diff --git a/src/gui/editorwidgets/core/qgseditorwidgetwrapper.cpp b/src/gui/editorwidgets/core/qgseditorwidgetwrapper.cpp
index 943736b99ad9..79e23a8a7ce0 100644
--- a/src/gui/editorwidgets/core/qgseditorwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/core/qgseditorwidgetwrapper.cpp
@@ -26,12 +26,12 @@ QgsEditorWidgetWrapper::QgsEditorWidgetWrapper( QgsVectorLayer* vl, int fieldIdx
 {
 }
 
-int QgsEditorWidgetWrapper::fieldIdx()
+int QgsEditorWidgetWrapper::fieldIdx() const
 {
   return mFieldIdx;
 }
 
-QgsField QgsEditorWidgetWrapper::field()
+QgsField QgsEditorWidgetWrapper::field() const
 {
   if ( mFieldIdx < layer()->fields().count() )
     return layer()->fields().at( mFieldIdx );
@@ -39,7 +39,7 @@ QgsField QgsEditorWidgetWrapper::field()
     return QgsField();
 }
 
-QVariant QgsEditorWidgetWrapper::defaultValue()
+QVariant QgsEditorWidgetWrapper::defaultValue() const
 {
   return layer()->dataProvider()->defaultValue( mFieldIdx );
 }
diff --git a/src/gui/editorwidgets/core/qgseditorwidgetwrapper.h b/src/gui/editorwidgets/core/qgseditorwidgetwrapper.h
index 14c2a3c90829..d1598061d736 100644
--- a/src/gui/editorwidgets/core/qgseditorwidgetwrapper.h
+++ b/src/gui/editorwidgets/core/qgseditorwidgetwrapper.h
@@ -61,7 +61,7 @@ class GUI_EXPORT QgsEditorWidgetWrapper : public QgsWidgetWrapper
      *
      * @return The current value the widget represents
      */
-    virtual QVariant value() = 0;
+    virtual QVariant value() const = 0;
 
     /**
      * Access the field index.
@@ -70,7 +70,7 @@ class GUI_EXPORT QgsEditorWidgetWrapper : public QgsWidgetWrapper
      *
      * @see layer()
      */
-    int fieldIdx();
+    int fieldIdx() const;
 
     /**
      * Access the field.
@@ -79,7 +79,7 @@ class GUI_EXPORT QgsEditorWidgetWrapper : public QgsWidgetWrapper
      *
      * @see layer()
      */
-    QgsField field();
+    QgsField field() const;
 
     /**
      * Access the default value of the field.
@@ -88,7 +88,7 @@ class GUI_EXPORT QgsEditorWidgetWrapper : public QgsWidgetWrapper
      *
      * @see layer()
      */
-    QVariant defaultValue();
+    QVariant defaultValue() const;
 
     /**
      * Will return a wrapper for a given widget
diff --git a/src/gui/editorwidgets/core/qgswidgetwrapper.cpp b/src/gui/editorwidgets/core/qgswidgetwrapper.cpp
index f89fa01e69cf..eac35107432b 100644
--- a/src/gui/editorwidgets/core/qgswidgetwrapper.cpp
+++ b/src/gui/editorwidgets/core/qgswidgetwrapper.cpp
@@ -52,7 +52,7 @@ void QgsWidgetWrapper::setContext( const QgsAttributeEditorContext &context )
   mContext = context;
 }
 
-const QVariant QgsWidgetWrapper::config( const QString& key, const QVariant& defaultVal )
+QVariant QgsWidgetWrapper::config( const QString& key, const QVariant& defaultVal ) const
 {
   if ( mConfig.contains( key ) )
   {
@@ -61,17 +61,17 @@ const QVariant QgsWidgetWrapper::config( const QString& key, const QVariant& def
   return defaultVal;
 }
 
-const QgsEditorWidgetConfig QgsWidgetWrapper::config()
+QgsEditorWidgetConfig QgsWidgetWrapper::config() const
 {
   return mConfig;
 }
 
-const QgsAttributeEditorContext& QgsWidgetWrapper::context()
+const QgsAttributeEditorContext& QgsWidgetWrapper::context() const
 {
   return mContext;
 }
 
