Added GUI for data-defined size legend (single/categorized/graduated renderer)

doc/api_break.dox

@@ -2110,6 +2110,7 @@ QgsSingleSymbolRendererWidget        {#qgis_api_break_3_0_QgsSingleSymbolRendere
 
 - sizeScaleFieldChanged() and scaleMethodChanged() were removed. These settings are no longer exposed in the widget's GUI.
 - The Mode enum was removed.
+- changeSingleSymbol() and showSymbolLevels() slots were made private.
 
 QgsSlider        {#qgis_api_break_3_0_QgsSlider}
 ---------

python/core/qgsdatadefinedsizelegend.sip

@@ -0,0 +1,178 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsdatadefinedsizelegend.h                                  *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+
+
+class QgsDataDefinedSizeLegend
+{
+%Docstring
+ Object that keeps configuration of appearance of marker symbol's data-defined size in legend.
+ For example: the list of classes (size values), whether the classes should appear in separate
+ legend nodes or whether to collapse them into one legend node.
+
+.. versionadded:: 3.0
+%End
+
+%TypeHeaderCode
+#include "qgsdatadefinedsizelegend.h"
+%End
+  public:
+    QgsDataDefinedSizeLegend();
+
+    QgsDataDefinedSizeLegend( const QgsDataDefinedSizeLegend &other );
+
+    enum LegendType
+    {
+      LegendSeparated,
+      LegendCollapsed,
+    };
+
+    enum VerticalAlignment
+    {
+      AlignCenter,
+      AlignBottom,
+    };
+
+    struct SizeClass
+    {
+      SizeClass( double size, const QString &label );
+
+      double size;    //!< Marker size in units used by the symbol (usually millimeters)
+      QString label;  //!< Label to be shown with the particular symbol size
+    };
+
+    void setLegendType( LegendType type );
+%Docstring
+Sets how the legend should be rendered
+%End
+    LegendType legendType() const;
+%Docstring
+Returns how the legend should be rendered
+ :rtype: LegendType
+%End
+
+    void setSymbol( QgsMarkerSymbol *symbol /Transfer/ );
+%Docstring
+Sets marker symbol that will be used to draw markers in legend
+%End
+    QgsMarkerSymbol *symbol() const;
+%Docstring
+Returns marker symbol that will be used to draw markers in legend
+ :rtype: QgsMarkerSymbol
+%End
+
+    void setClasses( const QList<QgsDataDefinedSizeLegend::SizeClass> &classes );
+%Docstring
+Sets list of classes: each class is a pair of symbol size (in units used by the symbol) and label
+%End
+    QList<QgsDataDefinedSizeLegend::SizeClass> classes() const;
+%Docstring
+Returns list of classes: each class is a pair of symbol size (in units used by the symbol) and label
+ :rtype: list of QgsDataDefinedSizeLegend.SizeClass
+%End
+
+    void setTitle( const QString &title );
+%Docstring
+Sets title label for data-defined size legend
+%End
+    QString title() const;
+%Docstring
+Returns title label for data-defined size legend
+ :rtype: str
+%End
+
+    void setVerticalAlignment( VerticalAlignment vAlign );
+%Docstring
+Sets vertical alignment of symbols - only valid for collapsed legend
+%End
+    VerticalAlignment verticalAlignment() const;
+%Docstring
+Returns vertical alignment of symbols - only valid for collapsed legend
+ :rtype: VerticalAlignment
+%End
+
+    void setFont( const QFont &font );
+%Docstring
+Sets font used for rendering of labels - only valid for collapsed legend
+%End
+    QFont font() const;
+%Docstring
+Returns font used for rendering of labels - only valid for collapsed legend
+ :rtype: QFont
+%End
+
+    void setTextColor( const QColor &color );
+%Docstring
+Sets text color for rendering of labels - only valid for collapsed legend
+%End
+    QColor textColor() const;
+%Docstring
+Returns text color for rendering of labels - only valid for collapsed legend
+ :rtype: QColor
+%End
+
+    void setTextAlignment( Qt::AlignmentFlag flag );
+%Docstring
+Sets horizontal text alignment for rendering of labels - only valid for collapsed legend
+%End
+    Qt::AlignmentFlag textAlignment() const;
+%Docstring
+Returns horizontal text alignment for rendering of labels - only valid for collapsed legend
+ :rtype: Qt.AlignmentFlag
+%End
+
+
+    void updateFromSymbolAndProperty( const QgsMarkerSymbol *symbol, const QgsProperty &ddSize );
+%Docstring
+Updates the list of classes, source symbol and title label from given symbol and property
+%End
+
+    QgsLegendSymbolList legendSymbolList() const;
+%Docstring
+Generates legend symbol items according to the configuration
+ :rtype: QgsLegendSymbolList
+%End
+
+    void drawCollapsedLegend( QgsRenderContext &context, QSize *outputSize /Out/ = 0, int *labelXOffset /Out/ = 0 ) const;
+%Docstring
+Does nothing if legend is not configured as collapsed.
+%End
+
+    QImage collapsedLegendImage( QgsRenderContext &context, double paddingMM = 1 ) const;
+%Docstring
+Returns output image that would be shown in the legend. Returns invalid image if legend is not configured as collapsed.
+ :rtype: QImage
+%End
+
+    static QgsDataDefinedSizeLegend *readTypeAndAlignmentFromXml( const QDomElement &elem ) /Factory/;
+%Docstring
+.. note::
+
+   This is a temporary method and may be removed in the future
+ :rtype: QgsDataDefinedSizeLegend
+%End
+
+    static void writeTypeAndAlignmentToXml( const QgsDataDefinedSizeLegend &ddsLegend, QDomElement &elem );
+%Docstring
+.. note::
+
+   This is a temporary method and may be removed in the future
+%End
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsdatadefinedsizelegend.h                                  *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/gui/gui.sip

