code: void handleValidationChange(CmsValidationContext validationContext) {
  
          if (validationContext.hasValidationErrors()) {
              String locales = "";
              for (String id : validationContext.getInvalidEntityIds()) {
                  if (locales.length() > 0) {
                      locales += ", ";
                  }
                  String locale = CmsContentDefinition.getLocaleFromId(id);
                  if (m_availableLocales.containsKey(locale)) {
                      locales += m_availableLocales.get(locale);
                  }
              }
              disableSave(Messages.get().key(Messages.GUI_TOOLBAR_VALIDATION_ERRORS_1, locales));
          } else if (!m_changedEntityIds.isEmpty()) {
              enableSave();
          }
      }
docs: Handles validation changes.<p>
  
  @param validationContext the changed validation context