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:
Sit et justo kasd. Lorem ipsum at magna option. No sit diam ea dignissim no et sea. Rebum duo eleifend est et sanctus ipsum ut vero ut. Eos eirmod aliquyam erat elitr dolor invidunt. Sit ut eum eirmod consequat erat tincidunt diam sit.