@@ -239,6 +239,7 @@
 %Include symbology-ng/qgscategorizedsymbolrendererwidget.sip
 %Include symbology-ng/qgscptcitycolorrampdialog.sip
 %Include symbology-ng/qgsdashspacedialog.sip
+%Include symbology-ng/qgsdatadefinedsizelegenddialog.sip
 %Include symbology-ng/qgsellipsesymbollayerwidget.sip
 %Include symbology-ng/qgsgraduatedhistogramwidget.sip
 %Include symbology-ng/qgsgraduatedsymbolrendererwidget.sip

python/gui/symbology-ng/qgsdatadefinedsizelegenddialog.sip

@@ -0,0 +1,57 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/gui/symbology-ng/qgsdatadefinedsizelegenddialog.h                *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+
+class QgsDataDefinedSizeLegendDialog : QDialog
+{
+%Docstring
+ Dialog for configuration of appearance of legend for marker symbols with data-defined size.
+
+.. versionadded:: 3.0
+%End
+
+%TypeHeaderCode
+#include "qgsdatadefinedsizelegenddialog.h"
+%End
+  public:
+    explicit QgsDataDefinedSizeLegendDialog( const QgsDataDefinedSizeLegend *ddsLegend, QWidget *parent /TransferThis/ = 0 );
+%Docstring
+Creates the dialog and initializes the content to what is passed in the legend configuration (may be null)
+%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.
+ :rtype: QgsDataDefinedSizeLegend
+%End
+
+  signals:
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/gui/symbology-ng/qgsdatadefinedsizelegenddialog.h                *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/gui/symbology-ng/qgsrendererwidget.sip

@@ -86,6 +86,12 @@ and by connecting the slot contextMenuViewCategories(const QPoint&)*
 %End
     virtual void refreshSymbolView();
 
+    QgsDataDefinedSizeLegend *showDataDefinedSizeLegendDialog( const QgsMarkerSymbol *symbol, const QgsDataDefinedSizeLegend *ddsLegend, bool *ok /Out/ ) /Factory/;
+%Docstring
+.. versionadded:: 3.0
+ :rtype: QgsDataDefinedSizeLegend
+%End
+
   protected slots:
     void  contextMenuViewCategories( QPoint p );
     void changeSymbolColor();

python/gui/symbology-ng/qgssinglesymbolrendererwidget.sip

@@ -35,13 +35,6 @@ class QgsSingleSymbolRendererWidget : QgsRendererWidget
  \param dockMode True to enable dock mode.
 %End
 
-  public slots:
-    void changeSingleSymbol();
-
-    void showSymbolLevels();
-
-  protected:
-
 };
 
