diff --git a/python/core/qgseditformconfig.sip b/python/core/qgseditformconfig.sip
index 06ecdc39d647..4148ac1127d5 100644
--- a/python/core/qgseditformconfig.sip
+++ b/python/core/qgseditformconfig.sip
@@ -474,7 +474,16 @@ class QgsEditFormConfig : QObject
     /**
      * If set to false, the widget at the given index will be read-only.
      */
-    void setReadOnly(int idx, bool readOnly );
+    void setReadOnly( int idx, bool readOnly = true );
+
+    /**
+     * Returns if the field at fieldidx should be treated as NOT NULL value
+     */
+    bool notNull( int fieldidx) const;
+    /**
+     * Set if the field at fieldidx should be treated as NOT NULL value
+     */
+    void setNotNull( int idx, bool notnull = true );
 
     /**
      * If this returns true, the widget at the given index will receive its label on the previous line
diff --git a/python/core/qgsfield.sip b/python/core/qgsfield.sip
index ce63bdc41f2d..a1bd42eef03f 100644
--- a/python/core/qgsfield.sip
+++ b/python/core/qgsfield.sip
@@ -165,7 +165,7 @@ class QgsField
     /* Raise an exception if the arguments couldn't be parsed. */
     sipNoMethod(sipParseErr, sipName_QgsField, sipName_convertCompatible, doc_QgsField_convertCompatible);
 
-    return NULL;
+    return nullptr;
 %End
 
     //! Allows direct construction of QVariants from fields.
diff --git a/src/app/qgsattributetypedialog.cpp b/src/app/qgsattributetypedialog.cpp
index 1d45831f3e44..0ed4bef46a84 100644
--- a/src/app/qgsattributetypedialog.cpp
+++ b/src/app/qgsattributetypedialog.cpp
@@ -163,16 +163,26 @@ void QgsAttributeTypeDialog::setWidgetV2Config( const QgsEditorWidgetConfig& con
   mWidgetV2Config = config;
 }
 
-bool QgsAttributeTypeDialog::fieldEditable()
+bool QgsAttributeTypeDialog::fieldEditable() const
 {
   return isFieldEditableCheckBox->isChecked();
 }
 
-bool QgsAttributeTypeDialog::labelOnTop()
+void QgsAttributeTypeDialog::setNotNull( bool notnull )
+{
+  notNullCheckBox->setChecked( notnull );
+}
+
+bool QgsAttributeTypeDialog::labelOnTop() const
 {
   return labelOnTopCheckBox->isChecked();
 }
 
+bool QgsAttributeTypeDialog::notNull() const
+{
+  return notNullCheckBox->isChecked();
+}
+
 void QgsAttributeTypeDialog::setFieldEditable( bool editable )
 {
   isFieldEditableCheckBox->setChecked( editable );
diff --git a/src/app/qgsattributetypedialog.h b/src/app/qgsattributetypedialog.h
index 578d2a003191..6ed6d73a7536 100644
--- a/src/app/qgsattributetypedialog.h
+++ b/src/app/qgsattributetypedialog.h
@@ -69,6 +69,11 @@ class APP_EXPORT QgsAttributeTypeDialog: public QDialog, private Ui::QgsAttribut
      */
     void setLabelOnTop( bool onTop );
 
+    /**
+     * Getter for checkbox for label on top of field
+     */
+    bool labelOnTop() const;
+
     /**
      * Setter for checkbox for editable state of field
      */
@@ -77,12 +82,17 @@ class APP_EXPORT QgsAttributeTypeDialog: public QDialog, private Ui::QgsAttribut
     /**
      * Getter for checkbox for editable state of field
      */
-    bool fieldEditable();
+    bool fieldEditable() const;
 
