Antiscroll: cross-browser native OS X Lion scrollbars

Antiscroll fixes a fundamental problem JavaScript UI developers commonly face: how do I customize scrollbars so that they get out of the way (for example, for different form widgets), but retain their native scrolling properties (like OS widge scrolling velocity, or OS specific inertia)?

Antiscroll addresses this issue by providing a cross-browser implementation of the scrollbars popularized by OS X Lion that retains native properties.

Features

Supports mousewheels, trackpads, other input devices natively.
Total size is 1kb minified and gzipped.
Doesn't magically autowrap your elements with divs (manual wrapping is necessary, please see index.html demo)
Fade in/out controlled with CSS3 animations.
Shows scrollbars upon hovering.
Scrollbars are draggable.
Size of container can be dynamically adjusted and scrollbars will adapt.
Supports IE7+, Firefox 3+, Chrome, Safari

Demo

Please click here to see it in action.

Installation

Wrap scrollable content with the class antiscroll-inner
Wrap the above with the class antiscroll-wrap
Include the following Javascript

   $(function () {
     $('.antiscroll-wrap').antiscroll();
   });

Configuration

You may remove automatic scrollbar hiding by passing in a key-value to the antiscroll() function like so:

   $(function () {
     $('.antiscroll-wrap').antiscroll({
       autoHide: false
     });
   });

What does it look like?

Firefox 8 overflow: scroll and antiscroll on OS X

IE 9 overflow: scroll and antiscroll

How does it work?

The idea behind Antiscroll is to leverage real scrollbars, but hide them from the view. The implementation consists of 3 steps.

1. Measure scrollbars width

In order to measure scrollbars width we use the following technique:

Insert a div with a fixed width and measure the inner width
Force overflow: scroll
Measure the inner width. The difference is the scrollbar width

The caveat of this technique is precisely OS X Lion. Since the scrollbars float on top of the content, their width is always zero but they still overlay your content. To address this issue we add an aditional step which consists of declaring ::-webkit-scrollbar and ::scrollbar CSS pseudo-properties that set the width of the scrollbars to zero for modern browsers.

2. Adjust the width of the inner element

The parent element receives overflow: hidden and the desired width and height for the widget.

The inner .antiscroll-inner element receives the same width and height, but the script augments this two values with the size of the scrollbars, effectively hiding them.

The inner element is always overflow: scroll.

3. Listen on the scroll event

We attach the scroll event to the scrollable element, and we create our scrollbars as absolutely positioned divs. We update our scrollbars based on the detected scrollLeft and scrollTop of the element.

Credits

This technique was inspired by Facebook's chat sidebar/ticker, which also reproduces Lion's scrollbars, but relying on setting the width of the inner container to an arbitrarily large width, therefore allowing scrolling of a single axis (vertical).

Scrollbar size detection based on the work of Jonathan Sharp.

Contributors

Alexandre Rocha Lima e marcondes @arlm
Othree @othree
PG Herveou @pgherveou
Fontaine Shu @fontaineshu

Dependencies

jQuery
jquery-mousewheel: optional, only needed if you want to block further scrolling when you reach the boundaries of scrollable element.

TODO

Automatically leverage Joe Hewitt's scrollability as a replacement technique if a touch-enabled browser is detected.
IE6 support

License

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Automattic/antiscroll