Optimise expression context creation

Sponsored by DB Fahrwegdienste GmbH

src/app/qgisapp.cpp

@@ -7345,11 +7345,7 @@ void QgisApp::editPaste( QgsMapLayer *destinationLayer )
     remap.insert( idx, dst );
   }
 
-  QgsExpressionContext context;
-  context << QgsExpressionContextUtils::globalScope()
-  << QgsExpressionContextUtils::projectScope()
-  << QgsExpressionContextUtils::layerScope( pasteVectorLayer );
-
+  QgsExpressionContext context = pasteVectorLayer->createExpressionContext();
   int dstAttrCount = pasteVectorLayer->fields().count();
 
   QgsFeatureList::iterator featureIt = features.begin();

src/app/qgsfeatureaction.cpp

@@ -145,10 +145,7 @@ bool QgsFeatureAction::addFeature( const QgsAttributeMap& defaultAttributes, boo
   bool reuseLastValues = settings.value( "/qgis/digitizing/reuseLastValues", false ).toBool();
   QgsDebugMsg( QString( "reuseLastValues: %1" ).arg( reuseLastValues ) );
 
-  QgsExpressionContext context;
-  context << QgsExpressionContextUtils::globalScope()
-  << QgsExpressionContextUtils::projectScope()
-  << QgsExpressionContextUtils::layerScope( mLayer );
+  QgsExpressionContext context = mLayer->createExpressionContext();
 
   // add the fields to the QgsFeature
   const QgsFields& fields = mLayer->fields();

src/app/qgsmergeattributesdialog.cpp

@@ -523,10 +523,7 @@ QgsAttributes QgsMergeAttributesDialog::mergedAttributes() const
     return QgsAttributes();
   }
 
-  QgsExpressionContext context;
-  context << QgsExpressionContextUtils::globalScope()
-  << QgsExpressionContextUtils::projectScope()
-  << QgsExpressionContextUtils::layerScope( mVectorLayer );
+  QgsExpressionContext context = mVectorLayer->createExpressionContext();
 
   int widgetIndex = 0;
   QgsAttributes results( mFields.count() );

src/core/qgsofflineediting.cpp

@@ -737,10 +737,7 @@ void QgsOfflineEditing::applyFeaturesAdded( QgsVectorLayer* offlineLayer, QgsVec
 
   QgsFields remoteFlds = remoteLayer->fields();
 
-  QgsExpressionContext context;
-  context << QgsExpressionContextUtils::globalScope()
-  << QgsExpressionContextUtils::projectScope()
-  << QgsExpressionContextUtils::layerScope( remoteLayer );
+  QgsExpressionContext context = remoteLayer->createExpressionContext();
 
   // get new features from offline layer
   QgsFeatureList features;