void topolTest::fillFeatureList( QgsVectorLayer *layer, const QgsRectangle &extent )
{
  QgsFeatureIterator fit;
  if ( extent.isEmpty() )
  {
    fit = layer->getFeatures( QgsFeatureRequest().setSubsetOfAttributes( QgsAttributeList() ) );
  }
  else
  {
    fit = layer->getFeatures( QgsFeatureRequest()
                              .setFilterRect( extent )
                              .setFlags( QgsFeatureRequest::ExactIntersect )
                              .setSubsetOfAttributes( QgsAttributeList() ) );
  }

  QgsFeature f;

  while ( fit.nextFeature( f ) )
  {
    if ( f.hasGeometry() )
    {
      mFeatureList1 << FeatureLayer( layer, f );
    }
  }

}

bool QgsReclassifyByLayerAlgorithm::_prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback * )
{
  std::unique_ptr< QgsFeatureSource >tableSource( parameterAsSource( parameters, QStringLiteral( "INPUT_TABLE" ), context ) );
  if ( !tableSource )
    throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT_TABLE" ) ) );

  QString fieldMin = parameterAsString( parameters, QStringLiteral( "MIN_FIELD" ), context );
  mMinFieldIdx = tableSource->fields().lookupField( fieldMin );
  if ( mMinFieldIdx < 0 )
    throw QgsProcessingException( QObject::tr( "Invalid field specified for MIN_FIELD: %1" ).arg( fieldMin ) );
  QString fieldMax = parameterAsString( parameters, QStringLiteral( "MAX_FIELD" ), context );
  mMaxFieldIdx = tableSource->fields().lookupField( fieldMax );
  if ( mMaxFieldIdx < 0 )
    throw QgsProcessingException( QObject::tr( "Invalid field specified for MAX_FIELD: %1" ).arg( fieldMax ) );
  QString fieldValue = parameterAsString( parameters, QStringLiteral( "VALUE_FIELD" ), context );
  mValueFieldIdx = tableSource->fields().lookupField( fieldValue );
  if ( mValueFieldIdx < 0 )
    throw QgsProcessingException( QObject::tr( "Invalid field specified for VALUE_FIELD: %1" ).arg( fieldValue ) );

  QgsFeatureRequest request;
  request.setFlags( QgsFeatureRequest::NoGeometry );
  request.setSubsetOfAttributes( QgsAttributeList() << mMinFieldIdx << mMaxFieldIdx << mValueFieldIdx );
  mTableIterator = tableSource->getFeatures( request );

  return true;
}

QgsFeaturePool::QgsFeaturePool( QgsVectorLayer *layer, double layerToMapUnits, const QgsCoordinateTransform &layerToMapTransform, bool selectedOnly )
  : mFeatureCache( CACHE_SIZE )
  , mLayer( layer )
  , mLayerToMapUnits( layerToMapUnits )
  , mLayerToMapTransform( layerToMapTransform )
  , mSelectedOnly( selectedOnly )
{
  if ( selectedOnly )
  {
    mFeatureIds = layer->selectedFeatureIds();
  }
  else
  {
    mFeatureIds = layer->allFeatureIds();
  }

  // Build spatial index
  QgsFeature feature;
  QgsFeatureRequest req;
  req.setSubsetOfAttributes( QgsAttributeList() );
  QgsFeatureIterator it = layer->getFeatures( req );
  while ( it.nextFeature( feature ) )
  {
    if ( mFeatureIds.contains( feature.id() ) && feature.geometry() )
    {
      mIndex.insertFeature( feature );
    }
    else
    {
      mFeatureIds.remove( feature.id() );
    }
  }
}

void QgsAttributeTableDelegate::setModelData( QWidget *editor, QAbstractItemModel *model, const QModelIndex &index ) const
{
  QgsVectorLayer *vl = layer( model );
  if ( !vl )
    return;

  int fieldIdx = model->data( index, QgsAttributeTableModel::FieldIndexRole ).toInt();
  QgsFeatureId fid = model->data( index, QgsAttributeTableModel::FeatureIdRole ).toLongLong();
  QVariant oldValue = model->data( index, Qt::EditRole );