     /**
-     * Getter for checkbox for label on top of field
+     * Getter for checkbox for not null
+     */
+    void setNotNull( bool notnull );
+
+    /**
+     * Getter for checkbox for not null
      */
-    bool labelOnTop();
+    bool notNull() const;
 
   private slots:
     /**
diff --git a/src/app/qgsfieldsproperties.cpp b/src/app/qgsfieldsproperties.cpp
index 9278c5581c66..03c38ad51a57 100644
--- a/src/app/qgsfieldsproperties.cpp
+++ b/src/app/qgsfieldsproperties.cpp
@@ -527,6 +527,7 @@ void QgsFieldsProperties::attributeTypeDialog()
 
   attributeTypeDialog.setFieldEditable( cfg.mEditable );
   attributeTypeDialog.setLabelOnTop( cfg.mLabelOnTop );
+  attributeTypeDialog.setNotNull( cfg.mNotNull );
 
   attributeTypeDialog.setWidgetV2Config( cfg.mEditorWidgetV2Config );
   attributeTypeDialog.setWidgetV2Type( cfg.mEditorWidgetV2Type );
@@ -536,6 +537,7 @@ void QgsFieldsProperties::attributeTypeDialog()
 
   cfg.mEditable = attributeTypeDialog.fieldEditable();
   cfg.mLabelOnTop = attributeTypeDialog.labelOnTop();
+  cfg.mNotNull = attributeTypeDialog.notNull();
 
   cfg.mEditorWidgetV2Type = attributeTypeDialog.editorWidgetV2Type();
   cfg.mEditorWidgetV2Config = attributeTypeDialog.editorWidgetV2Config();
@@ -908,6 +910,7 @@ void QgsFieldsProperties::apply()
 
     mLayer->editFormConfig()->setReadOnly( i, !cfg.mEditable );
     mLayer->editFormConfig()->setLabelOnTop( i, cfg.mLabelOnTop );
+    mLayer->editFormConfig()->setNotNull( i, cfg.mNotNull );
 
     mLayer->editFormConfig()->setWidgetType( idx, cfg.mEditorWidgetV2Type );
     mLayer->editFormConfig()->setWidgetConfig( idx, cfg.mEditorWidgetV2Config );
@@ -974,6 +977,7 @@ QgsFieldsProperties::FieldConfig::FieldConfig()
     : mEditable( true )
     , mEditableEnabled( true )
     , mLabelOnTop( false )
+    , mNotNull( false )
     , mButton( nullptr )
 {
 }
@@ -985,6 +989,7 @@ QgsFieldsProperties::FieldConfig::FieldConfig( QgsVectorLayer* layer, int idx )
   mEditableEnabled = layer->fields().fieldOrigin( idx ) != QgsFields::OriginJoin
                      && layer->fields().fieldOrigin( idx ) != QgsFields::OriginExpression;
   mLabelOnTop = layer->editFormConfig()->labelOnTop( idx );
+  mNotNull = layer->editFormConfig()->notNull( idx );
   mEditorWidgetV2Type = layer->editFormConfig()->widgetType( idx );
   mEditorWidgetV2Config = layer->editFormConfig()->widgetConfig( idx );
 
diff --git a/src/app/qgsfieldsproperties.h b/src/app/qgsfieldsproperties.h
index 2189e862a212..ae53b3d0bf1b 100644
--- a/src/app/qgsfieldsproperties.h
+++ b/src/app/qgsfieldsproperties.h
@@ -92,6 +92,7 @@ class APP_EXPORT QgsFieldsProperties : public QWidget, private Ui_QgsFieldsPrope
         bool mEditable;
         bool mEditableEnabled;
         bool mLabelOnTop;
+        bool mNotNull;
         QPushButton* mButton;
         QString mEditorWidgetV2Type;
         QMap<QString, QVariant> mEditorWidgetV2Config;
diff --git a/src/core/qgseditformconfig.cpp b/src/core/qgseditformconfig.cpp
index 4c9279010655..e98deda8afda 100644
--- a/src/core/qgseditformconfig.cpp
+++ b/src/core/qgseditformconfig.cpp
@@ -119,6 +119,14 @@ bool QgsEditFormConfig::labelOnTop( int idx ) const
     return false;
 }
 
