void QgsMarkerSymbolV2::setDataDefinedSize( const QgsDataDefined &dd )
{
  const double symbolSize = size();

  for ( QgsSymbolLayerV2List::iterator it = mLayers.begin(); it != mLayers.end(); ++it )
  {
    QgsMarkerSymbolLayerV2* layer = static_cast<QgsMarkerSymbolLayerV2 *>( *it );

    if ( dd.hasDefaultValues() )
    {
      layer->removeDataDefinedProperty( "size" );
      layer->removeDataDefinedProperty( "offset" );
    }
    else
    {
      if ( symbolSize == 0 || qgsDoubleNear( layer->size(), symbolSize ) )
      {
        layer->setDataDefinedProperty( "size", new QgsDataDefined( dd ) );
      }
      else
      {
        layer->setDataDefinedProperty( "size", scaleWholeSymbol( layer->size() / symbolSize, dd ) );
      }

      if ( layer->offset().x() || layer->offset().y() )
      {
        layer->setDataDefinedProperty( "offset", scaleWholeSymbol(
                                         layer->offset().x() / symbolSize,
                                         layer->offset().y() / symbolSize, dd ) );
      }
    }
  }
}
void QgsMarkerSymbolV2::setSize( double s )
{
  double origSize = size();

  for ( QgsSymbolLayerV2List::iterator it = mLayers.begin(); it != mLayers.end(); ++it )
  {
    QgsMarkerSymbolLayerV2* layer = static_cast<QgsMarkerSymbolLayerV2*>( *it );
    if ( layer->size() == origSize )
      layer->setSize( s );
    else if ( origSize != 0 )
    {
      // proportionally scale size
      layer->setSize( layer->size() * s / origSize );
    }
    // also scale offset to maintain relative position
    if ( origSize != 0 && ( layer->offset().x() || layer->offset().y() ) )
      layer->setOffset( QPointF( layer->offset().x() * s / origSize,
                                 layer->offset().y() * s / origSize ) );
  }
}