-QgsVectorLayer* QgsWidgetWrapper::layer()
+QgsVectorLayer* QgsWidgetWrapper::layer() const
 {
   return mLayer;
 }
diff --git a/src/gui/editorwidgets/core/qgswidgetwrapper.h b/src/gui/editorwidgets/core/qgswidgetwrapper.h
index 920a7ebcb89c..be920e83c155 100644
--- a/src/gui/editorwidgets/core/qgswidgetwrapper.h
+++ b/src/gui/editorwidgets/core/qgswidgetwrapper.h
@@ -87,21 +87,21 @@ class GUI_EXPORT QgsWidgetWrapper : public QObject
      *
      * @return the value assigned to this configuration option
      */
-    const QVariant config( const QString& key, const QVariant& defaultVal = QVariant() );
+    QVariant config( const QString& key, const QVariant& defaultVal = QVariant() ) const;
 
     /**
      * Returns the whole config
      *
      * @return The configuration
      */
-    const QgsEditorWidgetConfig config();
+    QgsEditorWidgetConfig config() const;
 
     /**
      * Returns information about the context in which this widget is shown
      *
      * @return context information
      */
-    const QgsAttributeEditorContext& context();
+    const QgsAttributeEditorContext& context() const;
 
     /**
      * Access the QgsVectorLayer, you are working on
@@ -110,7 +110,7 @@ class GUI_EXPORT QgsWidgetWrapper : public QObject
      *
      * @see field()
      */
-    QgsVectorLayer* layer();
+    QgsVectorLayer* layer() const;
 
     /**
      * Will return a wrapper for a given widget
@@ -130,7 +130,7 @@ class GUI_EXPORT QgsWidgetWrapper : public QObject
      *
      * @note Added in 2.12
      */
-    virtual bool valid() = 0;
+    virtual bool valid() const = 0;
 
   protected:
     /**
diff --git a/src/gui/editorwidgets/qgscheckboxwidgetwrapper.cpp b/src/gui/editorwidgets/qgscheckboxwidgetwrapper.cpp
index 41532705c990..289be91fed59 100644
--- a/src/gui/editorwidgets/qgscheckboxwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgscheckboxwidgetwrapper.cpp
@@ -23,7 +23,7 @@ QgsCheckboxWidgetWrapper::QgsCheckboxWidgetWrapper( QgsVectorLayer* vl, int fiel
 }
 
 
-QVariant QgsCheckboxWidgetWrapper::value()
+QVariant QgsCheckboxWidgetWrapper::value() const
 {
   QVariant v;
 
@@ -53,7 +53,7 @@ void QgsCheckboxWidgetWrapper::initWidget( QWidget* editor )
     connect( mGroupBox, SIGNAL( toggled( bool ) ), this, SLOT( valueChanged( bool ) ) );
 }
 
-bool QgsCheckboxWidgetWrapper::valid()
+bool QgsCheckboxWidgetWrapper::valid() const
 {
   return mCheckBox || mGroupBox;
 }
diff --git a/src/gui/editorwidgets/qgscheckboxwidgetwrapper.h b/src/gui/editorwidgets/qgscheckboxwidgetwrapper.h
index 5566165f59d4..e2b04000a0d6 100644
--- a/src/gui/editorwidgets/qgscheckboxwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgscheckboxwidgetwrapper.h
@@ -41,12 +41,12 @@ class GUI_EXPORT QgsCheckboxWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgsclassificationwidgetwrapper.cpp b/src/gui/editorwidgets/qgsclassificationwidgetwrapper.cpp
index 086cc8930f81..d8392eaa57cc 100644
--- a/src/gui/editorwidgets/qgsclassificationwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsclassificationwidgetwrapper.cpp
@@ -24,7 +24,7 @@ QgsClassificationWidgetWrapper::QgsClassificationWidgetWrapper( QgsVectorLayer*
 {
 }
 
-QVariant QgsClassificationWidgetWrapper::value()
+QVariant QgsClassificationWidgetWrapper::value() const
 {
   return mComboBox->itemData( mComboBox->currentIndex() );
 }
@@ -59,7 +59,7 @@ void QgsClassificationWidgetWrapper::initWidget( QWidget* editor )
   }
 }
 
