static void _createCategories( QgsCategoryList& cats, QList<QVariant>& values, QgsSymbolV2* symbol, QgsVectorColorRampV2* ramp )
{
  // sort the categories first
  //TODO: make the order configurable?
  QgsSymbolLayerV2Utils::sortVariantList( values, Qt::AscendingOrder );

  int num = values.count();

  bool hasNull = false;

  for ( int i = 0; i < num; i++ )
  {
    QVariant value = values[i];
    if ( value.toString().isNull() )
    {
      hasNull = true;
    }
    double x = i / ( double ) num;
    QgsSymbolV2* newSymbol = symbol->clone();
    newSymbol->setColor( ramp->color( x ) );

    cats.append( QgsRendererCategoryV2( value, newSymbol, value.toString() ) );
  }

  // add null (default) value if not exists
  if ( !hasNull )
  {
    QgsSymbolV2* newSymbol = symbol->clone();
    newSymbol->setColor( ramp->color( 1 ) );
    cats.append( QgsRendererCategoryV2( QVariant( "" ), newSymbol, QString() ) );
  }
}
static QgsFeatureRenderer* readOldUniqueValueRenderer( const QDomNode& rnode, QgsWkbTypes::GeometryType geomType )
{
  QDomNode classnode = rnode.namedItem( "classificationfield" );
  QString classificationField = classnode.toElement().text();

  // read categories and symbols
  QgsCategoryList cats;
  QDomNode symbolnode = rnode.namedItem( "symbol" );
  while ( !symbolnode.isNull() )
  {
    QgsSymbol* symbol = readOldSymbol( symbolnode, geomType );
    if ( symbol )
    {
      QgsOldSymbolMeta meta = readSymbolMeta( symbolnode );
      QVariant value = QVariant( meta.lowerValue );
      QString label = meta.label;
      if ( label.isEmpty() )
        label = value.toString();
      cats.append( QgsRendererCategory( value, symbol, label, true ) );
    }

    symbolnode = symbolnode.nextSibling();
  }

  QgsCategorizedSymbolRenderer* r = new QgsCategorizedSymbolRenderer( classificationField, cats );
  // source symbol and color ramp are not set (unknown)
  return r;
}
QgsFeatureRendererV2* QgsCategorizedSymbolRendererV2::create( QDomElement& element )
{
  QDomElement symbolsElem = element.firstChildElement( "symbols" );
  if ( symbolsElem.isNull() )
    return NULL;

  QDomElement catsElem = element.firstChildElement( "categories" );
  if ( catsElem.isNull() )
    return NULL;

  QgsSymbolV2Map symbolMap = QgsSymbolLayerV2Utils::loadSymbols( symbolsElem );
  QgsCategoryList cats;

  QDomElement catElem = catsElem.firstChildElement();
  while ( !catElem.isNull() )
  {
    if ( catElem.tagName() == "category" )
    {
      QVariant value = QVariant( catElem.attribute( "value" ) );
      QString symbolName = catElem.attribute( "symbol" );
      QString label = catElem.attribute( "label" );
      if ( symbolMap.contains( symbolName ) )
      {
        QgsSymbolV2* symbol = symbolMap.take( symbolName );
        cats.append( QgsRendererCategoryV2( value, symbol, label ) );
      }
    }
    catElem = catElem.nextSiblingElement();
  }

  QString attrName = element.attribute( "attr" );

  QgsCategorizedSymbolRendererV2* r = new QgsCategorizedSymbolRendererV2( attrName, cats );

  // delete symbols if there are any more
  QgsSymbolLayerV2Utils::clearSymbolMap( symbolMap );

  // try to load source symbol (optional)
  QDomElement sourceSymbolElem = element.firstChildElement( "source-symbol" );
  if ( !sourceSymbolElem.isNull() )
  {
    QgsSymbolV2Map sourceSymbolMap = QgsSymbolLayerV2Utils::loadSymbols( sourceSymbolElem );
    if ( sourceSymbolMap.contains( "0" ) )
    {
      r->setSourceSymbol( sourceSymbolMap.take( "0" ) );
    }
    QgsSymbolLayerV2Utils::clearSymbolMap( sourceSymbolMap );
  }

