code: public void setInternal(boolean internal) {
  
          m_internal = internal;
          m_textbox.setReadOnly(internal);
          m_editButton.setEnabled(internal);
          m_editButton.getElement().getStyle().setVisibility(internal ? Visibility.VISIBLE : Visibility.HIDDEN);
          //m_editButton.setVisible(internal);
          m_externalCheckbox.setChecked(!internal);
      }
docs: Sets the widget's mode to internal or external.<p>
  
  @param internal if true, sets the mode to internal, else to external