[NTG-context] Accessibility and Tagged PDFs: Bugs and Feature Requests

Hans Hagen pragma at wxs.nl
Fri Jul 3 19:19:58 CEST 2015


On 7/3/2015 10:12 AM, Dominik Klein wrote:
>
> On Wed Jul 1, 18:47:57 CEST 2015, Hans Hagen wrote:
>>>/  /Artifact
> />>/     BMC
> />>/     ..
> />>/     EMC
> />
>>i'll add the simple variant (i see no need to add properties to
>>something that is supposed to be ignored anyway)
>
> thanks!
>
>
>>>/  2.) Images without alternate text:
> />
>>i'll pass the label to the tag as alt text
>>
>>\externalfigure[t:/sources/cow.pdf][label=whatever]
>
> Again, thanks!
>
>>>/  3.) Tag names of the resulting tag structure:
> />>/  Section 14.8.4 of [1] defines standard structure types,
> //>
> />The set of those standard tags is rather limited and imo one of the
>>craziest things in pdf as we then end up with abuse of those html tags
>>(and probably endless discussions on what to map onto what). I don't
>>even have a clue what it would add to the concept either. Reflow is a
>>braindead thing anyway.
>
> Indeed, the set of those tags is very limited. Unfortunately, as
> far as I know, some screen readers (for the visually impaired)
> use these as navigation aids, i.e. press button "jump to next section",
> and the reader will look for the next section marked as <Sect> or something.
>
> Is it difficult to make the mapping user-defineable in the source tex-file?
> Say, like such a command:
> \definemapping[
>    section=Sect,
>    sectiontitle=H
>    sectionnumber=H,
>    ...
>    tablerow=TR
>    ...
> ]
>
> It would then give users the control on what to map onto what, depending
> on what kind of documents they create.
>
>>>/  All in all, these seem to be the only issues that prevent accessible PDF
>>/>/  documents with context. For those within an organization where
>>/>/  accessibility is required legally for all publications, compliance to at
>>/>/  least Acrobat Pro's checks is a huge issue. I do not know how difficult
>>/>/  these things are to implement in Context (personally I am just lost in
>>/>/  the code), but looking at e.g. tex.stackexchange
>>/>/  for question related to accessibility, this is indeed a major obstacle
>>/>/  for several people.
> />
>>In fact adding pdf tagging to context was rather easy. Some time was
>>So, it's not that difficult to add features, more a matter of priorities
>>and motivation (apart from the fact that my acrobat is a bit old by now
>>so I cannot really test).
>
> I can fully understand that such things are not of the highest priority.
> Nevertheless accessibility plays more and more a role, e.g. lately, even
> conferences likehttp://chi2015.acm.org/authors/guide-to-an-accessible-submission/
> require accessible pdfs (the workflow they suggest, i.e. tagging a pdf
> by acrobat pro after compiling of course doesn't work at all - the generated
> structure is useless).
>
> Hence, for some users, it makes all the difference. For example for me and
> some other friends, it would allow to change from using Microsoft Word to
> a ConTeXt based workflow.

\nopdfcompression

\setuptagging[state=start]

\starttext

     \chapter{whatever}

\stoptext

gives a pdf with a rolemap like:

11 0 obj
<< /ParentTree 12 0 R /K 29 0 R /RoleMap << /sectiontitle /H /section 
/Sect /sectionnumber /H /document /Div >> /Type /StructTreeRoot >>
endobj

but as usual it's hard to check what gets done with such things

(i'm pretty sure that context was one of the first to support for 
instance field (widget) trees but support for that in viewers changes 
each version so one never knows what is the right way as specs predate 
support in viewers)

(in the same fashion tagging and layers is/are useless till it gets 
supported in other viewers than acrobat)



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