Tuesday, November 18, 2014

Accessibility goes into DOM

PWFG group suggested two new methods for DOM Element interface. These methods reflect role and name accessibility concepts, and corresponding methods were named as computedRole and computedLabel.

I have bunch of issues with the approach I wanted to outline here. Just to keep things in one place.

The purpose

I've been told that primary reason is a testing propose, but having role and name only is not enough to run UAIG tests or any accessibility automation tool since it would require other accessibility properties.

Also they say that it might be used for non accessibility proposes. I realize that semantics, the ARIA adds, can be used by non assistive technologies. In Firefox we have a large number of non AT consumers but we don't have a good idea in most of cases what they are for. So I don't really have the use case, and thus it's hard to say whether accessible role and name only works well for non a11y proposes.

Concerning to assistive technologies I think they also need a much larger API.

Blowing the DOM

Anything useful should require extra accessible properties as I said above. These are accessible description, states, relations, ability to navigate the hierarchy etc. That means sooner or later the Element interface has to be changed to a great extent. Check out AtkObject to get an idea about possible changes.

In beginning of times accessibility interfaces was built on top of DOM and later they were turned into full APIs. Now we are faced to backward process, accessibility APIs are getting back to DOM. I'm not sure if that's a good idea because accessibility tasks are something very specific, and accessibility API might be not suitable for common needs of web apps.


Not every semantically meaningful piece on the screen has a DOM node, for example, list bullets don't necessary have DOM elements associated with them. So Element based accessibility API is too restrictive to fit the requirements of the assistive technologies.


Last but not least is performance issue. In most of browsers the accessibility engine is kept separately and it gets running on demand. If accessibility is merged with the DOM then nothing tells the user this method may trigger heavy accessibility computations and make his app slower. Surely the browsers will learn how to get smarter but the approach will have a perf hit either way.

What's it going to be then, eh?

The idea is to provide a separate accessibility interface. If you like it then it can be done by parts, for example, introduce role and name only for the first round same as the original proposal says. Later you can think of adding all other properties.

This idea was welcomed initially, then later it was rejected as being too complex and accessibility centric. But - and that's most important thing - it doesn't have disadvantages the Element approach has.

Wednesday, November 5, 2014


This might be a little bit strange post. It's not about the web, it's about people working at Yandex. Yandex is a largest IT company in Russia (some also refer to it as Russian Google). They invited me to visit their YaC conference this year to talk about accessibility and the web. I was curious about Yandex and I was interested in update of the accessibility in Russia so I decided to go.

The YaC conference itself was surprisingly short, one day long. Otherwise it looked very much the same as any other IT conference I visited. Maybe it felt a bit overcrowded, about 1500 people, long lines to coffee tables and some manoeuvres to avoid collisions with other people on your way. But that must be quite in Moscow spirit, a much overcrowded city.

I visited the front-end section on the conference. Front-end developers are guys who create accessibility use cases and I had a chance to learn something new. Also I was supposed to participate in panel discussion scheduled at the end of the section. Some talks were interesting, I have a rare chance to look at things from "other" side (after all I'm the browser guy), but some talks were rather strange. For example, one speaker said that the web standards development in Netscape times looked the following way:

I know few persons from Netscape times and no one of them looked that way so I'm sort of skeptic on the statement made. These talks didn't have any time reserved for questions so I was left behind with my comments. Yeah, I have a chance to say it here :)

Next day Yandex invited me to visit their office to give a talk about accessibility. I didn't have a good idea what kind of audience I will talk to so I planned a general talk. I talked about accessibility, desktop, mobile, web, about technologies and future, and I've got a bunch of interesting questions. I've been told that over one hundred persons participated (on-site and off-site) and that was exiting, partially because I didn't really expect the expressed interest.

Russia has WCAG based recommendations but afaik there's no laws that would force business to develop accessible solutions. I realize that Russia is very dynamic country and tomorrow you can get a new law requiring you to make your apps and services accessible but I don't think that's the case. I would guess there are some social stuff like earning kudos making the whole point but I didn't get any evidence of that. They might be targeting to new markets or this is some cultural feature. But they didn't show me their secret labs where they grow up the accessibility awareness so I failed to identify the reasons :)

Anyway, people at Yandex are interested in accessibility as matter of the fact and they know much more about accessibility I could guess, for example, they know well a11y tricks how to make web stuff accessible. But - and that was my impression - they are ready to learn and use any accessibility technology/standard but they are still behind in participation in creation and development of it. You have to share your ideas and thoughts, otherwise your voice is lost.

(Probably out of context but still representative example). I had a chat with one Yandex guy, I said:
- Guys, you do create the web.
- No, we don't.
- But you created so many cool web services, you have so many users.
- (skeptically) Ok, maybe runet.

So yeah, I think they should chime in into accessibility world more, after all they create the use case and that's where accessibility grows up from.

