HTML-ISSUE-157 (image-map-spec): A comprehensive, semantic image map specification [HTML 5 spec]

HTML-ISSUE-157 (image-map-spec): A comprehensive, semantic image map specification [HTML 5 spec]

http://www.w3.org/html/wg/tracker/issues/157

Raised by: Julian Reschke
On product: HTML 5 spec

Raised on behalf of Leif Halvard Silli, see also <http://www.w3.org/Bugs/Public/show_bug.cgi?id=10482>:

Image maps have a complex structure which UAs and AT understand 
differently. At the same time HTML5 adds ARIA, which also have no 
particular model for how image maps works.  This requires as fine 
grained understandig and specification of image maps.

The complex structure is caused by the fact that elements outside an 
<img> affects the image - thus conceptually, the <area>s are inside (or 
"around" - like anormal anchor elment) the <img> even if the container 
<map> element is outside the image map. (On the other side, image maps 
for object@usmap can be placed _inside_ the <object>.)

Examples of UA/AT differences:
- at least one UA (Opera) seems  treat <area> elements of the <map> 
element as the content of the  img@usemap element, causing that the 
@alt of the img@usemap element is ignored.
- another (VoiceOver) seems to treat image maps quite differently on 
OSX 10.6 compared to 10.5, and it is not  easy to conclude if there is 
progress 10.6 
- some AT (Jaws) seems to treat stray <area> elements as links, even 
outside <map>
- some AT treat the <area> as a links if they have @role="link", but 
VoiceOver seems not to 

HTML5 issues:
- <area> isn't listed amongst the interactive elements, while 
img@usemap/object@usemap are listed as interactive elements. E.g. 
<area> has role="link" but still isn't considered interactive (because, 
I assume, it "interactivates" the image and not itself.)

HTML4 issue
The editor's solution to Bug 10518 says that authors may place both 
<area> and <a> in the same <map>, for better maintainance. But HTML4 
(see HTML4 section 13.6 Image maps) then has rules which says that UAs 
then should ignore either the <area>s or the <a>s. (Yes, this is linked 
to the fact that <a> in HTML4 can take the @coords and @shape 
attributes. However, in my experience, some AT (VoiceOver, it could 
seem) may still work that way.)  And, as for instance text based 
browsers do handle the <area> elements, and we don't want them - or any 
other UA/AT - to get a double set of links. 

Other things:
- there is no method in ARIA for pointing from the img@usemap element 
to the <map> element. And this perhaps have implications of what one 
should *not* do. E.g. to point from the img@usemap element to the <map> 
element with aria-labelledby might not be a good idea, for instance, 
unless the purpose is to make the AT not treat the image map as an 
image map
- can the image of img@usemap be presentational? I.e. can it have an 
empty @alt ? And does this affect how AT treat the area elements.

This issue  is not about "fixing ARIA", but about establishing a image 
map model which, eventually, lets ARIA implement image maps. (In that 
regard, I also mentioned image maps in this comment to on the ARIA 1.0 
spec 
http://lists.w3.org/Archives/Public/public-pfwg-comments/2011JanMar/0001 
)

The purpose of this issue is to bring a clear specification of image 
maps with a clear understanding of how ARIA fits in.

Received on Saturday, 22 January 2011 10:40:27 UTC