void QgsGraduatedSymbolRendererV2::updateClasses( QgsVectorLayer *vlayer, Mode mode, int nclasses )
{
  if ( mAttrName.isEmpty() )
    return;

  setMode( mode );
  // Custom classes are not recalculated
  if ( mode == Custom )
    return;

  if ( nclasses < 1 )
    nclasses = 1;

  QList<double> values;
  bool valuesLoaded = false;
  double minimum;
  double maximum;

  int attrNum = vlayer->fieldNameIndex( mAttrName );

  bool ok;
  if ( attrNum == -1 )
  {
    values = vlayer->getDoubleValues( mAttrName, ok );
    if ( !ok || values.isEmpty() )
      return;

    qSort( values ); // vmora: is wondering if O( n log(n) ) is really necessary here, min and max are O( n )
    minimum = values.first();
    maximum = values.last();
    valuesLoaded = true;
  }
  else
  {
    minimum = vlayer->minimumValue( attrNum ).toDouble();
    maximum = vlayer->maximumValue( attrNum ).toDouble();
  }

  QgsDebugMsg( QString( "min %1 // max %2" ).arg( minimum ).arg( maximum ) );
  QList<double> breaks;
  QList<double> labels;
  if ( mode == EqualInterval )
  {
    breaks = _calcEqualIntervalBreaks( minimum, maximum, nclasses );
  }
  else if ( mode == Pretty )
  {
    breaks = QgsSymbolLayerV2Utils::prettyBreaks( minimum, maximum, nclasses );
  }
  else if ( mode == Quantile || mode == Jenks || mode == StdDev )
  {
    // get values from layer
    if ( !valuesLoaded )
    {
      values = vlayer->getDoubleValues( mAttrName, ok );
    }

    // calculate the breaks
    if ( mode == Quantile )
    {
      breaks = _calcQuantileBreaks( values, nclasses );
    }
    else if ( mode == Jenks )
    {
      breaks = _calcJenksBreaks( values, nclasses, minimum, maximum );
    }
    else if ( mode == StdDev )
    {
      breaks = _calcStdDevBreaks( values, nclasses, labels );
    }
  }
  else
  {
    Q_ASSERT( false );
  }

  double lower, upper = minimum;
  QString label;
  deleteAllClasses();

  // "breaks" list contains all values at class breaks plus maximum as last break

  int i = 0;
  for ( QList<double>::iterator it = breaks.begin(); it != breaks.end(); ++it, ++i )
  {
    lower = upper; // upper border from last interval
    upper = *it;

    // Label - either StdDev label or default label for a range
    if ( mode == StdDev )
    {
      if ( i == 0 )
      {
        label = "< " + QString::number( labels[i], 'f', 2 ) + " Std Dev";
      }
      else if ( i == labels.count() - 1 )
      {
        label = ">= " + QString::number( labels[i-1], 'f', 2 ) + " Std Dev";
      }
      else
      {
        label = QString::number( labels[i-1], 'f', 2 ) + " Std Dev" + " - " + QString::number( labels[i], 'f', 2 ) + " Std Dev";
      }
    }
    else
    {
      label = mLabelFormat.labelForRange( lower, upper );
    }
    QgsSymbolV2* newSymbol = mSourceSymbol ? mSourceSymbol->clone() : QgsSymbolV2::defaultSymbol( vlayer->geometryType() );
    addClass( QgsRendererRangeV2( lower, upper, newSymbol, label ) );
  }
  updateColorRamp( 0, mInvertedColorRamp );
}
QgsGraduatedSymbolRendererV2Widget::QgsGraduatedSymbolRendererV2Widget( QgsVectorLayer* layer, QgsStyleV2* style, QgsFeatureRendererV2* renderer )
    : QgsRendererV2Widget( layer, style )
    , mRenderer( nullptr )
    , mModel( nullptr )
{


  // try to recognize the previous renderer
  // (null renderer means "no previous renderer")
  if ( renderer )
  {
    mRenderer = QgsGraduatedSymbolRendererV2::convertFromRenderer( renderer );
  }
  if ( !mRenderer )
  {
    mRenderer = new QgsGraduatedSymbolRendererV2( "", QgsRangeList() );
  }