+bool QgsEditFormConfig::notNull( int idx ) const
+{
+  if ( idx >= 0 && idx < mFields.count() )
+    return mNotNull.value( mFields.at( idx ).name(), false );
+  else
+    return false;
+}
+
 void QgsEditFormConfig::setReadOnly( int idx, bool readOnly )
 {
   if ( idx >= 0 && idx < mFields.count() )
@@ -131,6 +139,12 @@ void QgsEditFormConfig::setLabelOnTop( int idx, bool onTop )
     mLabelOnTop[ mFields.at( idx ).name()] = onTop;
 }
 
+void QgsEditFormConfig::setNotNull( int idx, bool notnull )
+{
+  if ( idx >= 0 && idx < mFields.count() )
+    mNotNull[ mFields.at( idx ).name()] = notnull;
+}
+
 void QgsEditFormConfig::readXml( const QDomNode& node )
 {
   QDomNode editFormNode = node.namedItem( "editform" );
@@ -280,7 +294,6 @@ void QgsEditFormConfig::writeXml( QDomNode& node ) const
   efifpField.appendChild( doc.createTextNode( QgsProject::instance()->writePath( initFilePath() ) ) );
   node.appendChild( efifpField );
 
-
   QDomElement eficField  = doc.createElement( "editforminitcode" );
   eficField.appendChild( doc.createCDATASection( initCode() ) );
   node.appendChild( eficField );
@@ -337,6 +350,7 @@ void QgsEditFormConfig::writeXml( QDomNode& node ) const
     {
       QDomElement widgetElem = doc.createElement( "widget" );
       widgetElem.setAttribute( "name", configIt.key() );
+      // widgetElem.setAttribute( "notNull",  );
 
       QDomElement configElem = doc.createElement( "config" );
       widgetElem.appendChild( configElem );
diff --git a/src/core/qgseditformconfig.h b/src/core/qgseditformconfig.h
index 65e8689f6bb4..f34e7100859d 100644
--- a/src/core/qgseditformconfig.h
+++ b/src/core/qgseditformconfig.h
@@ -512,6 +512,15 @@ class CORE_EXPORT QgsEditFormConfig : public QObject
      */
     void setReadOnly( int idx, bool readOnly = true );
 
+    /**
+     * Returns if the field at fieldidx should be treated as NOT NULL value
+     */
+    bool notNull( int fieldidx ) const;
+    /**
+     * Set if the field at fieldidx should be treated as NOT NULL value
+     */
+    void setNotNull( int idx, bool notnull = true );
+
     /**
      * If this returns true, the widget at the given index will receive its label on the previous line
      * while if it returns false, the widget will receive its label on the left hand side.
@@ -633,6 +642,7 @@ class CORE_EXPORT QgsEditFormConfig : public QObject
 
     QMap< QString, bool> mFieldEditables;
     QMap< QString, bool> mLabelOnTop;
+    QMap< QString, bool> mNotNull;
 
     QMap<QString, QString> mEditorWidgetV2Types;
     QMap<QString, QgsEditorWidgetConfig > mWidgetConfigs;
diff --git a/src/core/qgseditorwidgetconfig.h b/src/core/qgseditorwidgetconfig.h
index a6dbceefb019..b9fdabdb4ad1 100644
--- a/src/core/qgseditorwidgetconfig.h
+++ b/src/core/qgseditorwidgetconfig.h
@@ -16,6 +16,8 @@
 #include <QString>
 #include <QVariant>
 
+#ifndef QGSEDITORWIDGETCONFIG_H
+#define QGSEDITORWIDGETCONFIG_H
 
 /**
  * Holds a set of configuration parameters for a editor widget wrapper.
@@ -30,4 +32,6 @@
  * You get these passed, for every new widget wrapper.
  */
 
-typedef QMap<QString, QVariant> QgsEditorWidgetConfig;
+typedef QVariantMap QgsEditorWidgetConfig;
+
+#endif // QGSEDITORWIDGETCONFIG_H
diff --git a/src/core/qgsfeature.cpp b/src/core/qgsfeature.cpp
index 0cef3ee28691..c71ff8241f1a 100644
--- a/src/core/qgsfeature.cpp
+++ b/src/core/qgsfeature.cpp
@@ -288,6 +288,12 @@ int QgsFeature::fieldNameIndex( const QString& fieldName ) const
   return d->fields.fieldNameIndex( fieldName );
 }
 
