Fix some const-issues

Author: m-kuhn

python/core/qgsvectorlayer.sip

@@ -191,7 +191,7 @@ class QgsVectorLayer : QgsMapLayer
     void setDisplayField( const QString& fldName = "" );
 
     /** Returns the primary display field name used in the identify results dialog */
-    const QString displayField() const;
+    QString displayField() const;
 
     /** Set the preview expression, used to create a human readable preview string.
      *  Used e.g. in the attribute table feature list. Uses { @link QgsExpression }.
@@ -207,7 +207,7 @@ class QgsVectorLayer : QgsMapLayer
      *
      *  @return The expression which will be used to preview features for this layer
      */
-    const QString displayExpression();
+    QString displayExpression() const;
 
     /** Returns the data provider */
     QgsVectorDataProvider* dataProvider();

src/core/qgsvectorlayer.cpp

@@ -2878,7 +2878,7 @@ void QgsVectorLayer::setCoordinateSystem()
 }
 
 
-const QString QgsVectorLayer::displayField() const
+QString QgsVectorLayer::displayField() const
 {
   return mDisplayField;
 }
@@ -2888,7 +2888,7 @@ void QgsVectorLayer::setDisplayExpression( const QString &displayExpression )
   mDisplayExpression = displayExpression;
 }
 
-const QString QgsVectorLayer::displayExpression()
+QString QgsVectorLayer::displayExpression() const
 {
   return mDisplayExpression;
 }

src/core/qgsvectorlayer.h

@@ -556,7 +556,7 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer
     void setDisplayField( const QString& fldName = "" );
 
     /** Returns the primary display field name used in the identify results dialog */
-    const QString displayField() const;
+    QString displayField() const;
 
     /** Set the preview expression, used to create a human readable preview string.
      *  Used e.g. in the attribute table feature list. Uses { @link QgsExpression }.
@@ -572,7 +572,7 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer
      *
      *  @return The expression which will be used to preview features for this layer
      */
-    const QString displayExpression();
+    QString displayExpression() const;
 
     /** Returns the data provider */
     QgsVectorDataProvider* dataProvider();