[NTG-context] Tagged PDF - Math

Christoph Reller christoph.reller at gmail.com
Fri May 30 09:33:32 CEST 2014


Hi,

ConTeXt can produce tagged PDF - this is really cool! (At the moment
ConTeXt/luaTeX seems to be the only macropackage/TeX-engine that is able to
do this.)

What is the status of producing structure information for math? After a
quick evaluation I observe two issues:

1. Empty entry in RoleMap:
ConTeXt wisely uses the RoleMap entry of the StructTreeRoot element in a
PDF to map structure element names to standard element names. In PDF terms,
RoleMap is a dictionary with keys and values. Unfortunately, certain math
elements seem to lead to a corrupt RoleMap, e.g., the usage of a square
root results in an empty dictionary key with corresponding value "\Span". A
minimal example is:

\setuptagging[state=start]
\starttext
\startformula
\sqrt{A}
\stopformula
\stoptext

2. Structure element contains index of type "real number":
According to the PDF Reference V 1.7 (see Table 10.10) a structure element
dictionary's "K" entry can be an integer (e.g. "2") that denotes an index
for a marked-content sequence. When tagging math, ConTeXt sometimes
produces a real value (e.g. "2.000") instead. A minimal example is: (In
this example the last element "B" receives such a "real number" index)

\setuptagging[state=start]
\starttext
\startformula
A = B
\stopformula
\stoptext

I am using ConTeXt version 2014.05.27 13:38.

Thanks in advance for any feedback.

Christoph
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