presentation mode in table tagging can not be reverted

[u-fischer]

If one use \tagpdfsetup{table/tagging=presentation} this changes the tag names but it is not possible to revert that, which is problem if one want to nest a real table inside the presentation table.

\DocumentMetadata
  {
    lang=en-US,
    pdfversion=2.0,
    pdfstandard=ua-2,
    testphase={latest},
  }

\documentclass{book}
\usepackage{lipsum}
\begin{document}
\tagpdfsetup{table/tagging=presentation}
\begin{tabular}{p{6cm}p{6cm}}
\lipsum[1] & \lipsum[2]\\
\end{tabular}

\tagpdfsetup{table/tagging} %does not work as intended.
\begin{tabular}{ll}
abc & abc
\end{tabular}

\end{document}

[davidcarlisle]

Clearly not being able to revert is a bug, but changing the names already causes some issues as the table structure is lost and so it is very hard to derive a reasonable layout. eg a 4x4 layout of paragraphs may just be "presentational" but if they are tagged as four Div and so derive to a 1x4 sequence of paragraphs it is hard to maintain the meaning. It would be good to be able to generate structure elements that would eventually derive to an html table with role=presentation. (This may require adjusting some constraints from the PDF tagging specs?)

See the derived html from the code above at

https://texlive.net/ngpdfb.html?%5CDocumentMetadata%0A%20%20%7B%0A%20%20%20%20lang=en-US,%0A%20%20%20%20pdfversion=2.0,%0A%20%20%20%20pdfstandard=ua-2,%0A%20%20%20%20testphase=%7Blatest%7D,%0A%20%20%7D%0A%0A%5Cdocumentclass%7Bbook%7D%0A%5Cusepackage%7Blipsum%7D%0A%5Cbegin%7Bdocument%7D%0A%5Ctagpdfsetup%7Btable/tagging=presentation%7D%0A%5Cbegin%7Btabular%7D%7Bp%7B6cm%7Dp%7B6cm%7D%7D%0A%5Clipsum%5B1%5D%20&%20%5Clipsum%5B2%5D%5C%5C%0A%5Cend%7Btabular%7D%0A%0A%5Ctagpdfsetup%7Btable/tagging%7D%20%25does%20not%20work%20as%20intended.%0A%5Cbegin%7Btabular%7D%7Bll%7D%0Aabc%20&%20abc%0A%5Cend%7Btabular%7D%0A%0A%5Cend%7Bdocument%7D

[u-fischer]

If I had an idea which structure in PDF correctly derives ... ;-) I have some doubt that we can use Table + some attribute in PDF.

[davidcarlisle]

Shame if we can't use /Table, otherwise you'd need to somehow inject enough CSS to recreate a table layout (although my comment doesn't block this issue, more a side comment, which perhaps I should open as a separate issue so this one can be closed by the current PR)

[John02139]

This issue arose when I asked Ulrike about the tabbing environment, which is not currently supported by tagging and which might be replaced by a presentation table. In HTML4/5, alignment in tables should be managed by a CSS attribute rather than by something like <td align="left">, and HTML validators throw errors when an "alignment table" is used rather than CSS. (Similarly, two column text is supposed to be generated using div and CSS.)

For the purpose of tagging a tabbing-like layout, however, would simply using a tabular environment for the rows/columns (rather than tabs and lines) produce appropriately tagged content? The rows and columns would be arranged in td and tr. Alignments would be lost in translation to HTML, I guess. I don't know enough about the details to judge this myself.

[u-fischer]

@John02139 The new code in latex3/latex2e#1607 will change the tagging of "presentation tables". They will have the normal table tags and set the ARIA attribute role=presentation (https://www.w3.org/WAI/ARIA/apg/practices/hiding-semantics/). This better for html derivation as it allows to keep the layout without lots of css.

Alignments would be lost in translation to HTML, I guess.

One can add an InlineAlign attribute to a table cell. For c,l and r cells that would be quite easy. For p-cells it is not so trivial to detect the alignment.

[John02139]

Thank, Ulrike, that sounds excellent. Will the addition of alignment attributes be handled automatically by the tagged latex code or by the end-user ?