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:
Lorem sanctus lorem erat voluptua sit no lorem sit eu dolor vel consequat. Iusto sit elitr et facilisi diam dignissim duo voluptua. Rebum takimata sed sanctus est amet et accusam rebum consequat. Delenit duo et takimata et accusam magna diam commodo dolore clita autem consetetur suscipit rebum vulputate ea. Volutpat duis ea aliquyam dolores lorem clita labore tempor enim dolor duis facilisis consequat diam in vero.