 

src/core/layertree/qgslayertreemodellegendnode.cpp

@@ -785,6 +785,11 @@ void QgsDataDefinedSizeLegendNode::cacheImage() const
   if ( mImage.isNull() )
   {
     std::unique_ptr<QgsRenderContext> context( createTemporaryRenderContext() );
+    if ( !context )
+    {
+      context.reset( new QgsRenderContext );
+      context->setScaleFactor( 96 / 25.4 );
+    }
     mImage = mSettings->collapsedLegendImage( *context.get() );
   }
 }

src/core/qgsdatadefinedsizelegend.cpp

@@ -28,6 +28,10 @@ QgsDataDefinedSizeLegend::QgsDataDefinedSizeLegend( const QgsDataDefinedSizeLege
   , mTitleLabel( other.mTitleLabel )
   , mSizeClasses( other.mSizeClasses )
   , mSymbol( other.mSymbol.get() ? other.mSymbol->clone() : nullptr )
+  , mVAlign( other.mVAlign )
+  , mFont( other.mFont )
+  , mTextColor( other.mTextColor )
+  , mTextAlignment( other.mTextAlignment )
 {
 }
 
@@ -39,10 +43,24 @@ QgsDataDefinedSizeLegend &QgsDataDefinedSizeLegend::operator=( const QgsDataDefi
     mTitleLabel = other.mTitleLabel;
     mSizeClasses = other.mSizeClasses;
     mSymbol.reset( other.mSymbol.get() ? other.mSymbol->clone() : nullptr );
+    mVAlign = other.mVAlign;
+    mFont = other.mFont;
+    mTextColor = other.mTextColor;
+    mTextAlignment = other.mTextAlignment;
   }
   return *this;
 }
 
+void QgsDataDefinedSizeLegend::setSymbol( QgsMarkerSymbol *symbol )
+{
+  mSymbol.reset( symbol );
+}
+
+QgsMarkerSymbol *QgsDataDefinedSizeLegend::symbol() const
+{
+  return mSymbol.get();
+}
+
 
 void QgsDataDefinedSizeLegend::updateFromSymbolAndProperty( const QgsMarkerSymbol *symbol, const QgsProperty &ddSize )
 {

src/core/qgsdatadefinedsizelegend.h

@@ -1,5 +1,5 @@
 /***************************************************************************
-  qgsdatadefinedsizelegend.cpp
+  qgsdatadefinedsizelegend.h
   --------------------------------------
   Date                 : June 2017
   Copyright            : (C) 2017 by Martin Dobias
@@ -71,9 +71,9 @@ class CORE_EXPORT QgsDataDefinedSizeLegend
     LegendType legendType() const { return mType; }
 
     //! Sets marker symbol that will be used to draw markers in legend
-    void setSymbol( QgsMarkerSymbol *symbol SIP_TRANSFER ) { mSymbol.reset( symbol ); }
+    void setSymbol( QgsMarkerSymbol *symbol SIP_TRANSFER );
     //! Returns marker symbol that will be used to draw markers in legend
-    QgsMarkerSymbol *symbol() const { return mSymbol.get(); }
+    QgsMarkerSymbol *symbol() const;
 
     //! Sets list of classes: each class is a pair of symbol size (in units used by the symbol) and label
     void setClasses( const QList<QgsDataDefinedSizeLegend::SizeClass> &classes ) { mSizeClasses = classes; }

src/core/symbology-ng/qgscategorizedsymbolrenderer.cpp

@@ -471,6 +471,7 @@ QgsCategorizedSymbolRenderer *QgsCategorizedSymbolRenderer::clone() const
     r->setSourceColorRamp( mSourceColorRamp->clone() );
   }
   r->setUsingSymbolLevels( usingSymbolLevels() );
+  r->setDataDefinedSizeLegend( mDataDefinedSizeLegend ? new QgsDataDefinedSizeLegend( *mDataDefinedSizeLegend ) : nullptr );
 
   copyRendererData( r );
   return r;

src/core/symbology-ng/qgsgraduatedsymbolrenderer.cpp

@@ -504,6 +504,7 @@ QgsGraduatedSymbolRenderer *QgsGraduatedSymbolRenderer::clone() const
     r->setSourceColorRamp( mSourceColorRamp->clone() );
   }
   r->setUsingSymbolLevels( usingSymbolLevels() );
+  r->setDataDefinedSizeLegend( mDataDefinedSizeLegend ? new QgsDataDefinedSizeLegend( *mDataDefinedSizeLegend ) : nullptr );
   r->setLabelFormat( labelFormat() );
   r->setGraduatedMethod( graduatedMethod() );
   copyRendererData( r );

src/core/symbology-ng/qgssinglesymbolrenderer.cpp

@@ -100,6 +100,7 @@ QgsSingleSymbolRenderer *QgsSingleSymbolRenderer::clone() const
 {
   QgsSingleSymbolRenderer *r = new QgsSingleSymbolRenderer( mSymbol->clone() );
   r->setUsingSymbolLevels( usingSymbolLevels() );
+  r->setDataDefinedSizeLegend( mDataDefinedSizeLegend ? new QgsDataDefinedSizeLegend( *mDataDefinedSizeLegend ) : nullptr );
   copyRendererData( r );
   return r;
 }
@@ -298,7 +299,6 @@ QDomElement QgsSingleSymbolRenderer::save( QDomDocument &doc, const QgsReadWrite
 