  QVariant newValue;
  QgsEditorWidgetWrapper *eww = QgsEditorWidgetWrapper::fromWidget( editor );
  if ( !eww )
    return;

  newValue = eww->value();

  if ( ( oldValue != newValue && newValue.isValid() ) || oldValue.isNull() != newValue.isNull() )
  {
    // This fixes https://issues.qgis.org/issues/16492
    QgsFeatureRequest request( fid );
    request.setFlags( QgsFeatureRequest::NoGeometry );
    request.setSubsetOfAttributes( QgsAttributeList() );
    QgsFeature feature;
    vl->getFeatures( request ).nextFeature( feature );
    if ( feature.isValid() )
    {
      vl->beginEditCommand( tr( "Attribute changed" ) );
      vl->changeAttributeValue( fid, fieldIdx, newValue, oldValue );
      vl->endEditCommand();
    }
  }
}

void QgsAttributeTypeLoadDialog::loadDataToValueMap()
{
  mValueMap.clear();
  int idx = keyComboBox->itemData( keyComboBox->currentIndex() ).toInt();
  int idx2 = valueComboBox->itemData( valueComboBox->currentIndex() ).toInt();
  QgsMapLayer* dataLayer = QgsMapLayerRegistry::instance()->mapLayer( layerComboBox->currentText() );
  QgsVectorLayer* vLayer = qobject_cast<QgsVectorLayer *>( dataLayer );
  if ( vLayer == NULL )
  {
    return;
  }

  QgsVectorDataProvider* dataProvider = vLayer->dataProvider();
  dataProvider->enableGeometrylessFeatures( true );

  QgsAttributeList attributeList = QgsAttributeList();
  attributeList.append( idx );
  attributeList.append( idx2 );
  vLayer->select( attributeList, QgsRectangle(), false );

  QgsFeature f;
  while ( vLayer->nextFeature( f ) )
  {
    QVariant val = f.attributeMap()[idx];
    if ( val.isValid() && !val.isNull() && !val.toString().isEmpty() )
    {
      mValueMap.insert( f.attributeMap()[idx2].toString(), val );
    }
  }
  dataProvider->enableGeometrylessFeatures( false );
}

QgsVectorLayerFeatureSource::QgsVectorLayerFeatureSource( const QgsVectorLayer *layer )
{
  QMutexLocker locker( &layer->mFeatureSourceConstructorMutex );
  mProviderFeatureSource = layer->dataProvider()->featureSource();
  mFields = layer->fields();
  mId = layer->id();

  // update layer's join caches if necessary
  if ( layer->mJoinBuffer->containsJoins() )
    layer->mJoinBuffer->createJoinCaches();

  mJoinBuffer = layer->mJoinBuffer->clone();

  mExpressionFieldBuffer = new QgsExpressionFieldBuffer( *layer->mExpressionFieldBuffer );
  mCrs = layer->crs();

  mHasEditBuffer = layer->editBuffer();
  if ( mHasEditBuffer )
  {
#if 0
    // TODO[MD]: after merge
    if ( request.filterType() == QgsFeatureRequest::FilterFid )
    {

      // only copy relevant parts
      if ( L->editBuffer()->addedFeatures().contains( request.filterFid() ) )
        mAddedFeatures.insert( request.filterFid(), L->editBuffer()->addedFeatures()[ request.filterFid()] );

      if ( L->editBuffer()->changedGeometries().contains( request.filterFid() ) )
        mChangedGeometries.insert( request.filterFid(), L->editBuffer()->changedGeometries()[ request.filterFid()] );

      if ( L->editBuffer()->deletedFeatureIds().contains( request.filterFid() ) )
        mDeletedFeatureIds.insert( request.filterFid() );

      if ( L->editBuffer()->changedAttributeValues().contains( request.filterFid() ) )
        mChangedAttributeValues.insert( request.filterFid(), L->editBuffer()->changedAttributeValues()[ request.filterFid()] );

