/* * Copyright 2006-2007 Aaron Seigo * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU Library General Public License as * published by the Free Software Foundation; either version 2, or * (at your option) any later version. * * 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_DATAENGINE_H #define PLASMA_DATAENGINE_H #include #include #include #include #include #include namespace Plasma { class DataContainer; /** * @class DataEngine * @brief Data provider for plasmoids (Plasma plugins) * * This is the base class for DataEngines, which provide access to bodies of * data via a common and consistent interface. The common use of a DataEngine * is to provide data to a widget for display. This allows a user interface * element to show all sorts of data: as long as there is a DataEngine, the * data is retrievable. * * DataEngines are loaded as plugins on demand and provide zero, one or more * data sources which are identified by name. For instance, a network * DataEngine might provide a data source for each network interface. **/ class PLASMA_EXPORT DataEngine : public QObject { Q_OBJECT Q_PROPERTY( QStringList sources READ sources ) Q_PROPERTY( bool valid READ isValid ) Q_PROPERTY( QString icon READ icon WRITE setIcon ) public: typedef QHash Dict; typedef QHash Data; typedef QHashIterator DataIterator; typedef QHash SourceDict; /** * Default constructor. * * @param parent The parent object. **/ explicit DataEngine(QObject* parent = 0); virtual ~DataEngine(); /** * @return a list of all the data sources available via this DataEngine * Whether these sources are currently available (which is what * the default implementation provides) or not is up to the * DataEngine to decide. **/ virtual QStringList sources() const; /** * Connects a source to an object for data updates. The object must * have a slot with the following signature: * * dataUpdated(const QString &sourceName, const Plasma::DataEngine::Data &data) * * The data is a QHash of QVariants keyed by QString names, allowing * one data source to provide sets of related data. * * @param source the name of the data source * @param visualization the object to connect the data source to * @param updateInterval the frequency, in milliseconds, with which to signal updates; * a value of 0 (the default) means to update only * when there is new data spontaneously generated * (e.g. by the engine); any other value results in * periodic updates from this source. This value is * per-visualization and can be handy for items that require * constant updates such as scrolling graphs or clocks. * @param intervalAlignedTo the number of ms to aling the interval to **/ Q_INVOKABLE void connectSource(const QString& source, QObject* visualization, uint updateInterval = 0, Plasma::IntervalAlignment intervalAlignment = NoAlignment) const; /** * Connects all sources to an object for data updates. The object must * have a slot with the following signature: * * SLOT(dataUpdated(QString, Plasma::DataEngine::Data)) * * The data is a QHash of QVariants keyed by QString names, allowing * one data source to provide sets of related data. * * This method may be called multiple times for the same visualization * without side-effects. This can be useful to change the updateInterval. * * @param visualization the object to connect the data source to * @param updateInterval the frequency, in milliseconds, with which to signal updates; * a value of 0 (the default) means to update only * when there is new data spontaneously generated * (e.g. by the engine); any other value results in * periodic updates from this source. This value is * per-visualization and can be handy for items that require * constant updates such as scrolling graphs or clocks. **/ Q_INVOKABLE void connectAllSources(QObject* viualization, uint updateInterval = 0, Plasma::IntervalAlignment intervalAlignment = NoAlignment) const; /** * Disconnects a source to an object that was receiving data updates. * * @param source the name of the data source * @param visualization the object to connect the data source to **/ Q_INVOKABLE void disconnectSource(const QString& source, QObject* visualization) const; /** * Retrevies a pointer to the DataContainer for a given source. This method * should not be used if possible. An exception is for script engines that * can not provide a QMetaObject as required by connectSource for the initial * call to dataUpdated. Using this method, such engines can provide their own * connectSource API. * * @arg source the name of the source. * @return pointer to a DataContainer, or zero on failure **/ Q_INVOKABLE DataContainer* containerForSource(const QString &source); /** * Gets the Data associated with a data source. * * The data is a QHash of QVariants keyed by QString names, allowing * one data source to provide sets of related data. * * @param source the data source to retrieve the data for * @return the Data associated with the source; if the source doesn't * exist an empty data set is returned **/ Q_INVOKABLE DataEngine::Data query(const QString& source) const; /** * Reference counting method. Calling this method increases the count * by one. **/ void ref(); /** * Reference counting method. Calling this method decreases the count * by one. **/ void deref(); /** * Reference counting method. Used to determine if this DataEngine is * used. * @return true if the reference count is non-zero **/ bool isUsed() const; /** * Returns true if this engine is valid, otherwise returns false **/ bool isValid() const; /** * Sets the icon for this data engine **/ void setIcon(const QString& icon); /** * @return the name of the icon for this data engine; and empty string * is returned if there is no associated icon. **/ QString icon() const; Q_SIGNALS: /** * Emitted when a new data source is created * @param source the name of the new data source **/ void newSource(const