Re: Action-1634: the switch element and <title> and <desc>

Hi Richard,

You're confusing two issues: language switching for <title> and <desc>
versus content switching with <switch>.  The multi-language alt text
options *won't* use <switch> because it wouldn't be backwards compatible.
My response is therefore two parts...

____________________

For the accessible text selection:

The current text mostly looks good, except that the final sentence seems to
be mangled.

Here is a light edit:

Otherwise, unless the element is marked as presentational
(role="presentation" or role="none"):


   - If performing a text alternative computation for an accessible name
   and the current node provides a descendant <title> element chosen based on
   the language rules for the SVG specification, return the <title>
   element's text content as a flat string.
   - If performing a text alternative computation for an accessible
   description, and the current node provides a descendant <desc> chosen based
   on the language rules for the SVG specification, return the concatenated
   text and child content of that <desc> element.


I've moved the "unless the element" bit to the top to make it clear that
we're talking about the element being named, not the title/desc element.
There should be no role on title/desc, and its obligatory role is none, but
that doesn't prevent it from being used as the name for its parent.

I've used "the concatenated text and child content of that <desc> element"
because the SVG 1.1 specifications allow complex content within <desc>,
including content from other namespaces.  This has been used in practice to
include HTML markup within the description, although the specs don't
specifically say what to do with it.  Feel free to replace with a better
wording. It really should be the same wording as for aria-describedby;
there is an editorial note in ACC-Name saying that they need to come up
with explicit wording for aria-describedby, so we would want to pass our
wording by them!

__________________

For <switch>:

A <switch> changes which elements are rendered to the screen, so it should
be addressed when building the accessibility tree.  A switch should never
have any title/desc of its own.  The SVG 1 specs didn't specifically say
that I can't have them, but they also don't exclude title/desc children
from the switching mechanism, so including them never has the intended
consequence!

I would therefore lean towards making <switch> an obligatory role="none" /
no role may be applied.  It's not quite presentational in the sense that
using tables for layout is presentational, but it's only impact is on which
other elements get displayed.  Does anyone think that is too strict?  It
would mean ignoring any aria-label or other attributes.  Authors might add
these if they are treating the <switch> as a group containing multiple
presentations of the same content.

As far as dealing with the switch behavior, that should go in section 5.1,
which currently just references CORE-AAM (
http://www.w3.org/TR/core-aam-1.1/#mapping_general).  In that spec, there
are rules for excluding or including elements in the accessibility tree.  I
think we need a paragraph (possibly more informative than normative) about
how those rules should apply to SVG: how they apply to non-rendered
graphical elements, as well as how they apply to switch-ed content.

I'll read over the CORE-AAM section and put together a draft text for the
SVG doc.
__________________

There are two other SVG elements that I think need special treatment:
<view> and <use>.  I'll send separate notes on them.

Best,
Amelia


On 14 May 2015 at 09:51, Richard Schwerdtfeger <schwer@us.ibm.com> wrote:

> https://www.w3.org/WAI/PF/Group/track/actions/1634
>
> I am proposing a modification to the text of the accessible name and
> description computation to better address the <switch> element. Please
> review:
>
> Here is the current text for step F of the SVG name and description
> computation (http://www.w3.org/TR/svg-aam-1.0/#mapping_additional_nd):
>
> Otherwise, if performing a text alternative computation for an accessible
> name and the current node provides a descendant <title> element chosen
> based on the language rules for the SVG specification, return the title
> text alternative as a flat string, unless the element is marked as
> presentational (role="presentation" or role="none"). If performing a text
> alternative computation for an accessible description, and the current node
> provides a descendant <desc> chosen based on the language rules for the SVG
> specification; return the description text alternative an accessible
> description computation attribute as presentational (role="presentation" or
> role="none").
>
> Proposed Text:
>
> Otherwise, if performing a text alternative computation for an accessible
> name and the current node provides a descendant <switch> element with one
> or more descendant <title>s return the title text alternative as a flat
> text string determined by the switch, unless the element is marked
> (role="presentation" or role="none"); otherwise if the current node does
> not provide a descendant switch element, but it does provide a descendant
> <text>, return the title text of the first descendant <title> element as a
> flat text string, unless the element is marked (role="presentation" or
> role="none"). If performing a text alternative computation for an
> accessible description and the current node provides a descendant <switch>
> element with one or more descendant <desc>s return the description text
> alternative as a flat text string determined by the switch, unless the
> element is marked (role="presentation" or role="none"); otherwise if the
> current node does not provide a descendant switch element, but it does
> provide a descendant <desc>, return the description text of the first
> descendant <desc> element as a flat text string, unless the element is
> marked (role="presentation" or role="none").
>
>
>
> Rich Schwerdtfeger
>