title: how to force a display update in canvas
body: <p>if I draw to the canvas a lot in quick succession, e.g. a context.fillRect in a loop, browsers seem to wait until the loop has finished before any of the drawing is displayed (possibly via double-buffering)</p>
  
  <p>Is there any way to force the browser to update the display, either explicitly or implicitly after each draw operation?</p>