-bool QgsClassificationWidgetWrapper::valid()
+bool QgsClassificationWidgetWrapper::valid() const
 {
   return mComboBox;
 }
diff --git a/src/gui/editorwidgets/qgsclassificationwidgetwrapper.h b/src/gui/editorwidgets/qgsclassificationwidgetwrapper.h
index 06f1cd03bc43..2673f27609eb 100644
--- a/src/gui/editorwidgets/qgsclassificationwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsclassificationwidgetwrapper.h
@@ -32,12 +32,12 @@ class GUI_EXPORT QgsClassificationWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
 
   protected:
     QWidget*createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgscolorwidgetwrapper.cpp b/src/gui/editorwidgets/qgscolorwidgetwrapper.cpp
index e8f5181201f0..5e0708a75542 100644
--- a/src/gui/editorwidgets/qgscolorwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgscolorwidgetwrapper.cpp
@@ -22,7 +22,7 @@ QgsColorWidgetWrapper::QgsColorWidgetWrapper( QgsVectorLayer* vl, int fieldIdx,
 }
 
 
-QVariant QgsColorWidgetWrapper::value()
+QVariant QgsColorWidgetWrapper::value() const
 {
   QVariant v;
 
@@ -46,7 +46,7 @@ void QgsColorWidgetWrapper::initWidget( QWidget* editor )
   connect( mColorButton, SIGNAL( colorChanged( QColor ) ), this, SLOT( valueChanged() ) );
 }
 
-bool QgsColorWidgetWrapper::valid()
+bool QgsColorWidgetWrapper::valid() const
 {
   return mColorButton;
 }
diff --git a/src/gui/editorwidgets/qgscolorwidgetwrapper.h b/src/gui/editorwidgets/qgscolorwidgetwrapper.h
index 8f45ccdd23ae..c66b85aa3dbd 100644
--- a/src/gui/editorwidgets/qgscolorwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgscolorwidgetwrapper.h
@@ -34,12 +34,12 @@ class GUI_EXPORT  QgsColorWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgsdatetimeeditwrapper.cpp b/src/gui/editorwidgets/qgsdatetimeeditwrapper.cpp
index 0ad247695c03..946b8230a85d 100644
--- a/src/gui/editorwidgets/qgsdatetimeeditwrapper.cpp
+++ b/src/gui/editorwidgets/qgsdatetimeeditwrapper.cpp
@@ -90,7 +90,7 @@ void QgsDateTimeEditWrapper::initWidget( QWidget *editor )
   }
 }
 
-bool QgsDateTimeEditWrapper::valid()
+bool QgsDateTimeEditWrapper::valid() const
 {
   return mQgsDateTimeEdit || mQDateTimeEdit;
 }
@@ -101,7 +101,7 @@ void QgsDateTimeEditWrapper::dateTimeChanged( const QDateTime& dateTime )
   emit valueChanged( dateTime.toString( fieldFormat ) );
 }
 
-QVariant QgsDateTimeEditWrapper::value()
+QVariant QgsDateTimeEditWrapper::value() const
 {
   if ( !mQDateTimeEdit )
     return QVariant( field().type() );
diff --git a/src/gui/editorwidgets/qgsdatetimeeditwrapper.h b/src/gui/editorwidgets/qgsdatetimeeditwrapper.h
index 960d645137a4..450e768fd996 100644
--- a/src/gui/editorwidgets/qgsdatetimeeditwrapper.h
+++ b/src/gui/editorwidgets/qgsdatetimeeditwrapper.h
@@ -51,10 +51,10 @@ class GUI_EXPORT QgsDateTimeEditWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
     QWidget *createWidget( QWidget *parent ) override;
     void initWidget( QWidget *editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant &value ) override;
diff --git a/src/gui/editorwidgets/qgsdefaultsearchwidgetwrapper.cpp b/src/gui/editorwidgets/qgsdefaultsearchwidgetwrapper.cpp
index 0d4176a82e67..4a7267b1e1d1 100644
--- a/src/gui/editorwidgets/qgsdefaultsearchwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsdefaultsearchwidgetwrapper.cpp
@@ -101,7 +101,7 @@ void QgsDefaultSearchWidgetWrapper::initWidget( QWidget* widget )
   mCaseString = "ILIKE";
 }
 
