Read/write also legend symbol in DDS legend, update DDS legend dialog

doc/api_break.dox

@@ -987,8 +987,7 @@ QgsDiagramRenderer        {#qgis_api_break_3_0_QgsDiagramRenderer}
 - renderDiagram() now takes an optional data defined overrides collection argument.
 - readXml(), _readXml(), writeXml(), _writeXml() do not take QgsVectorLayer as an argument anymore.
 - readXml(), _readXml(), writeXml(), _writeXml() require a new argument: a reference to QgsReadWriteContext
-- sizeLegend() and setSizeLegend() have been replaced by dataDefinedSizeLegend() and setDataDefinedSizeLegend() methods.
+- sizeLegend(), setSizeLegend(), sizeLegendSymbol() and setSizeLegendSymbol() have been replaced by dataDefinedSizeLegend() and setDataDefinedSizeLegend() methods in QgsLinearlyInterpolatedDiagramRenderer.
-- sizeLegendSymbol() and setSizeLegendSymbol() have been moved to QgsLinearlyInterpolatedDiagramRenderer subclass.
 
 
 QgsDiagramLayerSettings        {#qgis_api_break_3_0_QgsDiagramLayerSettings}

python/core/qgsdatadefinedsizelegend.sip

@@ -152,19 +152,15 @@ Returns output image that would be shown in the legend. Returns invalid image if
  :rtype: QImage
 %End
 
-    static QgsDataDefinedSizeLegend *readTypeAndAlignmentFromXml( const QDomElement &elem ) /Factory/;
+    static QgsDataDefinedSizeLegend *readXml( const QDomElement &elem, const QgsReadWriteContext &context ) /Factory/;
 %Docstring
-.. note::
+Creates instance from given element and returns it (caller takes ownership). Returns null on error.
-
-   This is a temporary method and may be removed in the future
  :rtype: QgsDataDefinedSizeLegend
 %End
 
-    static void writeTypeAndAlignmentToXml( const QgsDataDefinedSizeLegend &ddsLegend, QDomElement &elem );
+    void writeXml( QDomElement &elem, const QgsReadWriteContext &context ) const;
 %Docstring
-.. note::
+Writes configuration to the given XML element.
-
-   This is a temporary method and may be removed in the future
 %End
 
 };

python/core/qgsdiagramrenderer.sip

@@ -720,24 +720,6 @@ Returns list with all diagram settings in the renderer
     virtual QList< QgsLayerTreeModelLegendNode * > legendItems( QgsLayerTreeLayer *nodeLayer ) const /Factory/;
 
 
-    QgsMarkerSymbol *sizeLegendSymbol() const;
-%Docstring
- Returns the marker symbol used for rendering the diagram size legend.
-.. versionadded:: 2.16
-.. seealso:: setSizeLegendSymbol()
-.. seealso:: sizeLegend()
- :rtype: QgsMarkerSymbol
-%End
-
-    void setSizeLegendSymbol( QgsMarkerSymbol *symbol /Transfer/ );
-%Docstring
- Sets the marker symbol used for rendering the diagram size legend.
- \param symbol marker symbol, ownership is transferred to the renderer.
-.. versionadded:: 2.16
-.. seealso:: sizeLegendSymbol()
-.. seealso:: setSizeLegend()
-%End
-
     void setDataDefinedSizeLegend( QgsDataDefinedSizeLegend *settings /Transfer/ );
 %Docstring
  Configures appearance of legend. Takes ownership of the passed settings objects.

python/gui/symbology-ng/qgsdatadefinedsizelegenddialog.sip

@@ -10,6 +10,7 @@
 
 
 
+
 class QgsDataDefinedSizeLegendDialog : QDialog
 {
 %Docstring
@@ -22,22 +23,12 @@ class QgsDataDefinedSizeLegendDialog : QDialog
 #include "qgsdatadefinedsizelegenddialog.h"
 %End
   public:
-    explicit QgsDataDefinedSizeLegendDialog( const QgsDataDefinedSizeLegend *ddsLegend, QWidget *parent /TransferThis/ = 0 );
+    explicit QgsDataDefinedSizeLegendDialog( const QgsDataDefinedSizeLegend *ddsLegend, const QgsProperty &ddSize, QgsMarkerSymbol *overrideSymbol /Transfer/, QgsMapCanvas *canvas = 0, QWidget *parent /TransferThis/ = 0 );
 %Docstring
-Creates the dialog and initializes the content to what is passed in the legend configuration (may be null)
+when the symbol is given from outside rather than being set inside QgsDataDefinedSizeLegend.
 %End
     ~QgsDataDefinedSizeLegendDialog();
 
-    void setSourceSymbol( QgsMarkerSymbol *symbol /Transfer/ );
-%Docstring
-Use given symbol for preview. Takes ownership of the symbol. It should have data-defined size enabled + size scale transformer attached.
-%End
-
-    void setLegendMapViewData( double mapUnitsPerPixel, int dpi, double scale );
-%Docstring
-Setup map view details to make preview match the expected output
-%End
-
     QgsDataDefinedSizeLegend *dataDefinedSizeLegend() const /Factory/;
 %Docstring
 Returns configuration as set up in the dialog (may be null). Ownership is passed to the caller.

src/app/qgsdiagramproperties.cpp

@@ -190,8 +190,6 @@ QgsDiagramProperties::QgsDiagramProperties( QgsVectorLayer *layer, QWidget *pare
     newItem->setFlags( newItem->flags() & ~Qt::ItemIsDropEnabled );
   }
 
