diff --git a/python/gui/editorwidgets/core/qgseditorwidgetfactory.sip b/python/gui/editorwidgets/core/qgseditorwidgetfactory.sip
index 10d365fd2f8..f75fd18bf2d 100644
--- a/python/gui/editorwidgets/core/qgseditorwidgetfactory.sip
+++ b/python/gui/editorwidgets/core/qgseditorwidgetfactory.sip
@@ -189,4 +189,16 @@ class QgsEditorWidgetFactory
      * @see supportsField( QgsVectorLayer* vl, fieldIdx )
      */
     virtual unsigned int fieldScore( const QgsVectorLayer* vl, int fieldIdx ) const;
+
+  protected:
+
+    /**
+     * Copy the given config element to a XML attribute.
+     */
+    static void config2xml( const QgsEditorWidgetConfig& config, QDomElement& configElement, const QString& fieldName );
+
+    /**
+     * Copy the given XML attribute to the configuration element.
+     */
+    static void xml2config( const QDomElement& configElement, QgsEditorWidgetConfig& config, const QString& fieldName );
 };
diff --git a/src/gui/editorwidgets/core/qgseditorwidgetfactory.cpp b/src/gui/editorwidgets/core/qgseditorwidgetfactory.cpp
index d9a8dfe82d2..8d2d584c1ad 100644
--- a/src/gui/editorwidgets/core/qgseditorwidgetfactory.cpp
+++ b/src/gui/editorwidgets/core/qgseditorwidgetfactory.cpp
@@ -123,3 +123,27 @@ unsigned int QgsEditorWidgetFactory::fieldScore( const QgsVectorLayer* vl, int f
   return 5;
 }
 
+void QgsEditorWidgetFactory::config2xml( const QgsEditorWidgetConfig& config, QDomElement& configElement, const QString& fieldName )
+{
+  const QVariant value = config.value( fieldName );
+  if ( value.isValid() )
+  {
+    if ( value.type() == QVariant::Bool )
+    {
+      configElement.setAttribute( fieldName, value.toBool() ? "1" : "0" );
+    }
+    else
+    {
+      configElement.setAttribute( fieldName, value.toString() );
+    }
+  }
+}
+
+void QgsEditorWidgetFactory::xml2config( const QDomElement& configElement, QgsEditorWidgetConfig& config, const QString& fieldName )
+{
+  const QString value = configElement.attribute( fieldName );
+  if ( !value.isNull() )
+  {
+    config.insert( fieldName, value );
+  }
+}
\ No newline at end of file
diff --git a/src/gui/editorwidgets/core/qgseditorwidgetfactory.h b/src/gui/editorwidgets/core/qgseditorwidgetfactory.h
index b4ee3e21d8d..54583540138 100644
--- a/src/gui/editorwidgets/core/qgseditorwidgetfactory.h
+++ b/src/gui/editorwidgets/core/qgseditorwidgetfactory.h
@@ -207,6 +207,18 @@ class GUI_EXPORT QgsEditorWidgetFactory
      */
     virtual unsigned int fieldScore( const QgsVectorLayer* vl, int fieldIdx ) const;
 
+  protected:
+
+    /**
+     * Copy the given config element to a XML attribute.
+     */
+    static void config2xml( const QgsEditorWidgetConfig& config, QDomElement& configElement, const QString& fieldName );
+
+    /**
+     * Copy the given XML attribute to the configuration element.
+     */
+    static void xml2config( const QDomElement& configElement, QgsEditorWidgetConfig& config, const QString& fieldName );
+
   private:
     QString mName;
 };
diff --git a/src/gui/editorwidgets/qgscheckboxwidgetfactory.cpp b/src/gui/editorwidgets/qgscheckboxwidgetfactory.cpp
index 4c28516fa14..895e82e0980 100644
--- a/src/gui/editorwidgets/qgscheckboxwidgetfactory.cpp
+++ b/src/gui/editorwidgets/qgscheckboxwidgetfactory.cpp
@@ -45,8 +45,8 @@ QgsEditorWidgetConfig QgsCheckboxWidgetFactory::readConfig( const QDomElement& c
 
   QgsEditorWidgetConfig cfg;
 
-  cfg.insert( QStringLiteral( "CheckedState" ), configElement.attribute( QStringLiteral( "CheckedState" ) ) );
-  cfg.insert( QStringLiteral( "UncheckedState" ), configElement.attribute( QStringLiteral( "UncheckedState" ) ) );
+  xml2config( configElement, cfg, QStringLiteral( "CheckedState" ) );
+  xml2config( configElement, cfg, QStringLiteral( "UncheckedState" ) );
 
   return cfg;
 }
@@ -57,8 +57,8 @@ void QgsCheckboxWidgetFactory::writeConfig( const QgsEditorWidgetConfig& config,
   Q_UNUSED( layer )
   Q_UNUSED( fieldIdx )
 