-bool QgsDefaultSearchWidgetWrapper::valid()
+bool QgsDefaultSearchWidgetWrapper::valid() const
 {
   return true;
 }
diff --git a/src/gui/editorwidgets/qgsdefaultsearchwidgetwrapper.h b/src/gui/editorwidgets/qgsdefaultsearchwidgetwrapper.h
index 1ac261b5989b..e47b12245632 100644
--- a/src/gui/editorwidgets/qgsdefaultsearchwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsdefaultsearchwidgetwrapper.h
@@ -47,7 +47,7 @@ class GUI_EXPORT QgsDefaultSearchWidgetWrapper : public QgsSearchWidgetWrapper
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   private:
     QgsFilterLineEdit* mLineEdit;
diff --git a/src/gui/editorwidgets/qgsenumerationwidgetwrapper.cpp b/src/gui/editorwidgets/qgsenumerationwidgetwrapper.cpp
index dd466aec7147..dca7140f50bc 100644
--- a/src/gui/editorwidgets/qgsenumerationwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsenumerationwidgetwrapper.cpp
@@ -25,7 +25,7 @@ QgsEnumerationWidgetWrapper::QgsEnumerationWidgetWrapper( QgsVectorLayer* vl, in
 }
 
 
-QVariant QgsEnumerationWidgetWrapper::value()
+QVariant QgsEnumerationWidgetWrapper::value() const
 {
   QVariant value;
 
@@ -57,7 +57,7 @@ void QgsEnumerationWidgetWrapper::initWidget( QWidget* editor )
   }
 }
 
-bool QgsEnumerationWidgetWrapper::valid()
+bool QgsEnumerationWidgetWrapper::valid() const
 {
   return mComboBox;
 }
diff --git a/src/gui/editorwidgets/qgsenumerationwidgetwrapper.h b/src/gui/editorwidgets/qgsenumerationwidgetwrapper.h
index 6fdd93657020..45d23d01ab85 100644
--- a/src/gui/editorwidgets/qgsenumerationwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsenumerationwidgetwrapper.h
@@ -32,12 +32,12 @@ class GUI_EXPORT QgsEnumerationWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgsfilenamewidgetwrapper.cpp b/src/gui/editorwidgets/qgsfilenamewidgetwrapper.cpp
index d87b9a366eb0..66748e1539e0 100644
--- a/src/gui/editorwidgets/qgsfilenamewidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsfilenamewidgetwrapper.cpp
@@ -30,7 +30,7 @@ QgsFileNameWidgetWrapper::QgsFileNameWidgetWrapper( QgsVectorLayer* vl, int fiel
 {
 }
 
-QVariant QgsFileNameWidgetWrapper::value()
+QVariant QgsFileNameWidgetWrapper::value() const
 {
   QVariant value;
 
@@ -48,7 +48,7 @@ QVariant QgsFileNameWidgetWrapper::value()
   return value;
 }
 
-bool QgsFileNameWidgetWrapper::valid()
+bool QgsFileNameWidgetWrapper::valid() const
 {
   return mLineEdit || mLabel;
 }
diff --git a/src/gui/editorwidgets/qgsfilenamewidgetwrapper.h b/src/gui/editorwidgets/qgsfilenamewidgetwrapper.h
index da6936cdf248..be767d3be233 100644
--- a/src/gui/editorwidgets/qgsfilenamewidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsfilenamewidgetwrapper.h
@@ -39,8 +39,8 @@ class GUI_EXPORT QgsFileNameWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
-    bool valid() override;
+    QVariant value() const override;
+    bool valid() const override;
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
diff --git a/src/gui/editorwidgets/qgshiddenwidgetwrapper.cpp b/src/gui/editorwidgets/qgshiddenwidgetwrapper.cpp
index d0bd17854dc6..2ceb15f8fec6 100644
--- a/src/gui/editorwidgets/qgshiddenwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgshiddenwidgetwrapper.cpp
@@ -23,7 +23,7 @@ QgsHiddenWidgetWrapper::QgsHiddenWidgetWrapper( QgsVectorLayer* vl, int fieldIdx
 }
 
 
-QVariant QgsHiddenWidgetWrapper::value()
+QVariant QgsHiddenWidgetWrapper::value() const
 {
   return mValue;
 }
@@ -40,7 +40,7 @@ void QgsHiddenWidgetWrapper::initWidget( QWidget* editor )
   editor->setVisible( false );
 }
 
