Add option to scale by area/scale by diameter for PieChart and Text Diagram

Author: m-kuhn

src/app/qgsvectorlayerproperties.cpp

@@ -862,6 +862,15 @@ void QgsVectorLayerProperties::apply()
      ds.labelPlacementMethod = QgsDiagramSettings::XHeight;
     }
 
+    if ( tr( "Area" ) == mScaleDependencyComboBox->currentText() )
+    {
+      ds.scaleByArea = true;
+    }
+    else
+    {
+      ds.scaleByArea = false;
+    }
+
     if ( mIncreaseSmallDiagramsCheckBox->isChecked() )
     {
       ds.minimumSize = mIncreaseMinimumSizeSpinBox->value();
@@ -1374,6 +1383,17 @@ void QgsVectorLayerProperties::handleDiagramTypeChanged( const QString& itemtext
     mDiagramOptionsGroupBox->hide();
     mBarWidthLabel->hide();
   }
+
+  if ( tr( "Text diagram" ) == itemtext || tr( "Pie chart" ) == itemtext )
+  {
+    mScaleDependencyComboBox->show();
+    mScaleDependencyLabel->show();
+  }
+  else
+  {
+    mScaleDependencyComboBox->hide();
+    mScaleDependencyLabel->hide();
+  }
 }
 
 void QgsVectorLayerProperties::on_mIncreaseSmallDiagramsCheckBox_stateChanged( int state )
@@ -1672,6 +1692,9 @@ void QgsVectorLayerProperties::initDiagramTab()
   mLabelPlacementComboBox->addItem( tr( "Height" ) );
   mLabelPlacementComboBox->addItem( tr( "x-height" ) );
 
+  mScaleDependencyComboBox->addItem( tr( "Area" ) );
+  mScaleDependencyComboBox->addItem( tr( "Diameter" ) );
+
   //insert all attributes into the combo boxes
   const QgsFieldMap& layerFields = layer->pendingFields();
   QgsFieldMap::const_iterator fieldIt = layerFields.constBegin();

src/core/diagram/qgspiediagram.cpp

@@ -36,8 +36,6 @@ QSizeF QgsPieDiagram::diagramSize( const QgsAttributeMap& attributes, const QgsR
   {
     return QSizeF(); //zero size if attribute is missing
   }
-
-  bool scaleByArea = true;
 
   double scaledValue = attIt.value().toDouble();
   double scaledLowerValue = is.lowerValue;
@@ -48,7 +46,7 @@ QSizeF QgsPieDiagram::diagramSize( const QgsAttributeMap& attributes, const QgsR
   double scaledUpperSizeHeight = is.upperSize.height();
 
   // interpolate the squared value if scale by area
-  if ( scaleByArea )
+  if ( s.scaleByArea )
   {
     scaledValue = sqrt( scaledValue );
     scaledLowerValue = sqrt( scaledLowerValue );

src/core/diagram/qgstextdiagram.cpp

@@ -32,17 +32,37 @@ QgsTextDiagram::~QgsTextDiagram()
 
 QSizeF QgsTextDiagram::diagramSize( const QgsAttributeMap& attributes, const QgsRenderContext& c, const QgsDiagramSettings& s, const QgsDiagramInterpolationSettings& is )
 {
-  QgsAttributeMap::const_iterator attIt = attributes.find( is.classificationAttribute );
+    QgsAttributeMap::const_iterator attIt = attributes.find( is.classificationAttribute );
   if ( attIt == attributes.constEnd() )
   {
     return QSizeF(); //zero size if attribute is missing
   }
-  double value = attIt.value().toDouble();
+  
+  double scaledValue = attIt.value().toDouble();
+  double scaledLowerValue = is.lowerValue;
+  double scaledUpperValue = is.upperValue;
+  double scaledLowerSizeWidth = is.lowerSize.width();
+  double scaledLowerSizeHeight = is.lowerSize.height();
+  double scaledUpperSizeWidth = is.upperSize.width();
+  double scaledUpperSizeHeight = is.upperSize.height();
+
+  // interpolate the squared value if scale by area
+  if ( s.scaleByArea )
+  {
+    scaledValue = sqrt( scaledValue );
+    scaledLowerValue = sqrt( scaledLowerValue );
+    scaledUpperValue = sqrt( scaledUpperValue );
+    scaledLowerSizeWidth = sqrt( scaledLowerSizeWidth );
+    scaledLowerSizeHeight = sqrt( scaledLowerSizeHeight );
+    scaledUpperSizeWidth = sqrt( scaledUpperSizeWidth );
+    scaledUpperSizeHeight = sqrt( scaledUpperSizeHeight );
+  }
 
   //interpolate size
-  double ratio = ( value - is.lowerValue ) / ( is.upperValue - is.lowerValue );
-  QSizeF size = QSizeF( sqrt( is.upperSize.width() * ratio + is.lowerSize.width() * ( 1 - ratio ) ),
-                        sqrt( is.upperSize.height() * ratio + is.lowerSize.height() * ( 1 - ratio ) ) );
+  double scaledRatio = ( scaledValue - scaledLowerValue ) / ( scaledUpperValue - scaledLowerValue );
+
+  QSizeF size = QSizeF( is.upperSize.width() * scaledRatio + is.lowerSize.width() * ( 1 - scaledRatio ),
+                        is.upperSize.height() * scaledRatio + is.lowerSize.height() * ( 1 - scaledRatio ) );
 
   // Scale, if extension is smaller than the specified minimum
   if ( size.width() <= s.minimumSize && size.height() <= s.minimumSize )

src/core/qgsdiagramrendererv2.h

@@ -124,6 +124,7 @@ struct CORE_EXPORT QgsDiagramSettings
   LabelPlacementMethod labelPlacementMethod;
   DiagramOrientation diagramOrientation;
   double barWidth;
+  bool scaleByArea;
 
   //scale range (-1 if no lower / upper bound )
   double minScaleDenominator;

src/ui/qgsvectorlayerpropertiesbase.ui

@@ -1457,6 +1457,16 @@
                     </property>
                    </widget>
                   </item>
+                  <item>
+                   <widget class="QLabel" name="mScaleDependencyLabel">
+                    <property name="text">
+                     <string>Scale</string>
+                    </property>
+                   </widget>
+                  </item>
+                  <item>
+                   <widget class="QComboBox" name="mScaleDependencyComboBox"/>
+                  </item>
                  </layout>
                 </item>
                 <item row="0" column="2">