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Re: PDF reading order and tag order

for

From: Alastair Campbell
Date: Jun 12, 2017 5:07AM

Hi Duff,

On this bit:
> Software that does not use tagged PDF (such as the Reflow feature in
Adobe Reader, for example) has to guess to infer a reading-order.

That came up in a discussion about WCAG 2.1 where we are looking at
increasing the resize-content aspect:
https://github.com/w3c/wcag21/issues/77#issuecomment-306385027

Are there techniques for defining (or at least controlling) the order in
which a PDF document is reflowed?

Cheers,

-Alastair

On Wed, Jun 7, 2017 at 7:51 PM, Duff Johnson < <EMAIL REMOVED> > wrote:

> A couple of things to be said...
>
> > Add braille printers to the lineup that use the order panel, not the
> tags. At least that was the case a couple of years ago when some of our
> clients with visitors centers were printing braille visitor guides.
>
> No-one should be under the impression that there's anything about the
> "order panel" that's truly about accessibility. For the purposes of this
> conversation it can be boiled down as follows:
>
> - The 'order panel- in Acrobat Professional denotes the sequence in which
> objects are painted onto the page. This is fundamentally orthogonal to the
> question of 'reading order-, which is denoted *entirely* by the use of
> "tagged PDF-. Often, they align to one degree or another. In most cases,
> there are significant discontinuities.
>
> - Software either uses or does not use 'tagged PDF-
>
> - Software that does not use tagged PDF (such as the Reflow feature in
> Adobe Reader, for example) has to guess to infer a reading-order. Leaving
> such accessibility basics up to software heuristics is manifestly NOT what
> accessibility is all about.
>
> - As a concession to today's world where many AT software don't 'do-
> tagged PDF, Bevi's right that aligning content order and tag order to the
> extent possible creates value for users who are saddled with the
> aforementioned software.
>
> > Talking with a colleague, it's hard for us to know which technologies
> use which order and there's no central source of information that covers
> all of the A.T. on the market today. Plus people might be using older A.T.
> that could be using the order, not the tags.
>
> There's nothing fixed about this. While current-generation AT software may
> not used tagged PDF, the next version of that software may do so. But not,
> of course, if people don't ask for it.
>
> > Our recommendation: try to get both to synch up, but if you have to
> compromise, make the tags accurate and the order can slide a bit. Not too
> much, but a bit.
>
> Since the 'order panel- can't accommodate discontinuous content... or even a
> paragraph that spans two pages, compromise is indeed essential.
>
> It's just as important to educate service bureaus and the like to point
> out to them that if they are getting their 'reading order- from
> page-content instead of from tags (when present) they are doing their
> end-users a disservice.
>
> Trying to design a PDF file to accommodate software that does not use PDF
> accessibility is something one should consider carefully, and preferably,
> reject. In my view, it makes more sense to insist on software that actually
> understands accessible PDF files (contact the vendor!!!) rather than invest
> in the prodigious amounts of labor required to make PDF files sort-of
> 'work- with manifestly substandard software.
>
> Duff.
>
>
>
> > -----Original Message-----
> > From: WebAIM-Forum [mailto: <EMAIL REMOVED> ] On
> Behalf Of Jonathan Avila
> > Sent: Wednesday, June 7, 2017 1:46 PM
> > To: WebAIM Discussion List < <EMAIL REMOVED> >
> > Subject: Re: [WebAIM] PDF reading order and tag order
> >
> >> If you were deaf/blind, you'd be using a braille device like a braille
> keyboard, which most likely would use the Order reading order, not the Tag
> reading order.
> >
> > It is my experience that most refreshable Braille displays are driven by
> screen readers and that most screen readers use the tag order. The content
> order does appear to be used by a limited number of tools -- in some
> situations for the read out loud tool but not other means of navigation
> with read out loud. It also would likely be used via the reflow option.
> So both orders are important -- but I'd say the tag order is more often
> used anything that is in the tag order can be repurposed by other tools
> more easily such as the VIP Reader and thus is the most important if you
> couldn't synch them up.
> >
> > Jonathan
> >
> > Jonathan Avila
> > Chief Accessibility Officer
> > SSB BART Group (soon to be Level Access) <EMAIL REMOVED>
