renderPreview(header, body) {

    const snapshotTRef = this.view.snapshotTRef;
    const snapshotTObj = utils.getTiddler(snapshotTRef);

    const label = this.document.createElement('span');
    label.innerHTML = this.view.getLabel();
    label.className = 'tmap-view-label';
    header.appendChild(label);

    if (snapshotTObj) {

      // Construct child widget tree
      const tree = utils.getTiddlerNode(this.view.getRoot());
      tree.children.push(utils.getTranscludeNode(snapshotTRef));
      this.makeChildWidgets([ tree ]);
      this.renderChildren(body, body.firstChild);

    } else {

      $tw.utils.addClass(body, 'tmap-graph-placeholder');

    }

  }
When the widget is only previewed we do some alternative rendering.