+/***************************************************************************
+ * This class is considered CRITICAL and any change MUST be accompanied with
+ * full unit tests in testqgsfeature.cpp.
+ * See details in QEP #17
+ ****************************************************************************/
+
 QDataStream& operator<<( QDataStream& out, const QgsFeature& feature )
 {
   out << feature.id();
diff --git a/src/core/qgsvectorlayer.cpp b/src/core/qgsvectorlayer.cpp
index e1fa901b6947..b025b4aa5af2 100644
--- a/src/core/qgsvectorlayer.cpp
+++ b/src/core/qgsvectorlayer.cpp
@@ -1105,13 +1105,13 @@ QgsFeatureIterator QgsVectorLayer::getFeatures( const QgsFeatureRequest& request
 }
 
 
-bool QgsVectorLayer::addFeature( QgsFeature& f, bool alsoUpdateExtent )
+bool QgsVectorLayer::addFeature( QgsFeature& feature, bool alsoUpdateExtent )
 {
   Q_UNUSED( alsoUpdateExtent ); // TODO[MD]
   if ( !mValid || !mEditBuffer || !mDataProvider )
     return false;
 
-  bool success = mEditBuffer->addFeature( f );
+  bool success = mEditBuffer->addFeature( feature );
 
   if ( success )
     updateExtents();
diff --git a/src/core/qgsvectorlayer.h b/src/core/qgsvectorlayer.h
index ee902cb6ef53..3adb15401af7 100644
--- a/src/core/qgsvectorlayer.h
+++ b/src/core/qgsvectorlayer.h
@@ -975,11 +975,11 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer
     QgsFeatureIterator getFeatures( const QgsFeatureRequest& request = QgsFeatureRequest() );
 
     /** Adds a feature
-        @param f feature to add
+        @param feature feature to add
         @param alsoUpdateExtent If True, will also go to the effort of e.g. updating the extents.
         @return                    True in case of success and False in case of error
      */
-    bool addFeature( QgsFeature& f, bool alsoUpdateExtent = true );
+    bool addFeature( QgsFeature& feature, bool alsoUpdateExtent = true );
 
     /** Updates an existing feature. This method needs to query the datasource
         on every call. Consider using {@link changeAttributeValue()} or
diff --git a/src/gui/editorwidgets/core/qgseditorwidgetregistry.cpp b/src/gui/editorwidgets/core/qgseditorwidgetregistry.cpp
index 63184a75620c..9dc1116157e6 100644
--- a/src/gui/editorwidgets/core/qgseditorwidgetregistry.cpp
+++ b/src/gui/editorwidgets/core/qgseditorwidgetregistry.cpp
@@ -251,6 +251,7 @@ void QgsEditorWidgetRegistry::readMapLayer( QgsMapLayer* mapLayer, const QDomEle
 
       vectorLayer->editFormConfig()->setReadOnly( idx, ewv2CfgElem.attribute( "fieldEditable", "1" ) != "1" );
       vectorLayer->editFormConfig()->setLabelOnTop( idx, ewv2CfgElem.attribute( "labelOnTop", "0" ) == "1" );
+      vectorLayer->editFormConfig()->setNotNull( idx, ewv2CfgElem.attribute( "notNull", "0" ) == "1" );
       vectorLayer->editFormConfig()->setWidgetConfig( idx, cfg );
     }
     else
@@ -307,6 +308,7 @@ void QgsEditorWidgetRegistry::writeMapLayer( QgsMapLayer* mapLayer, QDomElement&
       QDomElement ewv2CfgElem = doc.createElement( "widgetv2config" );
       ewv2CfgElem.setAttribute( "fieldEditable", !vectorLayer->editFormConfig()->readOnly( idx ) );
       ewv2CfgElem.setAttribute( "labelOnTop", vectorLayer->editFormConfig()->labelOnTop( idx ) );
+      ewv2CfgElem.setAttribute( "notNull", vectorLayer->editFormConfig()->notNull( idx ) );
 