-bool QgsHiddenWidgetWrapper::valid()
+bool QgsHiddenWidgetWrapper::valid() const
 {
   return true;
 }
diff --git a/src/gui/editorwidgets/qgshiddenwidgetwrapper.h b/src/gui/editorwidgets/qgshiddenwidgetwrapper.h
index c67daa46f18f..0858297f0b01 100644
--- a/src/gui/editorwidgets/qgshiddenwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgshiddenwidgetwrapper.h
@@ -31,12 +31,12 @@ class GUI_EXPORT QgsHiddenWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgsphotowidgetwrapper.cpp b/src/gui/editorwidgets/qgsphotowidgetwrapper.cpp
index fe2fef1669d3..8a173420977e 100644
--- a/src/gui/editorwidgets/qgsphotowidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsphotowidgetwrapper.cpp
@@ -100,7 +100,7 @@ void QgsPhotoWidgetWrapper::loadPixmap( const QString& fileName )
   }
 }
 
-QVariant QgsPhotoWidgetWrapper::value()
+QVariant QgsPhotoWidgetWrapper::value() const
 {
   QVariant v;
 
@@ -186,7 +186,7 @@ void QgsPhotoWidgetWrapper::initWidget( QWidget* editor )
   }
 }
 
-bool QgsPhotoWidgetWrapper::valid()
+bool QgsPhotoWidgetWrapper::valid() const
 {
 #ifdef WITH_QTWEBKIT
   return mPhotoLabel || mLineEdit || mButton || mWebView;
diff --git a/src/gui/editorwidgets/qgsphotowidgetwrapper.h b/src/gui/editorwidgets/qgsphotowidgetwrapper.h
index 6f6414ce7bed..6223e08563cd 100644
--- a/src/gui/editorwidgets/qgsphotowidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsphotowidgetwrapper.h
@@ -48,12 +48,12 @@ class GUI_EXPORT QgsPhotoWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgsrangewidgetwrapper.cpp b/src/gui/editorwidgets/qgsrangewidgetwrapper.cpp
index 4c5f82ed8639..afc3aab24daf 100644
--- a/src/gui/editorwidgets/qgsrangewidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsrangewidgetwrapper.cpp
@@ -193,7 +193,7 @@ void QgsRangeWidgetWrapper::initWidget( QWidget* editor )
   }
 }
 
-bool QgsRangeWidgetWrapper::valid()
+bool QgsRangeWidgetWrapper::valid() const
 {
   return mSlider || mDial || mQgsDial || mQgsSlider || mIntSpinBox || mDoubleSpinBox;
 }
@@ -206,7 +206,7 @@ void QgsRangeWidgetWrapper::valueChanged( const QVariant& v )
     valueChanged( v.toDouble() );
 }
 
-QVariant QgsRangeWidgetWrapper::value()
+QVariant QgsRangeWidgetWrapper::value() const
 {
   QVariant value;
 
diff --git a/src/gui/editorwidgets/qgsrangewidgetwrapper.h b/src/gui/editorwidgets/qgsrangewidgetwrapper.h
index 3bd92ea42b57..7e58b88e67e6 100644
--- a/src/gui/editorwidgets/qgsrangewidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsrangewidgetwrapper.h
@@ -45,12 +45,12 @@ class GUI_EXPORT QgsRangeWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    virtual QVariant value() override;
+    virtual QVariant value() const override;
 
   protected:
     virtual QWidget* createWidget( QWidget* parent ) override;
     virtual void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     virtual void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgsrelationreferencewidgetwrapper.cpp b/src/gui/editorwidgets/qgsrelationreferencewidgetwrapper.cpp
index 11951411f7d7..a1512186c0d4 100644
--- a/src/gui/editorwidgets/qgsrelationreferencewidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsrelationreferencewidgetwrapper.cpp
@@ -82,7 +82,7 @@ void QgsRelationReferenceWidgetWrapper::initWidget( QWidget* editor )
   connect( mWidget, SIGNAL( foreignKeyChanged( QVariant ) ), this,  SLOT( foreignKeyChanged( QVariant ) ) );
 }
 
-QVariant QgsRelationReferenceWidgetWrapper::value()
+QVariant QgsRelationReferenceWidgetWrapper::value() const
 {
   if ( !mWidget )
     return QVariant( field().type() );
@@ -99,7 +99,7 @@ QVariant QgsRelationReferenceWidgetWrapper::value()
   }
 }
 
