code: protected void onkeyupevent() {
  
          String newText = m_comboBox.getFormValueAsString();
  
          if (!newText.equals(m_oldtext)) {
              fireChangeEvent();
              if (!newText.equals("")) {
                  m_comboBox.closeSelector();
              } else {
                  m_comboBox.openSelector();
              }
          }
  
          m_oldtext = newText;
      }
docs: Helper function to handle the popup of the combobox. <p>