       mWidgetFactories[widgetType]->writeConfig( vectorLayer->editFormConfig()->widgetConfig( idx ), ewv2CfgElem, doc, vectorLayer, idx );
 
diff --git a/src/gui/editorwidgets/core/qgseditorwidgetwrapper.cpp b/src/gui/editorwidgets/core/qgseditorwidgetwrapper.cpp
index 79e23a8a7ce0..403795f243b0 100644
--- a/src/gui/editorwidgets/core/qgseditorwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/core/qgseditorwidgetwrapper.cpp
@@ -24,6 +24,7 @@ QgsEditorWidgetWrapper::QgsEditorWidgetWrapper( QgsVectorLayer* vl, int fieldIdx
     : QgsWidgetWrapper( vl, editor, parent )
     , mFieldIdx( fieldIdx )
 {
+  connect( this, SIGNAL( valueChanged( QVariant ) ), this, SLOT( onValueChanged( QVariant ) ) );
 }
 
 int QgsEditorWidgetWrapper::fieldIdx() const
@@ -61,6 +62,7 @@ void QgsEditorWidgetWrapper::setEnabled( bool enabled )
 void QgsEditorWidgetWrapper::setFeature( const QgsFeature& feature )
 {
   setValue( feature.attribute( mFieldIdx ) );
+  onValueChanged( value() );
 }
 
 void QgsEditorWidgetWrapper::valueChanged( const QString& value )
@@ -92,3 +94,28 @@ void QgsEditorWidgetWrapper::valueChanged()
 {
   emit valueChanged( value() );
 }
+
+void QgsEditorWidgetWrapper::updateConstraintsOk( bool constraintStatus )
+{
+  if ( constraintStatus )
+  {
+    widget()->setStyleSheet( "" );
+  }
+  else
+  {
+    widget()->setStyleSheet( "QWidget{ background-color: '#dd7777': }" );
+  }
+}
+
+void QgsEditorWidgetWrapper::onValueChanged( const QVariant& value )
+{
+  if ( layer()->editFormConfig()->notNull( mFieldIdx ) )
+  {
+    if ( value.isNull() != mIsNull )
+    {
+      updateConstraintsOk( value.isNull() );
+      emit constraintStatusChanged( "NotNull", !value.isNull() );
+      mIsNull = value.isNull();
+    }
+  }
+}
diff --git a/src/gui/editorwidgets/core/qgseditorwidgetwrapper.h b/src/gui/editorwidgets/core/qgseditorwidgetwrapper.h
index ad30e2ad8797..182f0ecb244d 100644
--- a/src/gui/editorwidgets/core/qgseditorwidgetwrapper.h
+++ b/src/gui/editorwidgets/core/qgseditorwidgetwrapper.h
@@ -118,6 +118,13 @@ class GUI_EXPORT QgsEditorWidgetWrapper : public QgsWidgetWrapper
      */
     void valueChanged( const QVariant& value );
 
+    /**
+     * @brief constraintStatusChanged
+     * @param constraint
+     * @param status
+     */
+    void constraintStatusChanged( const QString& constraint, bool status );
+
   public slots:
     /**
      * Will be called when the feature changes
@@ -185,8 +192,28 @@ class GUI_EXPORT QgsEditorWidgetWrapper : public QgsWidgetWrapper
      */
     void valueChanged();
 
+  private:
+    /**
+     * This should update the widget with a visual cue if a constraint status
+     * changed.
+     *
+     * By default a stylesheet will be applied on the widget that changes the
+     * background color to red.
+     *
+     * This can be overwritten in subclasses to allow individual widgets to
+     * change the visual cue.
+     */
+    virtual void updateConstraintsOk( bool constraintStatus );
+
+  private slots:
+    /**
+     * @brief mFieldIdx
+     */
+    void onValueChanged( const QVariant& value );
+
   private:
     int mFieldIdx;
+    bool mIsNull;
 };
 