-bool QgsRelationReferenceWidgetWrapper::valid()
+bool QgsRelationReferenceWidgetWrapper::valid() const
 {
   return mWidget;
 }
diff --git a/src/gui/editorwidgets/qgsrelationreferencewidgetwrapper.h b/src/gui/editorwidgets/qgsrelationreferencewidgetwrapper.h
index 38b540a72f87..fa80fb77638d 100644
--- a/src/gui/editorwidgets/qgsrelationreferencewidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsrelationreferencewidgetwrapper.h
@@ -48,8 +48,8 @@ class GUI_EXPORT QgsRelationReferenceWidgetWrapper : public QgsEditorWidgetWrapp
 
     virtual QWidget* createWidget( QWidget* parent ) override;
     virtual void initWidget( QWidget* editor ) override;
-    virtual QVariant value() override;
-    bool valid() override;
+    virtual QVariant value() const override;
+    bool valid() const override;
 
   public slots:
     virtual void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgsrelationwidgetwrapper.cpp b/src/gui/editorwidgets/qgsrelationwidgetwrapper.cpp
index c61db70912c2..122189e8c19f 100644
--- a/src/gui/editorwidgets/qgsrelationwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsrelationwidgetwrapper.cpp
@@ -74,7 +74,7 @@ void QgsRelationWidgetWrapper::initWidget( QWidget* editor )
   mWidget = w;
 }
 
-bool QgsRelationWidgetWrapper::valid()
+bool QgsRelationWidgetWrapper::valid() const
 {
   return mWidget;
 }
diff --git a/src/gui/editorwidgets/qgsrelationwidgetwrapper.h b/src/gui/editorwidgets/qgsrelationwidgetwrapper.h
index c57007b4a9df..eb0dd0743063 100644
--- a/src/gui/editorwidgets/qgsrelationwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsrelationwidgetwrapper.h
@@ -34,7 +34,7 @@ class GUI_EXPORT QgsRelationWidgetWrapper : public QgsWidgetWrapper
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setFeature( const QgsFeature& feature ) override;
diff --git a/src/gui/editorwidgets/qgstexteditwrapper.cpp b/src/gui/editorwidgets/qgstexteditwrapper.cpp
index 7b3f2a6e3a25..4431dbe2232b 100644
--- a/src/gui/editorwidgets/qgstexteditwrapper.cpp
+++ b/src/gui/editorwidgets/qgstexteditwrapper.cpp
@@ -29,7 +29,7 @@ QgsTextEditWrapper::QgsTextEditWrapper( QgsVectorLayer* vl, int fieldIdx, QWidge
 {
 }
 
-QVariant QgsTextEditWrapper::value()
+QVariant QgsTextEditWrapper::value() const
 {
   QString v;
 
@@ -130,7 +130,7 @@ void QgsTextEditWrapper::initWidget( QWidget* editor )
   }
 }
 
-bool QgsTextEditWrapper::valid()
+bool QgsTextEditWrapper::valid() const
 {
   return mLineEdit || mTextEdit || mPlainTextEdit;
 }
diff --git a/src/gui/editorwidgets/qgstexteditwrapper.h b/src/gui/editorwidgets/qgstexteditwrapper.h
index 19527ff8e612..5165296acf0b 100644
--- a/src/gui/editorwidgets/qgstexteditwrapper.h
+++ b/src/gui/editorwidgets/qgstexteditwrapper.h
@@ -41,12 +41,12 @@ class GUI_EXPORT QgsTextEditWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
 
   protected:
     QWidget*createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgsuniquevaluewidgetwrapper.cpp b/src/gui/editorwidgets/qgsuniquevaluewidgetwrapper.cpp
index 945254c2d0f4..411a6ecde254 100644
--- a/src/gui/editorwidgets/qgsuniquevaluewidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsuniquevaluewidgetwrapper.cpp
@@ -28,7 +28,7 @@ QgsUniqueValuesWidgetWrapper::QgsUniqueValuesWidgetWrapper( QgsVectorLayer* vl,
 {
 }
 
-QVariant QgsUniqueValuesWidgetWrapper::value()
+QVariant QgsUniqueValuesWidgetWrapper::value() const
 {
   QVariant value;
 
@@ -100,7 +100,7 @@ void QgsUniqueValuesWidgetWrapper::initWidget( QWidget* editor )
   }
 }
 
