Category: longdesc

Longdesc Links, History, Future

Recently I Twittered daily about longdesc, the classic unsung HTML attribute which supports long descriptions of images. Here’s a summary of the tweets/links:

Some History

To make a long story short (pun intended), longdesc was made obsolete in HTML5 but then returned. I applaud @JohnFoliot, @Laura_Carlson, and @Chaals in their dedicated efforts to return longdesc. I agree it should remain as there is no sufficient ARIA replacement.

Here are more great links on the topic on long description over the last few years.

The Future

Check out the ARIA 1.1 spec for aria-describedat ARIA 1.1 spec for aria-describedat! The aria-describedby attribute is like a combination of longdesc and aria-describedby. I’m pretty excited about this as it seems to provide a method for long description that we can all agree on.

Book Review: Pro HTML5 Accessibility

Recently I finally made time to read the book Pro HTML5 Accessibility by Joshue O Connor (@joshueoconnor), released in late March 2012 by Apress. Let’s take a look at each chapter.

book cover

Chapter 1, Introduction to HTML5 Accessibility, covers exactly that. First, the differences between HTML5, HTML4, and XHTML are explained. Then the basics of web accessibility and theory are discussed including the four principles of WCAG 2.0 (POUR). Legislation is also discussed including Section 504/508 and ADA (US) and PAS78 and DDA (UK).

Accessibility should enhance your design—not destroy it.

Chapter 2, Understanding Disability and Assistive Technology, describes different types of disability, and goes into more detail about visual impairments. Assistive technology (AT) is explained such as screen readers, screen magnifiers, and switches; the most popular screen readers JAWS, VoiceOver, NVDA are discussed in more detail.

Chapter 3 is about JavaScript and ARIA, and sure covers a lot. Nice to see progressive enhancement (PE) explained first; along with semantic markup, PE is a grounding technique which still many developers do not practice, unfortunately. The chapter then discusses event handler best practices, use of tabindex and no script, and references WCAG2 scripting techniques and failures. The DOJO, jQuery UI, and FLUID JavaScript libraries are mentioned, but surprisingly not YUI.

The next section in this chapter provides great information on ARIA (Accessible Rich Internet Applications) including the explanation of the following important attributes: live region, label/describedby, menu, and landmark roles. An ARIA state and role reference is also included.

Accessible drag-and-drop is mentioned briefly at the end of the chapter, but would have liked to see more on this topic. I guess everything can’t be included! For more on this topic, start with Accessibility & Native Drag and Drop by the HTML5 Doctor.

Chapter 4, API and DOM, is a shorter and a bit dryer chapter, but definitely contains interesting and necessary information. The off-screen model (OSM) and accessibility APIs are defined, and how they work with browsers and AT. Accessibility APIs discussed include MSAA (the “older brother”); IAccessible 2; and the Apple, Webkit, and Linux versions.

Chapter 5 gives explanation and references to new HTML5 semantic elements and attributes. A lengthy list of event handler attributes is provided. The chapter also includes an interesting mapping of new elements against the implied ARIA role. In addition, I like that the importance of headings is explained; this is a very basic and vital practice that if often overlooked. The hgroup element is discussed a fair amount, but the rumor is that it is being dropped from the HTML5 specification.

Chapter 6 is titled Images, Rich Media, Audio, and Video in HTML5. The first half of the chapter alone (about 21 pages) discusses alternative text for images. This lengthy section is great because even though this is a basic requirement, implementing alt text can be quite tricky depending on the how an image is used (or not used) and is often done incorrectly if at all.

It’s great that the author is a supporter of the longdesc attribute which is now made obsolete in HTML5. I also advocate the longdesc attribute which points to an off-page resource; this behavior cannot be replicated with ARIA. Longdesc is not only used much in academia as the book states, but also for government websites and comics. A good example of alt text using describedby is given, but no solution for an external long description. Read more about this in my two-part article Longdesc & Other Long Image Description Solutions.

