libqgis-dev 2.14.11+dfsg-3+deb9u1 / usr / include / qgis / qgsdataprovider.h

/***************************************************************************
                qgsdataprovider.h - DataProvider Interface class
                     --------------------------------------
    Date                 : 09-Sep-2003
    Copyright            : (C) 2003 by Gary E.Sherman
    email                : sherman at mrcc.com
 ***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#ifndef QQGSDATAPROVIDER_H
#define QQGSDATAPROVIDER_H

#include <QDateTime>
#include <QObject>
#include <QString>
#include <QStringList>

//#include "qgsdataitem.h"
#include "qgsdatasourceuri.h"
#include "qgserror.h"

typedef int dataCapabilities_t();

class QgsRectangle;
class QgsCoordinateReferenceSystem;


/** \ingroup core
 * Abstract base class for spatial data provider implementations.
 * @author Gary E.Sherman
 *
 * This object needs to inherit from QObject to enable event
 * processing in the Postgres/PostGIS provider (QgsPostgresProvider).
 * It is called *here* so that this vtable and the vtable for
 * QgsPostgresProvider don't get misaligned -
 * the QgsVectorLayer class factory (which refers
 * to generic QgsVectorDataProvider's) depends on it.
 */


class CORE_EXPORT QgsDataProvider : public QObject
{
    Q_OBJECT

  public:

    Q_ENUMS( DataCapability )

    enum DataCapability
    {
      NoDataCapabilities  = 0,
      File                = 1,
      Dir                 = 1 << 1,
      Database            = 1 << 2,
      Net                 = 1 << 3  // Internet source
    };

    QgsDataProvider( QString const & uri = "" )
        : mDataSourceURI( uri )
    {}

    /**
     * We need this so the subclass destructors get called
     */
    virtual ~QgsDataProvider() {}


    /** Get the QgsCoordinateReferenceSystem for this layer
     * @note Must be reimplemented by each provider.
     * If the provider isn't capable of returning
     * its projection an empty srs will be return, ti will return 0
     */
    virtual QgsCoordinateReferenceSystem crs() = 0;


    /**
     * Set the data source specification. This may be a path or database
     * connection string
     * @param uri source specification
     */
    virtual void setDataSourceUri( const QString & uri )
    {
      mDataSourceURI = uri;
    }

    /**
     * Get the data source specification. This may be a path or database
     * connection string
     * @param expandAuthConfig Whether to expand any assigned authentication configuration
     * @return data source specification
     * @note The default authentication configuration expansion is FALSE. This keeps credentials
     * out of layer data source URIs and project files. Expansion should be specifically done
     * only when needed within a provider
     */
    virtual QString dataSourceUri( bool expandAuthConfig = false ) const
    {
      if ( expandAuthConfig && mDataSourceURI.contains( "authcfg" ) )
      {
        QgsDataSourceURI uri( mDataSourceURI );
        return uri.uri( expandAuthConfig );
      }
      else
      {
        return mDataSourceURI;
      }
    }


    /**
     * Get the extent of the layer
     * @return QgsRectangle containing the extent of the layer
     */
    virtual QgsRectangle extent() = 0;


    /**
     * Returns true if this is a valid layer. It is up to individual providers
     * to determine what constitutes a valid layer
     */
    virtual bool isValid() = 0;


    /**
     * Update the extents of the layer. Not implemented by default
     */
    virtual void updateExtents()
    {
      // NOP by default
    }


    /**
     * Set the subset string used to create a subset of features in
     * the layer. This may be a sql where clause or any other string
     * that can be used by the data provider to create a subset.
     * Must be implemented in the dataprovider.
     */
    virtual bool setSubsetString( const QString& subset, bool updateFeatureCount = true )
    {
      // NOP by default
      Q_UNUSED( subset );
      Q_UNUSED( updateFeatureCount );
      return false;
    }


    /** Provider supports setting of subset strings */
    virtual bool supportsSubsetString() { return false; }

    /**
     * Returns the subset definition string (typically sql) currently in
     * use by the layer and used by the provider to limit the feature set.
     * Must be overridden in the dataprovider, otherwise returns a null
     * QString.
     */
    virtual QString subsetString()
    {
      return QString::null;
    }


    /**
     * Sub-layers handled by this provider, in order from bottom to top
     *
     * Sub-layers are used when the provider's source can combine layers
     * it knows about in some way before it hands them off to the provider.
     */
    virtual QStringList subLayers() const
    {
      return QStringList();  // Empty
    }


    /**
     * Sub-layer styles for each sub-layer handled by this provider,
     * in order from bottom to top
     *
     * Sub-layer styles are used to abstract the way the provider's source can symbolise
     * layers in some way at the server, before it serves them to the provider.
     */
    virtual QStringList subLayerStyles() const
    {
      return QStringList();  // Empty
    }


    /**
     * return the number of layers for the current data source
     */
    virtual uint subLayerCount() const
    {
      return 0;
    }


    /**
     * Reorder the list of layer names to be rendered by this provider
     * (in order from bottom to top)
     * \note   layers must have been previously added.
     */
    virtual void setLayerOrder( const QStringList &layers )
    {
      //prevent unused var warnings
      if ( layers.count() < 1 )
      {
        return;
      }
      // NOOP
    }


