Am 30.04.2025 um 00:50 schrieb Ulrike Fischer:
Am Tue, 29 Apr 2025 13:13:39 -0400 schrieb Matthias Weber:
Dear All,
I am starting a new thread as requested.
I can confirm that
the following should work with current latest (from yesterday,
LuaMetaTeX 2.11.07 20250427 + ConTeXt LMTX 2025.04.28 14:29):
\enabledirectives [backend.usetags=testing]
\setuptagging[state=start]
\setupstructure[state=start]
\setupbackend
[format=PDF/A-3a]
\setupbackend[format=pdf/ua-1]
\setupexternalfigures[location=default]
\starttext
\externalfigure[hacker][label={this is an image}]
\startparagraph
a
\stopparagraph
\stoptext
produces a PDF that passes the accessibility check in the current Adobe
Acrobat. In particular, it passes the alternate text checks.
Hovering over the image shows the alternate text in Acrobat.
However, VoiceOver (on the Mac) does not read the alternate text;
The pdf produced by context maps every structure to NonStruct, that
means there is no tagging structure, it only fools the accessibility
check. You can and should not claim that this an ua-1 file. You can
check the structure by uploading your pdf to
https://texlive.net/showtags, that will produce an xml from the
structure.
I don't know if the missing structure is the reason that VoiceOver
fails, as I'm on windows, but you could try with a LaTeX document.
Go to https://texlive.net/ngpdf and compile there this example:
\DocumentMetadata{tagging=on}
\documentclass{article}
\usepackage{graphicx}
\begin{document}
some text
\includegraphics[alt=an image with a duck]{example-image-duck}
\end{document}
After the compilation you can download the pdf and compare the
reading.
I made a fast check with Adobe + NVDA: it reads the actual text of
your image, but it doesn't announce that there is graphic. So for
the context file you get simply
this is an image
while the LaTeX file is read as
graphic an image with a duck.
Hi Ulrike,
you should try the ConTeXt example with the attached tag name mapping
Pablo sent to the list a while ago.
Wolfgang
if not modules then modules = { } end modules ['lpdf-tag-imp-testing'] = {
version = 1.001,
comment = "companion to lpdf-tag.mkiv",
author = "Hans Hagen & Mikael Sundqvist",
copyright = "PRAGMA ADE / ConTeXt Development Team",
license = "see context related readme files"
}
-- You can enable this at your own risk by saying:
--
-- \enabledirectives[backend.usetags=testing]
--
-- which will try to satisfy the sloppy mapping in pdf. You can also use this
file to
-- roll out your own variant. We also use this file for testing so there coule
be subtle
-- changes over time.
return {
name = "old school pdf tagging",
version = "1.00",
comment = "This is our crappy level two mapping, sort of an example.",
author = "Hans Hagen",
copyright = "ConTeXt development team",
mapping = {
-- Part : no structure
-- Sect : structure
-- NonStruct : skip level
-- Sub : line with lbl numbers
document = { pua = "ua1", pdf = "Document" },
documentpart = { pua = "ua1", pdf = "NonStruct" },
division = { pua = "ua1", pdf = "Part" },
paragraph = { pua = "ua1", pdf = "P" },
subparagraph = { pua = "ua1", pdf = "P" },
p = { pua = "ua1", pdf = "P" },
highlight = { pua = "ua1", pdf = "Span" },
ornament = { pua = "ua1", pdf = "Span" },
textdisplay = { pua = "ua1", pdf = "Div" },
placeholder = { pua = "ua1", pdf = "Span" },
["break"] = { pua = "ua1", pdf = "Div" },
construct = { pua = "ua1", pdf = "Span" },
constructleft = { pua = "ua1", pdf = "Span" },
constructright = { pua = "ua1", pdf = "Span" },
constructcontent = { pua = "ua1", pdf = "NonStruct" },
sectionblock = { pua = "ua1", pdf = "Part" },
section = { pua = "ua1", pdf = "Sect" }, -- Part
sectioncaption = { pua = "ua1", pdf = "NonStruct" },
sectiontitle = { pua = "ua1", pdf = "H" },
sectionnumber = { pua = "ua1", pdf = "Lbl" },
sectioncontent = { pua = "ua1", pdf = "NonStruct" },
itemgroup = { pua = "ua1", pdf = "L" },
item = { pua = "ua1", pdf = "LI" },
itemtag = { pua = "ua1", pdf = "Lbl" },
itemcontent = { pua = "ua1", pdf = "LBody" },
