code: protected VBox buildDefaultContent(final SlideContent slideContent) {
  
          final VBox vbox = new VBox();
          // vbox.getStyleClass().add("content");
  
          // Link the class style of this slide content
          if (model().getSlide().getStyle() != null) {
              vbox.getStyleClass().add(model().getSlide().getStyle());
          }
  
          if (slideContent != null) {
              // Add all slide item into the vbox panel
              for (final SlideItem item : slideContent.getItem()) {
                  addSlideItem(vbox, item);
              }
  
              // Manage the secondary title if any
              if (slideContent.getTitle() != null) {
                  this.secondaryTitle.setText(slideContent.getTitle());
              }
          }
          return vbox;
      }
docs: Build the default content slide.
  
  @param slideContent the content of the slide to build
  
  @return the vbox with default content items