You do not have to re-draw the canvas during transitions. Believe it or not, it is possible to do AJAX declaratively and with progressive enhancement. My approach is to develop forms normally, then add a directive that intercepts them via AJAX, "cuts" certain pieces of the target page and "pastes" it into the current page. It is a very simple, generic and flexible approach. The markup looks like this:

  <form action="/something" submit-to="#x, #y"></form>
  <div id="x" />
  <div id="y" />

Normally, the only thing I need to add to go from non-AJAX to AJAX is submit-to="[CSS Selector Here]". Possibly, some IDs. Everything else works automatically. The library adds a certain attribute to the "pasted" parts, so I can add visual transitions via CSS3. I can use form's action URL to rewrite current URL via push state.