itemhead = { pua = "ua1", pdf = "NonStruct" },
itembody = { pua = "ua1", pdf = "NonStruct" },
items = { pua = "ua1", pdf = "Div" },
itemsymbols = { pua = "ua1", pdf = "Div" },
itemsymbol = { pua = "ua1", pdf = "Span" },
itemtexts = { pua = "ua1", pdf = "Div" },
itemtext = { pua = "ua1", pdf = "Span" },
description = { pua = "ua1", pdf = "Sect" },
descriptiontag = { pua = "ua1", pdf = "Lbl" },
descriptioncontent = { pua = "ua1", pdf = "NonStruct" },
descriptionsymbol = { pua = "ua1", pdf = "Lbl" },
verbatimblock = { pua = "ua1", pdf = "Part" },
verbatimlines = { pua = "ua1", pdf = "Part" },
verbatimline = { pua = "ua1", pdf = "Code" },
verbatim = { pua = "ua1", pdf = "Code" },
lines = { pua = "ua1", pdf = "Part" },
line = { pua = "ua1", pdf = "Code" },
linenumber = { pua = "ua1", pdf = "Span" },
synonym = { pua = "ua1", pdf = "Span" },
sorting = { pua = "ua1", pdf = "Span" },
register = { pua = "ua1", pdf = "Part" },
registerlocation = { pua = "ua1", pdf = "Span" },
registersection = { pua = "ua1", pdf = "Part" },
registertag = { pua = "ua1", pdf = "Span" },
registerentries = { pua = "ua1", pdf = "Part" },
registerentry = { pua = "ua1", pdf = "Part" },
registercontent = { pua = "ua1", pdf = "Span" },
registersee = { pua = "ua1", pdf = "Span" },
registerpages = { pua = "ua1", pdf = "Span" },
registerpage = { pua = "ua1", pdf = "Span" },
registerseparator = { pua = "ua1", pdf = "Span" },
registerpagerange = { pua = "ua1", pdf = "Span" },
table = { pua = "ua1", pdf = "Table" },
tablerow = { pua = "ua1", pdf = "TR" },
tablecell = { pua = "ua1", pdf = "TD" },
tableheadcell = { pua = "ua1", pdf = "TH" },
tablehead = { pua = "ua1", pdf = "THEAD" },
tablebody = { pua = "ua1", pdf = "TBODY" },
tablefoot = { pua = "ua1", pdf = "TFOOT" },
tabulate = { pua = "ua1", pdf = "Table" },
tabulaterow = { pua = "ua1", pdf = "TR" },
tabulatecell = { pua = "ua1", pdf = "TD" },
tabulateheadcell = { pua = "ua1", pdf = "TH" },
tabulatehead = { pua = "ua1", pdf = "THEAD" },
tabulatebody = { pua = "ua1", pdf = "TBODY" },
tabulatefoot = { pua = "ua1", pdf = "TFOOT" },
list = { pua = "ua1", pdf = "TOC" },
listitem = { pua = "ua1", pdf = "TOCI" },
listtag = { pua = "ua1", pdf = "Lbl" },
listcontent = { pua = "ua1", pdf = "NonStruct" },
listdata = { pua = "ua1", pdf = "NonStruct" },
listpage = { pua = "ua1", pdf = "Lbl" },
listtext = { pua = "ua1", pdf = "Span" },
delimitedblock = { pua = "ua1", pdf = "BlockQuote" },
delimited = { pua = "ua1", pdf = "Quote" },
delimitedcontent = { pua = "ua1", pdf = "NonStruct" },
delimitedsymbol = { pua = "ua1", pdf = "Span" },
subsentence = { pua = "ua1", pdf = "Span" },
subsentencecontent = { pua = "ua1", pdf = "Span" },
subsentencesymbol = { pua = "ua1", pdf = "Span" },
label = { pua = "ua1", pdf = "Span" },
number = { pua = "ua1", pdf = "Span" },
float = { pua = "ua1", pdf = "Part" },
floatcaption = { pua = "ua1", pdf = "Caption" },
floatlabel = { pua = "ua1", pdf = "Span" },
floatnumber = { pua = "ua1", pdf = "Span" },
floattext = { pua = "ua1", pdf = "Span" },
floatcontent = { pua = "ua1", pdf = "NonStruct" },
image = { pua = "ua1", pdf = "Figure" },
mpgraphic = { pua = "ua1", pdf = "Figure" },
formulaset = { pua = "ua1", pdf = "Part" },
formula = { pua = "ua1", pdf = "Formula" },
formulacaption = { pua = "ua1", pdf = "Span" },
formulalabel = { pua = "ua1", pdf = "Span" },
formulanumber = { pua = "ua1", pdf = "Span" },
formulacontent = { pua = "ua1", pdf = "NonStruct" },
subformula = { pua = "ua1", pdf = "Part" },
link = { pua = "ua1", pdf = "Link" },
reference = { pua = "ua1", pdf = "NonStruct" },
navigation = { pua = "ua1", pdf = "NonStruct" },
navigationbutton = { pua = "ua1", pdf = "NonStruct" },
navigationmenu = { pua = "ua1", pdf = "NonStruct" },
navigationmenuitem = { pua = "ua1", pdf = "NonStruct" },
navigationaction = { pua = "ua1", pdf = "NonStruct" },
navigationpage = { pua = "ua1", pdf = "NonStruct" },
margintextblock = { pua = "ua1", pdf = "Aside" },
margintext = { pua = "ua1", pdf = "NonStruct" },
