code: private void initOverviewPopup() {
  
          m_updateExceptionsButton = new CmsPushButton();
          m_updateExceptionsButton.setText(Messages.get().key(Messages.GUI_LOCALE_DIALOG_OK_0));
          m_updateExceptionsButton.addClickHandler(new ClickHandler() {
  
              public void onClick(ClickEvent event) {
  
                  if (handleChange()) {
                      m_controller.updateExceptions(m_overviewList.getUncheckedDates());
                      m_overviewPopup.hide();
                  }
  
              }
          });
          m_overviewPopup = new CmsPopup(Messages.get().key(Messages.GUI_SERIALDATE_OVERVIEW_POPUP_TITLE_0), 800);
          m_overviewPopup.center();
          m_overviewPopup.setAutoHideEnabled(true);
          m_overviewPopup.addDialogClose(null);
          m_overviewPopup.addButton(m_updateExceptionsButton);
          CmsScrollPanel panel = new CmsScrollPanel();
          m_overviewList = new CmsCheckableDatePanel(m_dateFormat, CmsCheckableDatePanel.Style.TWO_COLUMNS);
          m_overviewList.addDate(new Date());
          panel.getElement().getStyle().setPaddingLeft(10, Unit.PX);
          panel.getElement().getStyle().setProperty("maxHeight", m_overviewPopup.getAvailableHeight(0), Unit.PX);
          panel.add(m_overviewList);
          m_overviewPopup.add(panel);
          m_overviewPopup.hide();
  
      }
docs: Initialize the overview/handle exceptions popup.