Update smooth-scroll plugin to v1.4.10

Updated the smooth-scroll plugin to the latest release (v1.4.10).
This was done in order to fix jittery scrolling in Chrome 56+.

1 files changed, 674 insertions, 634 deletions

diff --git a/static/plugins/smooth-scroll/smooth-scroll.js b/static/plugins/smooth-scroll/smooth-scroll.js
index cfeb22a..3aeafa9 100644
--- a/static/plugins/smooth-scroll/smooth-scroll.js
+++ b/static/plugins/smooth-scroll/smooth-scroll.js
@@ -1,750 +1,790 @@
 //
-// SmoothScroll for websites v1.4.6 (Balazs Galambosi)
+// SmoothScroll for websites v1.4.10 (Balazs Galambosi)
 // http://www.smoothscroll.net/
 //
 // Licensed under the terms of the MIT license.
 //
-// You may use it in your theme if you credit me. 
+// You may use it in your theme if you credit me.
 // It is also free to use on any individual website.
 //
 // Exception:
-// The only restriction is to not publish any  
+// The only restriction is to not publish any
 // extension for browsers or native application
 // without getting a written permission first.
 //
 
 (function () {
 
-    // Scroll Variables (tweakable)
-    var defaultOptions = {
-
-        // Scrolling Core
-        frameRate: 60, // [Hz]
-        animationTime: 1000, // [ms]
-        stepSize: 80, // [px]
-
-        // Pulse (less tweakable)
-        // ratio of "tail" to "acceleration"
-        pulseAlgorithm: true,
-        pulseScale: 4,
-        pulseNormalize: 1,
-
-        // Acceleration
-        accelerationDelta: 50,  // 50
-        accelerationMax: 3,   // 3
-
-        // Keyboard Settings
-        keyboardSupport: true,  // option
-        arrowScroll: 50,    // [px]
+// Scroll Variables (tweakable)
+var defaultOptions = {
+
+    // Scrolling Core
+    frameRate        : 150, // [Hz]
+    animationTime    : 400, // [ms]
+    stepSize         : 100, // [px]
+
+    // Pulse (less tweakable)
+    // ratio of "tail" to "acceleration"
+    pulseAlgorithm   : true,
+    pulseScale       : 4,
+    pulseNormalize   : 1,
+
+    // Acceleration
+    accelerationDelta : 50,  // 50
+    accelerationMax   : 3,   // 3
+
+    // Keyboard Settings
+    keyboardSupport   : true,  // option
+    arrowScroll       : 50,    // [px]
+
+    // Other
+    fixedBackground   : true,
+    excluded          : ''
+};
+
+var options = defaultOptions;
+
+
+// Other Variables
+var isExcluded = false;
+var isFrame = false;
+var direction = { x: 0, y: 0 };
+var initDone  = false;
+var root = document.documentElement;
+var activeElement;
+var observer;
+var refreshSize;
+var deltaBuffer = [];
+var deltaBufferTimer;
+var isMac = /^Mac/.test(navigator.platform);
+
+var key = { left: 37, up: 38, right: 39, down: 40, spacebar: 32,
+            pageup: 33, pagedown: 34, end: 35, home: 36 };
+var arrowKeys = { 37: 1, 38: 1, 39: 1, 40: 1 };
+
+/***********************************************
+ * INITIALIZE
+ ***********************************************/
+
+/**
+ * Tests if smooth scrolling is allowed. Shuts down everything if not.
+ */
+function initTest() {
+    if (options.keyboardSupport) {
+        addEvent('keydown', keydown);
+    }
+}
 
-        // Other
-        fixedBackground: true,
-        excluded: ''
-    };
+/**
+ * Sets up scrolls array, determines if frames are involved.
+ */
+function init() {
 
-    var options = defaultOptions;
+    if (initDone || !document.body) return;
 
+    initDone = true;
 
-    // Other Variables
-    var isExcluded = false;
-    var isFrame = false;
-    var direction = { x: 0, y: 0 };
-    var initDone = false;
-    var root = document.documentElement;
-    var activeElement;
-    var observer;
-    var refreshSize;
-    var deltaBuffer = [];
-    var isMac = /^Mac/.test(navigator.platform);
+    var body = document.body;
+    var html = document.documentElement;
+    var windowHeight = window.innerHeight;
+    var scrollHeight = body.scrollHeight;
 
-    var key = {
-        left: 37, up: 38, right: 39, down: 40, spacebar: 32,
-        pageup: 33, pagedown: 34, end: 35, home: 36
-    };
-    var arrowKeys = { 37: 1, 38: 1, 39: 1, 40: 1 };
+    // check compat mode for root element
+    root = (document.compatMode.indexOf('CSS') >= 0) ? html : body;
+    activeElement = body;
 
-    /***********************************************
-     * INITIALIZE
-     ***********************************************/
+    initTest();
 
-    /**
-     * Tests if smooth scrolling is allowed. Shuts down everything if not.
-     */
-    function initTest() {
-        if (options.keyboardSupport) {
-            addEvent('keydown', keydown);
-        }
+    // Checks if this script is running in a frame
+    if (top != self) {
+        isFrame = true;
     }
 
     /**
-     * Sets up scrolls array, determines if frames are involved.
+     * Safari 10 fixed it, Chrome fixed it in v45:
+     * This fixes a bug where the areas left and right to
+     * the content does not trigger the onmousewheel event
+     * on some pages. e.g.: html, body { height: 100% }
      */
-    function init() {
-
-        if (initDone || !document.body) return;
-
-        initDone = true;
-
-        var body = document.body;
-        var html = document.documentElement;
-        var windowHeight = window.innerHeight;
-        var scrollHeight = body.scrollHeight;
+    else if (isOldSafari &&
+             scrollHeight > windowHeight &&
+            (body.offsetHeight <= windowHeight ||
+             html.offsetHeight <= windowHeight)) {
+
+        var fullPageElem = document.createElement('div');
+        fullPageElem.style.cssText = 'position:absolute; z-index:-10000; ' +
+                                     'top:0; left:0; right:0; height:' +
+                                      root.scrollHeight + 'px';
+        document.body.appendChild(fullPageElem);
+
+        // DOM changed (throttled) to fix height
+        var pendingRefresh;
+        refreshSize = function () {
+            if (pendingRefresh) return; // could also be: clearTimeout(pendingRefresh);
+            pendingRefresh = setTimeout(function () {
+                if (isExcluded) return; // could be running after cleanup
+                fullPageElem.style.height = '0';
+                fullPageElem.style.height = root.scrollHeight + 'px';
+                pendingRefresh = null;
+            }, 500); // act rarely to stay fast
+        };
 
