code: public void update(SwingBoxDocument doc, Viewport root, Dimension dim)
              throws IOException
      {
          ContentReader rdr = new ContentReader();
          List<ElementSpec> elements = rdr.update(root, dim, getCSSBoxAnalyzer());
          ElementSpec elementsArray[] = elements.toArray(new ElementSpec[0]);
          doc.create(elementsArray);
      }
docs: Updates layout, using new dimensions.
  
  @param doc
  the document
  @param root
  the root box
  @param dim
  new dimension
  @throws IOException
  Signals that an I/O exception has occurred.