Use feature from expression context in expression builder preview

instead of always getting first feature from the layer This means that e.g. expression builder previews in composer atlas will use the current atlas preview feature Also remove an unnecessary restriction that blocks the preview if a layer has no features
qgis · Jan 12, 2017 · a13ef7b · a13ef7b · NathanW2 · Jan 12, 2017
1 parent 55f6b11
commit a13ef7b
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Showing 2 changed files with 9 additions and 24 deletions.
diff --git a/src/gui/qgsexpressionbuilderwidget.cpp b/src/gui/qgsexpressionbuilderwidget.cpp
@@ -543,33 +543,19 @@ void QgsExpressionBuilderWidget::on_txtExpressionString_textChanged()
     // Only set calculator if we have layer, else use default.
     exp.setGeomCalculator( &mDa );
 
-    if ( !mFeature.isValid() )
+    if ( !mExpressionContext.feature().isValid() )
     {
-      mLayer->getFeatures().nextFeature( mFeature );
-    }
-
-    if ( mFeature.isValid() )
-    {
-      mExpressionContext.setFeature( mFeature );
-      QVariant value = exp.evaluate( &mExpressionContext );
-      if ( !exp.hasEvalError() )
-        lblPreview->setText( QgsExpression::formatPreviewString( value ) );
-    }
-    else
-    {
-      // The feature is invalid because we don't have one but that doesn't mean user can't
-      // build a expression string.  They just get no preview.
-      lblPreview->setText( QLatin1String( "" ) );
+      // no feature passed yet, try to get from layer
+      QgsFeature f;
+      mLayer->getFeatures().nextFeature( f );
+      mExpressionContext.setFeature( f );
     }
   }
-  else
+
+  QVariant value = exp.evaluate( &mExpressionContext );
+  if ( !exp.hasEvalError() )
   {
-    // No layer defined
-    QVariant value = exp.evaluate( &mExpressionContext );
-    if ( !exp.hasEvalError() )
-    {
-      lblPreview->setText( QgsExpression::formatPreviewString( value ) );
-    }
+    lblPreview->setText( QgsExpression::formatPreviewString( value ) );
   }
 
   if ( exp.hasParserError() || exp.hasEvalError() )

diff --git a/src/gui/qgsexpressionbuilderwidget.h b/src/gui/qgsexpressionbuilderwidget.h
@@ -307,7 +307,6 @@ class GUI_EXPORT QgsExpressionBuilderWidget : public QWidget, private Ui::QgsExp
     QSortFilterProxyModel *mProxyValues;
     QgsExpressionItemSearchProxy *mProxyModel;
     QMap<QString, QgsExpressionItem*> mExpressionGroups;
-    QgsFeature mFeature;
     QgsExpressionHighlighter* highlighter;
     bool mExpressionValid;
     QgsDistanceArea mDa;