-  configElement.setAttribute( QStringLiteral( "CheckedState" ), config.value( QStringLiteral( "CheckedState" ), "1" ).toString() );
-  configElement.setAttribute( QStringLiteral( "UncheckedState" ), config.value( QStringLiteral( "UncheckedState" ), "0" ).toString() );
+  config2xml( config, configElement, QStringLiteral( "CheckedState" ) );
+  config2xml( config, configElement, QStringLiteral( "UncheckedState" ) );
 }
 
 QHash<const char*, int> QgsCheckboxWidgetFactory::supportedWidgetTypes()
diff --git a/src/gui/editorwidgets/qgsdatetimeeditfactory.cpp b/src/gui/editorwidgets/qgsdatetimeeditfactory.cpp
index 6c581c4d07b..92fad6a6728 100644
--- a/src/gui/editorwidgets/qgsdatetimeeditfactory.cpp
+++ b/src/gui/editorwidgets/qgsdatetimeeditfactory.cpp
@@ -47,10 +47,10 @@ QgsEditorWidgetConfig QgsDateTimeEditFactory::readConfig( const QDomElement& con
   Q_UNUSED( fieldIdx );
   QgsEditorWidgetConfig cfg;
 
-  cfg.insert( QStringLiteral( "field_format" ), configElement.attribute( QStringLiteral( "field_format" ) ) );
-  cfg.insert( QStringLiteral( "display_format" ), configElement.attribute( QStringLiteral( "display_format" ) ) );
-  cfg.insert( QStringLiteral( "calendar_popup" ), configElement.attribute( QStringLiteral( "calendar_popup" ) ) == QLatin1String( "1" ) );
-  cfg.insert( QStringLiteral( "allow_null" ), configElement.attribute( QStringLiteral( "allow_null" ) ) == QLatin1String( "1" ) );
+  xml2config( configElement, cfg, QStringLiteral( "field_format" ) );
+  xml2config( configElement, cfg, QStringLiteral( "display_format" ) );
+  xml2config( configElement, cfg, QStringLiteral( "calendar_popup" ) );
+  xml2config( configElement, cfg, QStringLiteral( "allow_null" ) );
 
   return cfg;
 }
@@ -61,10 +61,10 @@ void QgsDateTimeEditFactory::writeConfig( const QgsEditorWidgetConfig& config, Q
   Q_UNUSED( layer );
   Q_UNUSED( fieldIdx );
 
-  configElement.setAttribute( QStringLiteral( "field_format" ), config[QStringLiteral( "field_format" )].toString() );
-  configElement.setAttribute( QStringLiteral( "display_format" ), config[QStringLiteral( "display_format" )].toString() );
-  configElement.setAttribute( QStringLiteral( "calendar_popup" ), config[QStringLiteral( "calendar_popup" )].toBool() );
-  configElement.setAttribute( QStringLiteral( "allow_null" ), config[QStringLiteral( "allow_null" )].toBool() );
+  config2xml( config, configElement, QStringLiteral( "field_format" ) );
+  config2xml( config, configElement, QStringLiteral( "display_format" ) );
+  config2xml( config, configElement, QStringLiteral( "calendar_popup" ) );
+  config2xml( config, configElement, QStringLiteral( "allow_null" ) );
 }
 
 QString QgsDateTimeEditFactory::representValue( QgsVectorLayer* vl, int fieldIdx, const QgsEditorWidgetConfig& config, const QVariant& cache, const QVariant& value ) const
diff --git a/src/gui/editorwidgets/qgsexternalresourcewidgetfactory.cpp b/src/gui/editorwidgets/qgsexternalresourcewidgetfactory.cpp
index 3193578e915..532471739c8 100644
--- a/src/gui/editorwidgets/qgsexternalresourcewidgetfactory.cpp
+++ b/src/gui/editorwidgets/qgsexternalresourcewidgetfactory.cpp
@@ -40,36 +40,17 @@ void QgsExternalResourceWidgetFactory::writeConfig( const QgsEditorWidgetConfig&
   Q_UNUSED( layer )
   Q_UNUSED( fieldIdx )
 