-        // check compat mode for root element
-        root = (document.compatMode.indexOf('CSS') >= 0) ? html : body;
-        activeElement = body;
+        setTimeout(refreshSize, 10);
 
-        initTest();
+        addEvent('resize', refreshSize);
 
-        // Checks if this script is running in a frame
-        if (top != self) {
-            isFrame = true;
-        }
+        // TODO: attributeFilter?
+        var config = {
+            attributes: true,
+            childList: true,
+            characterData: false
+            // subtree: true
+        };
 
-        /**
-         * Safari 10 fixed it, Chrome fixed it in v45:
-         * This fixes a bug where the areas left and right to 
-         * the content does not trigger the onmousewheel event
-         * on some pages. e.g.: html, body { height: 100% }
-         */
-        else if (isOldSafari &&
-            scrollHeight > windowHeight &&
-            (body.offsetHeight <= windowHeight ||
-                html.offsetHeight <= windowHeight)) {
-
-            var fullPageElem = document.createElement('div');
-            fullPageElem.style.cssText = 'position:absolute; z-index:-10000; ' +
-                'top:0; left:0; right:0; height:' +
-                root.scrollHeight + 'px';
-            document.body.appendChild(fullPageElem);
-
-            // DOM changed (throttled) to fix height
-            var pendingRefresh;
-            refreshSize = function () {
-                if (pendingRefresh) return; // could also be: clearTimeout(pendingRefresh);
-                pendingRefresh = setTimeout(function () {
-                    if (isExcluded) return; // could be running after cleanup
-                    fullPageElem.style.height = '0';
-                    fullPageElem.style.height = root.scrollHeight + 'px';
-                    pendingRefresh = null;
-                }, 500); // act rarely to stay fast
-            };
-
-            setTimeout(refreshSize, 10);
-
-            addEvent('resize', refreshSize);
-
-            // TODO: attributeFilter?
-            var config = {
-                attributes: true,
-                childList: true,
-                characterData: false
-                // subtree: true
-            };
-
-            observer = new MutationObserver(refreshSize);
-            observer.observe(body, config);
-
-            if (root.offsetHeight <= windowHeight) {
-                var clearfix = document.createElement('div');
-                clearfix.style.clear = 'both';
-                body.appendChild(clearfix);
-            }
-        }
+        observer = new MutationObserver(refreshSize);
+        observer.observe(body, config);
 
-        // disable fixed background
-        if (!options.fixedBackground && !isExcluded) {
-            body.style.backgroundAttachment = 'scroll';
-            html.style.backgroundAttachment = 'scroll';
+        if (root.offsetHeight <= windowHeight) {
+            var clearfix = document.createElement('div');
+            clearfix.style.clear = 'both';
+            body.appendChild(clearfix);
         }
     }
 
-    /**
-     * Removes event listeners and other traces left on the page.
-     */
-    function cleanup() {
-        observer && observer.disconnect();
-        removeEvent(wheelEvent, wheel);
-        removeEvent('mousedown', mousedown);
-        removeEvent('keydown', keydown);
-        removeEvent('resize', refreshSize);
-        removeEvent('load', init);
+    // disable fixed background
+    if (!options.fixedBackground && !isExcluded) {
+        body.style.backgroundAttachment = 'scroll';
+        html.style.backgroundAttachment = 'scroll';
     }
-
-
-    /************************************************
-     * SCROLLING 
-     ************************************************/
-
-    var que = [];
-    var pending = false;
-    var lastScroll = Date.now();
-
-    /**
-     * Pushes scroll actions to the scrolling queue.
-     */
-    function scrollArray(elem, left, top) {
-
-        directionCheck(left, top);
-
-        if (options.accelerationMax != 1) {
-            var now = Date.now();
-            var elapsed = now - lastScroll;
-            if (elapsed < options.accelerationDelta) {
-                var factor = (1 + (50 / elapsed)) / 2;
-                if (factor > 1) {
-                    factor = Math.min(factor, options.accelerationMax);
-                    left *= factor;
-                    top *= factor;
-                }
+}
+
+/**
+ * Removes event listeners and other traces left on the page.
+ */
+function cleanup() {
+    observer && observer.disconnect();
+    removeEvent(wheelEvent, wheel);
+    removeEvent('mousedown', mousedown);
+    removeEvent('keydown', keydown);
+    removeEvent('resize', refreshSize);
+    removeEvent('load', init);
+}
+
+
+/************************************************
+ * SCROLLING
+ ************************************************/
+
+var que = [];
+var pending = false;
+var lastScroll = Date.now();
+
+/**
+ * Pushes scroll actions to the scrolling queue.
+ */
+function scrollArray(elem, left, top) {
+
+    directionCheck(left, top);
+
+    if (options.accelerationMax != 1) {
+        var now = Date.now();
+        var elapsed = now - lastScroll;
+        if (elapsed < options.accelerationDelta) {
+            var factor = (1 + (50 / elapsed)) / 2;
+            if (factor > 1) {
+                factor = Math.min(factor, options.accelerationMax);
+                left *= factor;
+                top  *= factor;
             }
-            lastScroll = Date.now();
         }
+        lastScroll = Date.now();
+    }
 