> > 703.637.8957 (Office)
> > Visit us online: Website | Twitter | Facebook | LinkedIn | Blog Looking
> to boost your accessibility knowledge? Check out our free webinars!
> >
> > The information contained in this transmission may be attorney
> privileged and/or confidential information intended for the use of the
> individual or entity named above. If the reader of this message is not the
> intended recipient, you are hereby notified that any use, dissemination,
> distribution or copying of this communication is strictly prohibited.
> >
> > -----Original Message-----
> > From: WebAIM-Forum [mailto: <EMAIL REMOVED> ] On
> Behalf Of Chagnon | PubCom
> > Sent: Wednesday, June 07, 2017 1:07 PM
> > To: 'WebAIM Discussion List'
> > Subject: Re: [WebAIM] PDF reading order and tag order
> >
> > Quote: "The most important order in an accessible PDF is the tag order
> viewable in the Tags pane."
> >
> > I'd say that "most important" is in the mind of the individual!
> >
> > If you were deaf/blind, you'd be using a braille device like a braille
> keyboard, which most likely would use the Order reading order, not the Tag
> reading order.
> >
> > Many other A.T. for cognitive, neurologic, and mobility disabilities use
> the Order, too.
> >
> > Bottom line: both reading orders are important if you want to provide
> accessibility to all of your users.
> >
> > --Bevi Chagnon
> >
> > - - -
> > Bevi Chagnon | www.PubCom.com
> > Technologists, Consultants, Trainers, Designers, and Developers for
> publishing & communication
> > | Acrobat PDF | Print | EPUBS | Sec. 508 Accessibility |
> > - - -
> >
> > -----Original Message-----
> > From: WebAIM-Forum [mailto: <EMAIL REMOVED> ] On
> Behalf Of Philip Kiff
> > Sent: Wednesday, June 7, 2017 12:57 PM
> > To: <EMAIL REMOVED>
> > Subject: Re: [WebAIM] PDF reading order and tag order
> >
> > On 2017-06-07 12:18, Alan Zaitchik wrote:
> >> [....]
> >> But I have 2 questions.
> >> 1. The Acrobat Reading order tool jumps around with little regard (it
> >> seems) for my reordering and restructuring the tabs, even though I set
> >> my 'Preferences' for reading order to 'Infer from document structure'.
> >> Is this bogus? Need I be concerned? When I use the tool to reorder it
> >> screws up the tags!
> > The Acrobat "Touch Up Reading Order" tool is poorly named and the order
> shown by the numbers in Acrobat can be misleading until you understand that
> there is more than one "order" in a PDF.
> >
> > The most important order in an accessible PDF is the tag order viewable
> in the Tags pane. The Order pane does not show this order, but instead
> shows the "Content" order which is based on how the content is actually
> placed in the file.
> >
> > Screenreaders use the Tag order. Adobe's built-in Read Aloud feature I
> think uses the Content order.
> >
> > To change the Tag order you simply move tags up and down the Tags pane.
> > To make the Content order match the Tags order, you can try moving
> things around in the Order pane or directly in the Content pane itself.
> > However, your viewable content and your tags can easily get screwed up
> if you use the Order pane to move things around, especially if you have any
> tags nested inside other tags (like Spans or Figures inside P's inside
> Article's).
> >
> > The WebAIM site has a pretty good explanation of how to re-order a PDF
> file here:
> > http://webaim.org/techniques/acrobat/acrobat#touchup
> >
> > I like to think of the Content order as something like the "printing"
> > order, because if you start moving these items around you can end up
> making some items disappear behind others, as though they have been
> "printed" over by a non-transparent block of text or figure that appears
> after them in the content order.
> >
> > If forced to choose, always prioritize getting the tag order right
> rather than the Order panel order.
> >
> >> 2. I did indeed create 4 <article> sections but was unsure whether I
> >> should group the banner elements in some section or just list them as
> >> direct children of <document> ahead of the first <article>. My concern
> >> here is to use only well-supported HTML5 tags that will work with JAWS
> >> and other screen readers. Is the following structure OK?
> >> <Document>
> >> <Figure>
> >> <H1>
> >> <P>
> >> <Article>
> >> <Article>
> >>
> >> <Article>
> >>
> >> <Article>
> >>
> > Your structure looks okay to me!
> >
> > Phil.
> > > > > archives at http://webaim.org/discussion/archives
> > > >
> > > > > archives at http://webaim.org/discussion/archives
> > > > > > archives at http://webaim.org/discussion/archives
> > > >
> > > > > > > > >
> > > > >