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Raf.js
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Raf.js
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/*
* Scroller
* http://github.com/zynga/scroller
*
* Copyright 2011, Zynga Inc.
* Licensed under the MIT License.
* https://raw.github.com/zynga/scroller/master/MIT-LICENSE.txt
*
* Based on the work of: Unify Project (unify-project.org)
* http://unify-project.org
* Copyright 2011, Deutsche Telekom AG
* License: MIT + Apache (V2)
*
* Inspired by: https://github.com/inexorabletash/raf-shim/blob/master/raf.js
*/
(function(global)
{
if(global.requestAnimationFrame) {
return;
}
// Basic emulation of native methods for internal use
var now = Date.now || function() {
return +new Date;
};
var getKeys = Object.keys || function(obj) {
var keys = {};
for (var key in obj) {
keys[key] = true;
}
return keys;
};
var isEmpty = Object.empty || function(obj) {
for (var key in obj) {
return false;
}
return true;
};
// requestAnimationFrame polyfill
// http://webstuff.nfshost.com/anim-timing/Overview.html
var postfix = "RequestAnimationFrame";
var prefix = (function()
{
var all = "webkit,moz,o,ms".split(",");
for (var i=0; i<4; i++) {
if (global[all[i]+postfix] != null) {
return all[i];
}
}
})();
// Vendor specific implementation
if (prefix)
{
global.requestAnimationFrame = global[prefix+postfix];
global.cancelRequestAnimationFrame = global[prefix+"Cancel"+postfix];
return;
}
// Custom implementation
var TARGET_FPS = 60;
var requests = {};
var rafHandle = 1;
var timeoutHandle = null;
global.requestAnimationFrame = function(callback, root)
{
var callbackHandle = rafHandle++;
// Store callback
requests[callbackHandle] = callback;
// Create timeout at first request
if (timeoutHandle === null)
{
timeoutHandle = setTimeout(function()
{
var time = now();
var currentRequests = requests;
var keys = getKeys(currentRequests);
// Reset data structure before executing callbacks
requests = {};
timeoutHandle = null;
// Process all callbacks
for (var i=0, l=keys.length; i<l; i++) {
currentRequests[keys[i]](time);
}
}, 1000 / TARGET_FPS);
}
return callbackHandle;
};
global.cancelRequestAnimationFrame = function(handle)
{
delete requests[handle];
// Stop timeout if all where removed
if (isEmpty(requests))
{
clearTimeout(timeoutHandle);
timeoutHandle = null;
}
};
})(this);