-        // push a scroll command
-        que.push({
-            x: left,
-            y: top,
-            lastX: (left < 0) ? 0.99 : -0.99,
-            lastY: (top < 0) ? 0.99 : -0.99,
-            start: Date.now()
-        });
-
-        // don't act if there's a pending queue
-        if (pending) {
-            return;
-        }
-
-        var scrollWindow = (elem === document.body);
-
-        var step = function (time) {
-
-            var now = Date.now();
-            var scrollX = 0;
-            var scrollY = 0;
-
-            for (var i = 0; i < que.length; i++) {
-
-                var item = que[i];
-                var elapsed = now - item.start;
-                var finished = (elapsed >= options.animationTime);
-
-                // scroll position: [0, 1]
-                var position = (finished) ? 1 : elapsed / options.animationTime;
+    // push a scroll command
+    que.push({
+        x: left,
+        y: top,
+        lastX: (left < 0) ? 0.99 : -0.99,
+        lastY: (top  < 0) ? 0.99 : -0.99,
+        start: Date.now()
+    });
+
+    // don't act if there's a pending queue
+    if (pending) {
+        return;
+    }
 
-                // easing [optional]
-                if (options.pulseAlgorithm) {
-                    position = pulse(position);
-                }
+    var scrollRoot = getScrollRoot();
+    var isWindowScroll = (elem === scrollRoot || elem === document.body);
 
-                // only need the difference
-                var x = (item.x * position - item.lastX) >> 0;
-                var y = (item.y * position - item.lastY) >> 0;
+    // if we haven't already fixed the behavior,
+    // and it needs fixing for this sesh
+    if (elem.$scrollBehavior == null && isScrollBehaviorSmooth(elem)) {
+        elem.$scrollBehavior = elem.style.scrollBehavior;
+        elem.style.scrollBehavior = 'auto';
+    }
 
-                // add this to the total scrolling
-                scrollX += x;
-                scrollY += y;
+    var step = function (time) {
 
-                // update last values
-                item.lastX += x;
-                item.lastY += y;
+        var now = Date.now();
+        var scrollX = 0;
+        var scrollY = 0;
 
-                // delete and step back if it's over
-                if (finished) {
-                    que.splice(i, 1); i--;
-                }
-            }
+        for (var i = 0; i < que.length; i++) {
 
-            // scroll left and top
-            if (scrollWindow) {
-                window.scrollBy(scrollX, scrollY);
-            }
-            else {
-                if (scrollX) elem.scrollLeft += scrollX;
-                if (scrollY) elem.scrollTop += scrollY;
-            }
+            var item = que[i];
+            var elapsed  = now - item.start;
+            var finished = (elapsed >= options.animationTime);
 
-            // clean up if there's nothing left to do
-            if (!left && !top) {
-                que = [];
-            }
+            // scroll position: [0, 1]
+            var position = (finished) ? 1 : elapsed / options.animationTime;
 
-            if (que.length) {
-                requestFrame(step, elem, (1000 / options.frameRate + 1));
-            } else {
-                pending = false;
+            // easing [optional]
+            if (options.pulseAlgorithm) {
+                position = pulse(position);
             }
-        };
-
-        // start a new queue of actions
-        requestFrame(step, elem, 0);
-        pending = true;
-    }
 
+            // only need the difference
+            var x = (item.x * position - item.lastX) >> 0;
+            var y = (item.y * position - item.lastY) >> 0;
 
-    /***********************************************
-     * EVENTS
-     ***********************************************/
+            // add this to the total scrolling
+            scrollX += x;
+            scrollY += y;
 
-    /**
-     * Mouse wheel handler.
-     * @param {Object} event
-     */
-    function wheel(event) {
+            // update last values
+            item.lastX += x;
+            item.lastY += y;
 
-        if (!initDone) {
-            init();
-        }
-
-        var target = event.target;
-
-        // leave early if default action is prevented   
-        // or it's a zooming event with CTRL 
-        if (event.defaultPrevented || event.ctrlKey) {
-            return true;
+            // delete and step back if it's over
+            if (finished) {
+                que.splice(i, 1); i--;
+            }
         }
 
-        // leave embedded content alone (flash & pdf)
-        if (isNodeName(activeElement, 'embed') ||
-            (isNodeName(target, 'embed') && /\.pdf/i.test(target.src)) ||
-            isNodeName(activeElement, 'object') ||
-            target.shadowRoot) {
-            return true;
+        // scroll left and top
+        if (isWindowScroll) {
+            window.scrollBy(scrollX, scrollY);
         }
-
-        var deltaX = -event.wheelDeltaX || event.deltaX || 0;
-        var deltaY = -event.wheelDeltaY || event.deltaY || 0;
-
-        if (isMac) {
-            if (event.wheelDeltaX && isDivisible(event.wheelDeltaX, 120)) {
-                deltaX = -120 * (event.wheelDeltaX / Math.abs(event.wheelDeltaX));
-            }
-            if (event.wheelDeltaY && isDivisible(event.wheelDeltaY, 120)) {
-                deltaY = -120 * (event.wheelDeltaY / Math.abs(event.wheelDeltaY));
-            }
+        else {
+            if (scrollX) elem.scrollLeft += scrollX;
+            if (scrollY) elem.scrollTop  += scrollY;
         }
 
-        // use wheelDelta if deltaX/Y is not available
-        if (!deltaX && !deltaY) {
-            deltaY = -event.wheelDelta || 0;
+        // clean up if there's nothing left to do
+        if (!left && !top) {
+            que = [];
         }
 
-        // line based scrolling (Firefox mostly)
-        if (event.deltaMode === 1) {
-            deltaX *= 40;
-            deltaY *= 40;
+        if (que.length) {
+            requestFrame(step, elem, (1000 / options.frameRate + 1));
+        } else {
+            pending = false;
+            // restore default behavior at the end of scrolling sesh
+            if (elem.$scrollBehavior != null) {
+                elem.style.scrollBehavior = elem.$scrollBehavior;
+                elem.$scrollBehavior = null;
+            }
         }
+    };
 
-        var overflowing = overflowingAncestor(target);
+    // start a new queue of actions
+    requestFrame(step, elem, 0);
+    pending = true;
+}
 
