code: public void setRestoreLastValid (boolean restoreLastValid) {
  		if (hasSelection)
  			throw new IllegalStateException("Last valid text restore can't be changed while filed has selection");
  
  		this.restoreLastValid = restoreLastValid;
  
  		if (restoreLastValid) {
  			if (restoreFocusListener == null) restoreFocusListener = new LastValidFocusListener();
  			addListener(restoreFocusListener);
  		} else {
  			removeListener(restoreFocusListener);
  		}
  	}
docs: If true this field will automatically restore last valid text if it loses keyboard focus during text edition.
  This can't be called while field is selected, doing so will result in IllegalStateException. Default is false.