      if ( L->editBuffer()->changedAttributeValues().contains( request.filterFid() ) )
        mChangedFeaturesRequest.setFilterFids( QgsFeatureIds() << request.filterFid() );
    }
    else
    {
#endif
      mAddedFeatures = QgsFeatureMap( layer->editBuffer()->addedFeatures() );
      mChangedGeometries = QgsGeometryMap( layer->editBuffer()->changedGeometries() );
      mDeletedFeatureIds = QgsFeatureIds( layer->editBuffer()->deletedFeatureIds() );
      mChangedAttributeValues = QgsChangedAttributesMap( layer->editBuffer()->changedAttributeValues() );
      mAddedAttributes = QList<QgsField>( layer->editBuffer()->addedAttributes() );
      mDeletedAttributeIds = QgsAttributeList( layer->editBuffer()->deletedAttributeIds() );
#if 0
    }
#endif
  }

  std::unique_ptr< QgsExpressionContextScope > layerScope( QgsExpressionContextUtils::layerScope( layer ) );
  mLayerScope = *layerScope;
}

void QgsVectorLayerRenderer::prepareLabeling( QgsVectorLayer* layer, QStringList& attributeNames )
{
  if ( !mContext.labelingEngine() )
  {
    if ( QgsLabelingEngineV2* engine2 = mContext.labelingEngineV2() )
    {
      if ( layer->labeling() )
      {
        mLabelProvider = layer->labeling()->provider( layer );
        if ( mLabelProvider )
        {
          engine2->addProvider( mLabelProvider );
          if ( !mLabelProvider->prepare( mContext, attributeNames ) )
          {
            engine2->removeProvider( mLabelProvider );
            mLabelProvider = nullptr; // deleted by engine
          }
        }
      }
    }
    return;
  }

  if ( mContext.labelingEngine()->prepareLayer( layer, attributeNames, mContext ) )
  {
    mLabeling = true;

#if 0 // TODO: limit of labels, font not found
    QgsPalLayerSettings& palyr = mContext.labelingEngine()->layer( mLayerID );

    // see if feature count limit is set for labeling
    if ( palyr.limitNumLabels && palyr.maxNumLabels > 0 )
    {
      QgsFeatureIterator fit = getFeatures( QgsFeatureRequest()
                                            .setFilterRect( mContext.extent() )
                                            .setSubsetOfAttributes( QgsAttributeList() ) );

      // total number of features that may be labeled
      QgsFeature f;
      int nFeatsToLabel = 0;
      while ( fit.nextFeature( f ) )
      {
        nFeatsToLabel++;
      }
      palyr.mFeaturesToLabel = nFeatsToLabel;
    }

    // notify user about any font substitution
    if ( !palyr.mTextFontFound && !mLabelFontNotFoundNotified )
    {
      emit labelingFontNotFound( this, palyr.mTextFontFamily );
      mLabelFontNotFoundNotified = true;
    }
#endif
  }
}

void QgsMapToolSimplify::canvasPressEvent( QMouseEvent * e )
{
  QgsVectorLayer * vlayer = currentVectorLayer();
  QgsPoint layerCoords = mCanvas->getCoordinateTransform()->toMapPoint( e->pos().x(), e->pos().y() );

  double r = QgsTolerance::vertexSearchRadius( vlayer, mCanvas->mapRenderer() );
  QgsRectangle selectRect = QgsRectangle( layerCoords.x() - r, layerCoords.y() - r,
                                          layerCoords.x() + r, layerCoords.y() + r );
  vlayer->select( QgsAttributeList(), selectRect, true );

  QgsGeometry* geometry = QgsGeometry::fromPoint( layerCoords );
  double minDistance = DBL_MAX;
  double currentDistance;
  QgsFeature f;

  mSelectedFeature.setValid( false );

  while ( vlayer->nextFeature( f ) )
  {
    currentDistance = geometry->distance( *( f.geometry() ) );
    if ( currentDistance < minDistance )
    {
      minDistance = currentDistance;
      mSelectedFeature = f;
    }
  }