-        // nothing to do if there's no element that's scrollable
-        if (!overflowing) {
-            // except Chrome iframes seem to eat wheel events, which we need to 
-            // propagate up, if the iframe has nothing overflowing to scroll
-            if (isFrame && isChrome) {
-                // change target to iframe element itself for the parent frame
-                Object.defineProperty(event, "target", { value: window.frameElement });
-                return parent.wheel(event);
-            }
-            return true;
-        }
 
-        // check if it's a touchpad scroll that should be ignored
-        if (isTouchpad(deltaY)) {
-            return true;
-        }
+/***********************************************
+ * EVENTS
+ ***********************************************/
 
-        // scale by step size
-        // delta is 120 most of the time
-        // synaptics seems to send 1 sometimes
-        if (Math.abs(deltaX) > 1.2) {
-            deltaX *= options.stepSize / 120;
-        }
-        if (Math.abs(deltaY) > 1.2) {
-            deltaY *= options.stepSize / 120;
-        }
+/**
+ * Mouse wheel handler.
+ * @param {Object} event
+ */
+function wheel(event) {
 
-        scrollArray(overflowing, deltaX, deltaY);
-        event.preventDefault();
-        scheduleClearCache();
+    if (!initDone) {
+        init();
     }
 
-    /**
-     * Keydown event handler.
-     * @param {Object} event
-     */
-    function keydown(event) {
+    var target = event.target;
 
-        var target = event.target;
-        var modifier = event.ctrlKey || event.altKey || event.metaKey ||
-            (event.shiftKey && event.keyCode !== key.spacebar);
+    // leave early if default action is prevented
+    // or it's a zooming event with CTRL
+    if (event.defaultPrevented || event.ctrlKey) {
+        return true;
+    }
 
-        // our own tracked active element could've been removed from the DOM
-        if (!document.body.contains(activeElement)) {
-            activeElement = document.activeElement;
-        }
+    // leave embedded content alone (flash & pdf)
+    if (isNodeName(activeElement, 'embed') ||
+       (isNodeName(target, 'embed') && /\.pdf/i.test(target.src)) ||
+        isNodeName(activeElement, 'object') ||
+        target.shadowRoot) {
+        return true;
+    }
 
-        // do nothing if user is editing text
-        // or using a modifier key (except shift)
-        // or in a dropdown
-        // or inside interactive elements
-        var inputNodeNames = /^(textarea|select|embed|object)$/i;
-        var buttonTypes = /^(button|submit|radio|checkbox|file|color|image)$/i;
-        if (event.defaultPrevented ||
-            inputNodeNames.test(target.nodeName) ||
-            isNodeName(target, 'input') && !buttonTypes.test(target.type) ||
-            isNodeName(activeElement, 'video') ||
-            isInsideYoutubeVideo(event) ||
-            target.isContentEditable ||
-            modifier) {
-            return true;
-        }
+    var deltaX = -event.wheelDeltaX || event.deltaX || 0;
+    var deltaY = -event.wheelDeltaY || event.deltaY || 0;
 
-        // [spacebar] should trigger button press, leave it alone
-        if ((isNodeName(target, 'button') ||
-            isNodeName(target, 'input') && buttonTypes.test(target.type)) &&
-            event.keyCode === key.spacebar) {
-            return true;
+    if (isMac) {
+        if (event.wheelDeltaX && isDivisible(event.wheelDeltaX, 120)) {
+            deltaX = -120 * (event.wheelDeltaX / Math.abs(event.wheelDeltaX));
         }
-
-        // [arrwow keys] on radio buttons should be left alone
-        if (isNodeName(target, 'input') && target.type == 'radio' &&
-            arrowKeys[event.keyCode]) {
-            return true;
+        if (event.wheelDeltaY && isDivisible(event.wheelDeltaY, 120)) {
+            deltaY = -120 * (event.wheelDeltaY / Math.abs(event.wheelDeltaY));
         }
+    }
 
-        var shift, x = 0, y = 0;
-        var overflowing = overflowingAncestor(activeElement);
-
-        if (!overflowing) {
-            // Chrome iframes seem to eat key events, which we need to 
-            // propagate up, if the iframe has nothing overflowing to scroll
-            return (isFrame && isChrome) ? parent.keydown(event) : true;
-        }
+    // use wheelDelta if deltaX/Y is not available
+    if (!deltaX && !deltaY) {
+        deltaY = -event.wheelDelta || 0;
+    }
 
-        var clientHeight = overflowing.clientHeight;
+    // line based scrolling (Firefox mostly)
+    if (event.deltaMode === 1) {
+        deltaX *= 40;
+        deltaY *= 40;
+    }
 
-        if (overflowing == document.body) {
-            clientHeight = window.innerHeight;
-        }
+    var overflowing = overflowingAncestor(target);
 
-        switch (event.keyCode) {
-            case key.up:
-                y = -options.arrowScroll;
-                break;
-            case key.down:
-                y = options.arrowScroll;
-                break;
-            case key.spacebar: // (+ shift)
-                shift = event.shiftKey ? 1 : -1;
-                y = -shift * clientHeight * 0.9;
-                break;
-            case key.pageup:
-                y = -clientHeight * 0.9;
-                break;
-            case key.pagedown:
-                y = clientHeight * 0.9;
-                break;
-            case key.home:
-                y = -overflowing.scrollTop;
-                break;
-            case key.end:
-                var scroll = overflowing.scrollHeight - overflowing.scrollTop;
-                var scrollRemaining = scroll - clientHeight;
-                y = (scrollRemaining > 0) ? scrollRemaining + 10 : 0;
-                break;
-            case key.left:
-                x = -options.arrowScroll;
-                break;
-            case key.right:
-                x = options.arrowScroll;
-                break;
-            default:
-                return true; // a key we don't care about
+    // nothing to do if there's no element that's scrollable
+    if (!overflowing) {
+        // except Chrome iframes seem to eat wheel events, which we need to
+        // propagate up, if the iframe has nothing overflowing to scroll
+        if (isFrame && isChrome)  {
+            // change target to iframe element itself for the parent frame
+            Object.defineProperty(event, "target", {value: window.frameElement});
+            return parent.wheel(event);
         }
-
-        scrollArray(overflowing, x, y);
-        event.preventDefault();
-        scheduleClearCache();
+        return true;
     }
 
