// requestAnimationFrame() shim by Paul Irish
// http://paulirish.com/2011/requestanimationframe-for-smart-animating/
window.requestAnimFrame = (function() {
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function(/* function */ callback, /* DOMElement */ element){
window.setTimeout(callback, 1000 / 60);
};
})();
/**
* Behaves the same as setInterval except uses requestAnimationFrame() where possible for better performance
* @param {function} fn The callback function
* @param {int} delay The delay in milliseconds
*/
window.requestInterval = function(fn, delay) {
if( !window.requestAnimationFrame &&
!window.webkitRequestAnimationFrame &&
!(window.mozRequestAnimationFrame && window.mozCancelRequestAnimationFrame) && // Firefox 5 ships without cancel support
!window.oRequestAnimationFrame &&
!window.msRequestAnimationFrame)
return window.setInterval(fn, delay);

var start = new Date().getTime(),
handle = new Object();

function loop() {
var current = new Date().getTime(),
delta = current - start;

if(delta >= delay) {
fn.call();
start = new Date().getTime();
}

handle.value = requestAnimFrame(loop);
};

handle.value = requestAnimFrame(loop);
return handle;
}

/**
* Behaves the same as clearInterval except uses cancelRequestAnimationFrame() where possible for better performance
* @param {int|object} fn The callback function
*/
window.clearRequestInterval = function(handle) {
    window.cancelAnimationFrame ? window.cancelAnimationFrame(handle.value) :
    window.webkitCancelRequestAnimationFrame ? window.webkitCancelRequestAnimationFrame(handle.value) :
    window.mozCancelRequestAnimationFrame ? window.mozCancelRequestAnimationFrame(handle.value) :
    window.oCancelRequestAnimationFrame ? window.oCancelRequestAnimationFrame(handle.value) :
    window.msCancelRequestAnimationFrame ? msCancelRequestAnimationFrame(handle.value) :
    clearInterval(handle);
};