-  mSizeLegendSymbol.reset( QgsMarkerSymbol::createSimple( QgsStringMap() ) );
-
   const QgsDiagramRenderer *dr = layer->diagramRenderer();
   if ( !dr ) //no diagram renderer yet, insert reasonable default
   {
@@ -360,7 +358,6 @@ QgsDiagramProperties::QgsDiagramProperties( QgsVectorLayer *layer, QWidget *pare
           mSizeFieldExpressionWidget->setField( lidr->classificationField() );
         }
 
-        mSizeLegendSymbol.reset( lidr->sizeLegendSymbol() ? lidr->sizeLegendSymbol()->clone() : QgsMarkerSymbol::createSimple( QgsStringMap() ) );
         mSizeLegend.reset( lidr->dataDefinedSizeLegend() ? new QgsDataDefinedSizeLegend( *lidr->dataDefinedSizeLegend() ) : nullptr );
       }
     }
@@ -402,9 +399,6 @@ QgsDiagramProperties::QgsDiagramProperties( QgsVectorLayer *layer, QWidget *pare
     }
   }
 
-  QIcon icon = QgsSymbolLayerUtils::symbolPreviewIcon( mSizeLegendSymbol.get(), mButtonSizeLegendSymbol->iconSize() );
-  mButtonSizeLegendSymbol->setIcon( icon );
-
   connect( mAddAttributeExpression, &QPushButton::clicked, this, &QgsDiagramProperties::showAddAttributeExpressionDialog );
   registerDataDefinedButton( mBackgroundColorDDBtn, QgsDiagramLayerSettings::BackgroundColor );
   registerDataDefinedButton( mLineColorDDBtn, QgsDiagramLayerSettings::StrokeColor );
@@ -818,7 +812,6 @@ void QgsDiagramProperties::apply()
     }
     dr->setDiagramSettings( ds );
 
-    dr->setSizeLegendSymbol( mSizeLegendSymbol->clone() );
     dr->setDataDefinedSizeLegend( mSizeLegend ? new QgsDataDefinedSizeLegend( *mSizeLegend ) : nullptr );
 
     renderer = dr;
@@ -941,52 +934,20 @@ void QgsDiagramProperties::on_mPlacementComboBox_currentIndexChanged( int index
   chkLineOrientationDependent->setEnabled( linePlacementEnabled );
 }
 
-void QgsDiagramProperties::on_mButtonSizeLegendSymbol_clicked()
-{
-  QgsMarkerSymbol *newSymbol = mSizeLegendSymbol->clone();
-  QgsSymbolWidgetContext context;
-  context.setMapCanvas( mMapCanvas );
-  QgsExpressionContext ec = createExpressionContext();
-  context.setExpressionContext( &ec );
-
-  QgsSymbolSelectorDialog d( newSymbol, QgsStyle::defaultStyle(), mLayer, this );
-  d.setContext( context );
-
-  if ( d.exec() == QDialog::Accepted )
-  {
-    mSizeLegendSymbol.reset( newSymbol );
-    QIcon icon = QgsSymbolLayerUtils::symbolPreviewIcon( mSizeLegendSymbol.get(), mButtonSizeLegendSymbol->iconSize() );
-    mButtonSizeLegendSymbol->setIcon( icon );
-  }
-  else
-  {
-    delete newSymbol;
-  }
-}
-
 void QgsDiagramProperties::scalingTypeChanged()
 {
-  mSizeLegendGroupBox->setEnabled( mAttributeBasedScalingRadio->isChecked() );
+  mButtonSizeLegendSettings->setEnabled( mAttributeBasedScalingRadio->isChecked() );
 }
 
 void QgsDiagramProperties::showSizeLegendDialog()
 {
-  QgsDataDefinedSizeLegendDialog dlg( mSizeLegend.get() );
-  QgsMarkerSymbol *symbol = mSizeLegendSymbol->clone();
-
   // prepare size transformer
   bool isExpression;
   QString sizeFieldNameOrExp = mSizeFieldExpressionWidget->currentField( &isExpression );
   QgsProperty ddSize = isExpression ? QgsProperty::fromExpression( sizeFieldNameOrExp ) : QgsProperty::fromField( sizeFieldNameOrExp );
   ddSize.setTransformer( new QgsSizeScaleTransformer( QgsSizeScaleTransformer::Linear, 0.0, mMaxValueSpinBox->value(), 0.0, mSizeSpinBox->value() ) );
-  symbol->setDataDefinedSize( ddSize );
-  dlg.setSourceSymbol( symbol );
-
-  if ( mMapCanvas )
-  {
-    dlg.setLegendMapViewData( mMapCanvas->mapUnitsPerPixel(), mMapCanvas->mapSettings().outputDpi(), mMapCanvas->scale() );
-  }
 
+  QgsDataDefinedSizeLegendDialog dlg( mSizeLegend.get(), ddSize, nullptr, mMapCanvas );
   if ( !dlg.exec() )
     return;
 

src/app/qgsdiagramproperties.h

@@ -52,7 +52,6 @@ class APP_EXPORT QgsDiagramProperties : public QWidget, private Ui::QgsDiagramPr
     void showAddAttributeExpressionDialog();
     void on_mDiagramStackedWidget_currentChanged( int index );
     void on_mPlacementComboBox_currentIndexChanged( int index );
-    void on_mButtonSizeLegendSymbol_clicked();
     void scalingTypeChanged();
     void showSizeLegendDialog();
 
@@ -81,7 +80,6 @@ class APP_EXPORT QgsDiagramProperties : public QWidget, private Ui::QgsDiagramPr
 