-bool QgsUniqueValuesWidgetWrapper::valid()
+bool QgsUniqueValuesWidgetWrapper::valid() const
 {
   return mComboBox || mLineEdit;
 }
diff --git a/src/gui/editorwidgets/qgsuniquevaluewidgetwrapper.h b/src/gui/editorwidgets/qgsuniquevaluewidgetwrapper.h
index 15b97cbc039b..5aaec3909aeb 100644
--- a/src/gui/editorwidgets/qgsuniquevaluewidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsuniquevaluewidgetwrapper.h
@@ -39,12 +39,12 @@ class GUI_EXPORT QgsUniqueValuesWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgsuuidwidgetwrapper.cpp b/src/gui/editorwidgets/qgsuuidwidgetwrapper.cpp
index d4309a16bb3f..55ff56ac06b4 100644
--- a/src/gui/editorwidgets/qgsuuidwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsuuidwidgetwrapper.cpp
@@ -24,7 +24,7 @@ QgsUuidWidgetWrapper::QgsUuidWidgetWrapper( QgsVectorLayer* vl, int fieldIdx, QW
 {
 }
 
-QVariant QgsUuidWidgetWrapper::value()
+QVariant QgsUuidWidgetWrapper::value() const
 {
   QVariant v;
 
@@ -49,7 +49,7 @@ void QgsUuidWidgetWrapper::initWidget( QWidget* editor )
     mLineEdit->setEnabled( false );
 }
 
-bool QgsUuidWidgetWrapper::valid()
+bool QgsUuidWidgetWrapper::valid() const
 {
   return mLineEdit || mLabel;
 }
diff --git a/src/gui/editorwidgets/qgsuuidwidgetwrapper.h b/src/gui/editorwidgets/qgsuuidwidgetwrapper.h
index 16961dfc16fc..7977203f8aa0 100644
--- a/src/gui/editorwidgets/qgsuuidwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsuuidwidgetwrapper.h
@@ -35,12 +35,12 @@ class GUI_EXPORT QgsUuidWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgsvaluemapsearchwidgetwrapper.cpp b/src/gui/editorwidgets/qgsvaluemapsearchwidgetwrapper.cpp
index 368de908787a..61f0689684a7 100644
--- a/src/gui/editorwidgets/qgsvaluemapsearchwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsvaluemapsearchwidgetwrapper.cpp
@@ -59,7 +59,7 @@ QString QgsValueMapSearchWidgetWrapper::expression()
   return mExpression;
 }
 
-bool QgsValueMapSearchWidgetWrapper::valid()
+bool QgsValueMapSearchWidgetWrapper::valid() const
 {
   return true;
 }
diff --git a/src/gui/editorwidgets/qgsvaluemapsearchwidgetwrapper.h b/src/gui/editorwidgets/qgsvaluemapsearchwidgetwrapper.h
index 84b6dad1ef10..e60fcffa69cf 100644
--- a/src/gui/editorwidgets/qgsvaluemapsearchwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsvaluemapsearchwidgetwrapper.h
@@ -32,7 +32,7 @@ class GUI_EXPORT QgsValueMapSearchWidgetWrapper : public QgsSearchWidgetWrapper
     explicit QgsValueMapSearchWidgetWrapper( QgsVectorLayer* vl, int fieldIdx, QWidget* parent = 0 );
     bool applyDirectly() override;
     QString expression() override;
-    bool valid() override;
+    bool valid() const override;
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
diff --git a/src/gui/editorwidgets/qgsvaluemapwidgetwrapper.cpp b/src/gui/editorwidgets/qgsvaluemapwidgetwrapper.cpp
index 42a1eee34369..6fe31ed59b14 100644
--- a/src/gui/editorwidgets/qgsvaluemapwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsvaluemapwidgetwrapper.cpp
@@ -22,7 +22,7 @@ QgsValueMapWidgetWrapper::QgsValueMapWidgetWrapper( QgsVectorLayer* vl, int fiel
 }
 
 
-QVariant QgsValueMapWidgetWrapper::value()
+QVariant QgsValueMapWidgetWrapper::value() const
 {
   QVariant v;
 
@@ -55,7 +55,7 @@ void QgsValueMapWidgetWrapper::initWidget( QWidget* editor )
   }
 }
 
