[FEATURE][callouts] Add anchor point position settings for polygon features

python/core/auto_generated/callouts/qgscallout.sip.in

@@ -47,6 +47,7 @@ relevant symbology elements to render them.
       OffsetFromAnchor,
       OffsetFromLabel,
       DrawCalloutToAllParts,
+      AnchorPointPosition,
     };
 
     enum DrawOrder
@@ -55,6 +56,14 @@ relevant symbology elements to render them.
       OrderBelowIndividualLabels,
     };
 
+    enum AnchorPoint
+    {
+      PoleOfInaccessibility,
+      PointOnExterior,
+      PointOnSurface,
+      Centroid,
+    };
+
     QgsCallout();
 %Docstring
 Constructor for QgsCallout.
@@ -225,6 +234,42 @@ Any existing properties will be discarded.
     static QgsPropertiesDefinition propertyDefinitions();
 %Docstring
 Returns the definitions for data defined properties available for use in callouts.
+%End
+
+    AnchorPoint anchorPoint() const;
+%Docstring
+Returns the feature's anchor point position.
+
+.. seealso:: :py:func:`setAnchorPoint`
+%End
+
+    void setAnchorPoint( AnchorPoint anchor );
+%Docstring
+Sets the feature's ``anchor`` point position.
+
+.. seealso:: :py:func:`drawCalloutToAllParts`
+%End
+
+    static QString encodeAnchorPoint( AnchorPoint anchor );
+%Docstring
+Encodes an ``anchor`` point to its string representation.
+
+:return: encoded string
+
+.. seealso:: :py:func:`decodeAnchorPoint`
+%End
+
+    static QgsCallout::AnchorPoint decodeAnchorPoint( const QString &name, bool *ok = 0 );
+%Docstring
+Attempts to decode a string representation of an anchoir point name to the corresponding
+anchor point.
+
+:param name: encoded anchoir point name
+:param ok: if specified, will be set to ``True`` if the anchoir point was successfully decoded
+
+:return: decoded name
+
+.. seealso:: :py:func:`encodeAnchorPoint`
 %End
 
   protected:

python/gui/auto_generated/callouts/qgscalloutwidget.sip.in

@@ -71,6 +71,8 @@ Returns the vector layer associated with the widget.
 .. versionadded:: 2.12
 %End
 
+    virtual void setGeometryType( QgsWkbTypes::GeometryType type ) = 0;
+
   protected:
 
     void registerDataDefinedButton( QgsPropertyOverrideButton *button, QgsCallout::Property key );

src/core/callouts/qgscallout.cpp

@@ -38,6 +38,7 @@ void QgsCallout::initPropertyDefinitions()
     { QgsCallout::OffsetFromAnchor, QgsPropertyDefinition( "OffsetFromAnchor", QObject::tr( "Offset from feature" ), QgsPropertyDefinition::DoublePositive, origin ) },
     { QgsCallout::OffsetFromLabel, QgsPropertyDefinition( "OffsetFromLabel", QObject::tr( "Offset from label" ), QgsPropertyDefinition::DoublePositive, origin ) },
     { QgsCallout::DrawCalloutToAllParts, QgsPropertyDefinition( "DrawCalloutToAllParts", QObject::tr( "Draw lines to all feature parts" ), QgsPropertyDefinition::Boolean, origin ) },
+    { QgsCallout::AnchorPointPosition, QgsPropertyDefinition( "AnchorPointPosition", QObject::tr( "Feature's anchor point position" ), QgsPropertyDefinition::String, origin ) },
   };
 }
 
