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Normalize scrolling speed for Macbook Trackpads and different browsers. #57

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Normalize scrolling speed for Macbook Trackpads and different browsers. #57

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0a9cb0d
First attempt to normalize scrolling between browsers and input metho…
sjaq May 14, 2013
eb5f323
Final version which works pretty well, IE10 is slacking a bit but I'm…
sjaq May 16, 2013
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44 changes: 33 additions & 11 deletions src/sly.js
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Original file line number Diff line number Diff line change
Expand Up @@ -99,6 +99,7 @@
var historyID = 0;
var cycleID = 0;
var continuousID = 0;
var lowestDelta;
var i, l;

// Normalizing frame
Expand Down Expand Up @@ -1416,6 +1417,7 @@
*
* @return {Void}
*/

function scrollHandler(event) {
// Ignore if there is no scrolling to be done
if (!o.scrollBy || pos.start === pos.end) {
Expand All @@ -1425,24 +1427,44 @@
stopDefault(event, 1);

var orgEvent = event.originalEvent;
var isForward = 0;
var speed = normalizeScrollSpeed(orgEvent);

// Old school scrollwheel delta
if (orgEvent.wheelDelta) {
isForward = orgEvent.wheelDelta / 120 < 0;
}
if (orgEvent.detail) {
isForward = -orgEvent.detail / 3 < 0;
}
var isForward = speed < 0;

if (itemNav) {
if(itemNav) {
var nextItem = (centeredNav ? rel.centerItem : rel.firstItem) + (isForward ? o.scrollBy : -o.scrollBy);
self[centeredNav ? 'toCenter' : 'toStart'](nextItem);
} else {
self.slideBy(isForward ? o.scrollBy : -o.scrollBy);
var scroll = Math.abs(speed) * 500; // 500 feels the most logical
if(o.scrollBy) {
scroll = Math.abs(speed) * o.scrollBy;
}

self.slideBy(isForward ? scroll : -scroll);
}
}

/**
* Attempt to normalize mouse scrolling across various browsers (taken from: http://stackoverflow.com/a/13650579).
*
* @param {Event} orgEvent
*
* @return {Number}
*/
function normalizeScrollSpeed(o) {
var d = o.detail, w = o.wheelDelta,
n = 225, n1 = n-1;

// Normalize delta
d = d ? w && (f = w/d) ? d/f : -d/55 : w/120;
// Quadratic scale if |d| > 1
d = d < 1 ? d < -1 ? (-Math.pow(d, 2) - n1) / n : d : (Math.pow(d, 2) + n1) / n;
// Delta *should* not be greater than 2...
d = Math.min(Math.max(d / 2, -1), 1);

return (navigator.userAgent.indexOf("Safari") > -1) ? d / 2 : d;
}

/**
* Scrollbar click handler.
*
Expand Down Expand Up @@ -1658,7 +1680,7 @@
}

// Scrolling navigation
$scrollSource.on('DOMMouseScroll.' + namespace + ' mousewheel.' + namespace, scrollHandler);
$scrollSource.on('DOMMouseScroll.' + namespace + ' mousewheel.' + namespace + ' MozMousePixelScroll', scrollHandler);

// Clicking on scrollbar navigation
if ($sb[0]) {
Expand Down