window.requestAnimationFrame shim

rAFshim.coffee

###
http://paulirish.com/2011/requestanimationframe-for-smart-animating/
http://my.opera.com/emoller/blog/2011/12/20/requestanimationframe-for-smart-er-animating

requestAnimationFrame polyfill by Erik Möller
fixes from Paul Irish and Tino Zijdel

Coffeescript and AMD by Blaine Bublitz
###

define [], ->
    lastTime = 0;
    vendors = [ "ms", "moz", "webkit", "o" ]
    x = 0
    while x < vendors.length and not window.requestAnimationFrame
      window.requestAnimationFrame = window[vendors[x] + "RequestAnimationFrame"]
      window.cancelAnimationFrame = window[vendors[x] + "CancelAnimationFrame"] or window[vendors[x] + "CancelRequestAnimationFrame"]
      ++x

    unless window.requestAnimationFrame
      window.requestAnimationFrame = (callback, element) ->
        currTime = new Date().getTime()
        timeToCall = Math.max 0, 16 - (currTime - lastTime)
        id = window.setTimeout(-> 
          callback currTime + timeToCall
        , timeToCall)
        lastTime = currTime + timeToCall
        return id
        
    unless window.cancelAnimationFrame
      window.cancelAnimationFrame = (id) -> clearTimeout id