Most rollovers have become obsolete because they can be performed on background images with CSS sprites. If there are hover effects today, they usually come as text on a button background image, or as a text link with an icon next to it.

However, there are those rare cases when there is just an icon without text, like a “play” or “pause” button, or a magnification glass on an image to signal it can be enlarged. If you want to swap images when the element receives focus or on mouseover, traditionally you are stuck with two options:

1. JavaScript to change the image source, or
2. CSS sprites to change the position of a background image behind a transparent gif image.

I like neither. Using JavaScript and two images with pre-loading seems like a waste of resources when it can be done with CSS and one image only. Transparent gifs are so 1998, besides the background usually doesn’t get printed. So what we need on these occasions are CSS sprites for foreground images.

Until recently I thought that can’t be done, but then I stumbled upon some code for checkbox widgets in Dojo. Naturally they use a lot of JavaScript for the task. Anyway I like my default checkboxes and don’t have any urge to make them prettier (I have no doubt our design overlords would enforce aqua icons everywhere), but that made me think. Here’s a suggestion:

First a simple sprite which is 50px wide:

The HTML code uses the dimensions of a single icon for width and height to allow fast page rendering without reflow:

1. <a href="/big/" class="icon">
2. <img src="/img/icon-enlarge.gif" id="magnifier" width="19" height="15" alt="enlarge image" />
3. </a>

The corresponding CSS sets the link to display: block, uses the single icon dimensions for the container, prevents overflow, and resets the image dimensions to auto to prevent distortion. The actual image swapping is achieved by a negative left margin on hover.

1. a.icon {
2. display: block;
3. width: 19px;
4. height: 15px;
5. overflow: hidden;
6. }
7. a.icon img {
8. width: auto;
9. height: auto;
10. border: none;
11. }
12. a.icon:hover img, a.icon:focus img, a.icon img.hover {
13. margin-left: −31px;
14. }

For the sake of simplicity I ignored how the link would be floated or positioned. Also borders, a background color, or padding to increase the clickable area can be added to the parent element.

For simplicity I chose a link in the example, but the same can be done with a div surrounding an <input type="image" />. Then of course you need to define cursor: pointer, and for anything below IE7 bind the DOM event to the hovering element (get the source):

1. <!--[if lt IE 7]>
2. <script type="text/javascript">
3. oIcon = {
4. setHoverClass : function() {
5. this.className = 'hover';
6. },
7. resetHoverClass : function() {
8. this.className = '';
9. }
10. };
11. var elm = document.getElementById('magnifier');
12. if (elm) {
13. elm.onmouseover = elm.onfocus = oIcon.setHoverClass;
14. elm.onmouseout = elm.onblur = oIcon.resetHoverClass;
15. }
16. </script>
17. <![endif]-->

Here is a working example. You know how to adjust the code if you need more than one class on the image.

That was nice and easy. It’s tested in Firefox 2, Opera 9, Internet Explorer 5+, and Safari 2. Screen readers should be okay with the alt text.

Discussion

The trouble begins when people start turning off browser features.

People with disabled images won’t be able to read the alternative text because the visible area is limited by the parent container. That can be detected by comparing the known sprite size with the alt text size. Then the class is set to anything but icon so that the parent container expands.

More severe is when people disable style sheets because then they will see a squeezed image with multiple icons. If you are hyper-correct, you could replace the crushed multi-icon image with the correct single icon (you could use the class or rel attribute to define the icon type), but nobody wants to slice images. As a compromise I would suggest to replace the icon with its alt text.

See the script to detect disabled images or CSS. (Note: it isn’t implemented here because I couldn’t test it properly on IE6 with stuff turned off.)

If JavaScript is unavailable, the user is stranded with what we gave him. Also icons without text are inherently evil because they can’t be enlarged by zoom readers. Did I forget any politically correct disclaimer for obscure use scenarios?

So we ended up with a CSS only version, but still some JavaScript is needed for the extra effort to provide the same experience to users of IE 5-6, and some more for certain user scenarios. Wouldn’t it be easier to slice and swap foreground images the old way? But then again slicing is a pain, and people already start using background images. Do people actually turn off CSS and images? Or is that another remnant of WCAG 1.0 from 1999?

In this post:

• Eric Meyer: Keynote
• Jeremy Keith: Using DOM scripting to plug the holes in CSS
• Chris Wilson: IE: 7 and beyond
• The new accessibility guidelines: WCAG 2.0
• Jeffrey Veen: Designing the next generation of web apps

Introducing geeks to a social life

There was some socializing the evening before the conference where I met with a couple of Germans, like Jens Grochtdreis who initiated the German web standardista group “Webkrauts”, Jan Eric Hellbusch whose website I had noticed before for some master theses about accessibility, or Tomas Caspers who is a member of WaSP and the mastermind behind the accessibility portal Einfach für alle. Actually I wasn’t the only one to notice he looks like the lost fifth member of the German punk band “Die Toten Hosen”?… Also that’s where I met Roger Johansson, whose technical blog 456 Berea Street is a must-read for CSS and accessibility aware coders.

So my first day on @media began with a walk through polluted London air along surveillance cameras and anti-tank barriers along the Houses of Parliament over to the queue in front of the Queen Elizabeth II Conference Center (QE2CC) where we got nice bags and name tags. I would suggest shawls with the @media logo for next year to stand a chance against the bloody cold air conditioning while it was 28° C outside.