     // Keeps track of the diagram type to properly save / restore settings when the diagram type combo box is set to no diagram.
     QString mDiagramType;
-    std::unique_ptr< QgsMarkerSymbol > mSizeLegendSymbol;
     std::unique_ptr< QgsDataDefinedSizeLegend > mSizeLegend;
 
     QString guessLegendText( const QString &expression );

src/core/qgsdatadefinedsizelegend.cpp

@@ -290,18 +290,85 @@ QImage QgsDataDefinedSizeLegend::collapsedLegendImage( QgsRenderContext &context
   return img;
 }
 
-QgsDataDefinedSizeLegend *QgsDataDefinedSizeLegend::readTypeAndAlignmentFromXml( const QDomElement &elem )
+QgsDataDefinedSizeLegend *QgsDataDefinedSizeLegend::readXml( const QDomElement &elem, const QgsReadWriteContext &context )
 {
   if ( elem.isNull() )
     return nullptr;
   QgsDataDefinedSizeLegend *ddsLegend = new QgsDataDefinedSizeLegend;
   ddsLegend->setLegendType( elem.attribute( "type" ) == "collapsed" ? LegendCollapsed : LegendSeparated );
   ddsLegend->setVerticalAlignment( elem.attribute( "valign" ) == "center" ? AlignCenter : AlignBottom );
+  ddsLegend->setTitle( elem.attribute( "title" ) );
+
+  QDomElement elemSymbol = elem.firstChildElement( "symbol" );
+  if ( !elemSymbol.isNull() )
+  {
+    ddsLegend->setSymbol( QgsSymbolLayerUtils::loadSymbol<QgsMarkerSymbol>( elemSymbol, context ) );
+  }
+
+  QDomElement elemTextStyle = elem.firstChildElement( "text-style" );
+  if ( !elemTextStyle.isNull() )
+  {
+    QDomElement elemFont = elemTextStyle.firstChildElement( "font" );
+    if ( !elemFont.isNull() )
+    {
+      ddsLegend->setFont( QFont( elemFont.attribute( "family" ), elemFont.attribute( "size" ).toInt(),
+                                 elemFont.attribute( "weight" ).toInt(), elemFont.attribute( "italic" ).toInt() ) );
+    }
+    ddsLegend->setTextColor( QgsSymbolLayerUtils::decodeColor( elemTextStyle.attribute( "color" ) ) );
+    ddsLegend->setTextAlignment( static_cast<Qt::AlignmentFlag>( elemTextStyle.attribute( "align" ).toInt() ) );
+  }
+
+  QDomElement elemClasses = elem.firstChildElement( "classes" );
+  if ( !elemClasses.isNull() )
+  {
+    QList<SizeClass> classes;
+    QDomElement elemClass = elemClasses.firstChildElement( "class" );
+    while ( !elemClass.isNull() )
+    {
+      classes << SizeClass( elemClass.attribute( "size" ).toDouble(), elemClass.attribute( "label" ) );
+      elemClass = elemClass.nextSiblingElement();
+    }
+    ddsLegend->setClasses( classes );
+  }
+
   return ddsLegend;
 }
 
-void QgsDataDefinedSizeLegend::writeTypeAndAlignmentToXml( const QgsDataDefinedSizeLegend &ddsLegend, QDomElement &elem )
+void QgsDataDefinedSizeLegend::writeXml( QDomElement &elem, const QgsReadWriteContext &context ) const
 {
-  elem.setAttribute( "type", ddsLegend.legendType() == LegendCollapsed ? "collapsed" : "separated" );
+  QDomDocument doc = elem.ownerDocument();
-  elem.setAttribute( "valign", ddsLegend.verticalAlignment() == AlignCenter ? "center" : "bottom" );
+
+  elem.setAttribute( "type", mType == LegendCollapsed ? "collapsed" : "separated" );
+  elem.setAttribute( "valign", mVAlign == AlignCenter ? "center" : "bottom" );
+  elem.setAttribute( "title", mTitleLabel );
+
+  if ( mSymbol )
+  {
+    QgsSymbolLayerUtils::saveSymbol( "source", mSymbol.get(), doc, context );
+  }
+
+  QDomElement elemFont = doc.createElement( "font" );
+  elemFont.setAttribute( "family", mFont.family() );
+  elemFont.setAttribute( "size", mFont.pointSize() );
+  elemFont.setAttribute( "weight", mFont.weight() );
+  elemFont.setAttribute( "italic", mFont.italic() );
+
+  QDomElement elemTextStyle = doc.createElement( "text-style" );
+  elemTextStyle.setAttribute( "color", QgsSymbolLayerUtils::encodeColor( mTextColor ) );
+  elemTextStyle.setAttribute( "align", static_cast<int>( mTextAlignment ) );
+  elemTextStyle.appendChild( elemFont );
+  elem.appendChild( elemTextStyle );
+
+  if ( !mSizeClasses.isEmpty() )
+  {
+    QDomElement elemClasses = doc.createElement( "classes" );
+    Q_FOREACH ( const SizeClass &sc, mSizeClasses )
+    {
+      QDomElement elemClass = doc.createElement( "class" );
+      elemClass.setAttribute( "size", sc.size );
+      elemClass.setAttribute( "label", sc.label );
+      elemClasses.appendChild( elemClass );
+    }
+    elem.appendChild( elemClasses );
+  }
 }

src/core/qgsdatadefinedsizelegend.h

@@ -24,6 +24,7 @@
 class QDomElement;
 class QgsMarkerSymbol;
 class QgsProperty;
+class QgsReadWriteContext;
 class QgsRenderContext;
 