Thursday, June 19, 2014

Peculiarities of standardization

Sometimes standardization might have amusing consequences.

Some preliminary. Say the web author need to place an image for pure design purposes, it could be a background image for example, and of course the author doesn't want it to be visible for screen reader users. So the author can do:
<img src="blabla.jpg" alt=""/>
This technique is well known and was standardized by Techniques for UAAG published at 2002:
In some authoring scenarios, empty content (e.g., alt="" in HTML) may make an appropriate text equivalent, such as when non-text content has no other function than pure decoration, or when an image is part of a "mosaic" of several images and does not make sense out of the mosaic.
Neither browser nor assistive technology is supposed to repair the text equivalent for empty alt image or in other words it should be no image from the user perspective. This technique was supported by Firefox and by number of screen readers over the years. On implementation level the trick is accessible name of the image element is an empty string what is interpreted by screen reader the image should be ignored.

Then after years as accessibility standardization process goes on we've got a quite good initiative which is HTML accessibility mapping. Among other things, it has HTML to ARIA mapping. This is nice but brings ARIA on the level of universal accessibility language while it barely fits all nuances of HTML markup. When it comes to HTML img alt="" case then the closest thing popping up in ARIA is role="presentation". Semantically it looks good, however it doesn't match the accessibility API mapping we used to have for years. The change can be made both on browser and screen reader sides but it doesn't have any practical benefit.

By the way the topic seems constantly bother accessibility minds through years. Not taking into account the fresh bug, we had same bug 4 years ago.

Monday, January 20, 2014

Personalized web for the assistive technology

Sometimes the web authors provide a different content for screen readers than they do that for sighted users. That could be an additional content like "skip to content" navigational links or set of landmarks to create a more reliable document structure. In some cases the web author might want to remove a content, for instance, duping links, or make extra tricks to keep the content accessible if, for example, the author gets out of the standard HTML. In ideal case of course the content is supposed to be quite the same but because of design issues and HTML imperfection it doesn't really happen. The web repletes with examples of special content for the assistive technology.

The need of alternative content

Usually authors don't need to put significant changes into a web page to make it accessible. Keeping in mind usability aspects and following best practices is often enough for good results. In other words this is the kind of changes (except some ARIA) that is supposed to be useful for everybody. Sure it doesn't count the web pages having large pieces of ARIA but that's rather an area of large web apps and custom widgets.

That's how it is but nowadays tendency is getting changed and certain web apps want to provide whole portions of alternative content for the assistive technology.

A few examples are good for demo proposes.

Couple examples

Shared video example. If blind and sighted users want to share the device to watch the movie then it might be good idea to have audio descriptions shown (announced) for the blind user only.

Camera apps. It may be another use case of separate content for blind and sighted users. A camera app shows what's on the camera and may have graphic-only interface like green rectangle showing the thing that is currently in focus. A screen reader user may benefit if the face detection software beeped when face gets in focus since it gives a good chance of nice picture.

Another example can be QR code reader software which helps to find QR code label on the product. In general all camera apps may benefit from giving special instructions for assistive technology users.

Integration vs personalization

So alternative content for assistive technology can be a part of the web app design. A next question is how the alternative content can be added into the web page. Would it be one integral app explicitly and implicitly containing special content or will it be personalized version of the app designed for the assistive technology.

Both approaches have own benefits and disadvantages. So that personalization approach wins in performance since potentially the app doesn't need to combine two different versions into one (and actually it is a big concern of web apps vendors from what I hear). Benefit of integration is people get all-in-one solution what mean users share the app and usually have same experience.

Privacy concerns

A big issue of personalization the people talks about is privacy. If you want to have a personalized version of the web site then you have to tell the web site you use the assistive technology.

The idea of sharing personal information is not comfortable in general for many people and it's quite understandable. But you need to keep in mind that those who wants to know whether the user uses the assistive technology quite likely have a way to detect this. These are solutions like screen reader sniffing flash plugin or JS script based on the difference in content navigation. For example, it didn't take much time for me to write a simple script (can be found attached to Mozilla bug) to detect the NVDA screen reader. These solutions are not perfect and may give false positives but I'm pretty sure they can be improved if somebody wanted.

On the another hand if the user says he wants a specialized version for assistive technology then it doesn't necessary mean the user has the assistive technology running and of course it doesn't necessary mean the user have to share what kind of assistive technology he uses.

So of course there's a privacy concern but it's not bigger than, say, privacy concern of Geolocation API. The difference in sharing and not sharing is rather seeming. After all the user decides.

Tech party

Not sure which approach will get dominant, perhaps that will be some reasonable mix of them. Anyway it would be a good idea to provide web authors the different techniques to implement either approach.



