code: private void updateClassForTab(int index) {
  
          Widget widget = m_tabbedPanel.getWidget(index);
  
          String propertyTabStyle = STYLE_PROPERTIES_TAB_ACTIVE;
          if (widget == m_propertiesTab) {
              CmsImagePreviewDialog.this.addStyleName(propertyTabStyle);
          } else {
              CmsImagePreviewDialog.this.removeStyleName(propertyTabStyle);
          }
      }
docs: Updates the CSS classes of the preview dialog depending on selected tab.<p>
  
  @param index the tab index