- From: Maciej Stachowiak <mjs@apple.com>
- Date: Mon, 17 Aug 2009 02:56:17 -0700
- To: Benjamin Hawkes-Lewis <bhawkeslewis@googlemail.com>
- Cc: Steven Faulkner <faulkner.steve@gmail.com>, Ian Hickson <ian@hixie.ch>, HTMLWG WG <public-html@w3.org>, W3C WAI-XTECH <wai-xtech@w3.org>
On Aug 17, 2009, at 2:40 AM, Benjamin Hawkes-Lewis wrote: > On 17/08/2009 10:05, Maciej Stachowiak wrote: >>> In situations like: >>> >>> <a href="#"><img src="delete.png" alt=""></a> >>> >>> It's useful to AT for the "img" to be exposed and to be able to >>> access >>> "src" attributes for the purpose of providing a substitute for >>> proper >>> alternative text. >> >> If that's so, then wouldn't it be better for authors to use alt="" >> instead of role="presentation", so that AT can decide whether it >> needs >> to expose the image anyway? > > I don't think role="presentation" is appropriate in that case. It's > not a presentational image. I don't think alt="" is appropriate either, for the same reason. But you are right that such usage is common nonetheless. >> In particular, if your example was marked up >> like this: >> >> <a href="#"><img src="delete.png" role="presentation"></a> >> >> Then isn't it equally necessary and appropriate for AT to expose that >> image? > > I think it's important that W3C specs do not produce a situation > where "role='presentation'" is likely to be widely misused in that > way. The specific proposal on the table was as follows: - Every time the validator sees alt="" without role="presentation", it should issue a warning advising the author to add role="presentation". I believe this would lead to the kind of misuse that you are concerned about. Do you think this kind of warning is a good idea? > I don't think authors should add "role='presentation'" in such cases > (they should write "alt" text for the control), or that authoring > tools should add "role='presentation'" if authors fail to write > "alt" text for controls, or that checkers should suggest > "role='presentation'" for images that are the only content for > controls (they should suggest supplying "alt" text). > > There may well be a case for assuming authors will get this wrong, > and saying that UAs should ignore "role='presentation'" for the > purpose of calculating control text, but that should be fixed at the > ARIA spec layer, as it's not a problem specific to HTML. > >>> http://www.w3.org/TR/WAI-USERAGENT/guidelines.html#tech-missing-alt >>> >>> More tendentiously, perhaps, in situations like: >>> >>> <p>As you can see from the chart below, sales increased in 2008:</p> >>> <img alt="" src="chart.png"> >>> >>> Even if users can't consume the chart themselves, it's useful to >>> users >>> to be able to download or hotlink that referenced chart in a >>> collaborative environment (e.g. a corporate wiki). >>> >>> By contrast: >>> >>> <img alt="" src="bullet.png"> >>> >>> really is purely decorative; in a collaborative environment that >>> seems >>> likely to be generated by authoring software. >> >> And likewise for these examples - it seems like AT should be left >> free >> to apply heuristics. > > In the first case, I don't think "role='presentation'" should be > added (it a data chart not a presentational image); in the second > case I think it should (it's a bullet). > > Assuming correct use of the marker (I know, big assumption), the > advantage for AT is being able to /totally/ ignore the second > (purely decorative) image, while still providing some sort of access > to the first. Isn't that an improvement on heuristics? That depends on whether role="presentation" is likely to be used more correctly than alt="". I think just the existence of role="presentation" is not necessarily problematic, if alt="" is still allowed. After all, empty alt is shorter, so only thoughtful authors will go for the wordier option. But if the validator warns about empty alt and suggests adding role="presentation", then it seems like it would start to get used wrong with similar frequency to alt="". > > Furniture photo for a news article about sidewalk disrepair: > > <img alt="" src="walking-man.jpg" role="presentation"> > > Tangentially, I would prefer a way to demark decorative media that > was native to HTML, and that was mapped to but did not rely on the > ARIA layer, so that all UAs could make use of it. For example, "User > Style"-type views in Firefox and Opera, the mobile layout view in > Opera Mini and so on could omit images, videos, and audio marked as > decorative. The current ARIA draft seems to block this sort of use: > > http://www.w3.org/TR/wai-aria/#ua_noninterference (public) > > http://www.w3.org/WAI/PF/aria/#ua_noninterference (editor's) > > e.g. <img alt="" src="walking-man.jpg" presentational> > > <object data="walking-man.jpg" presentational> > > <video presentational> > > <audio presentational> > > (Yes, this might involve specifying error handling at the HTML layer > too. :( ) > > -- > Benjamin Hawkes-Lewis >
Received on Monday, 17 August 2009 09:57:01 UTC