 // We'll use this class inside a QVariant in the widgets properties
diff --git a/src/gui/editorwidgets/qgsrangewidgetfactory.cpp b/src/gui/editorwidgets/qgsrangewidgetfactory.cpp
index 9ef096d5c381..dbda88b42b79 100644
--- a/src/gui/editorwidgets/qgsrangewidgetfactory.cpp
+++ b/src/gui/editorwidgets/qgsrangewidgetfactory.cpp
@@ -38,7 +38,7 @@ QgsEditorWidgetConfig QgsRangeWidgetFactory::readConfig( const QDomElement& conf
 {
   Q_UNUSED( layer );
   Q_UNUSED( fieldIdx );
-  QMap<QString, QVariant> cfg;
+  QgsEditorWidgetConfig cfg;
 
   cfg.insert( "Style", configElement.attribute( "Style" ) );
   cfg.insert( "Min", configElement.attribute( "Min" ) );
diff --git a/src/gui/editorwidgets/qgsrelationreferenceconfigdlg.cpp b/src/gui/editorwidgets/qgsrelationreferenceconfigdlg.cpp
index 2c59588e075f..6b58462561d7 100644
--- a/src/gui/editorwidgets/qgsrelationreferenceconfigdlg.cpp
+++ b/src/gui/editorwidgets/qgsrelationreferenceconfigdlg.cpp
@@ -55,7 +55,7 @@ QgsRelationReferenceConfigDlg::QgsRelationReferenceConfigDlg( QgsVectorLayer* vl
   }
 }
 
-void QgsRelationReferenceConfigDlg::setConfig( const QMap<QString, QVariant>& config )
+void QgsRelationReferenceConfigDlg::setConfig( const QgsEditorWidgetConfig& config )
 {
   if ( config.contains( "AllowNULL" ) )
   {
diff --git a/src/gui/editorwidgets/qgsrelationreferencefactory.cpp b/src/gui/editorwidgets/qgsrelationreferencefactory.cpp
index 9315d14eb03a..b6cf3438535f 100644
--- a/src/gui/editorwidgets/qgsrelationreferencefactory.cpp
+++ b/src/gui/editorwidgets/qgsrelationreferencefactory.cpp
@@ -46,7 +46,7 @@ QgsEditorWidgetConfig QgsRelationReferenceFactory::readConfig( const QDomElement
 {
   Q_UNUSED( layer );
   Q_UNUSED( fieldIdx );
-  QMap<QString, QVariant> cfg;
+  QgsEditorWidgetConfig cfg;
 
   cfg.insert( "AllowNULL", configElement.attribute( "AllowNULL" ) == "1" );
   cfg.insert( "OrderByValue", configElement.attribute( "OrderByValue" ) == "1" );
diff --git a/src/gui/qgsattributeform.cpp b/src/gui/qgsattributeform.cpp
index ea65e175451a..9a31e6f76d56 100644
--- a/src/gui/qgsattributeform.cpp
+++ b/src/gui/qgsattributeform.cpp
@@ -655,6 +655,41 @@ void QgsAttributeForm::onAttributeChanged( const QVariant& value )
       //nothing to do
       break;
   }
+
+  if ( eww->layer()->editFormConfig()->notNull( eww->fieldIdx() ) )
+  {
+    QLabel* buddy = mBuddyMap.value( eww->widget() );
+
+    if ( buddy )
+    {
+      if ( !buddy->property( "originalText" ).isValid() )
+        buddy->setProperty( "originalText", buddy->text() );
+
+      QString text = buddy->property( "originalText" ).toString();
+
+      if ( value.isNull() )
+      {
+        // not good
+#if QT_VERSION >= 0x050000
+        buddy->setText( QString( "%1<font color=\"red\">❌</font>" ).arg( text ) );
+#else
+        buddy->setText( QString( "%1<font color=\"red\">*</font>" ).arg( text ) );
+#endif
+      }
+      else
+      {
+        // good
+#if QT_VERSION >= 0x050000
+        buddy->setText( QString( "%1<font color=\"green\">✔</font>" ).arg( text ) );
+#else
+        buddy->setText( QString( "%1<font color=\"green\">*</font>" ).arg( text ) );
+#endif
+      }
+    }
+  }
+
+
+  emit attributeChanged( eww->field().name(), value );
 }
 
 void QgsAttributeForm::onAttributeAdded( int idx )
@@ -714,6 +749,36 @@ void QgsAttributeForm::onUpdatedFields()
   setFeature( mFeature );
 }
 
