you're still in the SPA. You generally need some sort of painters algorithm to repaint the canvas anyway. When the canvas comes back you would just repaint it from JS memory.
Canvas in particular has issues web devs have to deal with beyond their "normal" duties. Accessibility is simply not even a thing in canvas. Google Docs had to implement an entire parallel invisible DOM structure to emulate what they draw on the canvas when they were switching over to the canvas. And, of course, that DOM structure has to be in sync with canvas.