-bool QgsValueMapWidgetWrapper::valid()
+bool QgsValueMapWidgetWrapper::valid() const
 {
   return mComboBox;
 }
diff --git a/src/gui/editorwidgets/qgsvaluemapwidgetwrapper.h b/src/gui/editorwidgets/qgsvaluemapwidgetwrapper.h
index d73350a4eda1..c3276fb957cf 100644
--- a/src/gui/editorwidgets/qgsvaluemapwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsvaluemapwidgetwrapper.h
@@ -41,12 +41,12 @@ class GUI_EXPORT QgsValueMapWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgsvaluerelationsearchwidgetwrapper.cpp b/src/gui/editorwidgets/qgsvaluerelationsearchwidgetwrapper.cpp
index 2c0fb325c62f..27f6ce725687 100644
--- a/src/gui/editorwidgets/qgsvaluerelationsearchwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsvaluerelationsearchwidgetwrapper.cpp
@@ -89,7 +89,7 @@ QVariant QgsValueRelationSearchWidgetWrapper::value() const
   return v;
 }
 
-bool QgsValueRelationSearchWidgetWrapper::valid()
+bool QgsValueRelationSearchWidgetWrapper::valid() const
 {
   return true;
 }
diff --git a/src/gui/editorwidgets/qgsvaluerelationsearchwidgetwrapper.h b/src/gui/editorwidgets/qgsvaluerelationsearchwidgetwrapper.h
index a2378ae10cf0..4729ed2c1a8f 100644
--- a/src/gui/editorwidgets/qgsvaluerelationsearchwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsvaluerelationsearchwidgetwrapper.h
@@ -43,7 +43,7 @@ class GUI_EXPORT QgsValueRelationSearchWidgetWrapper : public QgsSearchWidgetWra
     explicit QgsValueRelationSearchWidgetWrapper( QgsVectorLayer* vl, int fieldIdx, QWidget* parent = 0 );
     bool applyDirectly() override;
     QString expression() override;
-    bool valid() override;
+    bool valid() const override;
     QVariant value() const;
 
   protected:
diff --git a/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp b/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp
index b19282e73834..1edfb244992a 100644
--- a/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp
@@ -59,7 +59,7 @@ QgsValueRelationWidgetWrapper::QgsValueRelationWidgetWrapper( QgsVectorLayer* vl
 }
 
 
-QVariant QgsValueRelationWidgetWrapper::value()
+QVariant QgsValueRelationWidgetWrapper::value() const
 {
   QVariant v;
 
@@ -164,7 +164,7 @@ void QgsValueRelationWidgetWrapper::initWidget( QWidget* editor )
   }
 }
 
-bool QgsValueRelationWidgetWrapper::valid()
+bool QgsValueRelationWidgetWrapper::valid() const
 {
   return mListWidget || mLineEdit || mComboBox;
 }
diff --git a/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.h b/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.h
index 91a5b79adafe..1f505a4689d9 100644
--- a/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.h
@@ -63,14 +63,14 @@ class GUI_EXPORT QgsValueRelationWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
     // TODO or have friend class :)
     static ValueRelationCache createCache( const QgsEditorWidgetConfig& config );
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;
diff --git a/src/gui/editorwidgets/qgswebviewwidgetwrapper.cpp b/src/gui/editorwidgets/qgswebviewwidgetwrapper.cpp
index 13aa6f1f85df..5cff1d505430 100644
--- a/src/gui/editorwidgets/qgswebviewwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgswebviewwidgetwrapper.cpp
@@ -42,7 +42,7 @@ void QgsWebViewWidgetWrapper::loadUrl( const QString &url )
     mWebView->load( path );
 }
 
-QVariant QgsWebViewWidgetWrapper::value()
+QVariant QgsWebViewWidgetWrapper::value() const
 {
   QVariant v;
 
@@ -127,7 +127,7 @@ void QgsWebViewWidgetWrapper::initWidget( QWidget* editor )
   }
 }
 
-bool QgsWebViewWidgetWrapper::valid()
+bool QgsWebViewWidgetWrapper::valid() const
 {
   return mWebView || mButton || mLineEdit;
 }
diff --git a/src/gui/editorwidgets/qgswebviewwidgetwrapper.h b/src/gui/editorwidgets/qgswebviewwidgetwrapper.h
index f15b85fd8a84..3b749778f784 100644
--- a/src/gui/editorwidgets/qgswebviewwidgetwrapper.h
+++ b/src/gui/editorwidgets/qgswebviewwidgetwrapper.h
@@ -36,12 +36,12 @@ class GUI_EXPORT QgsWebViewWidgetWrapper : public QgsEditorWidgetWrapper
 
     // QgsEditorWidgetWrapper interface
   public:
-    QVariant value() override;
+    QVariant value() const override;
 
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
-    bool valid() override;
+    bool valid() const override;
 
   public slots:
     void setValue( const QVariant& value ) override;