 QgsLegendSymbolList QgsSingleSymbolRenderer::legendSymbolItems() const
 {
-  QgsLegendSymbolList lst;
   if ( mDataDefinedSizeLegend && mSymbol->type() == QgsSymbol::Marker )
   {
     const QgsMarkerSymbol *symbol = static_cast<const QgsMarkerSymbol *>( mSymbol.get() );
@@ -307,10 +307,11 @@ QgsLegendSymbolList QgsSingleSymbolRenderer::legendSymbolItems() const
     {
       QgsDataDefinedSizeLegend ddSizeLegend( *mDataDefinedSizeLegend );
       ddSizeLegend.updateFromSymbolAndProperty( static_cast<const QgsMarkerSymbol *>( mSymbol.get() ), sizeDD );
-      lst += ddSizeLegend.legendSymbolList();
+      return ddSizeLegend.legendSymbolList();
     }
   }
 
+  QgsLegendSymbolList lst;
   lst << QgsLegendSymbolItem( mSymbol.get(), QString(), QString() );
   return lst;
 }

src/gui/CMakeLists.txt

@@ -18,6 +18,7 @@ SET(QGIS_GUI_SRCS
   symbology-ng/qgscategorizedsymbolrendererwidget.cpp
   symbology-ng/qgscptcitycolorrampdialog.cpp
   symbology-ng/qgsdashspacedialog.cpp
+  symbology-ng/qgsdatadefinedsizelegenddialog.cpp
   symbology-ng/qgsellipsesymbollayerwidget.cpp
   symbology-ng/qgsgraduatedhistogramwidget.cpp
   symbology-ng/qgsgraduatedsymbolrendererwidget.cpp
@@ -493,6 +494,7 @@ SET(QGIS_GUI_MOC_HDRS
   symbology-ng/qgscategorizedsymbolrendererwidget.h
   symbology-ng/qgscptcitycolorrampdialog.h
   symbology-ng/qgsdashspacedialog.h
+  symbology-ng/qgsdatadefinedsizelegenddialog.h
   symbology-ng/qgsellipsesymbollayerwidget.h
   symbology-ng/qgsgraduatedhistogramwidget.h
   symbology-ng/qgsgraduatedsymbolrendererwidget.h

src/gui/symbology-ng/qgscategorizedsymbolrendererwidget.cpp

@@ -18,6 +18,7 @@
 
 #include "qgscategorizedsymbolrenderer.h"
 
+#include "qgsdatadefinedsizelegend.h"
 #include "qgssymbol.h"
 #include "qgssymbollayerutils.h"
 #include "qgscolorramp.h"
@@ -464,6 +465,8 @@ QgsCategorizedSymbolRendererWidget::QgsCategorizedSymbolRendererWidget( QgsVecto
   advMenu->addAction( tr( "Match to saved symbols" ), this, SLOT( matchToSymbolsFromLibrary() ) );
   advMenu->addAction( tr( "Match to symbols from file..." ), this, SLOT( matchToSymbolsFromXml() ) );
   advMenu->addAction( tr( "Symbol levels..." ), this, SLOT( showSymbolLevels() ) );
+  if ( mCategorizedSymbol->type() == QgsSymbol::Marker )
+    advMenu->addAction( tr( "Data-defined size legend..." ), this, &QgsCategorizedSymbolRendererWidget::dataDefinedSizeLegend );
 
   btnAdvanced->setMenu( advMenu );
 
