Give symbol widgets optional access to a map canvas

This allows symbol widgets to fetch properties from the main map
canvas, for instance fetching the current scale from the map.

python/gui/symbology-ng/qgslayerpropertieswidget.sip

@@ -15,6 +15,13 @@ class QgsLayerPropertiesWidget : QWidget
      */
     QgsExpressionContext* expressionContext() const;
 
+    /** Sets the map canvas associated with the widget. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    virtual void setMapCanvas( QgsMapCanvas* canvas );
+
   public slots:
     void layerTypeChanged();
     void emitSignalChanged();

python/gui/symbology-ng/qgspointdisplacementrendererwidget.sip

@@ -9,4 +9,5 @@ class QgsPointDisplacementRendererWidget: QgsRendererV2Widget
     ~QgsPointDisplacementRendererWidget();
 
     QgsFeatureRendererV2* renderer();
+    void setMapCanvas( QgsMapCanvas* canvas );
 };

python/gui/symbology-ng/qgsrendererv2propertiesdialog.sip

@@ -6,6 +6,14 @@ class QgsRendererV2PropertiesDialog : QDialog
 
   public:
     QgsRendererV2PropertiesDialog( QgsVectorLayer* layer, QgsStyleV2* style, bool embedded = false );
+    ~QgsRendererV2PropertiesDialog();
+
+    /** Sets the map canvas associated with the dialog. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    void setMapCanvas( QgsMapCanvas* canvas );
 
   public slots:
     //! called when user changes renderer type

python/gui/symbology-ng/qgsrendererv2widget.sip

@@ -15,6 +15,13 @@ class QgsRendererV2Widget : QWidget
     //! show a dialog with renderer's symbol level settings
     void showSymbolLevelsDialog( QgsFeatureRendererV2* r );
 
+    /** Sets the map canvas associated with the widget. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    virtual void setMapCanvas( QgsMapCanvas* canvas );
+
   protected:
     /** Subclasses may provide the capability of changing multiple symbols at once by implementing the following two methods
       and by connecting the slot contextMenuViewCategories(const QPoint&)*/

python/gui/symbology-ng/qgsrulebasedrendererv2widget.sip

@@ -106,7 +106,7 @@ class QgsRendererRulePropsDialog : QDialog
 %End
 
   public:
-    QgsRendererRulePropsDialog( QgsRuleBasedRendererV2::Rule* rule, QgsVectorLayer* layer, QgsStyleV2* style, QWidget* parent /TransferThis/ = 0 );
+    QgsRendererRulePropsDialog( QgsRuleBasedRendererV2::Rule* rule, QgsVectorLayer* layer, QgsStyleV2* style, QWidget* parent /TransferThis/ = 0, QgsMapCanvas* mapCanvas = 0 );
     ~QgsRendererRulePropsDialog();
 
     QgsRuleBasedRendererV2::Rule* rule();

python/gui/symbology-ng/qgssinglesymbolrendererv2widget.sip

@@ -11,6 +11,8 @@ class QgsSingleSymbolRendererV2Widget : QgsRendererV2Widget
 
     virtual QgsFeatureRendererV2* renderer();
 
+    virtual void setMapCanvas( QgsMapCanvas* canvas );
+
   public slots:
     void changeSingleSymbol();
 

python/gui/symbology-ng/qgssymbollayerv2widget.sip

@@ -20,6 +20,13 @@ class QgsSymbolLayerV2Widget : QWidget
      */
     QgsExpressionContext* expressionContext() const;
 
+    /** Sets the map canvas associated with the widget. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    virtual void setMapCanvas( QgsMapCanvas* canvas );
+
     /** Returns the vector layer associated with the widget.
      * @note added in QGIS 2.12
      */

python/gui/symbology-ng/qgssymbolslistwidget.sip

@@ -14,6 +14,13 @@ class QgsSymbolsListWidget : QWidget
      */
     QgsExpressionContext* expressionContext() const;
 
+    /** Sets the map canvas associated with the widget. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    virtual void setMapCanvas( QgsMapCanvas* canvas );
+
     /** Returns the vector layer associated with the widget.
      * @note added in QGIS 2.12
      */

python/gui/symbology-ng/qgssymbolv2selectordialog.sip

@@ -27,6 +27,13 @@ class QgsSymbolV2SelectorDialog : QDialog
      */
     QgsExpressionContext* expressionContext() const;
 
