(function($) {
// Define default scroll settings
var defaults = {
y: 0,
scrollHeight: 0,
elastic: !navigator.userAgent.match(/android/i),
momentum: true,
elasticDamp: 0.6,
elasticTime: 50,
reboundTime: 400,
momentumDamp: 0.9,
momentumTime: 300,
iPadMomentumDamp: 0.95,
iPadMomentumTime: 1200,
touchTags: ['select', 'input', 'textarea']
};
// Define methods
var methods = {
init: function(options) {
return this.each(function() {
var o = $.extend(defaults, options);
// Prevent double-init, just update instead
if (!!this._init) {
return this.update();
}
this._init = true;
// Define element variables
var $this = $(this),
scrollY = -o.y,
touchY = 0,
movedY = 0,
pollY = 0,
height = 0,
maxHeight = 0,
scrollHeight = 0,
scrolling = false,
bouncing = false,
moved = false,
timeoutID,
isiPad = !!navigator.platform.match(/ipad/i),
hasMatrix = 'WebKitCSSMatrix' in window,
has3d = hasMatrix && 'm11' in new WebKitCSSMatrix();
// Keep bottom of scroll area at the bottom on resize
var update = this.update = function() {
height = $this.height();
if (o.scrollHeight) {
scrollHeight = o.scrollHeight;
} else if ($this.prop) {
scrollHeight = $this.prop('scrollHeight'); // jQuery 1.6 uses .prop(), older versions use .attr()
} else {
scrollHeight = $this.attr('scrollHeight');
}
if (scrollHeight < height) {
scrollHeight = height;
}
maxHeight = height - scrollHeight;
clearTimeout(timeoutID);
clampScroll(false);
};
// Set up initial variables
update();
// Set up transform CSS
$this.css({'-webkit-transition-property': '-webkit-transform',
'-webkit-transition-timing-function': 'cubic-bezier(0,0,0.2,1)',
'-webkit-transition-duration': '0',
'-webkit-transform': cssTranslate(scrollY)});
// Listen for screen size change event
window.addEventListener('onorientationchange' in window ? 'orientationchange' : 'resize', update, false);
// Listen for touch events
$this.bind('touchstart.touchScroll', touchStart);
$this.bind('touchmove.touchScroll', touchMove);
$this.bind('touchend.touchScroll touchcancel.touchScroll', touchEnd);
$this.bind('webkitTransitionEnd.touchScroll', transitionEnd);
// Set the position of the scroll area using transform CSS
var setPosition = this.setPosition = function(y) {
scrollY = y;
$this.css('-webkit-transform', cssTranslate(scrollY));
};
// Transform using a 3D translate if available
function cssTranslate(y) {
return 'translate' + (has3d ? '3d(0,' : '(0,') + y + 'px' + (has3d ? ',0)' : ')');
}
// Set CSS transition time
function setTransitionTime(time) {
time = time || '0';
$this.css('-webkit-transition-duration', time + 'ms');
}
// Get the actual pixel position made by transform CSS
function getPosition() {
if (hasMatrix) {
var transform = window.getComputedStyle($this[0]).webkitTransform;
if (!!transform && transform !== 'none') {
var matrix = new WebKitCSSMatrix(transform);
return matrix.f;
}
}
return scrollY;
}
// Expose getPosition API
this.getPosition = function() {
return getPosition();
};
// Bounce back to the bounds after momentum scrolling
function reboundScroll() {
if (scrollY > 0) {
scrollTo(0, o.reboundTime);
} else if (scrollY < maxHeight) {
scrollTo(maxHeight, o.reboundTime);
}
}
// Stop everything once the CSS transition in complete
function transitionEnd() {
if (bouncing) {
bouncing = false;
reboundScroll();
}
clearTimeout(timeoutID);
}
// Limit the scrolling to within the bounds
function clampScroll(poll) {
if (!hasMatrix || bouncing) {
return;
}
var oldY = pollY;
pollY = getPosition();
if (pollY > 0) {
if (o.elastic) {
// Slow down outside top bound
bouncing = true;
scrollY = 0;
momentumScroll(pollY - oldY, o.elasticDamp, 1, height, o.elasticTime);
} else {
// Stop outside top bound
setTransitionTime(0);
setPosition(0);
}
} else if (pollY < maxHeight) {
if (o.elastic) {
// Slow down outside bottom bound
bouncing = true;
scrollY = maxHeight;
momentumScroll(pollY - oldY, o.elasticDamp, 1, height, o.elasticTime);
} else {
// Stop outside bottom bound
setTransitionTime(0);
setPosition(maxHeight);
}
} else if (poll) {
