// Note: For now, we limit both the header and footer to a single physical
// page. This safes me a lot of trouble for now.
// we have to iterate using a more complex schema here.
// Step one: layout the header-section. Record that height.
final PageAreaRenderBox headerArea = pageBox.getHeaderArea();
headerHeight = headerArea.getHeight();
// Step two: The footer. For the footer, we have to traverse the whole
// thing backwards. Nonetheless, we've got the height.
final PageAreaRenderBox footerArea = pageBox.getFooterArea();
footerHeight = footerArea.getHeight();
startProcessing(pageBox);
}