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Slider Gallery

Posted on 18th February 2008 — Michiel Kenis requested a tutorial explaining how to create a similar effect used to showcase the products on the Apple web site.

This ‘product slider’ is similar to a straight forward gallery, except that there is a slider to navigate the items, i.e. the bit the user controls to view the items. Simple stuff.

jQuery already has the plugins to create these effects so we don’t have to go about creating them ourselves from scratch.

How to Solve the Problem

To create the slider controlled gallery, we need the following:

  1. Markup that allows us to place several items within a list, and that overflows out of sight.
  2. A slider widget to control what subsection of products we can see.
  3. Logic to translate the sliders position to slide the products inversely (i.e. we slide left-to-right, the products go right-to-left).

I’ve provided a screencast to walk through how create this functionality. Details on how and what I used can be found below.

Watch the slider gallery screencast (alternative flash version)

View the demo and source code used in the screencast

jQuery UI

jQuery UI is “a set of themable widgets and interactions”. For this task, we don’t need much of jQuery UI, but for the UI slider widget, we’ll need the following:

  • jquery.dimensions.js
  • ui.mouse.js
  • ui.slider.js

Of course we’ll still need the latest jquery.js.

All the above scripts can be extracted from the jQuery UI download.

HTML Markup

The markup for the example is straight forward. It boils down to a ul holding the items you want in the gallery, and a div with another nested div, for the slider and it’s handle.

<div class="sliderGallery">
  <ul class="items">
    <li>Item one</li>
    <li>Item two</li>
    <li>Item three, etc...</li>
  </ul>
  <div class="slider">
    <!-- the handler to action the slide -->
    <div class="handle"></div>
    <!-- labels appear against the slider, as pointers to the user -->
    <span class="slider-lb1">slider label 1</span>
    <span class="slider-lb2">slider label 2</span>
    <span class="slider-lb3">slider label 3</span>
  </div>
</div>

CSS

One key feature about the CSS used: in my example, I assumed that I would not have a predefined width to the ul element. As such, I can’t float the li elements and have set widths. To ensure everything flows horizontally, I make use of white-space: nowrap.

I’ve only included the required CSS to create the sliding gallery effect. If you want to see the complete CSS used in the screencast just view the source for the demo

Slider Gallery Container

The overflow ensures the items are hidden, and the position: relative is used to absolutely position the ul element within it.

.sliderGallery {
    overflow: hidden;
    position: relative;
    padding: 10px;
    height: 160px;
    width: 960px;
}

Slider Gallery Items

The white-space: nowrap is what allows us to work with an unknown width in the ul element.

.sliderGallery UL {
    position: absolute;
    list-style: none;
    overflow: none;
    white-space: nowrap;
    padding: 0;
    margin: 0;
}

.sliderGallery UL LI {
    display: inline;
}

Slider Handle

In the screencast, the example uses a background image for the slider handle, and in particular from the example, the width of the handle is larger than the image to allow it to overlay on the left and right arrows. 

.handle {
    position: absolute;
    cursor: move;
    top: 0;
    z-index: 100;
    /* bespoke to your own solution */
    height: 17px;
    width: 181px;
}

jQuery

As stated above, we will need to include a series of plugins from the jQuery UI download, then we will add our dash of jQuery to create the sliding gallery effect.

Required Plugins

<script src="jquery.js" type="text/javascript"></script>
  
<script src="jquery.dimensions.js" type="text/javascript"></script>
<script src="ui.mouse.js" type="text/javascript"></script>
<script src="ui.slider.js" type="text/javascript"></script>

Slider Code

$(function () { // see note below
$(window).ready(function () {
  $('div.sliderGallery').each(function () {
    var ul = $('ul', this);
    var productWidth = ul.innerWidth() - $(this).outerWidth();

    var slider = $('.slider', this).slider({ 
      handle: '.handle',
      minValue: 0, 
      maxValue: productWidth, 
      slide: function (ev, ui) {
        ul.css('left', '-' + ui.value + 'px');
      }, 
      stop: function (ev, ui) {
        ul.animate({ 'left' : '-' + ui.value + 'px' }, 500, 'linear');
      }
    });
  });
});

Please note during the screencast I used $(function () {}) – but I’ve had to since change this to $(window).ready. This is because I’m using white-space: nowrap and the width isn’t calculated until after the images are loaded. jQuery’s document ready function fires before the images are loaded – to allow the JavaScript access to the DOM as early as possible.

This wasn’t a problem in the demo because the images were loaded from a local server, and thus loaded fast enough to allow the code to work out the width correctly.

The code breaks down as follows:

window.onload = function () {

When the DOM and images are ready (note that if you don’t use white-space: nowrap then you should use the standard $(document).ready() method).

$('div.sliderGallery').each(function () {

Loop through all the div.sliderGallery elements. This code design sets us up to convert our code to a reusable plugin.

var ul = $('ul', this);

Search for the ul in the context of this – which is currently a div.sliderGallery.

var productWidth = ul.innerWidth() - $(this).outerWidth();

.innerWidth() and .outerWidth() come from jquery.dimensions.js. We’re subtracting the current div.sliderGallery width because when we slide, we want it to stop once the last item is visible, rather than sliding it all the way left until it’s out of sight.

var slider = $('.slider', this).slider({

.slider() comes from ui.slider.js.

handle: '.handle',

The class of our slider handle.

slide: function (ev, ui) {
  ul.css('left', '-' + ui.value + 'px');
},

As the handle is moved, we move the ul of items, note that it moves negatively, creating the scrolling effect.

stop: function (ev, ui) {
  ul.animate({ 'left' : '-' + ui.value + 'px' }, 500, 'linear');
}

We use this for when slider area has been clicked, to create the scroll effect.

Taking it Further

When I have a working version of the code, I often try to think how the interaction could be better. Here’s a list of ways it could be improved, in no particular order – if you fancy a challenge:

  1. Better scrolling effect, in particular, fast scroll for the bulk of the animation, and slows down when it’s settling on the final item.
  2. Turn it in to a plugin.
  3. The arrow can be turned in to handlers to slide the handle only part of the distance, rather than all.
  4. A nice effect the Apple version has, is the jump labels, within the slider element, change class given the distance they are from the slider handle. They appear brighter as they’re closer and duller as they are further away from the handle.
  5. Anything else you can think of!