-    /**
-     * Mousedown event only for updating activeElement
-     */
-    function mousedown(event) {
-        activeElement = event.target;
+    // check if it's a touchpad scroll that should be ignored
+    if (isTouchpad(deltaY)) {
+        return true;
     }
 
+    // scale by step size
+    // delta is 120 most of the time
+    // synaptics seems to send 1 sometimes
+    if (Math.abs(deltaX) > 1.2) {
+        deltaX *= options.stepSize / 120;
+    }
+    if (Math.abs(deltaY) > 1.2) {
+        deltaY *= options.stepSize / 120;
+    }
 
-    /***********************************************
-     * OVERFLOW
-     ***********************************************/
-
-    var uniqueID = (function () {
-        var i = 0;
-        return function (el) {
-            return el.uniqueID || (el.uniqueID = i++);
-        };
-    })();
+    scrollArray(overflowing, deltaX, deltaY);
+    event.preventDefault();
+    scheduleClearCache();
+}
 
-    var cache = {}; // cleared out after a scrolling session
-    var clearCacheTimer;
+/**
+ * Keydown event handler.
+ * @param {Object} event
+ */
+function keydown(event) {
 
-    //setInterval(function () { cache = {}; }, 10 * 1000);
+    var target   = event.target;
+    var modifier = event.ctrlKey || event.altKey || event.metaKey ||
+                  (event.shiftKey && event.keyCode !== key.spacebar);
 
-    function scheduleClearCache() {
-        clearTimeout(clearCacheTimer);
-        clearCacheTimer = setInterval(function () { cache = {}; }, 1 * 1000);
+    // our own tracked active element could've been removed from the DOM
+    if (!document.body.contains(activeElement)) {
+        activeElement = document.activeElement;
     }
 
-    function setCache(elems, overflowing) {
-        for (var i = elems.length; i--;)
-            cache[uniqueID(elems[i])] = overflowing;
-        return overflowing;
+    // do nothing if user is editing text
+    // or using a modifier key (except shift)
+    // or in a dropdown
+    // or inside interactive elements
+    var inputNodeNames = /^(textarea|select|embed|object)$/i;
+    var buttonTypes = /^(button|submit|radio|checkbox|file|color|image)$/i;
+    if ( event.defaultPrevented ||
+         inputNodeNames.test(target.nodeName) ||
+         isNodeName(target, 'input') && !buttonTypes.test(target.type) ||
+         isNodeName(activeElement, 'video') ||
+         isInsideYoutubeVideo(event) ||
+         target.isContentEditable ||
+         modifier ) {
+      return true;
     }
 
-    //  (body)                (root)
-    //         | hidden | visible | scroll |  auto  |
-    // hidden  |   no   |    no   |   YES  |   YES  |
-    // visible |   no   |   YES   |   YES  |   YES  |
-    // scroll  |   no   |   YES   |   YES  |   YES  |
-    // auto    |   no   |   YES   |   YES  |   YES  |
-
-    function overflowingAncestor(el) {
-        var elems = [];
-        var body = document.body;
-        var rootScrollHeight = root.scrollHeight;
-        do {
-            var cached = cache[uniqueID(el)];
-            if (cached) {
-                return setCache(elems, cached);
-            }
-            elems.push(el);
-            if (rootScrollHeight === el.scrollHeight) {
-                var topOverflowsNotHidden = overflowNotHidden(root) && overflowNotHidden(body);
-                var isOverflowCSS = topOverflowsNotHidden || overflowAutoOrScroll(root);
-                if (isFrame && isContentOverflowing(root) ||
-                    !isFrame && isOverflowCSS) {
-                    return setCache(elems, getScrollRoot());
-                }
-            } else if (isContentOverflowing(el) && overflowAutoOrScroll(el)) {
-                return setCache(elems, el);
-            }
-        } while (el = el.parentElement);
+    // [spacebar] should trigger button press, leave it alone
+    if ((isNodeName(target, 'button') ||
+         isNodeName(target, 'input') && buttonTypes.test(target.type)) &&
+        event.keyCode === key.spacebar) {
+      return true;
     }
 
-    function isContentOverflowing(el) {
-        return (el.clientHeight + 10 < el.scrollHeight);
+    // [arrwow keys] on radio buttons should be left alone
+    if (isNodeName(target, 'input') && target.type == 'radio' &&
+        arrowKeys[event.keyCode])  {
+      return true;
     }
 
-    // typically for <body> and <html>
-    function overflowNotHidden(el) {
-        var overflow = getComputedStyle(el, '').getPropertyValue('overflow-y');
-        return (overflow !== 'hidden');
-    }
+    var shift, x = 0, y = 0;
+    var overflowing = overflowingAncestor(activeElement);
 
-    // for all other elements
-    function overflowAutoOrScroll(el) {
-        var overflow = getComputedStyle(el, '').getPropertyValue('overflow-y');
-        return (overflow === 'scroll' || overflow === 'auto');
+    if (!overflowing) {
+        // Chrome iframes seem to eat key events, which we need to
+        // propagate up, if the iframe has nothing overflowing to scroll
+        return (isFrame && isChrome) ? parent.keydown(event) : true;
     }
 
+    var clientHeight = overflowing.clientHeight;
 
-    /***********************************************
-     * HELPERS
-     ***********************************************/
-
-    function addEvent(type, fn) {
-        window.addEventListener(type, fn, false);
+    if (overflowing == document.body) {
+        clientHeight = window.innerHeight;
     }
 