 
@@ -122,14 +123,10 @@ class CORE_EXPORT QgsDataDefinedSizeLegend
     QImage collapsedLegendImage( QgsRenderContext &context, double paddingMM = 1 ) const;
 
     //! Creates instance from given element and returns it (caller takes ownership). Returns null on error.
-    //! \note only reads legend type and vertical alignment of symbols
+    static QgsDataDefinedSizeLegend *readXml( const QDomElement &elem, const QgsReadWriteContext &context ) SIP_FACTORY;
-    //! \note This is a temporary method and may be removed in the future
-    static QgsDataDefinedSizeLegend *readTypeAndAlignmentFromXml( const QDomElement &elem ) SIP_FACTORY;
 
     //! Writes configuration to the given XML element.
-    //! \note only writes legend type and vertical alignment of symbols
+    void writeXml( QDomElement &elem, const QgsReadWriteContext &context ) const;
-    //! \note This is a temporary method and may be removed in the future
-    static void writeTypeAndAlignmentToXml( const QgsDataDefinedSizeLegend &ddsLegend, QDomElement &elem );
 
   private:
     LegendType mType = LegendSeparated;

src/core/qgsdiagramrenderer.cpp

@@ -601,7 +601,6 @@ void QgsSingleCategoryDiagramRenderer::writeXml( QDomElement &layerElem, QDomDoc
 
 QgsLinearlyInterpolatedDiagramRenderer::QgsLinearlyInterpolatedDiagramRenderer()
   : QgsDiagramRenderer()
-  , mSizeLegendSymbol( QgsMarkerSymbol::createSimple( QgsStringMap() ) )
 {
   mInterpolationSettings.classificationAttributeIsExpression = false;
 }
@@ -610,7 +609,6 @@ QgsLinearlyInterpolatedDiagramRenderer::QgsLinearlyInterpolatedDiagramRenderer(
   : QgsDiagramRenderer( other )
   , mSettings( other.mSettings )
   , mInterpolationSettings( other.mInterpolationSettings )
-  , mSizeLegendSymbol( other.mSizeLegendSymbol ? other.mSizeLegendSymbol->clone() : nullptr )
   , mDataDefinedSizeLegend( other.mDataDefinedSizeLegend ? new QgsDataDefinedSizeLegend( *other.mDataDefinedSizeLegend ) : nullptr )
 {
 }
@@ -685,22 +683,27 @@ void QgsLinearlyInterpolatedDiagramRenderer::readXml( const QDomElement &elem, c
     mSettings.readXml( settingsElem );
   }
 
-  QDomElement sizeLegendSymbolElem = elem.firstChildElement( QStringLiteral( "symbol" ) );
-  if ( !sizeLegendSymbolElem.isNull() && sizeLegendSymbolElem.attribute( QStringLiteral( "name" ) ) == QLatin1String( "sizeSymbol" ) )
-  {
-    mSizeLegendSymbol.reset( QgsSymbolLayerUtils::loadSymbol<QgsMarkerSymbol>( sizeLegendSymbolElem, context ) );
-  }
-
   QDomElement ddsLegendSizeElem = elem.firstChildElement( "data-defined-size-legend" );
   if ( !ddsLegendSizeElem.isNull() )
   {
-    mDataDefinedSizeLegend.reset( QgsDataDefinedSizeLegend::readTypeAndAlignmentFromXml( ddsLegendSizeElem ) );
+    mDataDefinedSizeLegend.reset( QgsDataDefinedSizeLegend::readXml( ddsLegendSizeElem, context ) );
   }
   else
   {
     // pre-3.0 projects
-    bool enabled = elem.attribute( QStringLiteral( "sizeLegend" ), QStringLiteral( "0" ) ) != QLatin1String( "0" );
+    if ( elem.attribute( QStringLiteral( "sizeLegend" ), QStringLiteral( "0" ) ) != QLatin1String( "0" ) )
-    mDataDefinedSizeLegend.reset( enabled ? new QgsDataDefinedSizeLegend() : nullptr );
+    {
+      mDataDefinedSizeLegend.reset( new QgsDataDefinedSizeLegend() );
+      QDomElement sizeLegendSymbolElem = elem.firstChildElement( QStringLiteral( "symbol" ) );
+      if ( !sizeLegendSymbolElem.isNull() && sizeLegendSymbolElem.attribute( QStringLiteral( "name" ) ) == QLatin1String( "sizeSymbol" ) )
+      {
+        mDataDefinedSizeLegend->setSymbol( QgsSymbolLayerUtils::loadSymbol<QgsMarkerSymbol>( sizeLegendSymbolElem, context ) );
+      }
+    }
+    else
+    {
+      mDataDefinedSizeLegend.reset( nullptr );
+    }
   }
 
   _readXml( elem, context );
@@ -725,13 +728,10 @@ void QgsLinearlyInterpolatedDiagramRenderer::writeXml( QDomElement &layerElem, Q
   }
   mSettings.writeXml( rendererElem, doc );
 
-  QDomElement sizeLegendSymbolElem = QgsSymbolLayerUtils::saveSymbol( QStringLiteral( "sizeSymbol" ), mSizeLegendSymbol.get(), doc, context );
-  rendererElem.appendChild( sizeLegendSymbolElem );
-
   if ( mDataDefinedSizeLegend )
   {
     QDomElement ddsLegendElem = doc.createElement( QStringLiteral( "data-defined-size-legend" ) );
-    QgsDataDefinedSizeLegend::writeTypeAndAlignmentToXml( *mDataDefinedSizeLegend, ddsLegendElem );
+    mDataDefinedSizeLegend->writeXml( ddsLegendElem, context );
     rendererElem.appendChild( ddsLegendElem );
   }
 