+    /** Sets the map canvas associated with the dialog. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    void setMapCanvas( QgsMapCanvas* canvas );
+
   protected:
     //! Reimplements dialog keyPress event so we can ignore it
     void keyPressEvent( QKeyEvent * event );

src/app/qgsvectorlayerproperties.cpp

@@ -1237,6 +1237,7 @@ void QgsVectorLayerProperties::updateSymbologyPage()
   if ( layer->rendererV2() )
   {
     mRendererDialog = new QgsRendererV2PropertiesDialog( layer, QgsStyleV2::defaultStyle(), true );
+    mRendererDialog->setMapCanvas( QgisApp::instance()->mapCanvas() );
 
     // display the menu to choose the output format (fix #5136)
     mActionSaveStyleAs->setText( tr( "Save Style" ) );

src/app/qgsvectorlayerproperties.h

@@ -40,6 +40,7 @@ class QgsVectorLayer;
 class QgsLabelingGui;
 class QgsDiagramProperties;
 class QgsFieldsProperties;
+class QgsRendererV2PropertiesDialog;
 
 class APP_EXPORT QgsVectorLayerProperties : public QgsOptionsDialogBase, private Ui::QgsVectorLayerPropertiesBase
 {
@@ -164,7 +165,7 @@ class APP_EXPORT QgsVectorLayerProperties : public QgsOptionsDialogBase, private
     QAction* mActionSaveStyleAs;
 
     /** Renderer dialog which is shown*/
-    QDialog* mRendererDialog;
+    QgsRendererV2PropertiesDialog* mRendererDialog;
     /** Labeling dialog. If apply is pressed, options are applied to vector's QgsLabel */
     QgsLabelingGui* labelingDialog;
     /** Label dialog. If apply is pressed, options are applied to vector's QgsLabel */

src/gui/symbology-ng/qgscategorizedsymbolrendererv2widget.cpp

@@ -522,6 +522,7 @@ void QgsCategorizedSymbolRendererV2Widget::changeSelectedSymbols()
   {
     QgsSymbolV2* newSymbol = mCategorizedSymbol->clone();
     QgsSymbolV2SelectorDialog dlg( newSymbol, mStyle, mLayer, this );
+    dlg.setMapCanvas( mMapCanvas );
     if ( !dlg.exec() )
     {
       delete newSymbol;
@@ -555,6 +556,7 @@ void QgsCategorizedSymbolRendererV2Widget::changeCategorizedSymbol()
   QgsSymbolV2* newSymbol = mCategorizedSymbol->clone();
 
   QgsSymbolV2SelectorDialog dlg( newSymbol, mStyle, mLayer, this );
+  dlg.setMapCanvas( mMapCanvas );
   if ( !dlg.exec() )
   {
     delete newSymbol;
@@ -605,6 +607,7 @@ void QgsCategorizedSymbolRendererV2Widget::changeCategorySymbol()
   }
 
   QgsSymbolV2SelectorDialog dlg( symbol, mStyle, mLayer, this );
+  dlg.setMapCanvas( mMapCanvas );
   if ( !dlg.exec() )
   {
     delete symbol;

src/gui/symbology-ng/qgsgraduatedsymbolrendererv2widget.cpp

@@ -773,6 +773,7 @@ void QgsGraduatedSymbolRendererV2Widget::changeGraduatedSymbol()
   QgsSymbolV2* newSymbol = mGraduatedSymbol->clone();
 
   QgsSymbolV2SelectorDialog dlg( newSymbol, mStyle, mLayer, this );
+  dlg.setMapCanvas( mMapCanvas );
   if ( !dlg.exec() )
   {
     delete newSymbol;
@@ -860,6 +861,7 @@ void QgsGraduatedSymbolRendererV2Widget::changeSelectedSymbols()
   {
     QgsSymbolV2* newSymbol = mGraduatedSymbol->clone();
     QgsSymbolV2SelectorDialog dlg( newSymbol, mStyle, mLayer, this );
+    dlg.setMapCanvas( mMapCanvas );
     if ( !dlg.exec() )
     {
       delete newSymbol;
@@ -885,6 +887,7 @@ void QgsGraduatedSymbolRendererV2Widget::changeRangeSymbol( int rangeIdx )
   QgsSymbolV2* newSymbol = mRenderer->ranges()[rangeIdx].symbol()->clone();
 
   QgsSymbolV2SelectorDialog dlg( newSymbol, mStyle, mLayer, this );
+  dlg.setMapCanvas( mMapCanvas );
   if ( !dlg.exec() )
   {
     delete newSymbol;

src/gui/symbology-ng/qgsheatmaprendererwidget.cpp

@@ -120,6 +120,12 @@ QgsFeatureRendererV2* QgsHeatmapRendererWidget::renderer()
   return mRenderer;
 }
 