Although ARIA is great and HTML5 has made advances in many areas, neither currently provides a fully-functional replacement for @longdesc

I would have liked to read more on sprites as this is a popular design technique which causes many accessibility problems. For more on this topic, check out Notes on accessible CSS image sprites by Steve Faulkner.

The second part of Chapter 6 covers HTML5 audio and video. Issues with Flash for video are presented, and then the HTML5 media elements and attributes are covered. I’d like to point out that the autoplay attribute is bad for accessibility and usability as it automatically starts the media on page load and therefore removes control from the user.

A solid video code example is provided for embedding media and creating custom controls. I noticed that the fallback example was not what I expected as it didn’t include Flash nor a simple file download link. For more on this topic, start with Creating Your Own Accessible HTML5 Media Player by Terrill Thompson.

It’s great to see the Track element explained as it’s great for captions, audio description, etc. Although it’s not supported quite yet, many of us are in great anticipation and is definitely worth learning now.

Lastly, Chapter 6 suggests some great media encoding tools and explains the media types and supporting browsers.

Chapter 7, HTML5 and Accessible Data Tables, provides a great explanation and many code examples of basic and complex data tables, including the headers attribute technique. The author disagrees with deprecation of summary attribute, but I do not so much. The summary attribute is often not implemented correctly and is difficult to maintain; the content can be in the table caption or main content; screen readers can give the same information about a table that the summary attribute is originally intended for (an overview of the structure of the data table). But a great alternative method to summary is provided, using aria-describedby, which I do advocate.

In Chapter 8, HTML5 and Accessible Forms, a thorough explanation is given of the basics and complexities of accessible web forms. For form element labels, three techniques are described. I agree with the author in that explicit labeling (for/id) should be used over the implicit (wrapped) method. Or over any other method (such as title or placeholder) for that matter. Also discussed are many of the new HTML5 form elements (output, progress) and input types (tel, email, date, time) including a few details on browser support, or lack thereof.

However, in terms of making your forms more bulletproof and working with older legacy AT, I recommend sticking with the for/id method for now.

Useful tidbits are included such as the inconsistent screen reader support of optgroup element; how to style placeholder attribute for Webkit and Mozilla; and suggests to help the accessibility of the autofocus attribute. Speaking of placeholder, although the book points out that the placeholder attribute “represents a hint”, I had hoped it would more directly state that the placeholder attribute is not a replacement for the label element, as it’s often misused.

Error recovery and form validation is also discussed. The jQuery form validation plugin is mentioned; for details check out Paul Adam’s related article.

In Chapter 9, HTML5, Usability, and User-Centered Design, great information is given, but I wonder a little of how this content fits into the scope of the book. The chapter mostly discusses user testing and the 7 principles of universal design: equitable use; flexibility in use; simple and intuitive; perceptible information; tolerance for error; low physical effort; and size and space for approach and use. In addition to details from the book, you can also check out my article from last year on this topic, Popular Mistakes in Universal Web Design.

Chapter 10 discusses numerous tools and tips for accessibility testing, or “Assessing Your Accessible HTML5 Project”. Some popular tools are mentioned including WAT-C, WAVE, and Colour Contrast Analyser. Other notable tools not mentioned are aViewer, Accessibility Evaluation Toolbar, and Worldspace FireEyes.

In summary, Pro HTML5 Accessibility is a comprehensive and important book for any web developer and web designer. The read was excellent and contains many references and appropriate code examples. I highly recommend it. And now that you’ve read my review, you’re ready to buy the book!

AAP Provides Longdesc Feedback to W3C

There’s a debate over whether or not the longdesc attribute should be made obsolete in HTML5. I wrote a bit about it a few months ago in the article Longdesc & Other Long Image Description Solutions.