@@ -50,6 +51,7 @@ QVariantMap QgsCallout::properties( const QgsReadWriteContext & ) const
 {
   QVariantMap props;
   props.insert( QStringLiteral( "enabled" ), mEnabled ? "1" : "0" );
+  props.insert( QStringLiteral( "anchorPoint" ), encodeAnchorPoint( mAnchorPoint ) );
   props.insert( QStringLiteral( "ddProperties" ), mDataDefinedProperties.toVariant( propertyDefinitions() ) );
   return props;
 }
@@ -57,6 +59,7 @@ QVariantMap QgsCallout::properties( const QgsReadWriteContext & ) const
 void QgsCallout::readProperties( const QVariantMap &props, const QgsReadWriteContext & )
 {
   mEnabled = props.value( QStringLiteral( "enabled" ), QStringLiteral( "0" ) ).toInt();
+  mAnchorPoint = decodeAnchorPoint( props.value( QStringLiteral( "anchorPoint" ), QString( "" ) ).toString() );
   mDataDefinedProperties.loadVariant( props.value( QStringLiteral( "ddProperties" ) ), propertyDefinitions() );
 }
 
@@ -71,6 +74,7 @@ bool QgsCallout::saveProperties( QDomDocument &doc, QDomElement &element, const
 
   QDomElement calloutElement = doc.createElement( QStringLiteral( "callout" ) );
   calloutElement.setAttribute( QStringLiteral( "type" ), type() );
+  calloutElement.setAttribute( QStringLiteral( "anchorPoint" ), encodeAnchorPoint( mAnchorPoint ) );
   calloutElement.appendChild( calloutPropsElement );
 
   element.appendChild( calloutElement );
@@ -145,6 +149,41 @@ QgsPropertiesDefinition QgsCallout::propertyDefinitions()
   return sPropertyDefinitions;
 }
 
+QgsCallout::AnchorPoint QgsCallout::decodeAnchorPoint( const QString &name, bool *ok )
+{
+  if ( ok )
+    *ok = true;
+  QString cleaned = name.toLower().trimmed();
+
+  if ( cleaned == QLatin1String( "pole_of_inaccessibility" ) )
+    return PoleOfInaccessibility;
+  else if ( cleaned == QLatin1String( "point_on_exterior" ) )
+    return PointOnExterior;
+  else if ( cleaned == QLatin1String( "point_on_surface" ) )
+    return PointOnSurface;
+  else if ( cleaned == QLatin1String( "centroid" ) )
+    return Centroid;
+
+  if ( ok )
+    *ok = false;
+  return PoleOfInaccessibility;
+}
+
+QString QgsCallout::encodeAnchorPoint( AnchorPoint anchor )
+{
+  switch ( anchor )
+  {
+    case PoleOfInaccessibility:
+      return QStringLiteral( "pole_of_inaccessibility" );
+    case PointOnExterior:
+      return QStringLiteral( "point_on_exterior" );
+    case PointOnSurface:
+      return QStringLiteral( "point_on_surface" );
+    case Centroid:
+      return QStringLiteral( "centroid" );
+  }
+  return QString();
+}
 
 //
 // QgsSimpleLineCallout
@@ -280,6 +319,13 @@ void QgsSimpleLineCallout::draw( QgsRenderContext &context, QRectF rect, const d
   auto drawCalloutLine = [this, &context, &label]( const QgsGeometry & partAnchor )
   {
     QgsGeometry line;
+    AnchorPoint anchor = anchorPoint();
+    if ( dataDefinedProperties().isActive( QgsCallout::AnchorPointPosition ) )
+    {
+      QString encodedAnchor = encodeAnchorPoint( anchor );
+      context.expressionContext().setOriginalValueVariable( encodedAnchor );
+      anchor = decodeAnchorPoint( dataDefinedProperties().valueAsString( QgsCallout::AnchorPointPosition, context.expressionContext(), encodedAnchor ) );
+    }
     switch ( partAnchor.type() )
     {
       case QgsWkbTypes::PointGeometry:
@@ -294,7 +340,22 @@ void QgsSimpleLineCallout::draw( QgsRenderContext &context, QRectF rect, const d
         if ( label.intersects( partAnchor ) )
           return;
 