@@ -772,11 +772,10 @@ QList< QgsLayerTreeModelLegendNode * > QgsLinearlyInterpolatedDiagramRenderer::l
   if ( mShowAttributeLegend )
     nodes = mSettings.legendItems( nodeLayer );
 
-  if ( mDataDefinedSizeLegend && mDiagram && mSizeLegendSymbol )
+  if ( mDataDefinedSizeLegend && mDiagram )
   {
     // add size legend
-
+    QgsMarkerSymbol *legendSymbol = mDataDefinedSizeLegend->symbol() ? mDataDefinedSizeLegend->symbol()->clone() : QgsMarkerSymbol::createSimple( QgsStringMap() );
-    QgsMarkerSymbol *legendSymbol = mSizeLegendSymbol.get()->clone();
     legendSymbol->setSizeUnit( mSettings.sizeType );
     legendSymbol->setSizeMapUnitScale( mSettings.sizeScale );
 

src/core/qgsdiagramrenderer.h

@@ -685,21 +685,6 @@ class CORE_EXPORT QgsLinearlyInterpolatedDiagramRenderer : public QgsDiagramRend
 
     QList< QgsLayerTreeModelLegendNode * > legendItems( QgsLayerTreeLayer *nodeLayer ) const override SIP_FACTORY;
 
-    /** Returns the marker symbol used for rendering the diagram size legend.
-     * \since QGIS 2.16
-     * \see setSizeLegendSymbol()
-     * \see sizeLegend()
-     */
-    QgsMarkerSymbol *sizeLegendSymbol() const { return mSizeLegendSymbol.get(); }
-
-    /** Sets the marker symbol used for rendering the diagram size legend.
-     * \param symbol marker symbol, ownership is transferred to the renderer.
-     * \since QGIS 2.16
-     * \see sizeLegendSymbol()
-     * \see setSizeLegend()
-     */
-    void setSizeLegendSymbol( QgsMarkerSymbol *symbol SIP_TRANSFER ) { mSizeLegendSymbol.reset( symbol ); }
-
     /**
      * Configures appearance of legend. Takes ownership of the passed settings objects.
      * \since QGIS 3.0
@@ -723,9 +708,6 @@ class CORE_EXPORT QgsLinearlyInterpolatedDiagramRenderer : public QgsDiagramRend
     QgsDiagramSettings mSettings;
     QgsDiagramInterpolationSettings mInterpolationSettings;
 
-    //! Marker symbol to use in size legends
-    std::unique_ptr< QgsMarkerSymbol > mSizeLegendSymbol;
-
     //! Stores more settings about how legend for varying size of symbols should be rendered
     std::unique_ptr<QgsDataDefinedSizeLegend> mDataDefinedSizeLegend;
 };

src/core/symbology-ng/qgscategorizedsymbolrenderer.cpp

@@ -662,7 +662,7 @@ QgsFeatureRenderer *QgsCategorizedSymbolRenderer::create( QDomElement &element,
   QDomElement ddsLegendSizeElem = element.firstChildElement( "data-defined-size-legend" );
   if ( !ddsLegendSizeElem.isNull() )
   {
-    r->mDataDefinedSizeLegend.reset( QgsDataDefinedSizeLegend::readTypeAndAlignmentFromXml( ddsLegendSizeElem ) );
+    r->mDataDefinedSizeLegend.reset( QgsDataDefinedSizeLegend::readXml( ddsLegendSizeElem, context ) );
   }
 
   // TODO: symbol levels
@@ -742,7 +742,7 @@ QDomElement QgsCategorizedSymbolRenderer::save( QDomDocument &doc, const QgsRead
   if ( mDataDefinedSizeLegend )
   {
     QDomElement ddsLegendElem = doc.createElement( QStringLiteral( "data-defined-size-legend" ) );
-    QgsDataDefinedSizeLegend::writeTypeAndAlignmentToXml( *mDataDefinedSizeLegend, ddsLegendElem );
+    mDataDefinedSizeLegend->writeXml( ddsLegendElem, context );
     rendererElem.appendChild( ddsLegendElem );
   }
 

src/core/symbology-ng/qgsgraduatedsymbolrenderer.cpp

@@ -1043,7 +1043,7 @@ QgsFeatureRenderer *QgsGraduatedSymbolRenderer::create( QDomElement &element, co
   QDomElement ddsLegendSizeElem = element.firstChildElement( "data-defined-size-legend" );
   if ( !ddsLegendSizeElem.isNull() )
   {
-    r->mDataDefinedSizeLegend.reset( QgsDataDefinedSizeLegend::readTypeAndAlignmentFromXml( ddsLegendSizeElem ) );
+    r->mDataDefinedSizeLegend.reset( QgsDataDefinedSizeLegend::readXml( ddsLegendSizeElem, context ) );
   }
 
   // TODO: symbol levels
@@ -1145,7 +1145,7 @@ QDomElement QgsGraduatedSymbolRenderer::save( QDomDocument &doc, const QgsReadWr
   if ( mDataDefinedSizeLegend )
   {
     QDomElement ddsLegendElem = doc.createElement( QStringLiteral( "data-defined-size-legend" ) );
-    QgsDataDefinedSizeLegend::writeTypeAndAlignmentToXml( *mDataDefinedSizeLegend, ddsLegendElem );
+    mDataDefinedSizeLegend->writeXml( ddsLegendElem, context );
     rendererElem.appendChild( ddsLegendElem );
   }
 

src/core/symbology-ng/qgssinglesymbolrenderer.cpp

@@ -163,7 +163,7 @@ QgsFeatureRenderer *QgsSingleSymbolRenderer::create( QDomElement &element, const
   QDomElement ddsLegendSizeElem = element.firstChildElement( "data-defined-size-legend" );
   if ( !ddsLegendSizeElem.isNull() )
   {
-    r->mDataDefinedSizeLegend.reset( QgsDataDefinedSizeLegend::readTypeAndAlignmentFromXml( ddsLegendSizeElem ) );
+    r->mDataDefinedSizeLegend.reset( QgsDataDefinedSizeLegend::readXml( ddsLegendSizeElem, context ) );
   }
 
