[DRAFT 2] Comments on Resource Priorities

The User Agent Accessibility Guidelines Working Group (UAWG) was asked
by the Protocols and Formats Working Group (PFWG) to review the Resource 
Priorities FPWD.  We would like to make the following comments:

1) [minor] In the code example in 1.2 Optimizing download priority 
during network contention (and other code examples) there are images 
with no alternative text. Please change them to show best practices. 
(E.g. <img id="Logo" src="/images/Logo.png" alt="XYZ organization"/> )

2) In section 4.3 The @postpone attribute: The IF condition does not
appear to accommodate linear browsers, such as a screenreader, which
reads the page without scrolling. It is possible that the screenreader
would not change the User Agent's interpretation of the document's
viewport, and the material would not be downloaded or read to the user. 
Please keep in mind that screenreaders are also used by people with 
reading disabilities who will want to look at videos and images. We did 
not have consensus that this is a user agent issue or whether it is a 
responsibility of the screenreader to communicate back to the browser. 
We did have consensus that @postpone makes a page dynamic, and therefore 
the user agent must keep the assistive technology informed of dynamic 
changes. The ARIA language has features for that purpose. As currently 
written, this behavior of @postpone would require communication from the 
screenreader to the user agent, and we are not clear how that would work.

3) In section 4.3 @postpone:  If there were text material in a postponed 
iframe (or other resource), would that material be available to text 
search?  Please clarify that behavior.  Our concern is that if a user 
searches for a string in a page which includes a @postponed iframe, the 
search will not find content in the iframe because it has not yet been 
loaded. People who navigate by lists of links, or lists of headers would 
usually want to access all of the links on the page (including the 
postponed iframe), but we can imagine use cases where they would not be 
appropriate.

4) in Section 4.3 Postpone: It should explicitly state that print
overrides postponed. @postpone uses the term "User Agent's 
interpretation of the document's viewport", if user loads
a page and hits PRINT, then the viewport changes to the entire document, 
and all resources need to be downloaded, for the printing viewport.

5) We recommend that it be explicitly stated in the introduction that
user agents give the user the ability to disable @lazyload and @postpone 
to accommodate assistive technology that may block any content that is 
not available on pageload.  [UAWG: Do we still want to say this? I did 
not catch what the consensus was here.]

6) In Section 4.4 the "resource-priorities" CSS attribute:
    a) [minor] lazy-load in CSS and @lazyload in HTML are spelled 
differently. This adds to the cognitive load and increases errors
    b) It needs to be explicitly stated that the CSS lazy-load and
postpone need to be able to be overridden by a user stylesheet.


If you would like to discuss any of these issues further, UAWG would be 
available for email exchange, a joint phone call, or individuals
working together.

Regards,

Jim Allan, Co-Chair
Kelly Ford, Co-Chair
Jeanne Spellman, Staff Contact
on behalf of the UAWG

Received on Thursday, 16 January 2014 20:04:40 UTC