Recently the Association of American Publishers (AAP) submitted feedback on longdesc to the W3C HTML 5 Working Group. It’s very well written and thought it should be shared. I obtained permission to publish the response (thanks Suzanne and Ed). Here is the main part of it:

Use of structured text as a text alternative for an image is supported in HTML through the longdesc attribute. Though there are other options for presenting structured-text, the longdesc attribute provides following benefits:

For User Experience

  • The longdesc attribute is a dedicated mechanism for just this purpose, and it always works in the same way:
    • Students and instructors will find the same user interface throughout all materials, so they will not need to learn new interfaces product-to-product, which takes time and attention away from the learning content.
    • The longdesc attribute can be revealed programmatically through browser extensions, providing access for users who do not use screen readers. Many users benefit from text alternatives, especially users with low vision.
    • The longdesc attribute does not impact the visual design. So, authors do not have to worry about how the text might impact the visual user experience. Authors can, therefore, focus on the experience of students and instructors with visual impairment while they write text alternatives. This focus on the primary audience helps authors create text that is well-suited for its purpose.

For Production Processes and Quality Assurance:

  • The longdesc attribute is easy to code. There is no need for custom scripting.
  • The longdesc attribute works with assistive technology today. If the longdesc attribute continues to be supported, content that works well for users today can be used in future products without editing.
  • The longdesc attribute can be programmatically recognized and tracked, allowing publishers to locate existing long descriptions and to test for the presence of long descriptions.

We are using longdesc increasingly in our products. Unless a different mechanism is created that meets all these requirements, we urge the W3C to keep the longdesc attribute in HTML specifications moving forward.

We do acknowledge that user agent support for the longdesc attribute should be improved. In particular, users who have low vision or who find image descriptions helpful for any reason should be able to set their user agent to reveal the descriptions. The HTML 5 specification should clarify that user agents should provide this functionality in addition to passing information to assistive technologies. In this case, publisher documentation for products with numerous longdesc attributes might include tips about use of these user agent settings.

Evaluating Other Solutions

We discuss the aria-describedby attribute following to illustrate that solutions that at first seem to duplicate the qualities of the longdesc attribute may not actually be as useful when implemented.

The aria-describedby attribute takes the unique indentifier (“ID”) of another object on the same page as its value. In other words, it points to another object (e.g. a paragraph or a link) on the page. This attribute could become an effective way for developers to indicate that the information provided by an image is actually redundant with other information on the page.

Screen reader developers might implement this attribute so that it is silent in screen readers when used on an image by default. They might also allow those who want additional information to set their screen reader to announce aria-describedby and to provide a way to jump to the object indicated by the attribute. An instructor, for example, might choose this setting to be aware of what sighted students will be experiencing.

But, the aria-describedby attribute falls short as a mechanism to link to a separate page of structured text. The aria-describedby attribute could point to a link on the same page as the image, but:

  • Hiding the link visually would require custom CSS or scripting. The mechanism for hiding the link would therefore differ product-to-product, making browser extensions or features to show the links more complex to code and less reliable for users.
  • The link would have to be present on the page for screen reader users, creating redundancy for those users.
  • Since the aria-describedby attribute points to a link or to other content on the same page, its structure implies a two-step process to reach the text alternative. Compared with longdesc, the two step process is more tedious:
    • The user moves to the object that aria-describedby references.
    • If the object is or contains a link or a button, the user interacts with that object to move to the text alternative.

If the issues above are resolved and aria-describedby is used as a way to access descriptions that are otherwise hidden from all users (including screen reader users), another problem emerges. In that case, aria-describedby cannot be silent by default in screen readers when used on images, compromising its use to illustrate that the content of an image is already available on the page. Developers may not realize the distracting and frustratingly circular user experience that this would cause and might use aria-describedby to point to, for example, a paragraph just above the image. Users would then likely follow the aria-describedby announcement, expecting to find additional content, but they would arrive, instead, at a paragraph that they have likely just read.

We urge the W3C HTML Working Group to write out the expected implementation and user experience details of any proposed replacements for the longdesc attribute to be sure that they will be at least as effective as the longdesc attribute in practice.