  // try to load color ramp (optional)
  QDomElement sourceColorRampElem = element.firstChildElement( "colorramp" );
  if ( !sourceColorRampElem.isNull() && sourceColorRampElem.attribute( "name" ) == "[source]" )
  {
    r->setSourceColorRamp( QgsSymbolLayerV2Utils::loadColorRamp( sourceColorRampElem ) );
    QDomElement invertedColorRampElem = element.firstChildElement( "invertedcolorramp" );
    if ( !invertedColorRampElem.isNull() )
      r->setInvertedColorRamp( invertedColorRampElem.attribute( "value" ) == "1" );
  }

  QDomElement rotationElem = element.firstChildElement( "rotation" );
  if ( !rotationElem.isNull() )
    r->setRotationField( rotationElem.attribute( "field" ) );

  QDomElement sizeScaleElem = element.firstChildElement( "sizescale" );
  if ( !sizeScaleElem.isNull() )
  {
    r->setSizeScaleField( sizeScaleElem.attribute( "field" ) );
    r->setScaleMethod( QgsSymbolLayerV2Utils::decodeScaleMethod( sizeScaleElem.attribute( "scalemethod" ) ) );
  }

  // TODO: symbol levels
  return r;
}
void QgsCategorizedSymbolRendererV2Widget::addCategories()
{
  QString attrName = cboCategorizedColumn->currentText();
  int idx = mLayer->fieldNameIndex( attrName );
  QList<QVariant> unique_vals;
  mLayer->uniqueValues( idx, unique_vals );

  //DlgAddCategories dlg(mStyle, createDefaultSymbol(), unique_vals, this);
  //if (!dlg.exec())
  //  return;

  QgsVectorColorRampV2* ramp = cboCategorizedColorRamp->currentColorRamp();

  if ( ramp == NULL )
  {
    if ( cboCategorizedColorRamp->count() == 0 )
      QMessageBox::critical( this, tr( "Error" ), tr( "There are no available color ramps. You can add them in Style Manager." ) );
    else
      QMessageBox::critical( this, tr( "Error" ), tr( "The selected color ramp is not available." ) );
    return;
  }

  QgsCategoryList cats;
  _createCategories( cats, unique_vals, mCategorizedSymbol, ramp );

  bool deleteExisting = false;

  if ( !mOldClassificationAttribute.isEmpty() &&
       attrName != mOldClassificationAttribute &&
       mRenderer->categories().count() > 0 )
  {
    int res = QMessageBox::question( this,
                                     tr( "Confirm Delete" ),
                                     tr( "The classification field was changed from '%1' to '%2'.\n"
                                         "Should the existing classes be deleted before classification?" )
                                     .arg( mOldClassificationAttribute ).arg( attrName ),
                                     QMessageBox::Yes | QMessageBox::No | QMessageBox::Cancel );
    if ( res == QMessageBox::Cancel )
    {
      return;
    }

    deleteExisting = ( res == QMessageBox::Yes );
  }

  if ( !deleteExisting )
  {
    QgsCategoryList prevCats = mRenderer->categories();
    for ( int i = 0; i < cats.size(); ++i )
    {
      bool contains = false;
      QVariant value = cats.at( i ).value();
      for ( int j = 0; j < prevCats.size() && !contains; ++j )
      {
        if ( prevCats.at( j ).value() == value )
        {
          contains = true;
          break;
        }
      }

      if ( !contains )
        prevCats.append( cats.at( i ) );
    }
    cats = prevCats;
  }

  mOldClassificationAttribute = attrName;

  // TODO: if not all categories are desired, delete some!
  /*
  if (not dlg.readAllCats.isChecked())
  {
    cats2 = {}
    for item in dlg.listCategories.selectedItems():
      for k,c in cats.iteritems():
        if item.text() == k.toString():
          break
      cats2[k] = c
    cats = cats2
  }
  */

  // recreate renderer
  delete mRenderer;
  mRenderer = new QgsCategorizedSymbolRendererV2( attrName, cats );
  mRenderer->setSourceSymbol( mCategorizedSymbol->clone() );
  mRenderer->setSourceColorRamp( ramp->clone() );

  populateCategories();
}
QgsFeatureRendererV2* QgsCategorizedSymbolRendererV2::create( QDomElement& element )
{
  QDomElement symbolsElem = element.firstChildElement( "symbols" );
  if ( symbolsElem.isNull() )
    return NULL;

