media9 creates Widget annotation at corner of every page

[teepeemm]

It appears that ocgbase.sty (required by media9.sty) is creating a "Widget" annotation at the top left corner of every page in the pdf.

\DocumentMetadata{
  lang        = en,
  pdfversion  = 1.7,
  pdfstandard = ua-2,
  pdfstandard = a-4,
  testphase   = latest
}
\documentclass{article}
\usepackage{media9}
\title{My Title}
\begin{document}
\thispagestyle{empty}
Some text
\end{document}

PDF Accessibility Checker then complains "Widget" annotation not nested inside a "Form" structure element.

Something that confuses me is if I cp $(kpsewhich media9.sty) mymedia9.sty and cp $(kpsewhich ocgbase.sty) myocgbase.sty and then change the former to \RequirePackage{myocgbase}, then the annotations go away.

[u-fischer]

Something that confuses me ...

pdfbase contains a \@ifpackageloaded{ocgbase}. If you change the name of the package the relevant code is not longer executed.

Apart from this:

• You shouldn't mix 1.7 with UA-2. Either use 2.0 + UA/2 +pdf/A-4 or 1.7 + UA-1 and some earlier pdf/A standard.

• You can't use an A-standard here, verapdf will complain about /A key.

• In UA-2 the widget annotation should be fine: annotations that are not in the structure tree are automatically artifacts (well, verapdf complains about a missing /Contents key, but this looks wrong too me). But as PAC doesn't properly support PDF 2.0/UA-2 it will still complain.

• In UA-1 you could set the Hidden-Flag.

Alternatively you could tag the annotation as Form structure by uncommenting the tagging commands in the example below, but imho this is semantically wrong.

If you insert media in your document, you will need more tagging commands.

\DocumentMetadata{
  lang        = en,
  pdfversion  = 2.0,
  pdfstandard = ua-2,
  testphase   = latest,
}
\documentclass{article}
\usepackage{media9}

\RemoveFromHook{shipout/background}[pdfbase]
\ExplSyntaxOn

\AddToHook{shipout/background}{
  % workaround for curious AR bug (pdf annot or link placed on
  % OCG remains active although OCG is hidden)
  % This can be fixed by placing a dumb (non-interactive) Widget dummy
  % somewhere on the page.
  \bool_if:NT\g_pbs_ocgbase_loaded_bool{
    \put(1,-1){
      %\tag_struct_begin:n{tag=Form}
      \tl_if_exist:NF\g_pbs_blank_xform_tl{
        \hbox_set:Nn\l_tmpa_box{\phantom{\rule{1pt}{1pt}}}
        \pbs_pdfxform:nnnnn{0}{1}{}{}{\l_tmpa_box}
        \tl_const:Ne\g_pbs_blank_xform_tl{\pbs_pdflastxform:}
      }
      
      \pbs_pdfannot:nnnn{3bp}{\c_zero_dim}{3bp}{
        /Ff~65537/FT/Btn/Subtype/Widget/F~6 %< set Hidden Flag---------
        /Contents~(dummy) %<--- to keep verapdf happy
        /A~<</S/ResetForm>>% to make pdf.js happy
        /AP~<</N~<</On~\g_pbs_blank_xform_tl>>>>/AS/On
        /T~(pbs@ARFix@\int_use:N\g_pbs_page_int)
        %/StructParent\c_space_tl \tag_struct_parent_int:
      }
      %\exp_args:Nee
      %  \tag_struct_insert_annot:nn 
      %    {\pdfannot_box_ref_last: }{ \tag_struct_parent_int: }
      %\tagstructend
    }
  }
}
\ExplSyntaxOff
\title{My Title}
\begin{document}
\thispagestyle{empty}
Some text
\end{document}

[teepeemm]

My goal with media9 will be to embed prc files. I'll need to have it pass validation according to Ally, but I've already gotten that. I would also like to get PAC or VeraPDF to give their stamp of approval. I currently have:

\DocumentMetadata{
  lang        = en,
  pdfversion  = 1.7,
  pdfstandard = ua-1,
%  pdfversion  = 2.0,
%  pdfstandard = ua-2,
  testphase   = latest
}
\documentclass{article}
\usepackage{graphicx}
\usepackage[noplaybutton]{media9}
\title{My Title}
\RemoveFromHook{shipout/background}[pdfbase]
\ExplSyntaxOn
\AddToHook{shipout/background}{
  % workaround for curious AR bug (pdf annot or link placed on
  % OCG remains active although OCG is hidden)
  % This can be fixed by placing a dumb (non-interactive) Widget dummy
  % somewhere on the page.
  \bool_if:NT\g_pbs_ocgbase_loaded_bool{
    \put(1,-1){
      %\tag_struct_begin:n{tag=Form}
      \tl_if_exist:NF\g_pbs_blank_xform_tl{
        \hbox_set:Nn\l_tmpa_box{\phantom{\rule{1pt}{1pt}}}
        \pbs_pdfxform:nnnnn{0}{1}{}{}{\l_tmpa_box}
        \tl_const:Ne\g_pbs_blank_xform_tl{\pbs_pdflastxform:}
      }
      \pbs_pdfannot:nnnn{3bp}{\c_zero_dim}{3bp}{
        /Ff~65537/FT/Btn/Subtype/Widget/F~6 %< set Hidden Flag---------
        /Contents~(dummy) %<--- to keep verapdf happy
        /A~<</S/ResetForm>>% to make pdf.js happy
        /AP~<</N~<</On~\g_pbs_blank_xform_tl>>>>/AS/On
        /T~(pbs@ARFix@\int_use:N\g_pbs_page_int)
        %/StructParent\c_space_tl \tag_struct_parent_int:
      }
%      \exp_args:Nee
%        \tag_struct_insert_annot:nn 
%          {\pdfannot_box_ref_last: }{ \tag_struct_parent_int: }
%      %\tagstructend
    }
  }
}
\ExplSyntaxOff

\addmediapath{/usr/local/texlive/2025/texmf-dist/source/latex/media9/files}

\begin{document}
An embedded prc file:\bigskip

\includemedia[
width=0.8\linewidth,height=0.8\linewidth,
add3Djscript=asylabels.js, %upright text labels
add3Djscript=3Dspintool.js, %let scene rotate about z-axis
% 3Dcoo, 3Droo values found with `Generate Default View' from
% context menu
3Dmenu,
3Dc2c=4 2 3,
3Dcoo=4.413303375244141 2.195653200149536 -0.000011444091796875,
3Droo=429.49035778293376,
]{\includegraphics[alt={Some alt text}]{epixposter}}{epix.prc}
\end{document}

With 1.7/ua-1, both complain that I have four embedded files missing the "F" or "UF" key and that I have an Annotation improperly nested. With 2.0/ua-2, VeraPDF still complains about the annotation (PAC tries to validate it as 1.7 and gives the same errors as before). I wasn't able to get the Form structure to pass either, although I too would prefer semantically correct. Do you know what tagging commands I'll need for prc files?

[u-fischer]

Well the core tagging commands are demonstrated above. In short:

• Start Form structure

\tag_struct_begin:n{tag=Form} %add perhaps alt text, Contents entry

• insert annotation with attribute

  annotation command 
 ....
  /StructParent\c_space_tl \tag_struct_parent_int:

• record annotation in the structure

\tag_struct_insert_annot:nn 
%          {\pdfannot_box_ref_last: }{ \tag_struct_parent_int: }

• repeat with other annotations which should go into the same Form structure

• close the structure

\tag_struct_end:

For the dummy annotation this is not really needed, as it is an artifact. But your prc is real content and needs that code. But this is something media9 has to do. It also will have to take care of the embedding in the surrounding, and handle typeset stuff like text or rules.

[teepeemm]

To follow up: for my use, I needed to modify \includemedia and \mix_embedasset:n. Since they're ~350 and ~100 lines long, I created a separate style file that modifies those functions and incorporates your changes. My example now validates under 1.7/UA-1 and 2.0/UA-2. It does not validate under A-4, which is to be expected because it attaches files. It also doesn't validate under A-4F because of at least four different locations, which are commented on.