    /**
     * Set the visibility of the given sublayer name
     */
    virtual void setSubLayerVisibility( const QString &name, bool vis )
    {
      //prevent unused var warnings
      if ( name.isEmpty() || !vis )
      {
        return;
      }
      // NOOP
    }


    /** Return a provider name
     *
     * Essentially just returns the provider key.  Should be used to build file
     * dialogs so that providers can be shown with their supported types. Thus
     * if more than one provider supports a given format, the user is able to
     * select a specific provider to open that file.
     *
     * @note
     *
     * Instead of being pure virtual, might be better to generalize this
     * behavior and presume that none of the sub-classes are going to do
     * anything strange with regards to their name or description?
     *
     */
    virtual QString name() const = 0;


    /** Return description
     *
     * Return a terse string describing what the provider is.
     *
     * @note
     *
     * Instead of being pure virtual, might be better to generalize this
     * behavior and presume that none of the sub-classes are going to do
     * anything strange with regards to their name or description?
     *
     */
    virtual QString description() const = 0;


    /** Return vector file filter string
     *
     * Returns a string suitable for a QFileDialog of vector file formats
     * supported by the data provider.  Naturally this will be an empty string
     * for those data providers that do not deal with plain files, such as
     * databases and servers.
     *
     * @note It'd be nice to eventually be raster/vector neutral.
     */
    virtual QString fileVectorFilters() const
    {
      return "";
    }


    /** Return raster file filter string
     *
     * Returns a string suitable for a QFileDialog of raster file formats
     * supported by the data provider.  Naturally this will be an empty string
     * for those data providers that do not deal with plain files, such as
     * databases and servers.
     *
     * @note It'd be nice to eventually be raster/vector neutral.
     */
    virtual QString fileRasterFilters() const
    {
      return "";
    }

    /** Reloads the data from the source. Needs to be implemented by providers with data caches to
     * synchronize with changes in the data source
     */
    virtual void reloadData() {}

    /** Time stamp of data source in the moment when data/metadata were loaded by provider */
    virtual QDateTime timestamp() const { return mTimestamp; }

    /** Current time stamp of data source */
    virtual QDateTime dataTimestamp() const { return QDateTime(); }

    /** Get current status error. This error describes some principal problem
     *  for which provider cannot work and thus is not valid. It is not last error
     *  after accessing data by block(), identify() etc.
     */
    virtual QgsError error() const { return mError; }

    /** Invalidate connections corresponding to specified name
     * @note added in QGIS 2.16
     */
    virtual void invalidateConnections( const QString& connection ) { Q_UNUSED( connection ); }

    /** Enter update mode.
     *
     * This is aimed at providers that can open differently the connection to
     * the datasource, according it to be in update mode or in read-only mode.
     * A call to this method shall be balanced with a call to leaveUpdateMode(),
     * if this method returns true.
     *
     * Most providers will have an empty implementation for that method.
     *
     * For backward compatibility, providers that implement enterUpdateMode() should
     * still make sure to allow editing operations to work even if enterUpdateMode()
     * is not explicitly called.
     *
     * Several successive calls to enterUpdateMode() can be done. So there is
     * a concept of stack of calls that must be handled by the provider. Only the first
     * call to enterUpdateMode() will really turn update mode on.
     *
     * @return true in case of success (or no-op implementation), false in case of failure.
     *
     * @note added in QGIS 2.14.4
     */
    virtual bool enterUpdateMode() { return true; }

    /** Leave update mode.
     *
     * This is aimed at providers that can open differently the connection to
     * the datasource, according it to be in update mode or in read-only mode.
     * This method shall be balanced with a successful call to enterUpdateMode().
     *
     * Most providers will have an empty implementation for that method.
     *
     * Several successive calls to enterUpdateMode() can be done. So there is
     * a concept of stack of calls that must be handled by the provider. Only the last
     * call to leaveUpdateMode() will really turn update mode off.
     *
     * @return true in case of success (or no-op implementation), false in case of failure.
     *
     * @note added in QGIS 2.14.4
     */
    virtual bool leaveUpdateMode() { return true; }

  signals:

    /**
     *   This is emitted whenever the worker thread has fully calculated the
     *   PostGIS extents for this layer, and its event has been received by this
     *   provider.
     */
    void fullExtentCalculated();

    /**
     *   This is emitted whenever an asynchronous operation has finished
     *   and the data should be redrawn
     *
     *   When emitted from a QgsVectorDataProvider, any cached information such as
     *   feature ids should be invalidated.
     */
    void dataChanged();

    /**
     *   This is emitted whenever data or metadata (e.g. color table, extent) has changed
     *   @param changed binary combination of changes
     */
    void dataChanged( int changed );

  protected:
    /**
     * Timestamp of data in the moment when the data were loaded by provider.
     */
    QDateTime mTimestamp;

    /** \brief Error */
    QgsError mError;

    /** Add error message */
    void appendError( const QgsErrorMessage & theMessage ) { mError.append( theMessage );}

    /** Set error message */
    void setError( const QgsError & theError ) { mError = theError;}

  private:

    /**
     * Universal Resource Identifier for source data.
     * This could be a file, database, or server address.
     */
    QString mDataSourceURI;
};


#endif