-    function removeEvent(type, fn) {
-        window.removeEventListener(type, fn, false);
+    switch (event.keyCode) {
+        case key.up:
+            y = -options.arrowScroll;
+            break;
+        case key.down:
+            y = options.arrowScroll;
+            break;
+        case key.spacebar: // (+ shift)
+            shift = event.shiftKey ? 1 : -1;
+            y = -shift * clientHeight * 0.9;
+            break;
+        case key.pageup:
+            y = -clientHeight * 0.9;
+            break;
+        case key.pagedown:
+            y = clientHeight * 0.9;
+            break;
+        case key.home:
+            if (overflowing == document.body && document.scrollingElement)
+                overflowing = document.scrollingElement;
+            y = -overflowing.scrollTop;
+            break;
+        case key.end:
+            var scroll = overflowing.scrollHeight - overflowing.scrollTop;
+            var scrollRemaining = scroll - clientHeight;
+            y = (scrollRemaining > 0) ? scrollRemaining + 10 : 0;
+            break;
+        case key.left:
+            x = -options.arrowScroll;
+            break;
+        case key.right:
+            x = options.arrowScroll;
+            break;
+        default:
+            return true; // a key we don't care about
     }
 
-    function isNodeName(el, tag) {
-        return (el.nodeName || '').toLowerCase() === tag.toLowerCase();
-    }
+    scrollArray(overflowing, x, y);
+    event.preventDefault();
+    scheduleClearCache();
+}
 
-    function directionCheck(x, y) {
-        x = (x > 0) ? 1 : -1;
-        y = (y > 0) ? 1 : -1;
-        if (direction.x !== x || direction.y !== y) {
-            direction.x = x;
-            direction.y = y;
-            que = [];
-            lastScroll = 0;
-        }
-    }
+/**
+ * Mousedown event only for updating activeElement
+ */
+function mousedown(event) {
+    activeElement = event.target;
+}
 
-    var deltaBufferTimer;
 
-    if (window.localStorage && localStorage.SS_deltaBuffer) {
-        try { // #46 Safari throws in private browsing for localStorage 
-            deltaBuffer = localStorage.SS_deltaBuffer.split(',');
-        } catch (e) { }
-    }
+/***********************************************
+ * OVERFLOW
+ ***********************************************/
 
