Fixes to arrow line symbology:

- Fix crash in Python bindings caused by subsymbol ownership
- Make symbol work correctly with categorised and graduated
renderers

Author: nyalldawson

python/core/symbology-ng/qgsarrowsymbollayer.sip

@@ -23,7 +23,7 @@ class QgsArrowSymbolLayer : public QgsLineSymbolLayerV2
     virtual QgsSymbolV2* subSymbol();
 
     /** Set the sub symbol used for filling */
-    virtual bool setSubSymbol( QgsSymbolV2* symbol );
+    virtual bool setSubSymbol( QgsSymbolV2* symbol /Transfer/ );
 
     /** Return a list of attributes required to render this feature */
     virtual QSet<QString> usedAttributes() const;
@@ -106,6 +106,9 @@ class QgsArrowSymbolLayer : public QgsLineSymbolLayerV2
 
     /** Main drawing method */
     void renderPolyline( const QPolygonF& points, QgsSymbolV2RenderContext& context );
-private:
+
+    void setColor( const QColor& c );
+
+  private:
     QgsArrowSymbolLayer( const QgsArrowSymbolLayer& );
 };

src/core/symbology-ng/qgsarrowsymbollayer.cpp

@@ -45,6 +45,7 @@ bool QgsArrowSymbolLayer::setSubSymbol( QgsSymbolV2* symbol )
     mSymbol.reset( static_cast<QgsFillSymbolV2*>( symbol ) );
     return true;
   }
+  delete symbol;
   return false;
 }
 
@@ -604,3 +605,11 @@ void QgsArrowSymbolLayer::renderPolyline( const QPolygonF& points, QgsSymbolV2Re
   context.renderContext().expressionContext().popScope();
 }
 
+void QgsArrowSymbolLayer::setColor( const QColor& c )
+{
+  if ( mSymbol.data() )
+    mSymbol->setColor( c );
+
+  mColor = c;
+}
+

src/core/symbology-ng/qgsarrowsymbollayer.h

@@ -127,6 +127,8 @@ class CORE_EXPORT QgsArrowSymbolLayer : public QgsLineSymbolLayerV2
     /** Main drawing method */
     void renderPolyline( const QPolygonF& points, QgsSymbolV2RenderContext& context ) override;
 
+    void setColor( const QColor& c ) override;
+
   private:
     /** Filling sub symbol */
     QScopedPointer<QgsFillSymbolV2> mSymbol;