+void QgsHeatmapRendererWidget::setMapCanvas( QgsMapCanvas* canvas )
+{
+  QgsRendererV2Widget::setMapCanvas( canvas );
+  mRadiusUnitWidget->setMapCanvas( canvas );
+}
+
 void QgsHeatmapRendererWidget::applyColorRamp()
 {
   if ( !mRenderer )

src/gui/symbology-ng/qgsheatmaprendererwidget.h

@@ -43,6 +43,8 @@ class GUI_EXPORT QgsHeatmapRendererWidget : public QgsRendererV2Widget, private
     /** @returns the current feature renderer */
     virtual QgsFeatureRendererV2* renderer() override;
 
+    void setMapCanvas( QgsMapCanvas* canvas ) override;
+
   protected:
     QgsHeatmapRenderer* mRenderer;
 

src/gui/symbology-ng/qgsinvertedpolygonrendererwidget.cpp

@@ -111,6 +111,12 @@ QgsFeatureRendererV2* QgsInvertedPolygonRendererWidget::renderer()
   return mRenderer.data();
 }
 
+void QgsInvertedPolygonRendererWidget::setMapCanvas( QgsMapCanvas* canvas )
+{
+  QgsRendererV2Widget::setMapCanvas( canvas );
+  mEmbeddedRendererWidget->setMapCanvas( canvas );
+}
+
 void QgsInvertedPolygonRendererWidget::on_mRendererComboBox_currentIndexChanged( int index )
 {
   QString rendererId = mRendererComboBox->itemData( index ).toString();
@@ -118,6 +124,7 @@ void QgsInvertedPolygonRendererWidget::on_mRendererComboBox_currentIndexChanged(
   if ( m )
   {
     mEmbeddedRendererWidget.reset( m->createRendererWidget( mLayer, mStyle, const_cast<QgsFeatureRendererV2*>( mRenderer->embeddedRenderer() )->clone() ) );
+    mEmbeddedRendererWidget->setMapCanvas( mMapCanvas );
 
     if ( mLayout->count() > 2 )
     {

src/gui/symbology-ng/qgsinvertedpolygonrendererwidget.h

@@ -47,6 +47,7 @@ class GUI_EXPORT QgsInvertedPolygonRendererWidget : public QgsRendererV2Widget,
 
     /** @returns the current feature renderer */
     virtual QgsFeatureRendererV2* renderer() override;
+    void setMapCanvas( QgsMapCanvas* canvas ) override;
 
   protected:
     /** The mask renderer */

src/gui/symbology-ng/qgslayerpropertieswidget.cpp

@@ -83,6 +83,7 @@ static void _initWidgetFunctions()
 QgsLayerPropertiesWidget::QgsLayerPropertiesWidget( QgsSymbolLayerV2* layer, const QgsSymbolV2* symbol, const QgsVectorLayer* vl, QWidget* parent )
     : QWidget( parent )
     , mPresetExpressionContext( 0 )
+    , mMapCanvas( 0 )
 {
 
   mLayer = layer;
@@ -116,6 +117,14 @@ QgsLayerPropertiesWidget::QgsLayerPropertiesWidget( QgsSymbolLayerV2* layer, con
   mEffectWidget->setPaintEffect( mLayer->paintEffect() );
 }
 
+void QgsLayerPropertiesWidget::setMapCanvas( QgsMapCanvas *canvas )
+{
+  mMapCanvas = canvas;
+  QgsSymbolLayerV2Widget* w = dynamic_cast< QgsSymbolLayerV2Widget* >( stackedWidget->currentWidget() );
+  if ( w )
+    w->setMapCanvas( mMapCanvas );
+}
+
 void QgsLayerPropertiesWidget::setExpressionContext( QgsExpressionContext *context )
 {
   mPresetExpressionContext = context;
@@ -165,6 +174,8 @@ void QgsLayerPropertiesWidget::updateSymbolLayerWidget( QgsSymbolLayerV2* layer
     {
       w->setSymbolLayer( layer );
       w->setExpressionContext( mPresetExpressionContext );
+      if ( mMapCanvas )
+        w->setMapCanvas( mMapCanvas );
       stackedWidget->addWidget( w );
       stackedWidget->setCurrentWidget( w );
       // start receiving updates from widget

src/gui/symbology-ng/qgslayerpropertieswidget.h

@@ -22,6 +22,7 @@ class QgsSymbolV2;
 class QgsSymbolLayerV2;
 class QgsSymbolLayerV2Widget;
 class QgsVectorLayer;
+class QgsMapCanvas;
 
 class SymbolLayerItem;
 
@@ -44,6 +45,13 @@ class GUI_EXPORT QgsLayerPropertiesWidget : public QWidget, private Ui::LayerPro
      */
     QgsExpressionContext* expressionContext() const { return mPresetExpressionContext; }
 