-  configElement.setAttribute( QStringLiteral( "FileWidget" ), config.value( QStringLiteral( "FileWidget" ), true ).toBool() );
-  configElement.setAttribute( QStringLiteral( "FileWidgetButton" ), config.value( QStringLiteral( "FileWidgetButton" ), true ).toBool() );
-
-
-  // Non mandatory options are not saved into project file (to save some space).
-  if ( config.contains( QStringLiteral( "UseLink" ) ) )
-    configElement.setAttribute( QStringLiteral( "UseLink" ), config.value( QStringLiteral( "UseLink" ) ).toBool() );
-
-  if ( config.contains( QStringLiteral( "FullUrl" ) ) )
-    configElement.setAttribute( QStringLiteral( "FullUrl" ), config.value( QStringLiteral( "FullUrl" ) ).toBool() );
-
-  if ( config.contains( QStringLiteral( "DefaultRoot" ) ) )
-    configElement.setAttribute( QStringLiteral( "DefaultRoot" ), config.value( QStringLiteral( "DefaultRoot" ) ).toString() );
-
-  if ( config.contains( QStringLiteral( "RelativeStorage" ) ) )
-    configElement.setAttribute( QStringLiteral( "RelativeStorage" ) , config.value( QStringLiteral( "RelativeStorage" ) ).toString() );
-
-  if ( config.contains( QStringLiteral( "DocumentViewer" ) ) )
-    configElement.setAttribute( QStringLiteral( "DocumentViewer" ), config.value( QStringLiteral( "DocumentViewer" ) ).toInt() );
-
-  if ( config.contains( QStringLiteral( "DocumentViewerWidth" ) ) )
-    configElement.setAttribute( QStringLiteral( "DocumentViewerWidth" ), config.value( QStringLiteral( "DocumentViewerWidth" ) ).toInt() );
-
-  if ( config.contains( QStringLiteral( "DocumentViewerHeight" ) ) )
-    configElement.setAttribute( QStringLiteral( "DocumentViewerHeight" ), config.value( QStringLiteral( "DocumentViewerHeight" ) ).toInt() );
-
-  if ( config.contains( QStringLiteral( "FileWidgetFilter" ) ) )
-    configElement.setAttribute( QStringLiteral( "FileWidgetFilter" ), config.value( QStringLiteral( "FileWidgetFilter" ) ).toString() );
-
-  configElement.setAttribute( QStringLiteral( "StorageMode" ), config.value( QStringLiteral( "StorageMode" ) ).toString() );
+  config2xml( config, configElement, QStringLiteral( "FileWidget" ) );
+  config2xml( config, configElement, QStringLiteral( "FileWidgetButton" ) );
+  config2xml( config, configElement, QStringLiteral( "UseLink" ) );
+  config2xml( config, configElement, QStringLiteral( "FullUrl" ) );
+  config2xml( config, configElement, QStringLiteral( "DefaultRoot" ) );
+  config2xml( config, configElement, QStringLiteral( "RelativeStorage" ) );
+  config2xml( config, configElement, QStringLiteral( "DocumentViewer" ) );
+  config2xml( config, configElement, QStringLiteral( "DocumentViewerWidth" ) );
+  config2xml( config, configElement, QStringLiteral( "DocumentViewerHeight" ) );
+  config2xml( config, configElement, QStringLiteral( "FileWidgetFilter" ) );
+  config2xml( config, configElement, QStringLiteral( "StorageMode" ) );
 }
 
 QgsEditorWidgetConfig QgsExternalResourceWidgetFactory::readConfig( const QDomElement& configElement, QgsVectorLayer* layer, int fieldIdx )
@@ -79,42 +60,22 @@ QgsEditorWidgetConfig QgsExternalResourceWidgetFactory::readConfig( const QDomEl
 
   QgsEditorWidgetConfig cfg;
 