@@ -1034,3 +1037,15 @@ QgsExpressionContext QgsCategorizedSymbolRendererWidget::createExpressionContext
 
   return expContext;
 }
+
+void QgsCategorizedSymbolRendererWidget::dataDefinedSizeLegend()
+{
+  bool ok;
+  QgsMarkerSymbol *s = static_cast<QgsMarkerSymbol *>( mCategorizedSymbol ); // this should be only enabled for marker symbols
+  std::unique_ptr<QgsDataDefinedSizeLegend> ddsLegend( showDataDefinedSizeLegendDialog( s, mRenderer->dataDefinedSizeLegend(), &ok ) );
+  if ( ok )
+  {
+    mRenderer->setDataDefinedSizeLegend( ddsLegend.release() );  // ownership is passed from dlg to renderer
+    emit widgetChanged();
+  }
+}

src/gui/symbology-ng/qgscategorizedsymbolrendererwidget.h

@@ -145,6 +145,7 @@ class GUI_EXPORT QgsCategorizedSymbolRendererWidget : public QgsRendererWidget,
 
     void cleanUpSymbolSelector( QgsPanelWidget *container );
     void updateSymbolsFromWidget();
+    void dataDefinedSizeLegend();
 
   protected:
 

src/gui/symbology-ng/qgsdatadefinedsizelegenddialog.cpp

@@ -0,0 +1,105 @@
+/***************************************************************************
+  qgsdatadefinedsizelegenddialog.cpp
+  --------------------------------------
+  Date                 : June 2017
+  Copyright            : (C) 2017 by Martin Dobias
+  Email                : wonder dot sk at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsdatadefinedsizelegenddialog.h"
+
+#include "qgsdatadefinedsizelegend.h"
+#include "qgslayertree.h"
+#include "qgslayertreemodel.h"
+#include "qgssinglesymbolrenderer.h"
+#include "qgssymbol.h"
+#include "qgssymbollayer.h"
+#include "qgsvectorlayer.h"
+
+QgsDataDefinedSizeLegendDialog::QgsDataDefinedSizeLegendDialog( const QgsDataDefinedSizeLegend *ddsLegend, QWidget *parent )
+  : QDialog( parent )
+{
+  setupUi( this );
+
+  if ( !ddsLegend )
+  {
+    radDisabled->setChecked( true );
+  }
+  else
+  {
+    if ( ddsLegend->legendType() == QgsDataDefinedSizeLegend::LegendSeparated )
+      radSeparated->setChecked( true );
+    else
+      radCollapsed->setChecked( true );
+
+    if ( ddsLegend->verticalAlignment() == QgsDataDefinedSizeLegend::AlignBottom )
+      cboAlignSymbols->setCurrentIndex( 0 );
+    else
+      cboAlignSymbols->setCurrentIndex( 1 );
+  }
+
+  // prepare default source symbol - it should be hopefully replaced in setSourceSymbol() later
+  mSourceSymbol.reset( static_cast<QgsMarkerSymbol *>( QgsSymbol::defaultSymbol( QgsWkbTypes::PointGeometry ) ) );
+  QgsProperty property = QgsProperty::fromValue( 1 );
+  property.setTransformer( new QgsSizeScaleTransformer( QgsSizeScaleTransformer::Linear, 0, 1, 0, 20 ) );
+  mSourceSymbol->setDataDefinedSize( property );
+
+  // 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 );
+  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 );
+  updatePreview();
+}
+
+QgsDataDefinedSizeLegendDialog::~QgsDataDefinedSizeLegendDialog()
+{
+  delete mPreviewModel;
+  delete mPreviewTree;
+  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() )
+    return nullptr;
+
+  QgsDataDefinedSizeLegend *ddsLegend = new QgsDataDefinedSizeLegend;
+  ddsLegend->setLegendType( radSeparated->isChecked() ? QgsDataDefinedSizeLegend::LegendSeparated : QgsDataDefinedSizeLegend::LegendCollapsed );
+  ddsLegend->setVerticalAlignment( cboAlignSymbols->currentIndex() == 0 ? QgsDataDefinedSizeLegend::AlignBottom : QgsDataDefinedSizeLegend::AlignCenter );
+  return ddsLegend;
+}
+
+void QgsDataDefinedSizeLegendDialog::updatePreview()
+{
+  QgsSingleSymbolRenderer *r = new QgsSingleSymbolRenderer( mSourceSymbol->clone() );
+  r->setDataDefinedSizeLegend( dataDefinedSizeLegend() );
+  mPreviewLayer->setRenderer( r );
+  mPreviewModel->refreshLayerLegend( mPreviewLayerNode );
+  viewLayerTree->expandAll();
+}