QString& source); /** * Emitted when a data source is removed. * @param source the name of the data source that was removed **/ void sourceRemoved(const QString& source); protected: /** * This method is called when the DataEngine is started. When this * method is called the DataEngine is fully constructed and ready to be * used. This method should be reimplemented by DataEngine subclasses * which have the need to perform a startup routine. **/ virtual void init(); /** * When a source that does not currently exist is requested by the * consumer, this method is called to give the DataEngine the * opportunity to create one. * * The name of the data source (e.g. the source parameter passed into * setData) it must be the same as the name passed to sourceRequested * otherwise the requesting visualization may not receive notice of a * data update. * * If the source can not be populated with data immediately (e.g. due to * an asynchronous data acquisition method such as an HTTP request) * the source must still be created, even if it is empty. This can * be accomplished in these cases with the follow line: * * setData(name, DataEngine::Data()); * * @return true if a DataContainer was set up, false otherwise */ virtual bool sourceRequested(const QString &name); /** * Called by internal updating mechanisms to trigger the engine * to refresh the data contained in a given source. Reimplement this * method when using facilities such as setUpdateInterval. * @see setUpdateInterval * * @param source the name of the source that should be updated * @return true if the data was changed, or false if there was no * change or if the change will occur later **/ virtual bool updateSource(const QString& source); /** * Sets a value for a data source. If the source * doesn't exist then it is created. * * @param source the name of the data source * @param value the data to associated with the source **/ void setData(const QString &source, const QVariant &value); /** * Sets a value for a data source. If the source * doesn't exist then it is created. * * @param source the name of the data source * @param key the key to use for the data * @param value the data to associated with the source **/ void setData(const QString& source, const QString& key, const QVariant& value); /** * Adds a set of data to a data source. If the source * doesn't exist then it is created. * * @param source the name of the data source * @param data the data to add to the source **/ void setData(const QString &source, const Data &data); /** * Clears all the data associated with a data source. * * @param source the name of the data source **/ void clearData(const QString& source); /** * Removes a data entry from a source * * @param source the name of the data source * @param key the data entry to remove **/ void removeData(const QString& source, const QString& key); /** * Adds an already constructed data source. The DataEngine takes * ownership of the DataContainer object. * @param source the DataContainer to add to the DataEngine **/ void addSource(DataContainer* source); /** * Sets an upper limit on the number of data sources to keep in this engine. * If the limit is exceeded, then the oldest data source, as defined by last * update, is dropped. * * @param limit the maximum number of sources to keep active **/ void setSourceLimit(uint limit); /** * Sets the minimum amount of time, in milliseconds, that must pass between * successive updates of data. This can help prevent too many updates happening * due to multiple update requests coming in, which can be useful for * expensive (time- or resource-wise) update mechanisms. * * @arg minimumMs the minimum time lapse, in milliseconds, between updates. * A value less than 0 means to never perform automatic updates, * a value of 0 means update immediately on every update request, * a value >0 will result in a minimum time lapse being enforced. **/ void setMinimumUpdateInterval(int minimumMs); /** * @return the minimum time between updates. @see setMinimumupdateInterval **/ int minimumUpdateInterval() const; /** * Sets up an internal update tick for all data sources. On every update, * updateSource will be called for each applicable source. * @see updateSource * * @param frequency the time, in milliseconds, between updates. A value of 0 * will stop internally triggered updates. **/ void setUpdateInterval(uint frequency); /** * Returns the current update frequency. * @see setUpdateInterval NOTE: This is not implemented to prevent having to store the value internally. When there is a good use case for needing access to this value, we can add another member to the Private class and add this method. uint updateInterval(); **/ /** * Removes all data sources **/ void clearSources(); /** * Sets whether or not this engine is valid, e.g. can be used. * In practice, only the internal fall-back engine, the NullEngine * should have need for this. * * @param valid whether or not the engine is valid **/ void setValid(bool valid); /** * @return the list of active DataContainers. */ SourceDict sourceDict() const; /** * Reimplemented from QObject **/ void timerEvent(QTimerEvent *event); protected Q_SLOTS: /** * Call this method when you call setData directly on a DataContainer instead * of using the DataEngine::setData methods. * If this method is not called, no dataUpdated(..) signals will be emitted! */ void checkForUpdates(); /** * Removes a data source. * @param source the name of the data source to remove **/ void removeSource(const QString& source); /** * @internal **/ void startInit(); /** * @internal **/ void internalUpdateSource(DataContainer* source); private: class Private; Private* const d; }; } // Plasma namespace #define K_EXPORT_PLASMA_DATAENGINE(libname, classname) \ K_PLUGIN_FACTORY(factory, registerPlugin();) \ K_EXPORT_PLUGIN(factory("plasma_engine_" #libname)) #endif // multiple inclusion guard