-  if ( configElement.hasAttribute( QStringLiteral( "FileWidgetButton" ) ) )
-    cfg.insert( QStringLiteral( "FileWidgetButton" ), configElement.attribute( QStringLiteral( "FileWidgetButton" ) ) == QLatin1String( "1" ) );
-
-  if ( configElement.hasAttribute( QStringLiteral( "FileWidget" ) ) )
-    cfg.insert( QStringLiteral( "FileWidget" ), configElement.attribute( QStringLiteral( "FileWidget" ) ) == QLatin1String( "1" ) );
-
-  if ( configElement.hasAttribute( QStringLiteral( "UseLink" ) ) )
-    cfg.insert( QStringLiteral( "UseLink" ), configElement.attribute( QStringLiteral( "UseLink" ) ) == QLatin1String( "1" ) );
-
-  if ( configElement.hasAttribute( QStringLiteral( "FullUrl" ) ) )
-    cfg.insert( QStringLiteral( "FullUrl" ), configElement.attribute( QStringLiteral( "FullUrl" ) ) == QLatin1String( "1" ) );
-
-  if ( configElement.hasAttribute( QStringLiteral( "DefaultRoot" ) ) )
-    cfg.insert( QStringLiteral( "DefaultRoot" ), configElement.attribute( QStringLiteral( "DefaultRoot" ) ) );
-
+  xml2config( configElement, cfg, QStringLiteral( "FileWidget" ) );
+  xml2config( configElement, cfg, QStringLiteral( "FileWidgetButton" ) );
+  xml2config( configElement, cfg, QStringLiteral( "UseLink" ) );
+  xml2config( configElement, cfg, QStringLiteral( "FullUrl" ) );
+  xml2config( configElement, cfg, QStringLiteral( "DefaultRoot" ) );
   if ( configElement.hasAttribute( QStringLiteral( "RelativeStorage" ) ) )
   {
     if (( configElement.attribute( QStringLiteral( "RelativeStorage" ) ).toInt() == QgsFileWidget::RelativeDefaultPath && configElement.hasAttribute( QStringLiteral( "DefaultRoot" ) ) ) ||
         configElement.attribute( QStringLiteral( "RelativeStorage" ) ).toInt() == QgsFileWidget::RelativeProject )
-      cfg.insert( QStringLiteral( "RelativeStorage" ) , configElement.attribute( QStringLiteral( "RelativeStorage" ) ).toInt() );
+      xml2config( configElement, cfg, QStringLiteral( "RelativeStorage" ) );
   }
-
-  if ( configElement.hasAttribute( QStringLiteral( "DocumentViewer" ) ) )
-    cfg.insert( QStringLiteral( "DocumentViewer" ), configElement.attribute( QStringLiteral( "DocumentViewer" ) ) );
-
-  if ( configElement.hasAttribute( QStringLiteral( "DocumentViewerWidth" ) ) )
-    cfg.insert( QStringLiteral( "DocumentViewerWidth" ), configElement.attribute( QStringLiteral( "DocumentViewerWidth" ) ) );
-
-  if ( configElement.hasAttribute( QStringLiteral( "DocumentViewerHeight" ) ) )
-    cfg.insert( QStringLiteral( "DocumentViewerHeight" ), configElement.attribute( QStringLiteral( "DocumentViewerHeight" ) ) );
-
-  if ( configElement.hasAttribute( QStringLiteral( "FileWidgetFilter" ) ) )
-    cfg.insert( QStringLiteral( "FileWidgetFilter" ), configElement.attribute( QStringLiteral( "FileWidgetFilter" ) ) );
-
-
-  cfg.insert( QStringLiteral( "StorageMode" ), configElement.attribute( QStringLiteral( "StorageMode" ), QStringLiteral( "Files" ) ) );
+  xml2config( configElement, cfg, QStringLiteral( "DocumentViewer" ) );
+  xml2config( configElement, cfg, QStringLiteral( "DocumentViewerWidth" ) );
+  xml2config( configElement, cfg, QStringLiteral( "DocumentViewerHeight" ) );
+  xml2config( configElement, cfg, QStringLiteral( "FileWidgetFilter" ) );
+  xml2config( configElement, cfg, QStringLiteral( "StorageMode" ) );
 
   return cfg;
 }
diff --git a/src/gui/editorwidgets/qgsphotowidgetfactory.cpp b/src/gui/editorwidgets/qgsphotowidgetfactory.cpp
index 7fdb0840b8f..dd3cf79cf9c 100644
--- a/src/gui/editorwidgets/qgsphotowidgetfactory.cpp
+++ b/src/gui/editorwidgets/qgsphotowidgetfactory.cpp
@@ -41,8 +41,8 @@ QgsEditorWidgetConfig QgsPhotoWidgetFactory::readConfig( const QDomElement& conf
 
   QgsEditorWidgetConfig cfg;
 
-  cfg.insert( QStringLiteral( "Height" ), configElement.attribute( QStringLiteral( "Height" ), 0 ).toInt() );
-  cfg.insert( QStringLiteral( "Width" ), configElement.attribute( QStringLiteral( "Width" ), 0 ).toInt() );
+  xml2config( configElement, cfg, QStringLiteral( "Height" ) );
+  xml2config( configElement, cfg, QStringLiteral( "Width" ) );
 
   return cfg;
 }
@@ -53,6 +53,6 @@ void QgsPhotoWidgetFactory::writeConfig( const QgsEditorWidgetConfig& config, QD
   Q_UNUSED( layer )
   Q_UNUSED( fieldIdx )
 
-  configElement.setAttribute( QStringLiteral( "Height" ), config.value( QStringLiteral( "Height" ), 0 ).toString() );
-  configElement.setAttribute( QStringLiteral( "Width" ), config.value( QStringLiteral( "Width" ), 0 ).toString() );
+  config2xml( config, configElement, QStringLiteral( "Height" ) );
+  config2xml( config, configElement, QStringLiteral( "Width" ) );
 }
diff --git a/src/gui/editorwidgets/qgsrangewidgetfactory.cpp b/src/gui/editorwidgets/qgsrangewidgetfactory.cpp
index dce3b3b471c..3fb8cb8cfd0 100644
--- a/src/gui/editorwidgets/qgsrangewidgetfactory.cpp
+++ b/src/gui/editorwidgets/qgsrangewidgetfactory.cpp
@@ -40,16 +40,12 @@ QgsEditorWidgetConfig QgsRangeWidgetFactory::readConfig( const QDomElement& conf
   Q_UNUSED( fieldIdx );
   QgsEditorWidgetConfig cfg;
 