-        line = label.shortestLine( partAnchor.poleOfInaccessibility( std::max( partAnchor.boundingBox().width(), partAnchor.boundingBox().height() ) / 20.0 ) ); // really rough (but quick) pole of inaccessibility
+        switch ( anchor )
+        {
+          case QgsCallout::PoleOfInaccessibility:
+            line = label.shortestLine( partAnchor.poleOfInaccessibility( std::max( partAnchor.boundingBox().width(), partAnchor.boundingBox().height() ) / 20.0 ) ); // really rough (but quick) pole of inaccessibility
+            break;
+          case QgsCallout::PointOnSurface:
+            line = label.shortestLine( partAnchor.pointOnSurface() );
+            break;
+          case QgsCallout::PointOnExterior:
+            line = label.shortestLine( partAnchor );
+            break;
+          case QgsCallout::Centroid:
+          default:
+            line = label.shortestLine( partAnchor.centroid() );
+            break;
+        }
         break;
 
       case QgsWkbTypes::NullGeometry:
@@ -398,6 +459,13 @@ void QgsManhattanLineCallout::draw( QgsRenderContext &context, QRectF rect, cons
   auto drawCalloutLine = [this, &context, &label]( const QgsGeometry & partAnchor )
   {
     QgsGeometry line;
+    AnchorPoint anchor = anchorPoint();
+    if ( dataDefinedProperties().isActive( QgsCallout::AnchorPointPosition ) )
+    {
+      QString encodedAnchor = encodeAnchorPoint( anchor );
+      context.expressionContext().setOriginalValueVariable( encodedAnchor );
+      anchor = decodeAnchorPoint( dataDefinedProperties().valueAsString( QgsCallout::AnchorPointPosition, context.expressionContext(), encodedAnchor ) );
+    }
     switch ( partAnchor.type() )
     {
       case QgsWkbTypes::PointGeometry:
@@ -412,7 +480,22 @@ void QgsManhattanLineCallout::draw( QgsRenderContext &context, QRectF rect, cons
         if ( label.intersects( partAnchor ) )
           return;
 
-        line = label.shortestLine( partAnchor.poleOfInaccessibility( std::max( partAnchor.boundingBox().width(), partAnchor.boundingBox().height() ) / 20.0 ) ); // really rough (but quick) pole of inaccessibility
+        switch ( anchor )
+        {
+          case QgsCallout::PoleOfInaccessibility:
+            line = label.shortestLine( partAnchor.poleOfInaccessibility( std::max( partAnchor.boundingBox().width(), partAnchor.boundingBox().height() ) / 20.0 ) ); // really rough (but quick) pole of inaccessibility
+            break;
+          case QgsCallout::PointOnSurface:
+            line = label.shortestLine( partAnchor.pointOnSurface() );
+            break;
+          case QgsCallout::PointOnExterior:
+            line = label.shortestLine( partAnchor );
+            break;
+          case QgsCallout::Centroid:
+          default:
+            line = label.shortestLine( partAnchor.centroid() );
+            break;
+        }
         break;
 
       case QgsWkbTypes::NullGeometry:

src/core/callouts/qgscallout.h

@@ -72,6 +72,7 @@ class CORE_EXPORT QgsCallout
       OffsetFromAnchor, //!< Distance to offset lines from anchor points
       OffsetFromLabel, //!< Distance to offset lines from label area
       DrawCalloutToAllParts, //!< Whether callout lines should be drawn to all feature parts
+      AnchorPointPosition, //!< Feature's anchor point position
     };
 
     //! Options for draw order (stacking) of callouts
@@ -81,6 +82,15 @@ class CORE_EXPORT QgsCallout
       OrderBelowIndividualLabels, //!< Render callouts below their individual associated labels, some callouts may be drawn over other labels
     };
 
+    //! Feature's anchor point position
+    enum AnchorPoint
+    {
+      PoleOfInaccessibility = 0, //!< The surface's pole of inaccessibility used as anchor
+      PointOnExterior, //!< A point on the surface's outline closest to the label is used as anchor
+      PointOnSurface, //!< A point guaranteed to be on the surface is used as anchor
+      Centroid, //!< The surface's centroid is used as anchor
+    };
+
     /**
      * Constructor for QgsCallout.
      */
@@ -252,6 +262,37 @@ class CORE_EXPORT QgsCallout
      */
     static QgsPropertiesDefinition propertyDefinitions();
 
