Show current expression of virtual fields

Author: m-kuhn

src/app/qgsfieldsproperties.cpp

@@ -37,6 +37,7 @@
 #include <QMessageBox>
 #include <QSettings>
 #include <QFileDialog>
+#include <QHBoxLayout>
 
 QgsFieldsProperties::QgsFieldsProperties( QgsVectorLayer *layer, QWidget* parent )
     : QWidget( parent )
@@ -242,9 +243,23 @@ void QgsFieldsProperties::setRow( int row, int idx, const QgsField& field )
   mFieldsList->setItem( row, attrTypeNameCol, new QTableWidgetItem( field.typeName() ) );
   mFieldsList->setItem( row, attrLengthCol, new QTableWidgetItem( QString::number( field.length() ) ) );
   mFieldsList->setItem( row, attrPrecCol, new QTableWidgetItem( QString::number( field.precision() ) ) );
-  mFieldsList->setItem( row, attrCommentCol, new QTableWidgetItem( field.comment() ) );
+  if ( mLayer->pendingFields().fieldOrigin( idx ) == QgsFields::OriginExpression )
+  {
+    QWidget* expressionWidget = new QWidget;
+    expressionWidget->setLayout( new QHBoxLayout );
+    QToolButton* editExpressionButton = new QToolButton;
+    editExpressionButton->setIcon( QgsApplication::getThemeIcon( "/mIconExpression.svg" ) );
+    expressionWidget->layout()->setContentsMargins( 0, 0, 0, 0 );
+    expressionWidget->layout()->addWidget( editExpressionButton );
+    expressionWidget->layout()->addWidget( new QLabel( mLayer->expressionField( idx ) ) );
+    mFieldsList->setCellWidget( row, attrCommentCol, expressionWidget );
+  }
+  else
+  {
+    mFieldsList->setItem( row, attrCommentCol, new QTableWidgetItem( field.comment() ) );
+  }
 
-  for ( int i = 0; i < attrEditTypeCol; i++ )
+  for ( int i = 0; i < attrCommentCol; i++ )
     mFieldsList->item( row, i )->setFlags( mFieldsList->item( row, i )->flags() & ~Qt::ItemIsEditable );
 
   FieldConfig cfg( mLayer, idx );

src/core/qgsexpression.cpp

@@ -2235,8 +2235,8 @@ QVariant QgsExpression::NodeBinaryOperator::eval( QgsExpression* parent, const Q
     case boPlus:
       if ( vL.type() == QVariant::String && vR.type() == QVariant::String )
       {
-        QString sL = getStringValue( vL, parent ); ENSURE_NO_EVAL_ERROR;
-        QString sR = getStringValue( vR, parent ); ENSURE_NO_EVAL_ERROR;
+        QString sL = isNull( vL ) ? QString() : getStringValue( vL, parent ); ENSURE_NO_EVAL_ERROR;
+        QString sR = isNull( vR ) ? QString() : getStringValue( vR, parent ); ENSURE_NO_EVAL_ERROR;
         return QVariant( sL + sR );
       }
       //intentional fall-through

src/core/qgsexpressionfieldbuffer.h

@@ -75,7 +75,7 @@ class CORE_EXPORT QgsExpressionFieldBuffer
      */
     void updateFields( QgsFields& flds );
 
-    const QList<ExpressionField> expressions() const { return mExpressions; }
+    const QList<ExpressionField>& expressions() const { return mExpressions; }
 
   private:
     QList<ExpressionField> mExpressions;

src/core/qgsvectorlayer.cpp

@@ -2859,6 +2859,12 @@ void QgsVectorLayer::removeExpressionField( int index )
   emit attributeDeleted( index );
 }
 
+const QString QgsVectorLayer::expressionField( int index )
+{
+  int oi = mUpdatedFields.fieldOriginIndex( index );
+  return mExpressionFieldBuffer->expressions().value( oi ).expression;
+}
+
 void QgsVectorLayer::updateFields()
 {
   if ( !mDataProvider )

src/core/qgsvectorlayer.h

@@ -668,6 +668,8 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer
      */
     void removeExpressionField( int index );
 
+    const QString expressionField( int index );
+
     /** Get the label object associated with this layer */
     QgsLabel *label();