  // delete previous rubberband (if any)
  removeRubberBand();

  if ( mSelectedFeature.isValid() )
  {
    if ( mSelectedFeature.geometry()->isMultipart() )
    {
      QMessageBox::critical( 0, tr( "Unsupported operation" ), tr( "Multipart features are not supported for simplification." ) );
      return;
    }

    mRubberBand = new QgsRubberBand( mCanvas );
    mRubberBand->setToGeometry( mSelectedFeature.geometry(), 0 );
    mRubberBand->setColor( Qt::red );
    mRubberBand->setWidth( 2 );
    mRubberBand->show();
    //calculate boudaries for slidebar
    if ( calculateSliderBoudaries() )
    {
      // show dialog as a non-modal window
      mSimplifyDialog->show();
    }
    else
    {
      QMessageBox::warning( 0, tr( "Unsupported operation" ), tr( "This feature cannot be simplified. Check if feature has enough vertices to be simplified." ) );
    }
  }
}

int QgsGeometrySnapperSingleSource::run( const QgsFeatureSource &source, QgsFeatureSink &sink, double thresh, QgsFeedback *feedback )
{
  // the logic here comes from GRASS implementation of Vect_snap_lines_list()

  int count = 0;
  int totalCount = source.featureCount() * 2;

  // step 1: record all point locations in a spatial index + extra data structure to keep
  // reference to which other point they have been snapped to (in the next phase).

  QgsSpatialIndex index;
  QVector<AnchorPoint> pnts;
  QgsFeatureRequest request;
  request.setSubsetOfAttributes( QgsAttributeList() );
  QgsFeatureIterator fi = source.getFeatures( request );
  buildSnapIndex( fi, index, pnts, feedback, count, totalCount );

  if ( feedback->isCanceled() )
    return 0;

  // step 2: go through all registered points and if not yet marked mark it as anchor and
  // assign this anchor to all not yet marked points in threshold

  assignAnchors( index, pnts, thresh );

  // step 3: alignment of vertices and segments to the anchors
  // Go through all lines and:
  //   1) for all vertices: if not anchor snap it to its anchor
  //   2) for all segments: snap it to all anchors in threshold (except anchors of vertices of course)

  int modified = 0;
  QgsFeature f;
  fi = source.getFeatures();
  while ( fi.nextFeature( f ) )
  {
    if ( feedback->isCanceled() )
      break;

    QgsGeometry geom = f.geometry();
    if ( snapGeometry( geom.get(), index, pnts, thresh ) )
    {
      f.setGeometry( geom );
      ++modified;
    }

    sink.addFeature( f, QgsFeatureSink::FastInsert );

    ++count;
    feedback->setProgress( 100. * count / totalCount );
  }

  return modified;
}

QgsSpatialIndex *topolTest::createIndex( QgsVectorLayer *layer, const QgsRectangle &extent )
{
  QgsSpatialIndex *index = new QgsSpatialIndex();

  QgsFeatureIterator fit;
  if ( extent.isEmpty() )
  {
    fit = layer->getFeatures( QgsFeatureRequest().setSubsetOfAttributes( QgsAttributeList() ) );
  }
  else
  {
    fit = layer->getFeatures( QgsFeatureRequest()
                              .setFilterRect( extent )
                              .setFlags( QgsFeatureRequest::ExactIntersect )
                              .setSubsetOfAttributes( QgsAttributeList() ) );
  }


  int i = 0;
  QgsFeature f;
  while ( fit.nextFeature( f ) )
  {
    if ( !( ++i % 100 ) )
      emit progress( i );

    if ( testCanceled() )
    {
      delete index;
      return nullptr;
    }

    if ( f.hasGeometry() )
    {
      index->addFeature( f );
      mFeatureMap2[f.id()] = FeatureLayer( layer, f );
    }
  }

  return index;
}

void QgsExpressionSelectionDialog::mButtonZoomToFeatures_clicked()
{
  if ( mExpressionBuilder->expressionText().isEmpty() || !mMapCanvas )
    return;

  QgsExpressionContext context( QgsExpressionContextUtils::globalProjectLayerScopes( mLayer ) );

  QgsFeatureRequest request = QgsFeatureRequest().setFilterExpression( mExpressionBuilder->expressionText() )
                              .setExpressionContext( context )
                              .setSubsetOfAttributes( QgsAttributeList() );

  QgsFeatureIterator features = mLayer->getFeatures( request );

  QgsRectangle bbox;
  bbox.setMinimal();
  QgsFeature feat;
  int featureCount = 0;
  while ( features.nextFeature( feat ) )
  {
    QgsGeometry geom = feat.geometry();
    if ( geom.isNull() || geom.constGet()->isEmpty() )
      continue;

