[Draft] Comments on Resource Prioirities

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) 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 sections 1.2 and 4.2, please make it clear that text alternatives 
for lazyload resources should be displayed at initial load and not wait 
for the lazyload, since some assistive technologies like screenreaders 
take a snapshot of the page at load time, so a delayed load of the 
alternative text (including @alt, @longdesc and caption files) would 
result in that information being lost unless the screenreader reloaded 
the page.

3) In sections 4.2 The lazyload attribute (and 4.3 and 4.4): When the 
lazyload attribute is applied to an iframe (for example), will it also 
be applied to the child elements in that frame? How would a video in the 
iframe be handled? Similar to comment #2, our concern is that it may not 
be picked up by screenreaders loading the page. Please keep in mind that 
screenreaders are also used by sighted people with reading disabilities 
who are going to want to look at videos and images.

4) 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.

5) 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?  Search of postponed iframe (or other resource) need to make 
explicit to author that if a user searches for a string at the top of a 
page (which includes an iframe) the search will not find content in the 
iframe because it has not yet been loaded.

6) 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.

7) In Section 4.4 the "resource-priorities" CSS attribute:
   a) 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 override by a user stylesheet.

8) in Section 4.3 Postpone: It should explicitly state that print 
overrides postponed. @postpone uses the term @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.


If you would like to discuss any of these issues further, we would like 
to be available for email exchange, a joint phone call, or individuals 
working together. We hope our comments are helpful.

Regards,

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

Received on Thursday, 16 January 2014 18:42:32 UTC