src/gui/symbology-ng/qgsdatadefinedsizelegenddialog.h

@@ -0,0 +1,68 @@
+/***************************************************************************
+  qgsdatadefinedsizelegenddialog.h
+  --------------------------------------
+  Date                 : June 2017
+  Copyright            : (C) 2017 by Martin Dobias
+  Email                : wonder dot sk at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSDATADEFINEDSIZELEGENDDIALOG_H
+#define QGSDATADEFINEDSIZELEGENDDIALOG_H
+
+#include "qgis.h"
+#include "qgis_gui.h"
+
+#include <memory>
+#include <QDialog>
+#include <ui_qgsdatadefinedsizelegenddialog.h>
+
+class QgsDataDefinedSizeLegend;
+class QgsLayerTree;
+class QgsLayerTreeLayer;
+class QgsLayerTreeModel;
+class QgsMarkerSymbol;
+class QgsVectorLayer;
+
+/** \ingroup gui
+ * Dialog for configuration of appearance of legend for marker symbols with data-defined size.
+ *
+ * \since QGIS 3.0
+ */
+class GUI_EXPORT QgsDataDefinedSizeLegendDialog : public QDialog, private Ui::QgsDataDefinedSizeLegendDialog
+{
+    Q_OBJECT
+  public:
+    //! 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 );
+    ~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;
+
+  signals:
+
+  private slots:
+    void updatePreview();
+
+  private:
+    std::unique_ptr<QgsMarkerSymbol> mSourceSymbol;
+    QgsLayerTreeModel *mPreviewModel;
+    QgsLayerTree *mPreviewTree;
+    QgsLayerTreeLayer *mPreviewLayerNode;
+    QgsVectorLayer *mPreviewLayer;
+};
+
+#endif // QGSDATADEFINEDSIZELEGENDDIALOG_H

src/gui/symbology-ng/qgsgraduatedsymbolrendererwidget.cpp

@@ -15,6 +15,7 @@
 #include "qgsgraduatedsymbolrendererwidget.h"
 #include "qgspanelwidget.h"
 
+#include "qgsdatadefinedsizelegend.h"
 #include "qgssymbol.h"
 #include "qgssymbollayerutils.h"
 #include "qgscolorramp.h"
@@ -511,6 +512,8 @@ QgsGraduatedSymbolRendererWidget::QgsGraduatedSymbolRendererWidget( QgsVectorLay
   QMenu *advMenu = new QMenu( this );
 
   advMenu->addAction( tr( "Symbol levels..." ), this, SLOT( showSymbolLevels() ) );
+  if ( mGraduatedSymbol->type() == QgsSymbol::Marker )
+    advMenu->addAction( tr( "Data-defined size legend..." ), this, &QgsGraduatedSymbolRendererWidget::dataDefinedSizeLegend );
 
   btnAdvanced->setMenu( advMenu );
 
@@ -1166,3 +1169,15 @@ void QgsGraduatedSymbolRendererWidget::keyPressEvent( QKeyEvent *event )
     emit widgetChanged();
   }
 }
+
+void QgsGraduatedSymbolRendererWidget::dataDefinedSizeLegend()
+{
+  bool ok;
+  QgsMarkerSymbol *s = static_cast<QgsMarkerSymbol *>( mGraduatedSymbol ); // this should be only enabled for marker symbols
+  std::unique_ptr<QgsDataDefinedSizeLegend> ddsLegend( showDataDefinedSizeLegendDialog( s, mRenderer->dataDefinedSizeLegend(), &ok ) );
+  if ( ok )
+  {
+    mRenderer->setDataDefinedSizeLegend( ddsLegend.release() );  // ownership is passed from dlg to renderer
+    emit widgetChanged();
+  }
+}

src/gui/symbology-ng/qgsgraduatedsymbolrendererwidget.h

@@ -127,6 +127,7 @@ class GUI_EXPORT QgsGraduatedSymbolRendererWidget : public QgsRendererWidget, pr
     void cleanUpSymbolSelector( QgsPanelWidget *container );
     void updateSymbolsFromWidget();
     void toggleMethodWidgets( int idx );
+    void dataDefinedSizeLegend();
 
   protected:
     void updateUiFromRenderer( bool updateCount = true );

src/gui/symbology-ng/qgsrendererwidget.cpp

@@ -13,6 +13,8 @@
  *                                                                         *
  ***************************************************************************/
 #include "qgsrendererwidget.h"
+
+#include "qgsdatadefinedsizelegenddialog.h"
 #include "qgssymbol.h"
 #include "qgsvectorlayer.h"
 #include "qgscolordialog.h"
@@ -273,6 +275,37 @@ void QgsRendererWidget::applyChanges()
   apply();
 }
 