    QgsRectangle r = mMapCanvas->mapSettings().layerExtentToOutputExtent( mLayer, geom.boundingBox() );
    bbox.combineExtentWith( r );
    featureCount++;
  }
  features.close();

  QgsSettings settings;
  int timeout = settings.value( QStringLiteral( "qgis/messageTimeout" ), 5 ).toInt();
  if ( featureCount > 0 )
  {
    mMapCanvas->zoomToFeatureExtent( bbox );
    if ( mMessageBar )
    {
      mMessageBar->pushMessage( QString(),
                                tr( "Zoomed to %n matching feature(s)", "number of matching features", featureCount ),
                                Qgis::Info,
                                timeout );
    }
  }
  else if ( mMessageBar )
  {
    mMessageBar->pushMessage( QString(),
                              tr( "No matching features found" ),
                              Qgis::Info,
                              timeout );
  }
  saveRecent();
}

bool QgsMapToolShowHideLabels::selectedFeatures( QgsVectorLayer* vlayer,
    QgsFeatureIds& selectedFeatIds )
{
  // culled from QgsMapToolSelectUtils::setSelectFeatures()

  QgsGeometry* selectGeometry = mRubberBand->asGeometry();

  // toLayerCoordinates will throw an exception for any 'invalid' points in
  // the rubber band.
  // For example, if you project a world map onto a globe using EPSG 2163
  // and then click somewhere off the globe, an exception will be thrown.
  QgsGeometry selectGeomTrans( *selectGeometry );

  if ( mCanvas->hasCrsTransformEnabled() )
  {
    try
    {
      QgsCoordinateTransform ct( mCanvas->mapSettings().destinationCrs(), vlayer->crs() );
      selectGeomTrans.transform( ct );
    }
    catch ( QgsCsException &cse )
    {
      Q_UNUSED( cse );
      // catch exception for 'invalid' point and leave existing selection unchanged
      QgsLogger::warning( "Caught CRS exception " + QString( __FILE__ ) + ": " + QString::number( __LINE__ ) );
      emit messageEmitted( tr( "CRS Exception: selection extends beyond layer's coordinate system." ), QgsMessageBar::WARNING );
      return false;
    }
  }

  QApplication::setOverrideCursor( Qt::WaitCursor );

  QgsDebugMsg( "Selection layer: " + vlayer->name() );
  QgsDebugMsg( "Selection polygon: " + selectGeomTrans.exportToWkt() );

  QgsFeatureIterator fit = vlayer->getFeatures( QgsFeatureRequest()
                           .setFilterRect( selectGeomTrans.boundingBox() )
                           .setFlags( QgsFeatureRequest::NoGeometry | QgsFeatureRequest::ExactIntersect )
                           .setSubsetOfAttributes( QgsAttributeList() ) );

  QgsFeature f;
  while ( fit.nextFeature( f ) )
  {
    selectedFeatIds.insert( f.id() );
  }

  QApplication::restoreOverrideCursor();

  return true;
}

QgsVectorLayerFeatureIterator::QgsVectorLayerFeatureIterator( QgsVectorLayer* layer, const QgsFeatureRequest& request )
    : QgsAbstractFeatureIterator( request ), L( layer )
{
  QgsVectorLayerJoinBuffer* joinBuffer = L->mJoinBuffer;

  if ( L->editBuffer() )
  {
    mAddedFeatures = QgsFeatureMap( L->editBuffer()->addedFeatures() );
    mChangedGeometries = QgsGeometryMap( L->editBuffer()->changedGeometries() );
    mDeletedFeatureIds = QgsFeatureIds( L->editBuffer()->deletedFeatureIds() );
    mChangedAttributeValues = QgsChangedAttributesMap( L->editBuffer()->changedAttributeValues() );
    mAddedAttributes = QList<QgsField>( L->editBuffer()->addedAttributes() );
    mDeletedAttributeIds = QgsAttributeList( L->editBuffer()->deletedAttributeIds() );
  }

  // prepare joins: may add more attributes to fetch (in order to allow join)
  if ( joinBuffer->containsJoins() )
    prepareJoins();