  // setup user interface
  setupUi( this );

  mModel = new QgsGraduatedSymbolRendererV2Model( this );

  mExpressionWidget->setFilters( QgsFieldProxyModel::Numeric | QgsFieldProxyModel::Date );
  mExpressionWidget->setLayer( mLayer );

  mSizeUnitWidget->setUnits( QgsUnitTypes::RenderUnitList() << QgsUnitTypes::RenderMillimeters << QgsUnitTypes::RenderMapUnits << QgsUnitTypes::RenderPixels );

  cboGraduatedColorRamp->populate( mStyle );

  spinPrecision->setMinimum( QgsRendererRangeV2LabelFormat::MinPrecision );
  spinPrecision->setMaximum( QgsRendererRangeV2LabelFormat::MaxPrecision );

  // set project default color ramp
  QString defaultColorRamp = QgsProject::instance()->readEntry( "DefaultStyles", "/ColorRamp", "" );
  if ( defaultColorRamp != "" )
  {
    int index = cboGraduatedColorRamp->findText( defaultColorRamp, Qt::MatchCaseSensitive );
    if ( index >= 0 )
      cboGraduatedColorRamp->setCurrentIndex( index );
  }


  viewGraduated->setStyle( new QgsGraduatedSymbolRendererV2ViewStyle( viewGraduated->style() ) );

  mGraduatedSymbol = QgsSymbolV2::defaultSymbol( mLayer->geometryType() );

  methodComboBox->blockSignals( true );
  methodComboBox->addItem( "Color" );
  if ( mGraduatedSymbol->type() == QgsSymbolV2::Marker )
  {
    methodComboBox->addItem( "Size" );
    minSizeSpinBox->setValue( 1 );
    maxSizeSpinBox->setValue( 8 );
  }
  else if ( mGraduatedSymbol->type() == QgsSymbolV2::Line )
  {
    methodComboBox->addItem( "Size" );
    minSizeSpinBox->setValue( .1 );
    maxSizeSpinBox->setValue( 2 );
  }
  methodComboBox->blockSignals( false );

  connect( mExpressionWidget, SIGNAL( fieldChanged( QString ) ), this, SLOT( graduatedColumnChanged( QString ) ) );
  connect( viewGraduated, SIGNAL( doubleClicked( const QModelIndex & ) ), this, SLOT( rangesDoubleClicked( const QModelIndex & ) ) );
  connect( viewGraduated, SIGNAL( clicked( const QModelIndex & ) ), this, SLOT( rangesClicked( const QModelIndex & ) ) );
  connect( viewGraduated, SIGNAL( customContextMenuRequested( const QPoint& ) ),  this, SLOT( contextMenuViewCategories( const QPoint& ) ) );

  connect( btnGraduatedClassify, SIGNAL( clicked() ), this, SLOT( classifyGraduated() ) );
  connect( btnChangeGraduatedSymbol, SIGNAL( clicked() ), this, SLOT( changeGraduatedSymbol() ) );
  connect( btnGraduatedDelete, SIGNAL( clicked() ), this, SLOT( deleteClasses() ) );
  connect( btnDeleteAllClasses, SIGNAL( clicked() ), this, SLOT( deleteAllClasses() ) );
  connect( btnGraduatedAdd, SIGNAL( clicked() ), this, SLOT( addClass() ) );
  connect( cbxLinkBoundaries, SIGNAL( toggled( bool ) ), this, SLOT( toggleBoundariesLink( bool ) ) );

  connect( mSizeUnitWidget, SIGNAL( changed() ), this, SLOT( on_mSizeUnitWidget_changed() ) );

  connectUpdateHandlers();

  // initialize from previously set renderer
  updateUiFromRenderer();

  // menus for data-defined rotation/size
  QMenu* advMenu = new QMenu;

  advMenu->addAction( tr( "Symbol levels..." ), this, SLOT( showSymbolLevels() ) );

  btnAdvanced->setMenu( advMenu );

  mHistogramWidget->setLayer( mLayer );
  mHistogramWidget->setRenderer( mRenderer );
  connect( mHistogramWidget, SIGNAL( rangesModified( bool ) ), this, SLOT( refreshRanges( bool ) ) );
  connect( mExpressionWidget, SIGNAL( fieldChanged( QString ) ), mHistogramWidget, SLOT( setSourceFieldExp( QString ) ) );

  mExpressionWidget->registerGetExpressionContextCallback( &_getExpressionContext, this );
}
QgsGraduatedSymbolRendererV2Widget::QgsGraduatedSymbolRendererV2Widget( QgsVectorLayer* layer, QgsStyleV2* style, QgsFeatureRendererV2* renderer )
    : QgsRendererV2Widget( layer, style )
    , mRenderer( 0 )
    , mModel( 0 )
{