  QDomElement catsElem = element.firstChildElement( "categories" );
  if ( catsElem.isNull() )
    return NULL;

  QgsSymbolV2Map symbolMap = QgsSymbolLayerV2Utils::loadSymbols( symbolsElem );
  QgsCategoryList cats;

  QDomElement catElem = catsElem.firstChildElement();
  while ( !catElem.isNull() )
  {
    if ( catElem.tagName() == "category" )
    {
      QVariant value = QVariant( catElem.attribute( "value" ) );
      QString symbolName = catElem.attribute( "symbol" );
      QString label = catElem.attribute( "label" );
      bool render = catElem.attribute( "render" ) != "false";
      if ( symbolMap.contains( symbolName ) )
      {
        QgsSymbolV2* symbol = symbolMap.take( symbolName );
        cats.append( QgsRendererCategoryV2( value, symbol, label, render ) );
      }
    }
    catElem = catElem.nextSiblingElement();
  }

  QString attrName = element.attribute( "attr" );

  QgsCategorizedSymbolRendererV2* r = new QgsCategorizedSymbolRendererV2( attrName, cats );

  // delete symbols if there are any more
  QgsSymbolLayerV2Utils::clearSymbolMap( symbolMap );

  // try to load source symbol (optional)
  QDomElement sourceSymbolElem = element.firstChildElement( "source-symbol" );
  if ( !sourceSymbolElem.isNull() )
  {
    QgsSymbolV2Map sourceSymbolMap = QgsSymbolLayerV2Utils::loadSymbols( sourceSymbolElem );
    if ( sourceSymbolMap.contains( "0" ) )
    {
      r->setSourceSymbol( sourceSymbolMap.take( "0" ) );
    }
    QgsSymbolLayerV2Utils::clearSymbolMap( sourceSymbolMap );
  }

  // try to load color ramp (optional)
  QDomElement sourceColorRampElem = element.firstChildElement( "colorramp" );
  if ( !sourceColorRampElem.isNull() && sourceColorRampElem.attribute( "name" ) == "[source]" )
  {
    r->setSourceColorRamp( QgsSymbolLayerV2Utils::loadColorRamp( sourceColorRampElem ) );
    QDomElement invertedColorRampElem = element.firstChildElement( "invertedcolorramp" );
    if ( !invertedColorRampElem.isNull() )
      r->setInvertedColorRamp( invertedColorRampElem.attribute( "value" ) == "1" );
  }

  QDomElement rotationElem = element.firstChildElement( "rotation" );
  if ( !rotationElem.isNull() && !rotationElem.attribute( "field" ).isEmpty() )
  {
    QgsCategoryList::iterator it = r->mCategories.begin();
    for ( ; it != r->mCategories.end(); ++it )
    {
      convertSymbolRotation( it->symbol(), rotationElem.attribute( "field" ) );
    }
    if ( r->mSourceSymbol.data() )
    {
      convertSymbolRotation( r->mSourceSymbol.data(), rotationElem.attribute( "field" ) );
    }
  }

  QDomElement sizeScaleElem = element.firstChildElement( "sizescale" );
  if ( !sizeScaleElem.isNull() && !sizeScaleElem.attribute( "field" ).isEmpty() )
  {
    QgsCategoryList::iterator it = r->mCategories.begin();
    for ( ; it != r->mCategories.end(); ++it )
    {
      convertSymbolSizeScale( it->symbol(),
                              QgsSymbolLayerV2Utils::decodeScaleMethod( sizeScaleElem.attribute( "scalemethod" ) ),
                              sizeScaleElem.attribute( "field" ) );
    }
    if ( r->mSourceSymbol.data() && r->mSourceSymbol->type() == QgsSymbolV2::Marker )
    {
      convertSymbolSizeScale( r->mSourceSymbol.data(),
                              QgsSymbolLayerV2Utils::decodeScaleMethod( sizeScaleElem.attribute( "scalemethod" ) ),
                              sizeScaleElem.attribute( "field" ) );
    }
  }

  // TODO: symbol levels
  return r;
}