Just a method to detect the presence of assistive technology such as a screen reader allow the web app to load specialized scripts and build personalized version of the app. The idea in implementation can be quite similar to Geolocation API. If the web app wants to know whether an assistive technology is running then the user gets asked if he's ok to share this info. If the user agrees then personalized app is loaded.


It can be used to hide certain parts of the web page from the assistive technology and (quite a recent change) it can be used to create web page portions for assistive technology only (not visible/operable/etc for sighted users).

Actually at this point ARIA spec doesn't allow aria-hidden to create web content for AT. However w3c pushed this option into the law by resolving HTML5 bug. I admit that next ARIA spec should get in sync with the change. It's worth to notice however that WHATWG spec hasn't been changed yet and probably it won't be.

Also ARIA recommends very limited usage of aria-hidden:

Authors MAY, with caution, use aria-hidden to hide visibly rendered content from assistive technologies only if the act of hiding this content is intended to improve the experience for users of assistive technologies by removing redundant or extraneous content. Authors using aria-hidden to hide visible content from screen readers MUST ensure that identical or equivalent meaning and functionality is exposed to assistive technologies.
I suppose it may be considered as temporary advice and will be neutralized as soon as the web gets more apps having special versions for the assistive technology.

So here's a demo of the approach

  <div aria-hidden="true">An ordinal version</div>
  <div hidden aria-hidden="false">An assistive technology version</div>

The minus of the aria-hidden="true" is the user navigable content is hidden from the assistive technology. You may want to read the post why I didn't fell in love with aria-hidden="true" as it's stated. My opinion haven't really changed over years.

The minus of aria-hidden="false" is AT visible only content is not keyboard navigable until AT has special support of it, it's not focusable and has neither dimensions nor position what is a certain restriction for AT. Also it's good to note, screen readers like Orca would ignore aria-hidden="false" content in general because it requires a virtual buffer feature for content navigation but Orca doesn't have it in question.

So aria-hidden has bunch of disadvantages but I admit it has one good benefit which is its simplicity for the web author.

CSS media


CSS media features are designed to provide styling depending on features the device has. So if screen reader is detected then the web app can show or hide portions of the page when it makes sense for screen reader users, for example,
@media (screenreader) {
  .sr {
    display: none;
<div class="sr">hidden from AT</div>

As you see it's very easy to change the web page and personalize it for the assistive technology user. This technique doesn't have disadvantages of aria-hidden because all content is rendered on the screen. So that the content has position and size, it's focusable and navigable by standard ways.

Nevertheless CSS media is also disputable approach (check out Mozilla bug for details). Note, afaik it's not supported by web browsers yet.

Two screens option

Same screen approach looks quite appealing but it doesn't answer to all designing needs the web authors want. For example, in the case of shared screen to watch the movie it might be a nice option if audio descriptions were shown only for those who needs them.

This idea leads to the option to render CSS media styles virtually. Technically speaking that means the presence of two screens, i.e. one version is rendered on the display (that's a movie), the second version is rendered in memory, for assistive technology only (subtitles). Nowadays a similar thing is implemented for HTML 5 canvas shadow content: it's not visible on the display but the assistive technology literally sees it, i.e. it have an access to layout, position and dimensions, and it can navigate it.

It's not clear however how to share input devices like mouse and keyboard, but probably it could be nicely resolved this or that way. This approach is quite close to aria-hidden technique since it allows same design techniques but it doesn't have disadvantages of it because the content is still rendered.

The web is going to change the way it handles the assistive technology. Quite soon I think.

Monday, January 13, 2014

Accessible Mozilla: tech overview of Firefox 26 and Firefox 27

Here's a list of accessibility improvements for assistive technology in Firefox 26 (release) and Firefox 27 (beta).


HTML label gets a label accessible regardless used CSS styles (see bug), for example,

<label style="display: block; overflow: hidden;">Label</label>

LABEL_FOR relation is exposed on the label accessible implicitly associated with the control (see bug):



In Firefox 27 we started to create a generic accessible tree for MathML elements, you can read here for details.

Text interface

We've got a bunch of text interface fixes including regression fixes introduced in Firefox 25 timeframe.

Arabic and Herbew character bounds are exposed correctly now (see bug).

XUL link accessible (used by Firefox UI) implements text interface (see bug).

Text selection

We reworked the TEXT_SELECTION_CHANGE eventing. In particular that allowed to fix events in case of selection spanned through several text objects like HTML paragraphs (see bug) and one pretty old Thunderbird bug where caret move events were missed (see bug).


Firefox 27 has got IAccessible2::relationTargetsOfType (see bug) method from latest IAccessible2 release as well as new CONTAINING_DOCUMENT/TAB_PANE/APPLICATION relations (see bug). Check out this post for summary of IA2 1.3 release changes.


ISimpleDOMDocument interface is implemented as tear off in Firefox 27. The change is similar to the one we did a year ago so it shouldn't hurt anybody. Just in case.