  // try to recognize the previous renderer
  // (null renderer means "no previous renderer")
  if ( !renderer || renderer->type() != "graduatedSymbol" )
  {
    // we're not going to use it - so let's delete the renderer
    delete renderer;

    mRenderer = new QgsGraduatedSymbolRendererV2( "", QgsRangeList() );
  }
  else
  {
    mRenderer = static_cast<QgsGraduatedSymbolRendererV2*>( renderer );
  }

  // setup user interface
  setupUi( this );

  mExpressionWidget->setFilters( QgsFieldProxyModel::Numeric | QgsFieldProxyModel::Date );
  mExpressionWidget->setLayer( mLayer );

  cboGraduatedColorRamp->populate( mStyle );

  // set project default color ramp
  QString defaultColorRamp = QgsProject::instance()->readEntry( "DefaultStyles", "/ColorRamp", "" );
  if ( defaultColorRamp != "" )
  {
    int index = cboGraduatedColorRamp->findText( defaultColorRamp, Qt::MatchCaseSensitive );
    if ( index >= 0 )
      cboGraduatedColorRamp->setCurrentIndex( index );
  }

  mModel = new QgsGraduatedSymbolRendererV2Model( this );
  mModel->setRenderer( mRenderer );
  viewGraduated->setModel( mModel );
  viewGraduated->resizeColumnToContents( 0 );
  viewGraduated->resizeColumnToContents( 1 );
  viewGraduated->resizeColumnToContents( 2 );

  viewGraduated->setStyle( new QgsGraduatedSymbolRendererV2ViewStyle( viewGraduated->style() ) );

  mGraduatedSymbol = QgsSymbolV2::defaultSymbol( mLayer->geometryType() );

  connect( mExpressionWidget, SIGNAL( fieldChanged( QString ) ), this, SLOT( graduatedColumnChanged( QString ) ) );
  connect( viewGraduated, SIGNAL( doubleClicked( const QModelIndex & ) ), this, SLOT( rangesDoubleClicked( const QModelIndex & ) ) );
  connect( viewGraduated, SIGNAL( clicked( const QModelIndex & ) ), this, SLOT( rangesClicked( const QModelIndex & ) ) );
  connect( viewGraduated, SIGNAL( customContextMenuRequested( const QPoint& ) ),  this, SLOT( contextMenuViewCategories( const QPoint& ) ) );

  connect( mModel, SIGNAL( rowsMoved() ), this, SLOT( rowsMoved() ) );

  connect( btnGraduatedClassify, SIGNAL( clicked() ), this, SLOT( classifyGraduated() ) );
  connect( btnChangeGraduatedSymbol, SIGNAL( clicked() ), this, SLOT( changeGraduatedSymbol() ) );
  connect( btnGraduatedDelete, SIGNAL( clicked() ), this, SLOT( deleteClasses() ) );
  connect( btnDeleteAllClasses, SIGNAL( clicked() ), this, SLOT( deleteAllClasses() ) );
  connect( btnGraduatedAdd, SIGNAL( clicked() ), this, SLOT( addClass() ) );

  // initialize from previously set renderer
  updateUiFromRenderer();

  connect( spinGraduatedClasses, SIGNAL( valueChanged( int ) ) , this, SLOT( classifyGraduated() ) );
  connect( cboGraduatedMode, SIGNAL( currentIndexChanged( int ) ) , this, SLOT( classifyGraduated() ) );
  connect( cboGraduatedColorRamp, SIGNAL( currentIndexChanged( int ) ) , this, SLOT( reapplyColorRamp() ) );

  // menus for data-defined rotation/size
  QMenu* advMenu = new QMenu;

  advMenu->addAction( tr( "Symbol levels..." ), this, SLOT( showSymbolLevels() ) );

  mDataDefinedMenus = new QgsRendererV2DataDefinedMenus( advMenu, mLayer,
      mRenderer->rotationField(), mRenderer->sizeScaleField(), mRenderer->scaleMethod() );
  connect( mDataDefinedMenus, SIGNAL( rotationFieldChanged( QString ) ), this, SLOT( rotationFieldChanged( QString ) ) );
  connect( mDataDefinedMenus, SIGNAL( sizeScaleFieldChanged( QString ) ), this, SLOT( sizeScaleFieldChanged( QString ) ) );
  connect( mDataDefinedMenus, SIGNAL( scaleMethodChanged( QgsSymbolV2::ScaleMethod ) ), this, SLOT( scaleMethodChanged( QgsSymbolV2::ScaleMethod ) ) );
  btnAdvanced->setMenu( advMenu );
}