+QgsDataDefinedSizeLegend *QgsRendererWidget::showDataDefinedSizeLegendDialog( const QgsMarkerSymbol *symbol, const QgsDataDefinedSizeLegend *ddsLegend, bool *ok )
+{
+  *ok = false;
+
+  QgsProperty ddSize = symbol->dataDefinedSize();
+  if ( !ddSize || !ddSize.isActive() )
+  {
+    QMessageBox::warning( this, tr( "Data-defined size legend" ), tr( "Data-defined size is not enabled!" ) );
+    return nullptr;
+  }
+  if ( !ddSize.transformer() )
+  {
+    QMessageBox::warning( this, tr( "Data-defined size legend" ), tr( "Data-defined size is enabled, but without size scale transformer. Use assistant to define it." ) );
+    return nullptr;
+  }
+
+  QgsDataDefinedSizeLegendDialog dlg( ddsLegend );
+  dlg.setSourceSymbol( symbol->clone() );
+  if ( QgsMapCanvas *canvas = mContext.mapCanvas() )
+  {
+    dlg.setLegendMapViewData( canvas->mapUnitsPerPixel(), canvas->mapSettings().outputDpi(), canvas->scale() );
+  }
+
+  if ( !dlg.exec() )
+    return nullptr;
+
+  *ok = true;
+  return dlg.dataDefinedSizeLegend();
+}
+
+
 //
 // QgsDataDefinedValueDialog
 //

src/gui/symbology-ng/qgsrendererwidget.h

@@ -23,6 +23,7 @@
 #include "qgssymbolwidgetcontext.h"
 #include "qgssymbollayer.h"
 
+class QgsDataDefinedSizeLegend;
 class QgsVectorLayer;
 class QgsStyle;
 class QgsFeatureRenderer;
@@ -98,6 +99,11 @@ class GUI_EXPORT QgsRendererWidget : public QgsPanelWidget
     virtual QList<QgsSymbol *> selectedSymbols() { return QList<QgsSymbol *>(); }
     virtual void refreshSymbolView() {}
 
+    //! Shows GUI to setup data-defined size legend. If accepted, ok argument will be true and a new legend configuration is returned.
+    //! Caller takes ownership of the returned object.
+    //! \since QGIS 3.0
+    QgsDataDefinedSizeLegend *showDataDefinedSizeLegendDialog( const QgsMarkerSymbol *symbol, const QgsDataDefinedSizeLegend *ddsLegend, bool *ok SIP_OUT ) SIP_FACTORY;
+
   protected slots:
     void  contextMenuViewCategories( QPoint p );
     //! Change color of selected symbols

src/gui/symbology-ng/qgssinglesymbolrendererwidget.cpp

@@ -14,6 +14,7 @@
  ***************************************************************************/
 #include "qgssinglesymbolrendererwidget.h"
 
+#include "qgsdatadefinedsizelegend.h"
 #include "qgssinglesymbolrenderer.h"
 #include "qgssymbol.h"
 
@@ -24,6 +25,7 @@
 
 #include <QMenu>
 
+
 QgsRendererWidget *QgsSingleSymbolRendererWidget::create( QgsVectorLayer *layer, QgsStyle *style, QgsFeatureRenderer *renderer )
 {
   return new QgsSingleSymbolRendererWidget( layer, style, renderer );
@@ -62,7 +64,9 @@ QgsSingleSymbolRendererWidget::QgsSingleSymbolRendererWidget( QgsVectorLayer *la
   // advanced actions - data defined rendering
   QMenu *advMenu = mSelector->advancedMenu();
 
-  advMenu->addAction( tr( "Symbol levels..." ), this, SLOT( showSymbolLevels() ) );
+  advMenu->addAction( tr( "Symbol levels..." ), this, &QgsSingleSymbolRendererWidget::showSymbolLevels );
+  if ( mSingleSymbol->type() == QgsSymbol::Marker )
+    advMenu->addAction( tr( "Data-defined size legend..." ), this, &QgsSingleSymbolRendererWidget::dataDefinedSizeLegend );
 }
 
