expensive (time- or resource-wise) update mechanisms.
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*
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* @param minimumMs the minimum time lapse, in milliseconds, between updates.
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* A value less than 0 means to never perform automatic updates,
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* a value of 0 means update immediately on every update request,
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* a value >0 will result in a minimum time lapse being enforced.
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**/
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void setMinimumPollingInterval(int minimumMs);
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/**
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* @return the minimum time between updates. @see setMinimumPollingInterval
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**/
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int minimumPollingInterval() const;
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/**
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* Sets up an internal update tick for all data sources. On every update,
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* updateSource will be called for each applicable source.
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* @see updateSource
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*
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* @param frequency the time, in milliseconds, between updates. A value of 0
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* will stop internally triggered updates.
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**/
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void setPollingInterval(uint frequency);
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/**
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* Returns the current update frequency.
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* @see setPollingInterval
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NOTE: This is not implemented to prevent having to store the value internally.
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When there is a good use case for needing access to this value, we can
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add another member to the Private class and add this method.
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uint pollingInterval();
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**/
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/**
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* Removes all data sources
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**/
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void removeAllSources();
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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 DataContainers.
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*/
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SourceDict containerDict() const;
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/**
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* Reimplemented from QObject
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**/
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void timerEvent(QTimerEvent *event);
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/**
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* Sets the engine name for the DataEngine
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*/
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void setName(const QString &name);
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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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protected Q_SLOTS:
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/**
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* Call this method when you call setData directly on a DataContainer instead
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* of using the DataEngine::setData methods.
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* If this method is not called, no dataUpdated(..) 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 internalUpdateSource(DataContainer* source);
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private:
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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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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_PLUGIN_FACTORY(factory, registerPlugin<classname>();) \
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K_EXPORT_PLUGIN(factory("plasma_engine_" #libname))
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#endif // multiple inclusion guard
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