marginanchor = { pua = "ua1", pdf = "Span" },
linetext = { pua = "ua1", pdf = "NonStruct" },
-- no math here
ignore = { pua = "ua1", pdf = "NonStruct" },
private = { pua = "ua1", pdf = "NonStruct" },
metadata = { pua = "ua1", pdf = "Part" },
metavariable = { pua = "ua1", pdf = "Span" },
mid = { pua = "ua1", pdf = "Span" },
sub = { pua = "ua1", pdf = "Span" },
sup = { pua = "ua1", pdf = "Span" },
subsup = { pua = "ua1", pdf = "Span" },
combination = { pua = "ua1", pdf = "Table" },
combinationpair = { pua = "ua1", pdf = "TR" },
combinationcontent = { pua = "ua1", pdf = "TD" },
combinationcaption = { pua = "ua1", pdf = "TD" },
publications = { pua = "ua1", pdf = "Part" },
publication = { pua = "ua1", pdf = "NonStruct" },
pubfld = { pua = "ua1", pdf = "Span" },
citation = { pua = "ua1", pdf = "Span" },
cite = { pua = "ua1", pdf = "Span" },
narrower = { pua = "ua1", pdf = "Part" },
block = { pua = "ua1", pdf = "Part" },
userdata = { pua = "ua1", pdf = "Part" },
quantity = { pua = "ua1", pdf = "Span" },
unit = { pua = "ua1", pdf = "Span" },
verse = { pua = "ua1", pdf = "Part" },
versetag = { pua = "ua1", pdf = "Lbl" },
verseseparator = { pua = "ua1", pdf = "Span" },
versecontent = { pua = "ua1", pdf = "NonStruct" },
},
-- This is a hack to get around the specifications "We can't expect an
-- application to keep track of nested H's (but otherwise expect very
complex
-- things things to be properly dealt with)". A typical example of bugs
-- becoming features, standards being not really standards as they get
-- adapted, etc. That said: it is up to the user to decide what to do but
-- don't blame us for the resulting less optimal structure.
-- Because we don't want to spoil the otherwise rather clean structure in
-- ConTeXt, this kicks in very late in the backend. We might extend this
-- hackery but there are limits to what is desired. After all, in over a
-- decade of pdf tagging nothing significant happened (we're speaking 2024)
-- nor proper viewer support showed up and we can anyway expect LLM's to
deal
-- with proper tags anyway some day.
overloads = {
-- criterium : parent : use parent "detail"
-- parents : use first in parent "parents" list
-- otherwise : look at self "detail"
-- We need violate the proper structure by getting a Hn on the title so
we
-- have to backtrack to what we're in, thereby also denying the proper
-- section instance. Don't ask. The plural "parents" will make sure we
-- consult the first in the chain and not the instance that is encoded
in
-- "detail".
sectioncaption = {
criterium = "parents",
mapping = {
part = { pua = "ua1", tag =
"section_title_1", pdf = "H1" },
chapter = { pua = "ua1", tag =
"section_title_2", pdf = "H2" },
title = { pua = "ua1", tag =
"subject_title_2", pdf = "H2" },
section = { pua = "ua1", tag =
"section_title_3", pdf = "H3" },
subject = { pua = "ua1", tag =
"subject_title_3", pdf = "H3" },
subsection = { pua = "ua1", tag =
"section_title_4", pdf = "H4" },
subsubject = { pua = "ua1", tag =
"subject_title_4", pdf = "H4" },
subsubsection = { pua = "ua1", tag =
"section_title_5", pdf = "H5" },
subsubsubject = { pua = "ua1", tag =
"subject_title_5", pdf = "H5" },
subsubsubsection = { pua = "ua1", tag =
"section_title_6", pdf = "H6" },
subsubsubsubject = { pua = "ua1", tag =
"subject_title_6", pdf = "H6" },
subsubsubsubsection = { pua = "ua1", tag =
"section_title_7", pdf = "H7" },
subsubsubsubsubject = { pua = "ua1", tag =
"subject_title_7", pdf = "H7" },
subsubsubsubsubsection = { pua = "ua1", tag =
"section_title_8", pdf = "H8" },
subsubsubsubsubsubject = { pua = "ua1", tag =
"subject_title_8", pdf = "H8" },
subsubsubsubsubsubsection = { pua = "ua1", tag =
"section_title_9", pdf = "H9" },
subsubsubsubsubsubsubject = { pua = "ua1", tag =
"subject_title_9", pdf = "H9" },
subsubsubsubsubsubsubsection = { pua = "ua1", tag =
"section_title_10", pdf = "H10" },
subsubsubsubsubsubsubsubject = { pua = "ua1", tag =
"subject_title_10", pdf = "H10" },
},
},
},
}
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