-  cfg.insert( QStringLiteral( "Style" ), configElement.attribute( QStringLiteral( "Style" ) ) );
-  cfg.insert( QStringLiteral( "Min" ), configElement.attribute( QStringLiteral( "Min" ) ) );
-  cfg.insert( QStringLiteral( "Max" ), configElement.attribute( QStringLiteral( "Max" ) ) );
-  cfg.insert( QStringLiteral( "Step" ), configElement.attribute( QStringLiteral( "Step" ) ) );
-  cfg.insert( QStringLiteral( "AllowNull" ), configElement.attribute( QStringLiteral( "AllowNull" ) ) == QLatin1String( "1" ) );
-
-  if ( configElement.hasAttribute( QStringLiteral( "Suffix" ) ) )
-  {
-    cfg.insert( QStringLiteral( "Suffix" ), configElement.attribute( QStringLiteral( "Suffix" ) ) );
-  }
+  xml2config( configElement, cfg, QStringLiteral( "Style" ) );
+  xml2config( configElement, cfg, QStringLiteral( "Min" ) );
+  xml2config( configElement, cfg, QStringLiteral( "Max" ) );
+  xml2config( configElement, cfg, QStringLiteral( "Step" ) );
+  xml2config( configElement, cfg, QStringLiteral( "AllowNull" ) );
+  xml2config( configElement, cfg, QStringLiteral( "Suffix" ) );
 
   return cfg;
 }
@@ -60,15 +56,12 @@ void QgsRangeWidgetFactory::writeConfig( const QgsEditorWidgetConfig& config, QD
   Q_UNUSED( layer );
   Q_UNUSED( fieldIdx );
 
-  configElement.setAttribute( QStringLiteral( "Style" ), config[QStringLiteral( "Style" )].toString() );
-  configElement.setAttribute( QStringLiteral( "Min" ), config[QStringLiteral( "Min" )].toString() );
-  configElement.setAttribute( QStringLiteral( "Max" ), config[QStringLiteral( "Max" )].toString() );
-  configElement.setAttribute( QStringLiteral( "Step" ), config[QStringLiteral( "Step" )].toString() );
-  configElement.setAttribute( QStringLiteral( "AllowNull" ), config[QStringLiteral( "AllowNull" )].toBool() );
-  if ( config.contains( QStringLiteral( "Suffix" ) ) )
-  {
-    configElement.setAttribute( QStringLiteral( "Suffix" ), config[QStringLiteral( "Suffix" )].toString() );
-  }
+  config2xml( config, configElement, QStringLiteral( "Style" ) );
+  config2xml( config, configElement, QStringLiteral( "Min" ) );
+  config2xml( config, configElement, QStringLiteral( "Max" ) );
+  config2xml( config, configElement, QStringLiteral( "Step" ) );
+  config2xml( config, configElement, QStringLiteral( "AllowNull" ) );
+  config2xml( config, configElement, QStringLiteral( "Suffix" ) );
 }
 
 unsigned int QgsRangeWidgetFactory::fieldScore( const QgsVectorLayer* vl, int fieldIdx ) const
diff --git a/src/gui/editorwidgets/qgsrelationreferencefactory.cpp b/src/gui/editorwidgets/qgsrelationreferencefactory.cpp
index 24115e3ec7a..357b13282ea 100644
--- a/src/gui/editorwidgets/qgsrelationreferencefactory.cpp
+++ b/src/gui/editorwidgets/qgsrelationreferencefactory.cpp
@@ -53,13 +53,13 @@ QgsEditorWidgetConfig QgsRelationReferenceFactory::readConfig( const QDomElement
   Q_UNUSED( fieldIdx );
   QgsEditorWidgetConfig cfg;
 
