The <canvas> element is not natively supported by the backend formatting engine. However, what can be done is to replace the <canvas> with an image in the print <div> before sending to the formatter. There are a few Javascript drawn <canvas> elements on this page. They are processed to the output by the xepOnine.jgPlugin.js Javascript by converting them on-the-fly to image format.
This is a second <canvas> element on the page:
Option magna vero. Eirmod clita zzril lorem no iriure justo invidunt stet lobortis minim minim gubergren consequat eirmod. Ipsum amet est sea ipsum in eu amet. Nonumy no illum lorem kasd justo diam luptatum. Invidunt eirmod dolore sed in duo dolores nulla dignissim in diam et lorem aliquip ipsum adipiscing. Est gubergren vel invidunt elitr ipsum et et elitr sed. Ipsum dolor sit aliquyam rebum dolores magna amet et et aliquam velit consetetur dolor et diam justo commodo justo. Lorem ipsum ea amet tempor justo takimata consetetur accumsan stet ut lorem et aliquyam. Erat sea et est consequat lorem.