+    /**
+     * Returns the feature's anchor point position.
+     *
+     * \see setAnchorPoint()
+     */
+    AnchorPoint anchorPoint() const { return mAnchorPoint; }
+
+    /**
+     * Sets the feature's \a anchor point position.
+     *
+     * \see drawCalloutToAllParts()
+     */
+    void setAnchorPoint( AnchorPoint anchor ) { mAnchorPoint = anchor; }
+
+    /**
+     * Encodes an \a anchor point to its string representation.
+     * \returns encoded string
+     * \see decodeAnchorPoint()
+     */
+    static QString encodeAnchorPoint( AnchorPoint anchor );
+
+    /**
+     * Attempts to decode a string representation of an anchoir point name to the corresponding
+     * anchor point.
+     * \param name encoded anchoir point name
+     * \param ok if specified, will be set to TRUE if the anchoir point was successfully decoded
+     * \returns decoded name
+     * \see encodeAnchorPoint()
+     */
+    static QgsCallout::AnchorPoint decodeAnchorPoint( const QString &name, bool *ok = nullptr );
+
   protected:
 
     /**
@@ -278,6 +319,8 @@ class CORE_EXPORT QgsCallout
 
     bool mEnabled = false;
 
+    AnchorPoint mAnchorPoint = PoleOfInaccessibility;
+
     //! Property collection for data defined callout settings
     QgsPropertyCollection mDataDefinedProperties;
 

src/gui/callouts/qgscalloutwidget.cpp

@@ -160,6 +160,13 @@ QgsSimpleLineCalloutWidget::QgsSimpleLineCalloutWidget( QgsVectorLayer *vl, QWid
 
   connect( mDrawToAllPartsCheck, &QCheckBox::toggled, this, &QgsSimpleLineCalloutWidget::drawToAllPartsToggled );
 
+  // Anchor point options
+  mAnchorPointComboBox->addItem( tr( "Pole of inaccessibility" ), static_cast< int >( QgsCallout::PoleOfInaccessibility ) );
+  mAnchorPointComboBox->addItem( tr( "Point on exterior" ), static_cast< int >( QgsCallout::PointOnExterior ) );
+  mAnchorPointComboBox->addItem( tr( "Point on surface" ), static_cast< int >( QgsCallout::PointOnSurface ) );
+  mAnchorPointComboBox->addItem( tr( "Centroid" ), static_cast< int >( QgsCallout::Centroid ) );
+  connect( mAnchorPointComboBox, static_cast<void ( QComboBox::* )( int )>( &QComboBox::currentIndexChanged ), this, &QgsSimpleLineCalloutWidget::mAnchorPointComboBox_currentIndexChanged );
+
   connect( mCalloutLineStyleButton, &QgsSymbolButton::changed, this, &QgsSimpleLineCalloutWidget::lineSymbolChanged );
 }
 
@@ -194,10 +201,19 @@ void QgsSimpleLineCalloutWidget::setCallout( QgsCallout *callout )
 
   whileBlocking( mDrawToAllPartsCheck )->setChecked( mCallout->drawCalloutToAllParts() );
 
+  whileBlocking( mAnchorPointComboBox )->setCurrentIndex( mAnchorPointComboBox->findData( static_cast< int >( callout->anchorPoint() ) ) );
+
   registerDataDefinedButton( mMinCalloutLengthDDBtn, QgsCallout::MinimumCalloutLength );
   registerDataDefinedButton( mOffsetFromAnchorDDBtn, QgsCallout::OffsetFromAnchor );
   registerDataDefinedButton( mOffsetFromLabelDDBtn, QgsCallout::OffsetFromLabel );
   registerDataDefinedButton( mDrawToAllPartsDDBtn, QgsCallout::DrawCalloutToAllParts );
+  registerDataDefinedButton( mAnchorPointDDBtn, QgsCallout::AnchorPointPosition );
+}
+
+void QgsSimpleLineCalloutWidget::setGeometryType( QgsWkbTypes::GeometryType type )
+{
+  mAnchorPointComboBox->setEnabled( type == QgsWkbTypes::PolygonGeometry );
+  mAnchorPointDDBtn->setEnabled( type == QgsWkbTypes::PolygonGeometry );
 }
 