-  cfg.insert( QStringLiteral( "AllowNULL" ), configElement.attribute( QStringLiteral( "AllowNULL" ) ) == QLatin1String( "1" ) );
-  cfg.insert( QStringLiteral( "OrderByValue" ), configElement.attribute( QStringLiteral( "OrderByValue" ) ) == QLatin1String( "1" ) );
-  cfg.insert( QStringLiteral( "ShowForm" ), configElement.attribute( QStringLiteral( "ShowForm" ) ) == QLatin1String( "1" ) );
-  cfg.insert( QStringLiteral( "Relation" ), configElement.attribute( QStringLiteral( "Relation" ) ) );
-  cfg.insert( QStringLiteral( "MapIdentification" ), configElement.attribute( QStringLiteral( "MapIdentification" ) ) == QLatin1String( "1" ) );
-  cfg.insert( QStringLiteral( "ReadOnly" ), configElement.attribute( QStringLiteral( "ReadOnly" ) ) == QLatin1String( "1" ) );
-  cfg.insert( QStringLiteral( "AllowAddFeatures" ), configElement.attribute( QStringLiteral( "AllowAddFeatures" ) ) == QLatin1String( "1" ) );
+  xml2config( configElement, cfg, QStringLiteral( "AllowNULL" ) );
+  xml2config( configElement, cfg, QStringLiteral( "OrderByValue" ) );
+  xml2config( configElement, cfg, QStringLiteral( "ShowForm" ) );
+  xml2config( configElement, cfg, QStringLiteral( "Relation" ) );
+  xml2config( configElement, cfg, QStringLiteral( "MapIdentification" ) );
+  xml2config( configElement, cfg, QStringLiteral( "ReadOnly" ) );
+  xml2config( configElement, cfg, QStringLiteral( "AllowAddFeatures" ) );
 
   QDomNode filterNode = configElement.elementsByTagName( QStringLiteral( "FilterFields" ) ).at( 0 );
   if ( !filterNode.isNull() )
@@ -74,7 +74,7 @@ QgsEditorWidgetConfig QgsRelationReferenceFactory::readConfig( const QDomElement
     }
     cfg.insert( QStringLiteral( "FilterFields" ), filterFields );
 
-    cfg.insert( QStringLiteral( "ChainFilters" ), filterNode.toElement().attribute( QStringLiteral( "ChainFilters" ) ) == QLatin1String( "1" ) );
+    xml2config( configElement, cfg , QStringLiteral( "ChainFilters" ) );
   }
   return cfg;
 }
@@ -85,13 +85,13 @@ void QgsRelationReferenceFactory::writeConfig( const QgsEditorWidgetConfig& conf
   Q_UNUSED( layer );
   Q_UNUSED( fieldIdx );
 
-  configElement.setAttribute( QStringLiteral( "AllowNULL" ), config[QStringLiteral( "AllowNULL" )].toBool() );
-  configElement.setAttribute( QStringLiteral( "OrderByValue" ), config[QStringLiteral( "OrderByValue" )].toBool() );
-  configElement.setAttribute( QStringLiteral( "ShowForm" ), config[QStringLiteral( "ShowForm" )].toBool() );
-  configElement.setAttribute( QStringLiteral( "Relation" ), config[QStringLiteral( "Relation" )].toString() );
-  configElement.setAttribute( QStringLiteral( "MapIdentification" ), config[QStringLiteral( "MapIdentification" )].toBool() );
-  configElement.setAttribute( QStringLiteral( "ReadOnly" ), config[QStringLiteral( "ReadOnly" )].toBool() );
-  configElement.setAttribute( QStringLiteral( "AllowAddFeatures" ), config[QStringLiteral( "AllowAddFeatures" )].toBool() );
+  config2xml( config, configElement, QStringLiteral( "AllowNULL" ) );
+  config2xml( config, configElement, QStringLiteral( "OrderByValue" ) );
+  config2xml( config, configElement, QStringLiteral( "ShowForm" ) );
+  config2xml( config, configElement, QStringLiteral( "Relation" ) );
+  config2xml( config, configElement, QStringLiteral( "MapIdentification" ) );
+  config2xml( config, configElement, QStringLiteral( "ReadOnly" ) );
+  config2xml( config, configElement, QStringLiteral( "AllowAddFeatures" ) );
 
   if ( config.contains( QStringLiteral( "FilterFields" ) ) )
   {
@@ -105,7 +105,7 @@ void QgsRelationReferenceFactory::writeConfig( const QgsEditorWidgetConfig& conf
     }
     configElement.appendChild( filterFields );
 
-    filterFields.setAttribute( QStringLiteral( "ChainFilters" ), config[QStringLiteral( "ChainFilters" )].toBool() );
+    config2xml( config, configElement, QStringLiteral( "ChainFilters" ) );
   }
 }
 
diff --git a/src/gui/editorwidgets/qgstexteditwidgetfactory.cpp b/src/gui/editorwidgets/qgstexteditwidgetfactory.cpp
index 71b5a34f334..66dd51a90f5 100644
--- a/src/gui/editorwidgets/qgstexteditwidgetfactory.cpp
+++ b/src/gui/editorwidgets/qgstexteditwidgetfactory.cpp
@@ -46,8 +46,8 @@ void QgsTextEditWidgetFactory::writeConfig( const QgsEditorWidgetConfig& config,
   Q_UNUSED( layer )
   Q_UNUSED( fieldIdx )
 