+    /** Sets the map canvas associated with the widget. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    virtual void setMapCanvas( QgsMapCanvas* canvas );
+
   public slots:
     void layerTypeChanged();
     void emitSignalChanged();
@@ -74,6 +82,8 @@ class GUI_EXPORT QgsLayerPropertiesWidget : public QWidget, private Ui::LayerPro
 
   private:
     QgsExpressionContext* mPresetExpressionContext;
+    QgsMapCanvas* mMapCanvas;
+
 };
 
 #endif //QGSLAYERPROPERTIESWIDGET_H

src/gui/symbology-ng/qgspointdisplacementrendererwidget.cpp

@@ -160,6 +160,13 @@ QgsFeatureRendererV2* QgsPointDisplacementRendererWidget::renderer()
   return mRenderer;
 }
 
+void QgsPointDisplacementRendererWidget::setMapCanvas( QgsMapCanvas* canvas )
+{
+  QgsRendererV2Widget::setMapCanvas( canvas );
+  mDistanceUnitWidget->setMapCanvas( canvas );
+  mEmbeddedRendererWidget->setMapCanvas( canvas );
+}
+
 void QgsPointDisplacementRendererWidget::on_mLabelFieldComboBox_currentIndexChanged( const QString& text )
 {
   if ( mRenderer )
@@ -183,6 +190,7 @@ void QgsPointDisplacementRendererWidget::on_mRendererComboBox_currentIndexChange
   {
     delete mEmbeddedRendererWidget;
     mEmbeddedRendererWidget = m->createRendererWidget( mLayer, mStyle, mRenderer->embeddedRenderer()->clone() );
+    mEmbeddedRendererWidget->setMapCanvas( mMapCanvas );
   }
 }
 
@@ -332,6 +340,7 @@ void QgsPointDisplacementRendererWidget::on_mCenterSymbolPushButton_clicked()
   }
   QgsMarkerSymbolV2* markerSymbol = dynamic_cast<QgsMarkerSymbolV2*>( mRenderer->centerSymbol()->clone() );
   QgsSymbolV2SelectorDialog dlg( markerSymbol, QgsStyleV2::defaultStyle(), mLayer, this );
+  dlg.setMapCanvas( mMapCanvas );
   if ( dlg.exec() == QDialog::Rejected )
   {
     delete markerSymbol;

src/gui/symbology-ng/qgspointdisplacementrendererwidget.h

@@ -32,6 +32,7 @@ class GUI_EXPORT QgsPointDisplacementRendererWidget: public QgsRendererV2Widget,
     ~QgsPointDisplacementRendererWidget();
 
     QgsFeatureRendererV2* renderer() override;
+    void setMapCanvas( QgsMapCanvas* canvas ) override;
 
   private:
     QgsPointDisplacementRenderer* mRenderer;

src/gui/symbology-ng/qgsrendererv2propertiesdialog.cpp

@@ -78,6 +78,7 @@ QgsRendererV2PropertiesDialog::QgsRendererV2PropertiesDialog( QgsVectorLayer* la
     , mStyle( style )
     , mActiveWidget( NULL )
     , mPaintEffect( 0 )
+    , mMapCanvas( 0 )
 {
   setupUi( this );
 
@@ -149,6 +150,13 @@ QgsRendererV2PropertiesDialog::~QgsRendererV2PropertiesDialog()
   delete mPaintEffect;
 }
 
+void QgsRendererV2PropertiesDialog::setMapCanvas( QgsMapCanvas* canvas )
+{
+  mMapCanvas = canvas;
+  if ( mActiveWidget )
+    mActiveWidget->setMapCanvas( mMapCanvas );
+}
+
 
 void QgsRendererV2PropertiesDialog::rendererChanged()
 {
@@ -193,6 +201,8 @@ void QgsRendererV2PropertiesDialog::rendererChanged()
     mActiveWidget = w;
     stackedWidget->addWidget( mActiveWidget );
     stackedWidget->setCurrentWidget( mActiveWidget );
+    if ( mMapCanvas )
+      mActiveWidget->setMapCanvas( mMapCanvas );
   }
   else
   {

src/gui/symbology-ng/qgsrendererv2propertiesdialog.h

@@ -28,6 +28,7 @@ class QgsStyleV2;
 class QgsSymbolV2;
 class QgsPaintEffect;
 class QgsRendererV2Widget;
+class QgsMapCanvas;
 
 class GUI_EXPORT QgsRendererV2PropertiesDialog : public QDialog, private Ui::QgsRendererV2PropsDialogBase
 {
@@ -37,6 +38,13 @@ class GUI_EXPORT QgsRendererV2PropertiesDialog : public QDialog, private Ui::Qgs
     QgsRendererV2PropertiesDialog( QgsVectorLayer* layer, QgsStyleV2* style, bool embedded = false );
     ~QgsRendererV2PropertiesDialog();
 
