Avoid unused expression context updates in more places

Author: nyalldawson

src/core/symbology/qgssymbol.cpp

@@ -710,10 +710,11 @@ void QgsSymbol::renderFeature( const QgsFeature &feature, QgsRenderContext &cont
   mSymbolRenderContext->setGeometryPartCount( segmentizedGeometry.constGet()->partCount() );
   mSymbolRenderContext->setGeometryPartNum( 1 );
 
+  bool needsExpressionContext = hasDataDefinedProperties();
   ExpressionContextScopePopper scopePopper;
   if ( mSymbolRenderContext->expressionContextScope() )
   {
-    if ( hasDataDefinedProperties() )
+    if ( needsExpressionContext )
     {
       // this is somewhat nasty - by appending this scope here it's now owned
       // by both mSymbolRenderContext AND context.expressionContext()
@@ -835,7 +836,8 @@ void QgsSymbol::renderFeature( const QgsFeature &feature, QgsRenderContext &cont
       for ( int i = 0; i < mp.numGeometries(); ++i )
       {
         mSymbolRenderContext->setGeometryPartNum( i + 1 );
-        mSymbolRenderContext->expressionContextScope()->addVariable( QgsExpressionContextScope::StaticVariable( QgsExpressionContext::EXPR_GEOMETRY_PART_NUM, i + 1, true ) );
+        if ( needsExpressionContext )
+          mSymbolRenderContext->expressionContextScope()->addVariable( QgsExpressionContextScope::StaticVariable( QgsExpressionContext::EXPR_GEOMETRY_PART_NUM, i + 1, true ) );
 
         const QgsPoint &point = static_cast< const QgsPoint & >( *mp.geometryN( i ) );
         const QPointF pt = _getPoint( context, point );
@@ -864,7 +866,8 @@ void QgsSymbol::renderFeature( const QgsFeature &feature, QgsRenderContext &cont
       for ( unsigned int i = 0; i < num; ++i )
       {
         mSymbolRenderContext->setGeometryPartNum( i + 1 );
-        mSymbolRenderContext->expressionContextScope()->addVariable( QgsExpressionContextScope::StaticVariable( QgsExpressionContext::EXPR_GEOMETRY_PART_NUM, i + 1, true ) );
+        if ( needsExpressionContext )
+          mSymbolRenderContext->expressionContextScope()->addVariable( QgsExpressionContextScope::StaticVariable( QgsExpressionContext::EXPR_GEOMETRY_PART_NUM, i + 1, true ) );
 
         context.setGeometry( geomCollection.geometryN( i ) );
         const QgsCurve &curve = dynamic_cast<const QgsCurve &>( *geomCollection.geometryN( i ) );
@@ -922,7 +925,8 @@ void QgsSymbol::renderFeature( const QgsFeature &feature, QgsRenderContext &cont
         {
           const unsigned i = listPartIndex[idx];
           mSymbolRenderContext->setGeometryPartNum( i + 1 );
-          mSymbolRenderContext->expressionContextScope()->addVariable( QgsExpressionContextScope::StaticVariable( QgsExpressionContext::EXPR_GEOMETRY_PART_NUM, i + 1, true ) );
+          if ( needsExpressionContext )
+            mSymbolRenderContext->expressionContextScope()->addVariable( QgsExpressionContextScope::StaticVariable( QgsExpressionContext::EXPR_GEOMETRY_PART_NUM, i + 1, true ) );
 
           context.setGeometry( geomCollection.geometryN( i ) );
           const QgsPolygon &polygon = dynamic_cast<const QgsPolygon &>( *geomCollection.geometryN( i ) );