  // by default provider's request is the same
  mProviderRequest = mRequest;

  if ( mProviderRequest.flags() & QgsFeatureRequest::SubsetOfAttributes )
  {
    // prepare list of attributes to match provider fields
    QgsAttributeList providerSubset;
    QgsAttributeList subset = mProviderRequest.subsetOfAttributes();
    const QgsFields &pendingFields = L->pendingFields();
    int nPendingFields = pendingFields.count();
    for ( int i = 0; i < subset.count(); ++i )
    {
      int attrIndex = subset[i];
      if ( attrIndex < 0 || attrIndex >= nPendingFields ) continue;
      if ( L->pendingFields().fieldOrigin( attrIndex ) == QgsFields::OriginProvider )
        providerSubset << L->pendingFields().fieldOriginIndex( attrIndex );
    }
    mProviderRequest.setSubsetOfAttributes( providerSubset );
  }

  if ( request.filterType() == QgsFeatureRequest::FilterFid )
  {
    mFetchedFid = false;
  }
  else // no filter or filter by rect
  {
    mProviderIterator = L->dataProvider()->getFeatures( mProviderRequest );

    rewindEditBuffer();
  }
}

QgsVectorLayerFeatureSource::QgsVectorLayerFeatureSource( QgsVectorLayer *layer )
    : mCrsId( 0 )
{
  mProviderFeatureSource = layer->dataProvider()->featureSource();
  mFields = layer->fields();
  mJoinBuffer = layer->mJoinBuffer->clone();
  mExpressionFieldBuffer = new QgsExpressionFieldBuffer( *layer->mExpressionFieldBuffer );
  mCrsId = layer->crs().srsid();

  mCanBeSimplified = layer->hasGeometryType() && layer->geometryType() != QGis::Point;

  mHasEditBuffer = layer->editBuffer();
  if ( mHasEditBuffer )
  {
#if 0
    // TODO[MD]: after merge
    if ( request.filterType() == QgsFeatureRequest::FilterFid )
    {

      // only copy relevant parts
      if ( L->editBuffer()->addedFeatures().contains( request.filterFid() ) )
        mAddedFeatures.insert( request.filterFid(), L->editBuffer()->addedFeatures()[ request.filterFid()] );

      if ( L->editBuffer()->changedGeometries().contains( request.filterFid() ) )
        mChangedGeometries.insert( request.filterFid(), L->editBuffer()->changedGeometries()[ request.filterFid()] );

      if ( L->editBuffer()->deletedFeatureIds().contains( request.filterFid() ) )
        mDeletedFeatureIds.insert( request.filterFid() );

      if ( L->editBuffer()->changedAttributeValues().contains( request.filterFid() ) )
        mChangedAttributeValues.insert( request.filterFid(), L->editBuffer()->changedAttributeValues()[ request.filterFid()] );

      if ( L->editBuffer()->changedAttributeValues().contains( request.filterFid() ) )
        mChangedFeaturesRequest.setFilterFids( QgsFeatureIds() << request.filterFid() );
    }
    else
    {
#endif
      mAddedFeatures = QgsFeatureMap( layer->editBuffer()->addedFeatures() );
      mChangedGeometries = QgsGeometryMap( layer->editBuffer()->changedGeometries() );
      mDeletedFeatureIds = QgsFeatureIds( layer->editBuffer()->deletedFeatureIds() );
      mChangedAttributeValues = QgsChangedAttributesMap( layer->editBuffer()->changedAttributeValues() );
      mAddedAttributes = QList<QgsField>( layer->editBuffer()->addedAttributes() );
      mDeletedAttributeIds = QgsAttributeList( layer->editBuffer()->deletedAttributeIds() );
#if 0
    }
#endif
  }
}

void QgsReaderFeatures::initReader( bool useSelection )
{
  if ( useSelection )
  {
    mListSelectedFeature = mLayer->selectedFeatures();
    mIterSelectedFeature = mListSelectedFeature.begin();
    mFuncNextFeature = &QgsReaderFeatures::nextFeatureSelected;
  }
  else
  {
    mLayer->select( QgsAttributeList() );
    mFuncNextFeature = &QgsReaderFeatures::nextFeatureTotal;
  }