+    /** Sets the map canvas associated with the dialog. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    void setMapCanvas( QgsMapCanvas* canvas );
+
   public slots:
     //! called when user changes renderer type
     void rendererChanged();
@@ -56,6 +64,8 @@ class GUI_EXPORT QgsRendererV2PropertiesDialog : public QDialog, private Ui::Qgs
     QgsRendererV2Widget* mActiveWidget;
 
     QgsPaintEffect* mPaintEffect;
+
+    QgsMapCanvas* mMapCanvas;
 };
 
 

src/gui/symbology-ng/qgsrendererv2widget.cpp

@@ -24,7 +24,10 @@
 #include <QMenu>
 
 QgsRendererV2Widget::QgsRendererV2Widget( QgsVectorLayer* layer, QgsStyleV2* style )
-    : QWidget(), mLayer( layer ), mStyle( style )
+    : QWidget()
+    , mLayer( layer )
+    , mStyle( style )
+    , mMapCanvas( 0 )
 {
   contextMenu = new QMenu( tr( "Renderer Options" ), this );
 
@@ -207,6 +210,11 @@ void QgsRendererV2Widget::showSymbolLevelsDialog( QgsFeatureRendererV2* r )
   }
 }
 
+void QgsRendererV2Widget::setMapCanvas( QgsMapCanvas *canvas )
+{
+  mMapCanvas = canvas;
+}
+
 
 ////////////
 

src/gui/symbology-ng/qgsrendererv2widget.h

@@ -24,7 +24,7 @@ class QgsVectorLayer;
 class QgsStyleV2;
 class QgsFeatureRendererV2;
 class QgsSymbolV2SelectorDialog;
-
+class QgsMapCanvas;
 
 /**
   Base class for renderer settings widgets
@@ -50,12 +50,20 @@ class GUI_EXPORT QgsRendererV2Widget : public QWidget
     //! show a dialog with renderer's symbol level settings
     void showSymbolLevelsDialog( QgsFeatureRendererV2* r );
 
+    /** Sets the map canvas associated with the widget. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    virtual void setMapCanvas( QgsMapCanvas* canvas );
+
   protected:
     QgsVectorLayer* mLayer;
     QgsStyleV2* mStyle;
     QMenu* contextMenu;
     QAction* mCopyAction;
     QAction* mPasteAction;
+    QgsMapCanvas* mMapCanvas;
 
     /** Subclasses may provide the capability of changing multiple symbols at once by implementing the following two methods
       and by connecting the slot contextMenuViewCategories(const QPoint&)*/

src/gui/symbology-ng/qgsrulebasedrendererv2widget.cpp

@@ -129,7 +129,7 @@ void QgsRuleBasedRendererV2Widget::addRule()
   QgsSymbolV2* s = QgsSymbolV2::defaultSymbol( mLayer->geometryType() );
   QgsRuleBasedRendererV2::Rule* newrule = new QgsRuleBasedRendererV2::Rule( s );
 
-  QgsRendererRulePropsDialog dlg( newrule, mLayer, mStyle, this );
+  QgsRendererRulePropsDialog dlg( newrule, mLayer, mStyle, this, mMapCanvas );
   if ( dlg.exec() )
   {
     QgsRuleBasedRendererV2::Rule* current = currentRule();
@@ -173,7 +173,7 @@ void QgsRuleBasedRendererV2Widget::editRule( const QModelIndex& index )
     return;
   QgsRuleBasedRendererV2::Rule* rule = mModel->ruleForIndex( index );
 
-  QgsRendererRulePropsDialog dlg( rule, mLayer, mStyle, this );
+  QgsRendererRulePropsDialog dlg( rule, mLayer, mStyle, this, mMapCanvas );
   if ( dlg.exec() )
   {
     // model should know about the change and emit dataChanged signal for the view
@@ -256,6 +256,7 @@ void QgsRuleBasedRendererV2Widget::refineRuleCategoriesGui( const QModelIndexLis
   dlg.setWindowTitle( tr( "Refine a rule to categories" ) );
   QVBoxLayout* l = new QVBoxLayout();
   QgsCategorizedSymbolRendererV2Widget* w = new QgsCategorizedSymbolRendererV2Widget( mLayer, mStyle, NULL );
+  w->setMapCanvas( mMapCanvas );
   l->addWidget( w );
   QDialogButtonBox* bb = new QDialogButtonBox( QDialogButtonBox::Ok | QDialogButtonBox::Cancel );
   l->addWidget( bb );
@@ -286,6 +287,7 @@ void QgsRuleBasedRendererV2Widget::refineRuleRangesGui( const QModelIndexList& i
   dlg.setWindowTitle( tr( "Refine a rule to ranges" ) );
   QVBoxLayout* l = new QVBoxLayout();
   QgsGraduatedSymbolRendererV2Widget* w = new QgsGraduatedSymbolRendererV2Widget( mLayer, mStyle, NULL );
+  w->setMapCanvas( mMapCanvas );
   l->addWidget( w );
   QDialogButtonBox* bb = new QDialogButtonBox( QDialogButtonBox::Ok | QDialogButtonBox::Cancel );
   l->addWidget( bb );
@@ -571,8 +573,8 @@ void QgsRuleBasedRendererV2Widget::countFeatures()
 
