code: @UiHandler("m_editButton")
      void showEditPopup(ClickEvent clickEvent) {
  
          m_editButton.clearHoverState();
          m_popup = new CmsPopup(m_title, -1);
          m_popup.setModal(true);
          m_popup.setAutoHideEnabled(true);
          m_popup.removePadding();
          m_popup.addCloseHandler(new CloseHandler<PopupPanel>() {
  
              public void onClose(CloseEvent<PopupPanel> event) {
  
                  onPopupClose();
              }
          });
          m_hasChanges = false;
          m_requireShowPopup = false;
          m_entityChangeHandlerRegistration = m_parentEntity.addValueChangeHandler(new ValueChangeHandler<CmsEntity>() {
  
              public void onValueChange(ValueChangeEvent<CmsEntity> event) {
  
                  onEntityChange();
              }
          });
          CmsType type = CmsEntityBackend.getInstance().getType(m_parentEntity.getTypeName());
          FlowPanel formPanel = new FormPanel();
          formPanel.setStyleName(I_CmsLayoutBundle.INSTANCE.form().formParent());
          formPanel.getElement().getStyle().setMargin(0, Unit.PX);
          formPanel.getElement().getStyle().setBorderWidth(0, Unit.PX);
          formPanel.getElement().getStyle().setPropertyPx("minHeight", 30);
          m_popup.add(formPanel);
          m_popup.addDialogClose(null);
          I_CmsLayoutBundle.INSTANCE.dialogCss().ensureInjected();
          m_popup.show();
          CmsAttributeHandler.setScrollElement(formPanel.getElement());
          CmsAttributeHandler.setResizeHandler(new ResizeHandler() {
  
              public void onResize(ResizeEvent event) {
  
                  positionPopup();
              }
          });
          m_widgetService.getRendererForType(
              type).renderAttributeValue(m_parentEntity, m_attributeHandler, m_attributeIndex, formPanel);
          CmsInlineEditOverlay.addOverlayForElement(m_referenceElement);
          positionPopup();
          m_popup.getElement().getStyle().setZIndex(I_CmsLayoutBundle.INSTANCE.constants().css().zIndexPopup());
          m_popupClosed = false;
      }
docs: Opens the form popup.<p>
  
  @param clickEvent the click event