-  configElement.setAttribute( QStringLiteral( "IsMultiline" ), config.value( QStringLiteral( "IsMultiline" ), false ).toBool() );
-  configElement.setAttribute( QStringLiteral( "UseHtml" ), config.value( QStringLiteral( "UseHtml" ), false ).toBool() );
+  config2xml( config, configElement, QStringLiteral( "IsMultiline" ) );
+  config2xml( config, configElement, QStringLiteral( "UseHtml" ) );
 }
 
 QgsEditorWidgetConfig QgsTextEditWidgetFactory::readConfig( const QDomElement& configElement, QgsVectorLayer* layer, int fieldIdx )
@@ -57,8 +57,8 @@ QgsEditorWidgetConfig QgsTextEditWidgetFactory::readConfig( const QDomElement& c
 
   QgsEditorWidgetConfig cfg;
 
-  cfg.insert( QStringLiteral( "IsMultiline" ), configElement.attribute( QStringLiteral( "IsMultiline" ), QStringLiteral( "0" ) ) == QLatin1String( "1" ) );
-  cfg.insert( QStringLiteral( "UseHtml" ), configElement.attribute( QStringLiteral( "UseHtml" ), QStringLiteral( "0" ) ) == QLatin1String( "1" ) );
+  xml2config( configElement, cfg, QStringLiteral( "IsMultiline" ) );
+  xml2config( configElement, cfg, QStringLiteral( "UseHtml" ) );
 
   return cfg;
 }
diff --git a/src/gui/editorwidgets/qgsuniquevaluewidgetfactory.cpp b/src/gui/editorwidgets/qgsuniquevaluewidgetfactory.cpp
index 5416d8111a6..52ab3f5fcba 100644
--- a/src/gui/editorwidgets/qgsuniquevaluewidgetfactory.cpp
+++ b/src/gui/editorwidgets/qgsuniquevaluewidgetfactory.cpp
@@ -41,7 +41,7 @@ QgsEditorWidgetConfig QgsUniqueValueWidgetFactory::readConfig( const QDomElement
 
   QgsEditorWidgetConfig cfg;
 
-  cfg.insert( QStringLiteral( "Editable" ), configElement.attribute( QStringLiteral( "Editable" ), QStringLiteral( "0" ) ) == QLatin1String( "1" ) );
+  xml2config( configElement, cfg, QStringLiteral( "Editable" ) );
 
   return cfg;
 }
@@ -51,5 +51,5 @@ void QgsUniqueValueWidgetFactory::writeConfig( const QgsEditorWidgetConfig& conf
   Q_UNUSED( doc )
   Q_UNUSED( layer )
   Q_UNUSED( fieldIdx )
-  configElement.setAttribute( QStringLiteral( "Editable" ), config.value( QStringLiteral( "Editable" ), false ).toBool() );
+  config2xml( config, configElement, QStringLiteral( "Editable" ) );
 }
diff --git a/src/gui/editorwidgets/qgsvaluerelationwidgetfactory.cpp b/src/gui/editorwidgets/qgsvaluerelationwidgetfactory.cpp
index 6df733d2782..faeafd452df 100644
--- a/src/gui/editorwidgets/qgsvaluerelationwidgetfactory.cpp
+++ b/src/gui/editorwidgets/qgsvaluerelationwidgetfactory.cpp
@@ -52,14 +52,14 @@ QgsEditorWidgetConfig QgsValueRelationWidgetFactory::readConfig( const QDomEleme
 
   QgsEditorWidgetConfig cfg;
 
-  cfg.insert( QStringLiteral( "Layer" ), configElement.attribute( QStringLiteral( "Layer" ) ) );
-  cfg.insert( QStringLiteral( "Key" ), configElement.attribute( QStringLiteral( "Key" ) ) );
-  cfg.insert( QStringLiteral( "Value" ), configElement.attribute( QStringLiteral( "Value" ) ) );
-  cfg.insert( QStringLiteral( "FilterExpression" ), configElement.attribute( QStringLiteral( "FilterExpression" ) ) );
-  cfg.insert( QStringLiteral( "OrderByValue" ), configElement.attribute( QStringLiteral( "OrderByValue" ) ) );
-  cfg.insert( QStringLiteral( "AllowMulti" ), configElement.attribute( QStringLiteral( "AllowMulti" ) ) );
-  cfg.insert( QStringLiteral( "AllowNull" ), configElement.attribute( QStringLiteral( "AllowNull" ) ) );
-  cfg.insert( QStringLiteral( "UseCompleter" ), configElement.attribute( QStringLiteral( "UseCompleter" ) ) );
+  xml2config( configElement, cfg, QStringLiteral( "Layer" ) );
+  xml2config( configElement, cfg, QStringLiteral( "Key" ) );
+  xml2config( configElement, cfg, QStringLiteral( "Value" ) );
+  xml2config( configElement, cfg, QStringLiteral( "FilterExpression" ) );
+  xml2config( configElement, cfg, QStringLiteral( "OrderByValue" ) );
+  xml2config( configElement, cfg, QStringLiteral( "AllowMulti" ) );
+  xml2config( configElement, cfg, QStringLiteral( "AllowNull" ) );
+  xml2config( configElement, cfg, QStringLiteral( "UseCompleter" ) );
 