} // void QgsReaderFeatures::initReader()

QgsFeatureIds QgsFeatureSource::allFeatureIds() const
{
  QgsFeatureIterator fit = getFeatures( QgsFeatureRequest()
                                        .setFlags( QgsFeatureRequest::NoGeometry )
                                        .setSubsetOfAttributes( QgsAttributeList() ) );

  QgsFeatureIds ids;

  QgsFeature fet;
  while ( fit.nextFeature( fet ) )
  {
    ids << fet.id();
  }

  return ids;
}

QgsRectangle QgsFeatureSource::sourceExtent() const
{
  QgsRectangle r;

  QgsFeatureRequest req;
  req.setSubsetOfAttributes( QgsAttributeList() );

  QgsFeatureIterator it = getFeatures( req );
  QgsFeature f;
  while ( it.nextFeature( f ) )
  {
    if ( f.hasGeometry() )
      r.combineExtentWith( f.geometry().boundingBox() );
  }
  return r;
}

void QgsOfflineEditing::updateFidLookup( QgsVectorLayer* remoteLayer, sqlite3* db, int layerId )
{
  // update fid lookup for added features

  // get remote added fids
  // NOTE: use QMap for sorted fids
  QMap < int, bool /*dummy*/ > newRemoteFids;
  QgsFeature f;
  remoteLayer->select( QgsAttributeList(), QgsRectangle(), false, false );

  mProgressDialog->setupProgressBar( tr( "%v / %m features processed" ), remoteLayer->featureCount() );

  int i = 1;
  while ( remoteLayer->nextFeature( f ) )
  {
    if ( offlineFid( db, layerId, f.id() ) == -1 )
    {
      newRemoteFids[ f.id()] = true;
    }

    mProgressDialog->setProgressValue( i++ );
  }

  // get local added fids
  // NOTE: fids are sorted
  QString sql = QString( "SELECT \"fid\" FROM 'log_added_features' WHERE \"layer_id\" = %1" ).arg( layerId );
  QList<int> newOfflineFids = sqlQueryInts( db, sql );

  if ( newRemoteFids.size() != newOfflineFids.size() )
  {
    //showWarning( QString( "Different number of new features on offline layer (%1) and remote layer (%2)" ).arg(newOfflineFids.size()).arg(newRemoteFids.size()) );
  }
  else
  {
    // add new fid lookups
    i = 0;
    sqlExec( db, "BEGIN" );
    for ( QMap<int, bool>::const_iterator it = newRemoteFids.begin(); it != newRemoteFids.end(); ++it )
    {
      addFidLookup( db, layerId, newOfflineFids.at( i++ ), it.key() );
    }
    sqlExec( db, "COMMIT" );
  }
}

QSet<QVariant> QgsFeatureSource::uniqueValues( int fieldIndex, int limit ) const
{
  if ( fieldIndex < 0 || fieldIndex >= fields().count() )
    return QSet<QVariant>();

  QgsFeatureRequest req;
  req.setFlags( QgsFeatureRequest::NoGeometry );
  req.setSubsetOfAttributes( QgsAttributeList() << fieldIndex );

  QSet<QVariant> values;
  QgsFeatureIterator it = getFeatures( req );
  QgsFeature f;
  while ( it.nextFeature( f ) )
  {
    values.insert( f.attribute( fieldIndex ) );
    if ( limit > 0 && values.size() >= limit )
      return values;
  }
  return values;
}

QVariant QgsFeatureSource::minimumValue( int fieldIndex ) const
{
  if ( fieldIndex < 0 || fieldIndex >= fields().count() )
    return QVariant();

  QgsFeatureRequest req;
  req.setFlags( QgsFeatureRequest::NoGeometry );
  req.setSubsetOfAttributes( QgsAttributeList() << fieldIndex );

  QVariant min;
  QgsFeatureIterator it = getFeatures( req );
  QgsFeature f;
  while ( it.nextFeature( f ) )
  {
    QVariant v = f.attribute( fieldIndex );
    if ( v.isValid() && qgsVariantLessThan( v, min ) )
    {
      min = v;
    }
  }
  return min;
}