 QgsSingleSymbolRendererWidget::~QgsSingleSymbolRendererWidget()
@@ -105,3 +109,15 @@ void QgsSingleSymbolRendererWidget::showSymbolLevels()
 {
   showSymbolLevelsDialog( mRenderer );
 }
+
+void QgsSingleSymbolRendererWidget::dataDefinedSizeLegend()
+{
+  bool ok;
+  QgsMarkerSymbol *s = static_cast<QgsMarkerSymbol *>( mSingleSymbol ); // this should be only enabled for marker symbols
+  std::unique_ptr<QgsDataDefinedSizeLegend> ddsLegend( showDataDefinedSizeLegendDialog( s, mRenderer->dataDefinedSizeLegend(), &ok ) );
+  if ( ok )
+  {
+    mRenderer->setDataDefinedSizeLegend( ddsLegend.release() );  // ownership is passed from dlg to renderer
+    emit widgetChanged();
+  }
+}

src/gui/symbology-ng/qgssinglesymbolrendererwidget.h

@@ -48,12 +48,14 @@ class GUI_EXPORT QgsSingleSymbolRendererWidget : public QgsRendererWidget
      */
     virtual void setDockMode( bool dockMode ) override;
 
-  public slots:
+  private slots:
     void changeSingleSymbol();
 
     void showSymbolLevels();
 
-  protected:
+    void dataDefinedSizeLegend();
+
+  private:
 
     QgsSingleSymbolRenderer *mRenderer = nullptr;
     QgsSymbolSelectorWidget *mSelector = nullptr;

src/ui/qgsdatadefinedsizelegenddialog.ui

@@ -0,0 +1,136 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>QgsDataDefinedSizeLegendDialog</class>
+ <widget class="QDialog" name="QgsDataDefinedSizeLegendDialog">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>674</width>
+    <height>393</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string>Data-defined size legend</string>
+  </property>
+  <layout class="QGridLayout" name="gridLayout">
+   <item row="0" column="0">
+    <layout class="QVBoxLayout" name="verticalLayout">
+     <item>
+      <widget class="QRadioButton" name="radDisabled">
+       <property name="text">
+        <string>Legend not enabled</string>
+       </property>
+       <property name="checked">
+        <bool>true</bool>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <widget class="QRadioButton" name="radSeparated">
+       <property name="text">
+        <string>Separated legend items</string>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <widget class="QRadioButton" name="radCollapsed">
+       <property name="text">
+        <string>Collapsed legend</string>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <widget class="QGroupBox" name="groupBox">
+       <property name="title">
+        <string>Options (collapsed only)</string>
+       </property>
+       <layout class="QHBoxLayout" name="horizontalLayout">
+        <item>
+         <widget class="QLabel" name="label">
+          <property name="text">
+           <string>Align symbols</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QComboBox" name="cboAlignSymbols">
+          <item>
+           <property name="text">
+            <string>Bottom</string>
+           </property>
+          </item>
+          <item>
+           <property name="text">
+            <string>Center</string>
+           </property>
+          </item>
+         </widget>
+        </item>
+       </layout>
+      </widget>
+     </item>
+    </layout>
+   </item>
+   <item row="0" column="1">
+    <widget class="QTreeView" name="viewLayerTree">
+     <property name="headerHidden">
+      <bool>true</bool>
+     </property>
+    </widget>
+   </item>
+   <item row="1" column="0" colspan="2">
+    <widget class="QDialogButtonBox" name="buttonBox">
+     <property name="orientation">
+      <enum>Qt::Horizontal</enum>
+     </property>
+     <property name="standardButtons">
+      <set>QDialogButtonBox::Cancel|QDialogButtonBox::Ok</set>
+     </property>
+    </widget>
+   </item>
+  </layout>
+ </widget>
+ <tabstops>
+  <tabstop>radDisabled</tabstop>
+  <tabstop>radSeparated</tabstop>
+  <tabstop>radCollapsed</tabstop>
+  <tabstop>cboAlignSymbols</tabstop>
+  <tabstop>viewLayerTree</tabstop>
+ </tabstops>
+ <resources/>
+ <connections>
+  <connection>
+   <sender>buttonBox</sender>
+   <signal>accepted()</signal>
+   <receiver>QgsDataDefinedSizeLegendDialog</receiver>
+   <slot>accept()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>248</x>
+     <y>254</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>157</x>
+     <y>274</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>buttonBox</sender>
+   <signal>rejected()</signal>
+   <receiver>QgsDataDefinedSizeLegendDialog</receiver>
+   <slot>reject()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>316</x>
+     <y>260</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>286</x>
+     <y>274</y>
+    </hint>
+   </hints>
+  </connection>
+ </connections>
+</ui>