+void QgsAttributeForm::onConstraintStatusChanged( const QString& constraint, bool ok )
+{
+  Q_UNUSED( constraint )
+
+
+  QgsEditorWidgetWrapper* eww = qobject_cast<QgsEditorWidgetWrapper*>( sender() );
+  Q_ASSERT( eww );
+
+  QLabel* buddy = mBuddyMap.value( eww->widget() );
+
+  if ( buddy )
+  {
+    if ( !buddy->property( "originalText" ).isValid() )
+      buddy->setProperty( "originalText", buddy->text() );
+
+    QString text = buddy->property( "originalText" ).toString();
+
+    if ( !ok )
+    {
+      // not good
+      buddy->setText( QString( "%1<font color=\"red\">*</font>" ).arg( text ) );
+    }
+    else
+    {
+      // good
+      buddy->setText( QString( "%1<font color=\"green\">*</font>" ).arg( text ) );
+    }
+  }
+}
+
 void QgsAttributeForm::preventFeatureRefresh()
 {
   mPreventFeatureRefresh = true;
@@ -899,7 +964,7 @@ void QgsAttributeForm::init()
       bool labelOnTop = mLayer->editFormConfig()->labelOnTop( idx );
 
       // This will also create the widget
-      QWidget *l = new QLabel( fieldName );
+      QLabel *l = new QLabel( fieldName );
       QgsEditorWidgetWrapper* eww = QgsEditorWidgetRegistry::instance()->create( widgetType, mLayer, idx, widgetConfig, nullptr, this, mContext );
 
       QWidget* w = nullptr;
@@ -915,6 +980,11 @@ void QgsAttributeForm::init()
         w = new QLabel( QString( "<p style=\"color: red; font-style: italic;\">Failed to create widget with type '%1'</p>" ).arg( widgetType ) );
       }
 
+      l->setBuddy( w );
+
+      if ( w )
+        w->setObjectName( field.name() );
+
       if ( eww )
         addWidgetWrapper( eww );
 
@@ -957,6 +1027,7 @@ void QgsAttributeForm::init()
   }
   mButtonBox->setVisible( buttonBoxVisible );
 
+<<<<<<< HEAD
   if ( !mSearchButtonBox )
   {
     mSearchButtonBox = new QWidget();
@@ -1011,7 +1082,7 @@ void QgsAttributeForm::init()
   }
   mSearchButtonBox->setVisible( mMode == SearchMode );
 
-  connectWrappers();
+  afterWidgetInit();
 
   connect( mButtonBox, SIGNAL( accepted() ), this, SLOT( accept() ) );
   connect( mButtonBox, SIGNAL( rejected() ), this, SLOT( resetValues() ) );
@@ -1251,6 +1322,8 @@ QgsAttributeForm::WidgetInfo QgsAttributeForm::createWidgetFromDef( const QgsAtt
             mypLabel->setAlignment( Qt::AlignRight | Qt::AlignVCenter );
           }
 
+          mypLabel->setBuddy( widgetInfo.widget );
+
           if ( widgetInfo.labelOnTop )
           {
             QVBoxLayout* c = new QVBoxLayout();
@@ -1350,7 +1423,7 @@ void QgsAttributeForm::createWrappers()
   }
 }
 
-void QgsAttributeForm::connectWrappers()
+void QgsAttributeForm::afterWidgetInit()
 {
   bool isFirstEww = true;
 