 QgsCallout *QgsSimpleLineCalloutWidget::callout()
@@ -250,6 +266,12 @@ void QgsSimpleLineCalloutWidget::lineSymbolChanged()
   emit changed();
 }
 
+void QgsSimpleLineCalloutWidget::mAnchorPointComboBox_currentIndexChanged( int index )
+{
+  mCallout->setAnchorPoint( static_cast<QgsCallout::AnchorPoint>( mAnchorPointComboBox->itemData( index ).toInt() ) );
+  emit changed();
+}
+
 void QgsSimpleLineCalloutWidget::drawToAllPartsToggled( bool active )
 {
   mCallout->setDrawCalloutToAllParts( active );

src/gui/callouts/qgscalloutwidget.h

@@ -81,6 +81,8 @@ class GUI_EXPORT QgsCalloutWidget : public QWidget, protected QgsExpressionConte
      */
     const QgsVectorLayer *vectorLayer() const { return mVectorLayer; }
 
+    virtual void setGeometryType( QgsWkbTypes::GeometryType type ) = 0;
+
   protected:
 
     /**
@@ -135,8 +137,11 @@ class GUI_EXPORT QgsSimpleLineCalloutWidget : public QgsCalloutWidget, private U
     static QgsCalloutWidget *create( QgsVectorLayer *vl ) SIP_FACTORY { return new QgsSimpleLineCalloutWidget( vl ); }
 
     void setCallout( QgsCallout *callout ) override;
+
     QgsCallout *callout() override;
 
+    void setGeometryType( QgsWkbTypes::GeometryType type ) override;
+
   private slots:
 
     void minimumLengthChanged();
@@ -146,6 +151,7 @@ class GUI_EXPORT QgsSimpleLineCalloutWidget : public QgsCalloutWidget, private U
     void offsetFromLabelUnitWidgetChanged();
     void offsetFromLabelChanged();
     void lineSymbolChanged();
+    void mAnchorPointComboBox_currentIndexChanged( int index );
     void drawToAllPartsToggled( bool active );
 
   private:

src/gui/qgslabelinggui.cpp

@@ -103,6 +103,13 @@ void QgsLabelingGui::updateCalloutWidget( QgsCallout *callout )
   {
     if ( QgsCalloutWidget *w = am->createCalloutWidget( mLayer ) )
     {
+
+      QgsWkbTypes::GeometryType geometryType = mGeomType;
+      if ( mGeometryGeneratorGroupBox->isChecked() )
+        geometryType = mGeometryGeneratorType->currentData().value<QgsWkbTypes::GeometryType>();
+      else if ( mLayer )
+        geometryType = mLayer->geometryType();
+      w->setGeometryType( geometryType );
       w->setCallout( callout );
 
       w->setContext( context() );

src/ui/callouts/widget_simplelinecallout.ui

@@ -224,6 +224,23 @@
        </property>
       </widget>
      </item>
+     <item row="5" column="0">
+      <widget class="QLabel" name="label_48">
+       <property name="text">
+        <string>Anchor point</string>
+       </property>
+      </widget>
+     </item>
+     <item row="5" column="1" colspan="2">
+      <widget class="QComboBox" name="mAnchorPointComboBox"></widget>
+     </item>
+     <item row="5" column="3">
+      <widget class="QgsPropertyOverrideButton" name="mAnchorPointDDBtn">
+       <property name="text">
+        <string>…</string>
+       </property>
+      </widget>
+     </item>
     </layout>
    </item>
    <item>