 ///////////
 
-QgsRendererRulePropsDialog::QgsRendererRulePropsDialog( QgsRuleBasedRendererV2::Rule* rule, QgsVectorLayer* layer, QgsStyleV2* style, QWidget* parent )
-    : QDialog( parent ), mRule( rule ), mLayer( layer ), mSymbolSelector( NULL ), mSymbol( NULL )
+QgsRendererRulePropsDialog::QgsRendererRulePropsDialog( QgsRuleBasedRendererV2::Rule* rule, QgsVectorLayer* layer, QgsStyleV2* style, QWidget* parent , QgsMapCanvas* mapCanvas )
+    : QDialog( parent ), mRule( rule ), mLayer( layer ), mSymbolSelector( NULL ), mSymbol( NULL ), mMapCanvas( mapCanvas )
 {
   setupUi( this );
 #ifdef Q_OS_MAC
@@ -597,6 +599,7 @@ QgsRendererRulePropsDialog::QgsRendererRulePropsDialog( QgsRuleBasedRendererV2::
     if ( rule->scaleMaxDenom() > 0 )
       mScaleRangeWidget->setMinimumScale( 1.0 / rule->scaleMaxDenom() );
   }
+  mScaleRangeWidget->setMapCanvas( mMapCanvas );
 
   if ( mRule->symbol() )
   {
@@ -610,6 +613,7 @@ QgsRendererRulePropsDialog::QgsRendererRulePropsDialog( QgsRuleBasedRendererV2::
   }
 
   mSymbolSelector = new QgsSymbolV2SelectorDialog( mSymbol, style, mLayer, this, true );
+  mSymbolSelector->setMapCanvas( mMapCanvas );
   QVBoxLayout* l = new QVBoxLayout;
   l->addWidget( mSymbolSelector );
   groupSymbol->setLayout( l );

src/gui/symbology-ng/qgsrulebasedrendererv2widget.h

@@ -167,7 +167,7 @@ class GUI_EXPORT QgsRendererRulePropsDialog : public QDialog, private Ui::QgsRen
     Q_OBJECT
 
   public:
-    QgsRendererRulePropsDialog( QgsRuleBasedRendererV2::Rule* rule, QgsVectorLayer* layer, QgsStyleV2* style, QWidget* parent = 0 );
+    QgsRendererRulePropsDialog( QgsRuleBasedRendererV2::Rule* rule, QgsVectorLayer* layer, QgsStyleV2* style, QWidget* parent = 0, QgsMapCanvas* mapCanvas = 0 );
     ~QgsRendererRulePropsDialog();
 
     QgsRuleBasedRendererV2::Rule* rule() { return mRule; }
@@ -183,6 +183,8 @@ class GUI_EXPORT QgsRendererRulePropsDialog : public QDialog, private Ui::QgsRen
 
     QgsSymbolV2SelectorDialog* mSymbolSelector;
     QgsSymbolV2* mSymbol; // a clone of original symbol
+
+    QgsMapCanvas* mMapCanvas;
 };
 
 

src/gui/symbology-ng/qgssinglesymbolrendererv2widget.cpp

@@ -80,6 +80,12 @@ QgsFeatureRendererV2* QgsSingleSymbolRendererV2Widget::renderer()
   return mRenderer;
 }
 
+void QgsSingleSymbolRendererV2Widget::setMapCanvas( QgsMapCanvas* canvas )
+{
+  QgsRendererV2Widget::setMapCanvas( canvas );
+  mSelector->setMapCanvas( canvas );
+}
+
 void QgsSingleSymbolRendererV2Widget::changeSingleSymbol()
 {
   // update symbol from the GUI

src/gui/symbology-ng/qgssinglesymbolrendererv2widget.h

@@ -34,6 +34,9 @@ class GUI_EXPORT QgsSingleSymbolRendererV2Widget : public QgsRendererV2Widget
 
     virtual QgsFeatureRendererV2* renderer() override;
 