@@ -1367,8 +1440,20 @@ void QgsAttributeForm::connectWrappers()
       }
 
       connect( eww, SIGNAL( valueChanged( const QVariant& ) ), this, SLOT( onAttributeChanged( const QVariant& ) ) );
+      connect( eww, SIGNAL( constraintStatusChanged( QString, bool ) ), this, SLOT( onConstraintStatusChanged( QString, bool ) ) );
     }
   }
+
+  // Update buddy widget list
+
+  mBuddyMap.clear();
+  QList<QLabel*> labels = findChildren<QLabel*>();
+
+  Q_FOREACH ( QLabel* label, labels )
+  {
+    if ( label->buddy() )
+      mBuddyMap.insert( label->buddy(), label );
+  }
 }
 
 
diff --git a/src/gui/qgsattributeform.h b/src/gui/qgsattributeform.h
index 89770ebc2886..a49c6546a28a 100644
--- a/src/gui/qgsattributeform.h
+++ b/src/gui/qgsattributeform.h
@@ -21,6 +21,7 @@
 #include "qgsattributeeditorcontext.h"
 
 #include <QWidget>
+#include <QLabel>
 #include <QDialogButtonBox>
 
 class QgsAttributeFormInterface;
@@ -233,6 +234,7 @@ class GUI_EXPORT QgsAttributeForm : public QWidget
     void onAttributeAdded( int idx );
     void onAttributeDeleted( int idx );
     void onUpdatedFields();
+    void onConstraintStatusChanged( const QString& constraint, bool ok );
 
     void preventFeatureRefresh();
     void synchronizeEnabledState();
@@ -282,7 +284,7 @@ class GUI_EXPORT QgsAttributeForm : public QWidget
      * Called once maximally.
      */
     void createWrappers();
-    void connectWrappers();
+    void afterWidgetInit();
 
     void scanForEqualAttributes( QgsFeatureIterator& fit, QSet< int >& mixedValueFields, QHash< int, QVariant >& fieldSharedValues ) const;
 
@@ -330,6 +332,9 @@ class GUI_EXPORT QgsAttributeForm : public QWidget
 
     Mode mMode;
 
+    //! Backlinks widgets to buddies.
+    QMap<QWidget*, QLabel*> mBuddyMap;
+
     friend class TestQgsDualView;
 };
 
diff --git a/src/ui/qgsattributetypeedit.ui b/src/ui/qgsattributetypeedit.ui
index 5f774a4adb82..adb2cb02bd8b 100644
--- a/src/ui/qgsattributetypeedit.ui
+++ b/src/ui/qgsattributetypeedit.ui
@@ -14,17 +14,7 @@
    <string>Edit Widget Properties</string>
   </property>
   <layout class="QGridLayout" name="gridLayout">
-   <item row="6" column="1">
-    <widget class="QDialogButtonBox" name="buttonBox">
-     <property name="orientation">
-      <enum>Qt::Horizontal</enum>
-     </property>
-     <property name="standardButtons">
-      <set>QDialogButtonBox::Cancel|QDialogButtonBox::Ok</set>
-     </property>
-    </widget>
-   </item>
-   <item row="2" column="1">
+   <item row="3" column="1">
     <widget class="QStackedWidget" name="stackedWidget"/>
    </item>
    <item row="0" column="1">
@@ -47,9 +37,26 @@
      </property>
     </widget>
    </item>
-   <item row="0" column="0" rowspan="7">
+   <item row="0" column="0" rowspan="8">
     <widget class="QListWidget" name="selectionListWidget"/>
    </item>
+   <item row="7" column="1">
+    <widget class="QDialogButtonBox" name="buttonBox">
+     <property name="orientation">
+      <enum>Qt::Horizontal</enum>
+     </property>
+     <property name="standardButtons">
+      <set>QDialogButtonBox::Cancel|QDialogButtonBox::Ok</set>
+     </property>
+    </widget>
+   </item>
+   <item row="2" column="1">
+    <widget class="QCheckBox" name="notNullCheckBox">
+     <property name="text">
+      <string>Not Null</string>
+     </property>
+    </widget>
+   </item>
   </layout>
  </widget>
  <tabstops>