switch (constraint.getConstraintValueType()) {
case SingleFieldConstraint.TYPE_LITERAL:
if (this.constraint instanceof SingleFieldConstraint) {
final SingleFieldConstraint con = (SingleFieldConstraint) this.constraint;
CustomFormConfiguration customFormConfiguration = WorkingSetManager.getInstance().getCustomFormConfiguration(modeller.getAsset().metaData.packageName, pattern.factType, fieldName);
if (customFormConfiguration != null) {
constraintWidget = new Button(con.getValue(), new ClickHandler() {
public void onClick(ClickEvent event) {
showTypeChoice((Widget) event.getSource(), constraint);