// Poll the computed position to check if element is out of bounds
timeoutID = setTimeout(clampScroll, 20, true);
}
}
// Animate to a position using CSS
function scrollTo(destY, time) {
if (destY === scrollY) {
return;
}
moved = true;
setTransitionTime(time);
setPosition(destY);
}
// Perform a momentum-based scroll using CSS
function momentumScroll(d, k, minDist, maxDist, t) {
var ad = Math.abs(d),
dy = 0;
// Calculate the total distance
while (ad > 0.1) {
ad *= k;
dy += ad;
}
// Limit to within min and max distances
if (dy > maxDist) {
dy = maxDist;
}
if (dy > minDist) {
if (d < 0) {
dy = -dy;
}
dy += scrollY;
// If outside the bounds, don't go too far
if (height > 0) {
if (dy > height * 2) {
var ody = dy;
dy = height * 2;
} else if (dy < maxHeight - height * 2) {
dy = maxHeight - height * 2;
}
}
// Perform scroll
scrollTo(Math.round(dy), t);
}
clampScroll(true);
}
// Get the touch points from this event
function getTouches(e) {
if (e.originalEvent) {
if (e.originalEvent.touches && e.originalEvent.touches.length) {
return e.originalEvent.touches;
} else if (e.originalEvent.changedTouches && e.originalEvent.changedTouches.length) {
return e.originalEvent.changedTouches;
}
}
return e.touches;
}
// Dispatches a fake mouse event from a touch event
function dispatchMouseEvent(name, touch, target) {
var e = document.createEvent('MouseEvent');
e.initMouseEvent(name, true, true, touch.view, 1, touch.screenX, touch.screenY, touch.clientX, touch.clientY, false, false, false, false, 0, null);
target.dispatchEvent(e);
}
// Find the root node of this target
function getRootNode(target) {
while (target.nodeType !== 1) {
target = target.parentNode;
}
return target;
}
// Perform a touch start event
function touchStart(e) {
// Allow certain HTML tags to receive touch events
if ($.inArray(e.target.tagName.toLowerCase(), o.touchTags) !== -1) {
return;
}
// Stop the default touches
e.preventDefault();
e.stopPropagation();
var touch = getTouches(e)[0];
// Dispatch a fake mouse down event
dispatchMouseEvent('mousedown', touch, getRootNode(touch.target));
scrolling = true;
moved = false;
movedY = 0;
clearTimeout(timeoutID);
setTransitionTime(0);
// Check scroll position
if (o.momentum) {
var y = getPosition();
if (y !== scrollY) {
setPosition(y);
moved = true;
}
}
touchY = touch.pageY - scrollY;
}
// Perform a touch move event
function touchMove(e) {
if (!scrolling) {
return;
}
var dy = getTouches(e)[0].pageY - touchY;
// Elastic-drag or stop when moving outside of boundaries
if (dy > 0) {
if (o.elastic) {
dy /= 2;
} else {
dy = 0;
}
} else if (dy < maxHeight) {
if (o.elastic) {
dy = (dy + maxHeight) / 2;
} else {
dy = maxHeight;
}
}
movedY = dy - scrollY;
moved = true;
setPosition(dy);
}
// Perform a touch end event
function touchEnd(e) {
if (!scrolling) {
return;
}
scrolling = false;
if (moved) {
// Ease back to within boundaries
if (scrollY > 0 || scrollY < maxHeight) {
reboundScroll();
} else if (o.momentum) {
// Free scroll with momentum
momentumScroll(movedY, isiPad ? o.iPadMomentumDamp : o.momentumDamp, 40, 2000, isiPad ? o.iPadMomentumTime : o.momentumTime);
}
} else {
var touch = getTouches(e)[0],
target = getRootNode(touch.target);
// Dispatch fake mouse up and click events if this touch event did not move
dispatchMouseEvent('mouseup', touch, target);
dispatchMouseEvent('click', touch, target);
}
}
});
},
update: function() {
return this.each(function() {
this.update();
});
},
getPosition: function() {
var a = [];
this.each(function() {
a.push(-this.getPosition());
});
return a;
},
setPosition: function(y) {
return this.each(function() {
this.setPosition(-y);
});
}
};
// Public method for touchScroll
$.fn.touchScroll = function(method) {
if (methods[method]) {
return methods[method].apply(this, Array.prototype.slice.call(arguments, 1));
} else if (typeof method === 'object' || !method) {
return methods.init.apply(this, arguments);
} else {
$.error('Method ' + method + ' does not exist on jQuery.touchScroll');
}
};
})(jQuery);