Eric Meyer: Keynote

The conference started with a keynote by Eric Meyer with his personal impressions of the last ten years of the web. Quite interesting since I’ve been reading his articles on Web Review, where he published among other things the famous CSS browser compatibility chart, a great companion in my struggle with 4th generation browsers.

Looking back, he realized the following truths:

1. Small groups of dedicated experts can change a lot (e.g. the CSS Samurai, or Tantek Çelik who introduced doctype switching).
2. Free information is an essential part of any new web technology’s adoption.
3. You don’t hear much anymore from people or companies who kept information as a “personal advantage.”
4. You might be the first who thought about a certain solution. Savour this moment, and then share it.

Using DOM scripting to plug the holes in CSS

As an example, Jeremy Keith introduced the techniques of Buck Owens, the first musician to “hack” the tinny sound of early radios by replacing the bass with a regular guitar. So his tracks sounded better and got more airtime. Using DOM scripting to work around incomplete CSS implementations or to simulate CSS 3 behavior is basically the same, as long as there aren’t yet browsers with “great bass.”

Okay, most of the stuff in his presentation sounded familiar, and I’d rather set zebra stripes on table row backgrounds server side. Still I got some inspiration how to do some things better. For example it never occurred to me to combine selectors like

1. document.getElementById("id") .getElementsByTagName("p")

Or I never thought of using a universal selector in JavaScript:

document.getElementsByTagName("*")

Also the next time I’m manipulating an object’s class, I promise to do it by writing some reusable functions like

1. document.getElementByClassName()
2. function addClass(element, className)

And after I createElement I should set more attributes by setting a className instead of adding each attribute separately.

When he mentioned CSS 3, I learned that Safari is already capable of handling multiple background images. And I liked his introduction of the geeky Star Trek term of a “Kobayashi Maru scenario” for a no-win situation, or his translation of object detection

1. if (document.getElementById) { }

with “you must be this high to ride.” Rather cool, and a very entertaining presentation.

IE: 7 and beyond

Chris Wilson worked on the Mosaic browser (that’s, like, Netscape 1 — scary, isn’t it?) and on IE ever since version 2. Praise him for first implementing CSS in IE3, blame him for some nasty bugs he’s personally responsible for in IE6. Also he’s the one who wrote he will quit (and probably become a professional surfer) the day he loses his passion or IE gets mothballed again.

After some blatant promotion for all the outstanding new features and fixes in IE7, things you can read about in the IEBlog if you haven’t yet, he came to the interesting facts:

First of all, they are planning the next two releases now, and it won’t take another five years until IE8 will emerge. Also IE7+ for Windows Vista is only marketing speak, what counts is that it has the same features as IE7 for Windows XP, except for some vista-only security and parental control. IE7 will ship in “second half 2006.” More precisely, the Malaysian Vista developer Jabez Gan disclosed earlier that December 6 will be the release date.

Because of the deep interaction with the operating system they can’t push it as a critical Windows update, but they will “strongly encourage people to update.” The new fonts won’t be deployed with the update, more likely in a separate package, simply because with Unicode support some are too large.

On a technical side they are aware of developer’s problems to test on multiple versions of IE. Though it is technically hard to have a friendly co-existence of multiple IEs because they provide the operating system, it should be possible to create side-by-side versions of the browser only. Yay, that’s what we want!

Also they would like to support the XHTML MIME type, but want to do it right, later. Same is true for advanced DOM support, or passing the Acid2 test. What’s next for the web? Mashups, RSS, microformats, and XMLHttpRequest (did you know there’s a W3C working draft?). XForms is on their radar, but they need to coordinate efforts with other browser vendors.

Besides Chris recommended some tools like an expression finder to spot CSS hacks, or an application compatibility toolkit, stuff you can download as part of the Internet Explorer 7 Readiness Toolkit from Microsoft with a genuine copy or from someplace else without.

The new accessibility guidelines: WCAG 2.0

I had hoped that by visiting the panel about WCAG ['wu:kæg] I could avoid having to read the unreadable myself, but I was disappointed. You will read in another post about it. Not much else to tell about that panel, except WCAG 2.0 is probably not as bad as we have thought. There are notes and the slides available on accessify.com.

Designing the next generation of web apps

Jeffrey Veen is the partner of Jesse James Garrett who gets all the attention for coining the term “Ajax.” Anyway, Ajax is so going to change our world. Like the automobile, or the Great Depression. Some will get more mobile, some will get greatly depressed when the web becomes inaccessible.

In another panel the speakers agreed that Ajax can make live easier as an enhancement (Jeremy Keith calls it “Hijax”), but shouldn’t be a world of pain for the others. Actually I can see some of Jeff’s examples (use Stuart Colville’s notes to understand the slides) as an enhancement. Like giving immediate feedback when input fields in a form validate, while degrading gracefully by giving feedback after a regular submit.

You can enhance understanding by coloring and visualizing rainfall values in a nicely designed table, or you can further enhance it by making it interactive with a fader to choose cities on a map. But I can’t imagine how to have both.

In another example he showed a mashup of Google Maps with a Chicago crime database. Nice, but how can that be made accessible? So that people without JavaScript, or screen reader and braille display users with JavaScript can access the raw data table that lies under the visualization?

There was a lot of talk how today’s websites will be tomorrow’s web applications, but like Nate Koechley put it: You can’t just copy one aspect of desktop applications while ignoring the accessible alternatives. Desktop applications are accessible with multiple input devices, like a mouse or a keyboard. Screen readers can get the content. Don’t you forget it when developing the “next generation off apps.” There’s more than just good looks.