-    function isTouchpad(deltaY) {
-        if (!deltaY) return;
-        if (!deltaBuffer.length) {
-            deltaBuffer = [deltaY, deltaY, deltaY];
+var uniqueID = (function () {
+    var i = 0;
+    return function (el) {
+        return el.uniqueID || (el.uniqueID = i++);
+    };
+})();
+
+var cacheX = {}; // cleared out after a scrolling session
+var cacheY = {}; // cleared out after a scrolling session
+var clearCacheTimer;
+var smoothBehaviorForElement = {};
+
+//setInterval(function () { cache = {}; }, 10 * 1000);
+
+function scheduleClearCache() {
+    clearTimeout(clearCacheTimer);
+    clearCacheTimer = setInterval(function () {
+        cacheX = cacheY = smoothBehaviorForElement = {};
+    }, 1*1000);
+}
+
+function setCache(elems, overflowing, x) {
+    var cache = x ? cacheX : cacheY;
+    for (var i = elems.length; i--;)
+        cache[uniqueID(elems[i])] = overflowing;
+    return overflowing;
+}
+
+function getCache(el, x) {
+    return (x ? cacheX : cacheY)[uniqueID(el)];
+}
+
+//  (body)                (root)
+//         | hidden | visible | scroll |  auto  |
+// hidden  |   no   |    no   |   YES  |   YES  |
+// visible |   no   |   YES   |   YES  |   YES  |
+// scroll  |   no   |   YES   |   YES  |   YES  |
+// auto    |   no   |   YES   |   YES  |   YES  |
+
+function overflowingAncestor(el) {
+    var elems = [];
+    var body = document.body;
+    var rootScrollHeight = root.scrollHeight;
+    do {
+        var cached = getCache(el, false);
+        if (cached) {
+            return setCache(elems, cached);
+        }
+        elems.push(el);
+        if (rootScrollHeight === el.scrollHeight) {
+            var topOverflowsNotHidden = overflowNotHidden(root) && overflowNotHidden(body);
+            var isOverflowCSS = topOverflowsNotHidden || overflowAutoOrScroll(root);
+            if (isFrame && isContentOverflowing(root) ||
+               !isFrame && isOverflowCSS) {
+                return setCache(elems, getScrollRoot());
+            }
+        } else if (isContentOverflowing(el) && overflowAutoOrScroll(el)) {
+            return setCache(elems, el);
         }
-        deltaY = Math.abs(deltaY);
-        deltaBuffer.push(deltaY);
-        deltaBuffer.shift();
-        clearTimeout(deltaBufferTimer);
-        deltaBufferTimer = setTimeout(function () {
-            try { // #46 Safari throws in private browsing for localStorage
-                localStorage.SS_deltaBuffer = deltaBuffer.join(',');
-            } catch (e) { }
-        }, 1000);
-        return !allDeltasDivisableBy(120) && !allDeltasDivisableBy(100);
+    } while ((el = el.parentElement));
+}
+
+function isContentOverflowing(el) {
+    return (el.clientHeight + 10 < el.scrollHeight);
+}
+
+// typically for <body> and <html>
+function overflowNotHidden(el) {
+    var overflow = getComputedStyle(el, '').getPropertyValue('overflow-y');
+    return (overflow !== 'hidden');
+}
+
+// for all other elements
+function overflowAutoOrScroll(el) {
+    var overflow = getComputedStyle(el, '').getPropertyValue('overflow-y');
+    return (overflow === 'scroll' || overflow === 'auto');
+}
+
+// for all other elements
+function isScrollBehaviorSmooth(el) {
+    var id = uniqueID(el);
+    if (smoothBehaviorForElement[id] == null) {
+        var scrollBehavior = getComputedStyle(el, '')['scroll-behavior'];
+        smoothBehaviorForElement[id] = ('smooth' == scrollBehavior);
     }
-
-    function isDivisible(n, divisor) {
-        return (Math.floor(n / divisor) == n / divisor);
+    return smoothBehaviorForElement[id];
+}
+
+
+/***********************************************
+ * HELPERS
+ ***********************************************/
+
+function addEvent(type, fn, arg) {
+    window.addEventListener(type, fn, arg || false);
+}
+
+function removeEvent(type, fn, arg) {
+    window.removeEventListener(type, fn, arg || false);
+}
+
+function isNodeName(el, tag) {
+    return el && (el.nodeName||'').toLowerCase() === tag.toLowerCase();
+}
+
+function directionCheck(x, y) {
+    x = (x > 0) ? 1 : -1;
+    y = (y > 0) ? 1 : -1;
+    if (direction.x !== x || direction.y !== y) {
+        direction.x = x;
+        direction.y = y;
+        que = [];
+        lastScroll = 0;
     }
-
-    function allDeltasDivisableBy(divisor) {
-        return (isDivisible(deltaBuffer[0], divisor) &&
+}
+
+if (window.localStorage && localStorage.SS_deltaBuffer) {
+    try { // #46 Safari throws in private browsing for localStorage
+        deltaBuffer = localStorage.SS_deltaBuffer.split(',');
+    } catch (e) { }
+}
+
+function isTouchpad(deltaY) {
+    if (!deltaY) return;
+    if (!deltaBuffer.length) {
+        deltaBuffer = [deltaY, deltaY, deltaY];
+    }
+    deltaY = Math.abs(deltaY);
+    deltaBuffer.push(deltaY);
+    deltaBuffer.shift();
+    clearTimeout(deltaBufferTimer);
+    deltaBufferTimer = setTimeout(function () {
+        try { // #46 Safari throws in private browsing for localStorage
+            localStorage.SS_deltaBuffer = deltaBuffer.join(',');
+        } catch (e) { }
+    }, 1000);
+    var dpiScaledWheelDelta = deltaY > 120 && allDeltasDivisableBy(deltaY); // win64
+    var tp = !allDeltasDivisableBy(120) && !allDeltasDivisableBy(100) && !dpiScaledWheelDelta;
+    if (deltaY < 50) return true;
+    return tp;
+}
+
+function isDivisible(n, divisor) {
+    return (Math.floor(n / divisor) == n / divisor);
+}
+
+function allDeltasDivisableBy(divisor) {
+    return (isDivisible(deltaBuffer[0], divisor) &&
             isDivisible(deltaBuffer[1], divisor) &&
             isDivisible(deltaBuffer[2], divisor));
-    }
-
-    function isInsideYoutubeVideo(event) {
-        var elem = event.target;
-        var isControl = false;
-        if (document.URL.indexOf('www.youtube.com/watch') != -1) {
-            do {
-                isControl = (elem.classList &&
-                    elem.classList.contains('html5-video-controls'));
-                if (isControl) break;
-            } while (elem = elem.parentNode);
-        }
-        return isControl;
-    }
-
-    var requestFrame = (function () {
-        return (window.requestAnimationFrame ||
-            window.webkitRequestAnimationFrame ||
-            window.mozRequestAnimationFrame ||
-            function (callback, element, delay) {
-                window.setTimeout(callback, delay || (1000 / 60));
-            });
-    })();
-
-    var MutationObserver = (window.MutationObserver ||
-        window.WebKitMutationObserver ||
-        window.MozMutationObserver);
-
-    var getScrollRoot = (function () {
-        var SCROLL_ROOT;
-        return function () {
-            if (!SCROLL_ROOT) {
-                var dummy = document.createElement('div');
-                dummy.style.cssText = 'height:10000px;width:1px;';
-                document.body.appendChild(dummy);
-                var bodyScrollTop = document.body.scrollTop;
-                var docElScrollTop = document.documentElement.scrollTop;
-                window.scrollBy(0, 3);
-                if (document.body.scrollTop != bodyScrollTop)
-                    (SCROLL_ROOT = document.body);
-                else
-                    (SCROLL_ROOT = document.documentElement);
-                window.scrollBy(0, -3);
-                document.body.removeChild(dummy);
-            }
-            return SCROLL_ROOT;
-        };
-    })();
-
+}
 