   return cfg;
 }
@@ -70,14 +70,14 @@ void QgsValueRelationWidgetFactory::writeConfig( const QgsEditorWidgetConfig& co
   Q_UNUSED( layer )
   Q_UNUSED( fieldIdx )
 
-  configElement.setAttribute( QStringLiteral( "Layer" ), config.value( QStringLiteral( "Layer" ) ).toString() );
-  configElement.setAttribute( QStringLiteral( "Key" ), config.value( QStringLiteral( "Key" ) ).toString() );
-  configElement.setAttribute( QStringLiteral( "Value" ), config.value( QStringLiteral( "Value" ) ).toString() );
-  configElement.setAttribute( QStringLiteral( "FilterExpression" ), config.value( QStringLiteral( "FilterExpression" ) ).toString() );
-  configElement.setAttribute( QStringLiteral( "OrderByValue" ), config.value( QStringLiteral( "OrderByValue" ) ).toBool() );
-  configElement.setAttribute( QStringLiteral( "AllowMulti" ), config.value( QStringLiteral( "AllowMulti" ) ).toBool() );
-  configElement.setAttribute( QStringLiteral( "AllowNull" ), config.value( QStringLiteral( "AllowNull" ) ).toBool() );
-  configElement.setAttribute( QStringLiteral( "UseCompleter" ), config.value( QStringLiteral( "UseCompleter" ) ).toBool() );
+  config2xml( config, configElement, QStringLiteral( "Layer" ) );
+  config2xml( config, configElement, QStringLiteral( "Key" ) );
+  config2xml( config, configElement, QStringLiteral( "Value" ) );
+  config2xml( config, configElement, QStringLiteral( "FilterExpression" ) );
+  config2xml( config, configElement, QStringLiteral( "OrderByValue" ) );
+  config2xml( config, configElement, QStringLiteral( "AllowMulti" ) );
+  config2xml( config, configElement, QStringLiteral( "AllowNull" ) );
+  config2xml( config, configElement, QStringLiteral( "UseCompleter" ) );
 }
 
 QString QgsValueRelationWidgetFactory::representValue( QgsVectorLayer* vl, int fieldIdx, const QgsEditorWidgetConfig& config, const QVariant& cache, const QVariant& value ) const
diff --git a/src/gui/editorwidgets/qgswebviewwidgetfactory.cpp b/src/gui/editorwidgets/qgswebviewwidgetfactory.cpp
index 899105a6592..702f868e808 100644
--- a/src/gui/editorwidgets/qgswebviewwidgetfactory.cpp
+++ b/src/gui/editorwidgets/qgswebviewwidgetfactory.cpp
@@ -41,8 +41,8 @@ QgsEditorWidgetConfig QgsWebViewWidgetFactory::readConfig( const QDomElement& co
 
   QgsEditorWidgetConfig cfg;
 
-  cfg.insert( QStringLiteral( "Height" ), configElement.attribute( QStringLiteral( "Height" ), 0 ).toInt() );
-  cfg.insert( QStringLiteral( "Width" ), configElement.attribute( QStringLiteral( "Width" ), 0 ).toInt() );
+  xml2config( configElement, cfg, QStringLiteral( "Height" ) );
+  xml2config( configElement, cfg, QStringLiteral( "Width" ) );
 
   return cfg;
 }
@@ -53,6 +53,6 @@ void QgsWebViewWidgetFactory::writeConfig( const QgsEditorWidgetConfig& config,
   Q_UNUSED( layer )
   Q_UNUSED( fieldIdx )
 
-  configElement.setAttribute( QStringLiteral( "Height" ), config.value( QStringLiteral( "Height" ), 0 ).toString() );
-  configElement.setAttribute( QStringLiteral( "Width" ), config.value( QStringLiteral( "Width" ), 0 ).toString() );
+  config2xml( config, configElement, QStringLiteral( "Height" ) );
+  config2xml( config, configElement, QStringLiteral( "Width" ) );
 }