+
+    virtual void setMapCanvas( QgsMapCanvas* canvas ) override;
+
   public slots:
     void changeSingleSymbol();
 

src/gui/symbology-ng/qgssymbollayerv2widget.cpp

@@ -68,6 +68,15 @@ static QgsExpressionContext _getExpressionContext( const void* context )
   return expContext;
 }
 
+void QgsSymbolLayerV2Widget::setMapCanvas( QgsMapCanvas *canvas )
+{
+  mMapCanvas = canvas;
+  Q_FOREACH ( QgsUnitSelectionWidget* unitWidget, findChildren<QgsUnitSelectionWidget*>() )
+  {
+    unitWidget->setMapCanvas( mMapCanvas );
+  }
+}
+
 void QgsSymbolLayerV2Widget::registerDataDefinedButton( QgsDataDefinedButton * button, const QString & propertyName, QgsDataDefinedButton::DataType type, const QString & description )
 {
   const QgsDataDefined* dd = symbolLayer()->getDataDefinedProperty( propertyName );

src/gui/symbology-ng/qgssymbollayerv2widget.h

@@ -23,13 +23,14 @@
 
 class QgsSymbolLayerV2;
 class QgsVectorLayer;
+class QgsMapCanvas;
 
 class GUI_EXPORT QgsSymbolLayerV2Widget : public QWidget
 {
     Q_OBJECT
 
   public:
-    QgsSymbolLayerV2Widget( QWidget* parent, const QgsVectorLayer* vl = 0 ) : QWidget( parent ), mVectorLayer( vl ), mPresetExpressionContext( 0 ) {}
+    QgsSymbolLayerV2Widget( QWidget* parent, const QgsVectorLayer* vl = 0 ) : QWidget( parent ), mVectorLayer( vl ), mPresetExpressionContext( 0 ), mMapCanvas( 0 ) {}
     virtual ~QgsSymbolLayerV2Widget() {}
 
     virtual void setSymbolLayer( QgsSymbolLayerV2* layer ) = 0;
@@ -43,6 +44,13 @@ class GUI_EXPORT QgsSymbolLayerV2Widget : public QWidget
      */
     QgsExpressionContext* expressionContext() const { return mPresetExpressionContext; }
 
+    /** Sets the map canvas associated with the widget. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    virtual void setMapCanvas( QgsMapCanvas* canvas );
+
     /** Returns the vector layer associated with the widget.
      * @note added in QGIS 2.12
      */
@@ -66,6 +74,8 @@ class GUI_EXPORT QgsSymbolLayerV2Widget : public QWidget
     //! Optional preset expression context
     QgsExpressionContext* mPresetExpressionContext;
 
+    QgsMapCanvas* mMapCanvas;
+
     void registerDataDefinedButton( QgsDataDefinedButton * button, const QString & propertyName, QgsDataDefinedButton::DataType type, const QString & description );
 
     /** Get label for data defined entry.

src/gui/symbology-ng/qgssymbolslistwidget.cpp

@@ -117,6 +117,14 @@ QgsSymbolsListWidget::QgsSymbolsListWidget( QgsSymbolV2* symbol, QgsStyleV2* sty
   btnColor->setContext( "symbology" );
 }
 
+void QgsSymbolsListWidget::setMapCanvas( QgsMapCanvas* canvas )
+{
+  Q_FOREACH ( QgsUnitSelectionWidget* unitWidget, findChildren<QgsUnitSelectionWidget*>() )
+  {
+    unitWidget->setMapCanvas( canvas );
+  }
+}
+
 void QgsSymbolsListWidget::setExpressionContext( QgsExpressionContext *context )
 {
   mPresetExpressionContext = context;

src/gui/symbology-ng/qgssymbolslistwidget.h

@@ -40,6 +40,13 @@ class GUI_EXPORT QgsSymbolsListWidget : public QWidget, private Ui::SymbolsListW
      */
     QgsExpressionContext* expressionContext() const { return mPresetExpressionContext; }
 
+    /** Sets the map canvas associated with the widget. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    virtual void setMapCanvas( QgsMapCanvas* canvas );
+
     /** Returns the vector layer associated with the widget.
      * @note added in QGIS 2.12
      */

src/gui/symbology-ng/qgssymbolv2selectordialog.cpp

@@ -205,7 +205,10 @@ class SymbolLayerItem : public QStandardItem
 //////////
 
 QgsSymbolV2SelectorDialog::QgsSymbolV2SelectorDialog( QgsSymbolV2* symbol, QgsStyleV2* style, const QgsVectorLayer* vl, QWidget* parent, bool embedded )
-    : QDialog( parent ), mAdvancedMenu( NULL ), mVectorLayer( vl )
+    : QDialog( parent )
+    , mAdvancedMenu( NULL )
+    , mVectorLayer( vl )
+    , mMapCanvas( 0 )
 {
 #ifdef Q_OS_MAC
   setWindowModality( Qt::WindowModal );
@@ -287,6 +290,20 @@ void QgsSymbolV2SelectorDialog::setExpressionContext( QgsExpressionContext *cont
   updatePreview();
 }
 
