docs: public void setReadOnly(RuleProxyField ruleProxyField,
              RuleContext ruleContext)
      {
          if (!ruleProxyField.isReadOnly()) // only do it if the field changes
          {
              m_readOnlyFields.add(ruleProxyField.getProxyField());
              ruleContext.addReadOnly(ruleProxyField);
          }
      }