code: public void setButtonTooltipText(final String TEXT) {
          if (null == buttonTooltipText) {
              _buttonTooltipText = TEXT;
              fireUpdateEvent(REDRAW_EVENT);
          } else {
              buttonTooltipText.set(TEXT);
          }
      }
docs: Defines the text that will be shown in the button tooltip. The
  knob in the radial gauges acts as button if interactive == true.
  
  @param TEXT