Fixes value relation widget to always keep scrollbar activated. Fixes #…

…16654

src/gui/editorwidgets/core/qgseditorwidgetwrapper.h

@@ -122,7 +122,7 @@ class GUI_EXPORT QgsEditorWidgetWrapper : public QgsWidgetWrapper
      *
      * \param enabled  Enable or Disable?
      */
-    void setEnabled( bool enabled ) override;
+    virtual void setEnabled( bool enabled ) override;
 
     /** Sets the widget to display in an indeterminate "mixed value" state.
      * \since QGIS 2.16

src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp

@@ -33,6 +33,7 @@ QgsValueRelationWidgetWrapper::QgsValueRelationWidgetWrapper( QgsVectorLayer *vl
   , mListWidget( nullptr )
   , mLineEdit( nullptr )
   , mLayer( nullptr )
+  , mUpdating( false )
 {
 }
 
@@ -198,3 +199,26 @@ void QgsValueRelationWidgetWrapper::showIndeterminateState()
     whileBlocking( mLineEdit )->clear();
   }
 }
+
+void QgsValueRelationWidgetWrapper::setEnabled( bool enabled )
+{
+  if ( mUpdating )
+    return;
+
+  if ( mListWidget )
+  {
+    mUpdating = true;
+    for ( int i = 0; i < mListWidget->count(); ++i )
+    {
+      QListWidgetItem *item = mListWidget->item( i );
+
+      if ( enabled )
+        item->setFlags( item->flags() | Qt::ItemIsEnabled );
+      else
+        item->setFlags( item->flags() & ~Qt::ItemIsEnabled );
+    }
+    mUpdating = false;
+  }
+  else
+    QgsEditorWidgetWrapper::setEnabled( enabled );
+}

src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.h

@@ -59,6 +59,8 @@ class GUI_EXPORT QgsValueRelationWidgetWrapper : public QgsEditorWidgetWrapper
 
     void showIndeterminateState() override;
 
+    void setEnabled( bool enabled ) override;
+
   protected:
     QWidget *createWidget( QWidget *parent ) override;
     void initWidget( QWidget *editor ) override;
@@ -75,6 +77,8 @@ class GUI_EXPORT QgsValueRelationWidgetWrapper : public QgsEditorWidgetWrapper
     QgsValueRelationFieldFormatter::ValueRelationCache mCache;
     QgsVectorLayer *mLayer = nullptr;
 
+    bool mUpdating;
+
     friend class QgsValueRelationWidgetFactory;
 };