   // TODO: symbol levels
@@ -290,7 +290,7 @@ QDomElement QgsSingleSymbolRenderer::save( QDomDocument &doc, const QgsReadWrite
   if ( mDataDefinedSizeLegend )
   {
     QDomElement ddsLegendElem = doc.createElement( QStringLiteral( "data-defined-size-legend" ) );
-    QgsDataDefinedSizeLegend::writeTypeAndAlignmentToXml( *mDataDefinedSizeLegend, ddsLegendElem );
+    mDataDefinedSizeLegend->writeXml( ddsLegendElem, context );
     rendererElem.appendChild( ddsLegendElem );
   }
 

src/gui/symbology-ng/qgsdatadefinedsizelegenddialog.cpp

@@ -18,16 +18,23 @@
 #include "qgsdatadefinedsizelegend.h"
 #include "qgslayertree.h"
 #include "qgslayertreemodel.h"
+#include "qgsmapcanvas.h"
 #include "qgssinglesymbolrenderer.h"
+#include "qgsstyle.h"
 #include "qgssymbol.h"
 #include "qgssymbollayer.h"
+#include "qgssymbolselectordialog.h"
 #include "qgsvectorlayer.h"
 
-QgsDataDefinedSizeLegendDialog::QgsDataDefinedSizeLegendDialog( const QgsDataDefinedSizeLegend *ddsLegend, QWidget *parent )
+QgsDataDefinedSizeLegendDialog::QgsDataDefinedSizeLegendDialog( const QgsDataDefinedSizeLegend *ddsLegend, const QgsProperty &ddSize, QgsMarkerSymbol *overrideSymbol, QgsMapCanvas *canvas, QWidget *parent )
   : QDialog( parent )
+  , mSizeProperty( ddSize )
+  , mMapCanvas( canvas )
 {
   setupUi( this );
 
+  QgsMarkerSymbol *symbol = nullptr;
+
   if ( !ddsLegend )
   {
     radDisabled->setChecked( true );
@@ -43,25 +50,41 @@ QgsDataDefinedSizeLegendDialog::QgsDataDefinedSizeLegendDialog( const QgsDataDef
       cboAlignSymbols->setCurrentIndex( 0 );
     else
       cboAlignSymbols->setCurrentIndex( 1 );
+
+    symbol = ddsLegend->symbol();  // may be null (undefined)
   }
 
-  // prepare default source symbol - it should be hopefully replaced in setSourceSymbol() later
+  if ( overrideSymbol )
-  mSourceSymbol.reset( static_cast<QgsMarkerSymbol *>( QgsSymbol::defaultSymbol( QgsWkbTypes::PointGeometry ) ) );
+  {
-  QgsProperty property = QgsProperty::fromValue( 1 );
+    symbol = overrideSymbol;   // takes ownership
-  property.setTransformer( new QgsSizeScaleTransformer( QgsSizeScaleTransformer::Linear, 0, 1, 0, 20 ) );
+    mOverrideSymbol = true;
-  mSourceSymbol->setDataDefinedSize( property );
+  }
+
+  if ( !symbol )
+  {
+    symbol = QgsMarkerSymbol::createSimple( QgsStringMap() );
+  }
+  mSourceSymbol.reset( symbol );
+
+  btnChangeSymbol->setEnabled( !mOverrideSymbol );
+
+  QIcon icon = QgsSymbolLayerUtils::symbolPreviewIcon( mSourceSymbol.get(), btnChangeSymbol->iconSize() );
+  btnChangeSymbol->setIcon( icon );
 
   // prepare layer and model to preview legend
   mPreviewLayer = new QgsVectorLayer( "Point?crs=EPSG:4326", "Preview", "memory" );
   mPreviewTree = new QgsLayerTree;
   mPreviewLayerNode = mPreviewTree->addLayer( mPreviewLayer );  // node owned by the tree
   mPreviewModel = new QgsLayerTreeModel( mPreviewTree );
+  if ( canvas )
+    mPreviewModel->setLegendMapViewData( canvas->mapUnitsPerPixel(), canvas->mapSettings().outputDpi(), canvas->scale() );
   viewLayerTree->setModel( mPreviewModel );
 
   connect( cboAlignSymbols, static_cast<void ( QComboBox::* )( int )>( &QComboBox::currentIndexChanged ), [ = ] { updatePreview(); } );
   connect( radDisabled, &QRadioButton::clicked, this, &QgsDataDefinedSizeLegendDialog::updatePreview );
   connect( radSeparated, &QRadioButton::clicked, this, &QgsDataDefinedSizeLegendDialog::updatePreview );
   connect( radCollapsed, &QRadioButton::clicked, this, &QgsDataDefinedSizeLegendDialog::updatePreview );
+  connect( btnChangeSymbol, &QPushButton::clicked, this, &QgsDataDefinedSizeLegendDialog::changeSymbol );
   updatePreview();
 }
 
@@ -72,18 +95,6 @@ QgsDataDefinedSizeLegendDialog::~QgsDataDefinedSizeLegendDialog()
   delete mPreviewLayer;
 }
 
