requestAnimationFrame Shim/Polyfill

Trying out GitHub just for kicks. (Still preferring Mercurial as a VCS though.)

Don't use this - see the code in Web Standards Polyfill instead

// requestAnimationFrame polyfill
// http://webstuff.nfshost.com/anim-timing/Overview.html

/*jslint browser:true*/

window.requestAnimationFrame = 
    window.requestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.oRequestAnimationFrame ||
    window.msRequestAnimationFrame ||
    (function () {

        var requests = {},
            TARGET_FPS = 60,
            raf_handle = 1,
            timeout_handle = -1;
        
        function isVisible(element) {
            return element.offsetWidth > 0 && element.offsetHeight > 0;
        }
        
        window.requestAnimationFrame = function requestAnimationFrame(callback, element) {
            var cb_handle = raf_handle;
            raf_handle = raf_handle + 1;
            requests[cb_handle] = {callback: callback, element: element};

            if (timeout_handle === -1) {
                timeout_handle = setTimeout(function () {
                    var cur_requests = requests,
                        time = +new Date(),
                        keys = Object.keys(cur_requests),
                        len = keys.length,
                        i, 
                        request;
                    
                    requests = {};
                    timeout_handle = -1;
                    
                    for (i = 0; i < len; i += 1) {
                        request = cur_requests[keys[i]];
                        if (!request.element || isVisible(request.element)) {
                            request.callback(time);
                        }
                    }
                }, 1000 / TARGET_FPS);
            }

            return cb_handle;
        };

        window.cancelRequestAnimationFrame = function cancelRequestAnimationFrame(handle) {

            delete requests[handle];
            
            if (Object.keys(requests).length === 0) {
                clearTimeout(timeout_handle);
                timeout_handle = -1;
            }
        };
    
        return window.requestAnimationFrame;
    }());

window.cancelRequestAnimationFrame = 
    window.cancelRequestAnimationFrame ||
    window.webkitCancelRequestAnimationFrame ||
    window.mozCancelRequestAnimationFrame ||
    window.oCancelRequestAnimationFrame ||
    window.msCancelRequestAnimationFrame;

Go to the raf-shim repo on GitHub for the latest version.