-    /***********************************************
-     * PULSE (by Michael Herf)
-     ***********************************************/
-
-    /**
-     * Viscous fluid with a pulse for part and decay for the rest.
-     * - Applies a fixed force over an interval (a damped acceleration), and
-     * - Lets the exponential bleed away the velocity over a longer interval
-     * - Michael Herf, http://stereopsis.com/stopping/
-     */
-    function pulse_(x) {
-        var val, start, expx;
-        // test
-        x = x * options.pulseScale;
-        if (x < 1) { // acceleartion
-            val = x - (1 - Math.exp(-x));
-        } else {     // tail
-            // the previous animation ended here:
-            start = Math.exp(-1);
-            // simple viscous drag
-            x -= 1;
-            expx = 1 - Math.exp(-x);
-            val = start + (expx * (1 - start));
-        }
-        return val * options.pulseNormalize;
+function isInsideYoutubeVideo(event) {
+    var elem = event.target;
+    var isControl = false;
+    if (document.URL.indexOf ('www.youtube.com/watch') != -1) {
+        do {
+            isControl = (elem.classList &&
+                         elem.classList.contains('html5-video-controls'));
+            if (isControl) break;
+        } while ((elem = elem.parentNode));
     }
-
-    function pulse(x) {
-        if (x >= 1) return 1;
-        if (x <= 0) return 0;
-
-        if (options.pulseNormalize == 1) {
-            options.pulseNormalize /= pulse_(1);
-        }
-        return pulse_(x);
+    return isControl;
+}
+
+var requestFrame = (function () {
+      return (window.requestAnimationFrame       ||
+              window.webkitRequestAnimationFrame ||
+              window.mozRequestAnimationFrame    ||
+              function (callback, element, delay) {
+                 window.setTimeout(callback, delay || (1000/60));
+             });
+})();
+
+var MutationObserver = (window.MutationObserver ||
+                        window.WebKitMutationObserver ||
+                        window.MozMutationObserver);
+
+var getScrollRoot = (function() {
+  var SCROLL_ROOT = document.scrollingElement;
+  return function() {
+    if (!SCROLL_ROOT) {
+      var dummy = document.createElement('div');
+      dummy.style.cssText = 'height:10000px;width:1px;';
+      document.body.appendChild(dummy);
+      var bodyScrollTop  = document.body.scrollTop;
+      var docElScrollTop = document.documentElement.scrollTop;
+      window.scrollBy(0, 3);
+      if (document.body.scrollTop != bodyScrollTop)
+        (SCROLL_ROOT = document.body);
+      else
+        (SCROLL_ROOT = document.documentElement);
+      window.scrollBy(0, -3);
+      document.body.removeChild(dummy);
     }
-
-
-    /***********************************************
-     * FIRST RUN
-     ***********************************************/
-
-    var userAgent = window.navigator.userAgent;
-    var isEdge = /Edge/.test(userAgent); // thank you MS
-    var isChrome = /chrome/i.test(userAgent) && !isEdge;
-    var isSafari = /safari/i.test(userAgent) && !isEdge;
-    var isMobile = /mobile/i.test(userAgent);
-    var isIEWin7 = /Windows NT 6.1/i.test(userAgent) && /rv:11/i.test(userAgent);
-    var isOldSafari = isSafari && (/Version\/8/i.test(userAgent) || /Version\/9/i.test(userAgent));
-    var isEnabledForBrowser = (isChrome || isSafari || isIEWin7) && !isMobile;
-
-    var wheelEvent;
-    if ('onwheel' in document.createElement('div'))
-        wheelEvent = 'wheel';
-    else if ('onmousewheel' in document.createElement('div'))
-        wheelEvent = 'mousewheel';
-
-    if (wheelEvent && isEnabledForBrowser) {
-        addEvent(wheelEvent, wheel);
-        addEvent('mousedown', mousedown);
-        addEvent('load', init);
+    return SCROLL_ROOT;
+  };
+})();
+
+
+/***********************************************
+ * PULSE (by Michael Herf)
+ ***********************************************/
+
+/**
+ * Viscous fluid with a pulse for part and decay for the rest.
+ * - Applies a fixed force over an interval (a damped acceleration), and
+ * - Lets the exponential bleed away the velocity over a longer interval
+ * - Michael Herf, http://stereopsis.com/stopping/
+ */
+function pulse_(x) {
+    var val, start, expx;
+    // test
+    x = x * options.pulseScale;
+    if (x < 1) { // acceleartion
+        val = x - (1 - Math.exp(-x));
+    } else {     // tail
+        // the previous animation ended here:
+        start = Math.exp(-1);
+        // simple viscous drag
+        x -= 1;
+        expx = 1 - Math.exp(-x);
+        val = start + (expx * (1 - start));
     }
+    return val * options.pulseNormalize;
+}
 
+function pulse(x) {
+    if (x >= 1) return 1;
+    if (x <= 0) return 0;
 
-    /***********************************************
-     * PUBLIC INTERFACE
-     ***********************************************/
-
-    function SmoothScroll(optionsToSet) {
-        for (var key in optionsToSet)
-            if (defaultOptions.hasOwnProperty(key))
-                options[key] = optionsToSet[key];
+    if (options.pulseNormalize == 1) {
+        options.pulseNormalize /= pulse_(1);
     }
-    SmoothScroll.destroy = cleanup;
-
-    if (window.SmoothScrollOptions) // async API
-        SmoothScroll(window.SmoothScrollOptions);
-
-    if (typeof define === 'function' && define.amd)
-        define(function () {
-            return SmoothScroll;
-        });
-    else if ('object' == typeof exports)
-        module.exports = SmoothScroll;
-    else
-        window.SmoothScroll = SmoothScroll;
-
-})();
\ No newline at end of file
+    return pulse_(x);
+}
+
+
+/***********************************************
+ * FIRST RUN
+ ***********************************************/
+
+var userAgent = window.navigator.userAgent;
+var isEdge    = /Edge/.test(userAgent); // thank you MS
+var isChrome  = /chrome/i.test(userAgent) && !isEdge;
+var isSafari  = /safari/i.test(userAgent) && !isEdge;
+var isMobile  = /mobile/i.test(userAgent);
+var isIEWin7  = /Windows NT 6.1/i.test(userAgent) && /rv:11/i.test(userAgent);
+var isOldSafari = isSafari && (/Version\/8/i.test(userAgent) || /Version\/9/i.test(userAgent));
+var isEnabledForBrowser = (isChrome || isSafari || isIEWin7) && !isMobile;
+
+var supportsPassive = false;
+try {
+  window.addEventListener("test", null, Object.defineProperty({}, 'passive', {
+    get: function () {
+            supportsPassive = true;
+        }
+    }));
+} catch(e) {}
+
+var wheelOpt = supportsPassive ? { passive: false } : false;
+var wheelEvent = 'onwheel' in document.createElement('div') ? 'wheel' : 'mousewheel';
+
+if (wheelEvent && isEnabledForBrowser) {
+    addEvent(wheelEvent, wheel, wheelOpt);
+    addEvent('mousedown', mousedown);
+    addEvent('load', init);
+}
+
+
+/***********************************************
+ * PUBLIC INTERFACE
+ ***********************************************/
+
+function SmoothScroll(optionsToSet) {
+    for (var key in optionsToSet)
+        if (defaultOptions.hasOwnProperty(key))
+            options[key] = optionsToSet[key];
+}
+SmoothScroll.destroy = cleanup;
+
+if (window.SmoothScrollOptions) // async API
+    SmoothScroll(window.SmoothScrollOptions);
+
+if (typeof define === 'function' && define.amd)
+    define(function() {
+        return SmoothScroll;
+    });
+else if ('object' == typeof exports)
+    module.exports = SmoothScroll;
+else
+    window.SmoothScroll = SmoothScroll;
+
+})();