-void QgsDataDefinedSizeLegendDialog::setSourceSymbol( QgsMarkerSymbol *symbol )
-{
-  mSourceSymbol.reset( symbol );
-  updatePreview();
-}
-
-void QgsDataDefinedSizeLegendDialog::setLegendMapViewData( double mapUnitsPerPixel, int dpi, double scale )
-{
-  mPreviewModel->setLegendMapViewData( mapUnitsPerPixel, dpi, scale );
-  updatePreview();
-}
-
 QgsDataDefinedSizeLegend *QgsDataDefinedSizeLegendDialog::dataDefinedSizeLegend() const
 {
   if ( radDisabled->isChecked() )
@@ -92,14 +103,50 @@ QgsDataDefinedSizeLegend *QgsDataDefinedSizeLegendDialog::dataDefinedSizeLegend(
   QgsDataDefinedSizeLegend *ddsLegend = new QgsDataDefinedSizeLegend;
   ddsLegend->setLegendType( radSeparated->isChecked() ? QgsDataDefinedSizeLegend::LegendSeparated : QgsDataDefinedSizeLegend::LegendCollapsed );
   ddsLegend->setVerticalAlignment( cboAlignSymbols->currentIndex() == 0 ? QgsDataDefinedSizeLegend::AlignBottom : QgsDataDefinedSizeLegend::AlignCenter );
+  if ( !mOverrideSymbol )
+  {
+    ddsLegend->setSymbol( mSourceSymbol->clone() );
+  }
   return ddsLegend;
 }
 
 void QgsDataDefinedSizeLegendDialog::updatePreview()
 {
-  QgsSingleSymbolRenderer *r = new QgsSingleSymbolRenderer( mSourceSymbol->clone() );
+  QgsMarkerSymbol *symbol = mSourceSymbol->clone();
+  symbol->setDataDefinedSize( mSizeProperty );
+  QgsSingleSymbolRenderer *r = new QgsSingleSymbolRenderer( symbol );
   r->setDataDefinedSizeLegend( dataDefinedSizeLegend() );
   mPreviewLayer->setRenderer( r );
   mPreviewModel->refreshLayerLegend( mPreviewLayerNode );
   viewLayerTree->expandAll();
 }
+
+void QgsDataDefinedSizeLegendDialog::changeSymbol()
+{
+  std::unique_ptr<QgsMarkerSymbol> newSymbol( mSourceSymbol->clone() );
+  QgsSymbolWidgetContext context;
+  if ( mMapCanvas )
+    context.setMapCanvas( mMapCanvas );
+
+  QgsExpressionContext ec;
+  ec << QgsExpressionContextUtils::globalScope()
+     << QgsExpressionContextUtils::projectScope( QgsProject::instance() )
+     << QgsExpressionContextUtils::atlasScope( nullptr );
+  if ( mMapCanvas )
+    ec << QgsExpressionContextUtils::mapSettingsScope( mMapCanvas->mapSettings() );
+  context.setExpressionContext( &ec );
+
+  std::unique_ptr<QgsVectorLayer> layer( new QgsVectorLayer( "Point", "tmp", "memory" ) );
+
+  QgsSymbolSelectorDialog d( newSymbol.get(), QgsStyle::defaultStyle(), layer.get(), this );
+  d.setContext( context );
+
+  if ( d.exec() != QDialog::Accepted )
+    return;
+
+  mSourceSymbol.reset( newSymbol.release() );
+  QIcon icon = QgsSymbolLayerUtils::symbolPreviewIcon( mSourceSymbol.get(), btnChangeSymbol->iconSize() );
+  btnChangeSymbol->setIcon( icon );
+
+  updatePreview();
+}

src/gui/symbology-ng/qgsdatadefinedsizelegenddialog.h

@@ -23,11 +23,15 @@
 #include <QDialog>
 #include <ui_qgsdatadefinedsizelegenddialog.h>
 
+#include "qgsproperty.h"
+
 class QgsDataDefinedSizeLegend;
 class QgsLayerTree;
 class QgsLayerTreeLayer;
 class QgsLayerTreeModel;
+class QgsMapCanvas;
 class QgsMarkerSymbol;
+class QgsProperty;
 class QgsVectorLayer;
 
 /** \ingroup gui
@@ -39,16 +43,13 @@ class GUI_EXPORT QgsDataDefinedSizeLegendDialog : public QDialog, private Ui::Qg
 {
     Q_OBJECT
   public:
-    //! Creates the dialog and initializes the content to what is passed in the legend configuration (may be null)
+    //! Creates the dialog and initializes the content to what is passed in the legend configuration (may be null).
-    explicit QgsDataDefinedSizeLegendDialog( const QgsDataDefinedSizeLegend *ddsLegend, QWidget *parent SIP_TRANSFERTHIS = nullptr );
+    //! The ddSize argument determines scaling of the marker symbol - it should have a size scale transformer assigned
+    //! to know the range of sizes. The overrideSymbol argument may override the source symbol: this is useful in case
+    //! when the symbol is given from outside rather than being set inside QgsDataDefinedSizeLegend.
+    explicit QgsDataDefinedSizeLegendDialog( const QgsDataDefinedSizeLegend *ddsLegend, const QgsProperty &ddSize, QgsMarkerSymbol *overrideSymbol SIP_TRANSFER, QgsMapCanvas *canvas = nullptr, QWidget *parent SIP_TRANSFERTHIS = nullptr );
     ~QgsDataDefinedSizeLegendDialog();
 