+void QgsSymbolV2SelectorDialog::setMapCanvas( QgsMapCanvas *canvas )
+{
+  mMapCanvas = canvas;
+
+  QWidget* widget = stackedWidget->currentWidget();
+  QgsLayerPropertiesWidget* layerProp = dynamic_cast< QgsLayerPropertiesWidget* >( widget );
+  QgsSymbolsListWidget* listWidget = dynamic_cast< QgsSymbolsListWidget* >( widget );
+
+  if ( layerProp )
+    layerProp->setMapCanvas( canvas );
+  if ( listWidget )
+    listWidget->setMapCanvas( canvas );
+}
+
 void QgsSymbolV2SelectorDialog::loadSymbol( QgsSymbolV2* symbol, SymbolLayerItem* parent )
 {
   SymbolLayerItem* symbolItem = new SymbolLayerItem( symbol );
@@ -399,6 +416,7 @@ void QgsSymbolV2SelectorDialog::layerChanged()
     mDataDefineRestorer.reset( new DataDefinedRestorer( parent->symbol(), currentItem->layer() ) );
     QgsLayerPropertiesWidget *layerProp = new QgsLayerPropertiesWidget( currentItem->layer(), parent->symbol(), mVectorLayer );
     layerProp->setExpressionContext( mPresetExpressionContext.data() );
+    layerProp->setMapCanvas( mMapCanvas );
     setWidget( layerProp );
     connect( layerProp, SIGNAL( changed() ), mDataDefineRestorer.data(), SLOT( restore() ) );
     connect( layerProp, SIGNAL( changed() ), this, SLOT( updateLayerPreview() ) );
@@ -413,6 +431,7 @@ void QgsSymbolV2SelectorDialog::layerChanged()
     // Now populate symbols of that type using the symbols list widget:
     QgsSymbolsListWidget *symbolsList = new QgsSymbolsListWidget( currentItem->symbol(), mStyle, mAdvancedMenu, this, mVectorLayer );
     symbolsList->setExpressionContext( mPresetExpressionContext.data() );
+    symbolsList->setMapCanvas( mMapCanvas );
 
     setWidget( symbolsList );
     connect( symbolsList, SIGNAL( changed() ), this, SLOT( symbolChanged() ) );

src/gui/symbology-ng/qgssymbolv2selectordialog.h

@@ -39,6 +39,8 @@ class QgsLineSymbolV2;
 class QgsMarkerSymbolLayerV2;
 class QgsLineSymbolLayerV2;
 
+class QgsMapCanvas;
+
 class DataDefinedRestorer: public QObject
 {
     Q_OBJECT
@@ -93,6 +95,13 @@ class GUI_EXPORT QgsSymbolV2SelectorDialog : public QDialog, private Ui::QgsSymb
      */
     QgsExpressionContext* expressionContext() const { return mPresetExpressionContext.data(); }
 
+    /** Sets the map canvas associated with the dialog. This allows the widget to retrieve the current
+     * map scale and other properties from the canvas.
+     * @param canvas map canvas
+     * @note added in QGIS 2.12
+     */
+    void setMapCanvas( QgsMapCanvas* canvas );
+
   protected:
     //! Reimplements dialog keyPress event so we can ignore it
     void keyPressEvent( QKeyEvent * event ) override;
@@ -150,6 +159,8 @@ class GUI_EXPORT QgsSymbolV2SelectorDialog : public QDialog, private Ui::QgsSymb
   private:
     QScopedPointer<DataDefinedRestorer> mDataDefineRestorer;
     QScopedPointer< QgsExpressionContext > mPresetExpressionContext;
+
+    QgsMapCanvas* mMapCanvas;
 };
 
 #endif

tests/src/python/test_qgsdoccoverage.py

@@ -33,7 +33,7 @@ from PyQt4.QtCore import qDebug
 # DON'T RAISE THIS THRESHOLD!!!
 # (changes which lower this threshold are welcomed though!)
 
-ACCEPTABLE_MISSING_DOCS = 4038
+ACCEPTABLE_MISSING_DOCS = 4036
 
 
 def elemIsDocumentableClass(elem):