a11y - add support for tagpdf

[cscheid]

This won't work until we pull Pandoc 3.7.0.2 as a binary dependency. But when we do, the test tests/docs/smoke-all/latex/tagpdf.qmd should pass.

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[cscheid]

We're still going to be missing math support: https://theaccessibilityguy.com/how-to-use-latex-for-accessible-math-in-pdfs/

[cderv]

I wonder if this should be configurable for users who desire to configure the \DocumentMetadata. There are a few options with different values like lang or pdfstandard

Documented at https://mirrors.ctan.org/macros/latex/required/latex-lab/documentmetadata-support-code.pdf

I guess this is how Pandoc would add it in its template.

Otherwise, if we put it in its own partials (taggedpdf.tex for example), then this would be really easy for a user to pass its own version with modified options. Could be worth it if we are not sure yet what to expose as config

pdf:
  tagpdf:
    pdfstandard: ...

[cscheid]

I like having a taggedpdf.tex partial.

[tarleb]

The docs suggest to use lualatex-dev to compile the document. Can we support that by setting pdf-engine?

[cderv]

Yes it should, but is lualatex-dev ship with TeX Live ?

On my installation I don't see it

❯ ls C:\Users\chris\AppData\Roaming\TinyTeX\bin\windows\lua*

    Directory: C:\Users\chris\AppData\Roaming\TinyTeX\bin\windows

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a---          23/07/2025    17:19         215040 lua53w64.dll
-a---          23/07/2025    17:19        7132160 luahbtex.dll
-a---          23/07/2025    17:19           6656 luahbtex.exe
-a---          23/07/2025    17:19           6656 lualatex.exe
-a---          23/07/2025    17:19           6144 luaotfload-tool.exe
-a---          23/07/2025    17:19        6097408 luatex.dll
-a---          23/07/2025    17:19           6656 luatex.exe

[tarleb]

I found an old Dockerfile from last year that I had written to experiment with tagging. This is what I used:

FROM pandoc/latex
RUN tlmgr install \
        l3experimental \
        latex-base-dev \
        latex-bin-dev \
        pdfmanagement-testphase \
        tagpdf && \
    mv /opt/texlive/texdir/bin/default/lualatex \
        /opt/texlive/texdir/bin/default/lualatex-original && \
    ln -s /opt/texlive/texdir/bin/default/lualatex-dev \
          /opt/texlive/texdir/bin/default/lualatex

I think the linking was necessary because pandoc doesn't accept a program named lualatex-dev as the LaTeX compiler.

[cscheid]

For what's worth, I didn't need to call lualatex-dev in order for the document to be tagged. Locally for me at least, it worked with just lualatex.