-    //! Use given symbol for preview. Takes ownership of the symbol. It should have data-defined size enabled + size scale transformer attached.
-    void setSourceSymbol( QgsMarkerSymbol *symbol SIP_TRANSFER );
-
-    //! Setup map view details to make preview match the expected output
-    void setLegendMapViewData( double mapUnitsPerPixel, int dpi, double scale );
-
     //! Returns configuration as set up in the dialog (may be null). Ownership is passed to the caller.
     QgsDataDefinedSizeLegend *dataDefinedSizeLegend() const SIP_FACTORY;
 
@@ -56,13 +57,17 @@ class GUI_EXPORT QgsDataDefinedSizeLegendDialog : public QDialog, private Ui::Qg
 
   private slots:
     void updatePreview();
+    void changeSymbol();
 
   private:
-    std::unique_ptr<QgsMarkerSymbol> mSourceSymbol;
+    std::unique_ptr<QgsMarkerSymbol> mSourceSymbol;   //!< Source symbol (without data-defined size set)
+    bool mOverrideSymbol = false;  //!< If true, symbol should not be editable because it will be overridden
+    QgsProperty mSizeProperty;    //!< Definition of data-defined size of symbol (should have a size scale transformer associated)
     QgsLayerTreeModel *mPreviewModel;
     QgsLayerTree *mPreviewTree;
     QgsLayerTreeLayer *mPreviewLayerNode;
     QgsVectorLayer *mPreviewLayer;
+    QgsMapCanvas *mMapCanvas = nullptr;
 };
 
 #endif // QGSDATADEFINEDSIZELEGENDDIALOG_H

src/gui/symbology-ng/qgsrendererwidget.cpp

@@ -291,13 +291,7 @@ QgsDataDefinedSizeLegend *QgsRendererWidget::showDataDefinedSizeLegendDialog( co
     return nullptr;
   }
 
-  QgsDataDefinedSizeLegendDialog dlg( ddsLegend );
+  QgsDataDefinedSizeLegendDialog dlg( ddsLegend, ddSize, symbol->clone(), mContext.mapCanvas() );
-  dlg.setSourceSymbol( symbol->clone() );
-  if ( QgsMapCanvas *canvas = mContext.mapCanvas() )
-  {
-    dlg.setLegendMapViewData( canvas->mapUnitsPerPixel(), canvas->mapSettings().outputDpi(), canvas->scale() );
-  }
-
   if ( !dlg.exec() )
     return nullptr;
 

src/ui/qgsdatadefinedsizelegenddialog.ui

@@ -7,7 +7,7 @@
     <x>0</x>
     <y>0</y>
     <width>674</width>
-    <height>393</height>
+    <height>492</height>
    </rect>
   </property>
   <property name="windowTitle">
@@ -40,6 +40,13 @@
        </property>
       </widget>
      </item>
+     <item>
+      <widget class="QPushButton" name="btnChangeSymbol">
+       <property name="text">
+        <string>Legend symbol...</string>
+       </property>
+      </widget>
+     </item>
      <item>
       <widget class="QGroupBox" name="groupBox">
        <property name="title">

src/ui/qgsdiagrampropertiesbase.ui

@@ -2066,40 +2066,28 @@
                    </widget>
                   </item>
                   <item>
-                   <widget class="QgsCollapsibleGroupBox" name="mSizeLegendGroupBox">
+                   <layout class="QHBoxLayout" name="horizontalLayout_5">
-                    <property name="title">
+                    <item>
-                     <string>Legend entries for diagram size</string>
+                     <widget class="QPushButton" name="mButtonSizeLegendSettings">
-                    </property>
+                      <property name="text">
-                    <layout class="QHBoxLayout" name="horizontalLayout_71">
+                       <string>Legend entries for diagram size...</string>
-                     <item>
+                      </property>
-                      <widget class="QPushButton" name="mButtonSizeLegendSettings">
+                     </widget>
-                       <property name="text">
+                    </item>
-                        <string>Legend settings...</string>
+                    <item>
-                       </property>
+                     <spacer name="horizontalSpacer_111">
-                      </widget>
+                      <property name="orientation">
-                     </item>
+                       <enum>Qt::Horizontal</enum>
-                     <item>
+                      </property>
-                      <widget class="QPushButton" name="mButtonSizeLegendSymbol">
+                      <property name="sizeHint" stdset="0">
-                       <property name="text">
+                       <size>
-                        <string>Legend symbol...</string>
+                        <width>40</width>
-                       </property>
+                        <height>20</height>
-                      </widget>
+                       </size>
-                     </item>
+                      </property>
-                     <item>
+                     </spacer>
-                      <spacer name="horizontalSpacer_111">
+                    </item>
-                       <property name="orientation">
+                   </layout>
-                        <enum>Qt::Horizontal</enum>
-                       </property>
-                       <property name="sizeHint" stdset="0">
-                        <size>
-                         <width>40</width>
-                         <height>20</height>
-                        </size>
-                       </property>
-                      </spacer>
-                     </item>
-                    </layout>
-                   </widget>
                   </item>
                   <item>
                    <spacer name="verticalSpacer_7">
@@ -2236,8 +2224,6 @@
   <tabstop>mOrientationLeftButton</tabstop>
   <tabstop>scrollArea_2</tabstop>
   <tabstop>mCheckBoxAttributeLegend</tabstop>
-  <tabstop>mSizeLegendGroupBox</tabstop>
-  <tabstop>mButtonSizeLegendSymbol</tabstop>
   <tabstop>mBackgroundColorDDBtn</tabstop>
   <tabstop>mLineColorDDBtn</tabstop>
   <tabstop>mDiagramLineUnitComboBox</tabstop>