(A similar question has been sent to the tex live list for pdftex)
After some discussion in the latex team I have two questions about
\pdfextension startlink/endlink in luatex and boxing levels.
1.
Currently the commands give a fatal error if used in different
boxing levels:
x\hbox{\pdfextension startlink
attr {/Border[0 0 1]}
user{
/Subtype/Link%
/A<<%
/Type/Action%
/S/URI%
/URI(blkub)%
>>%
} Linktext}
\pdfextension endlink
\bye
! error: (pdf backend): 'endlink' ended up in different nesting level than
'startlink'
! ==> Fatal error occurred, no output PDF file produced!
This doesn't happen very often in documents, but if the galley is
split and reboxed it is possible that long links end in different
levels. One example involving two column mode and top floats has
been discussed on the latex2e github:
https://github.com/latex3/latex2e/issues/94
Is the fatal error really sensible here? Couldn't the engine close
the last annotation with some more or less sensible coordinate and
continue with a warning? A pdf with a wrong link area seems better
than no pdf at all (and would release formats and packages from
the need to carefully keep track of boxing levels when splitting and
reassembling stuff).
2. The engine interrupts linking if the boxing level of
intermediate text is less than the boxing level at the start of the
link:
x\hbox{\hbox{\pdfextension startlink
attr {/Border[0 0 1]}
user{
/Subtype/Link%
/A<<%
/Type/Action%
/S/URI%
/URI(blkub)%
>>%
} Linktext}}
not linked
\hbox{\hbox{still not linked}
\hbox{\hbox{more Linktext\pdfextension endlink}}
\bye
This allows to some extend to exclude e.g. header and footer from
link areas. But doesn't work e.g. with the latex package fancyhdr
which adds an additional box level to the footer. xetex/xdvidfpmx
has here a quite useful special \special{pdf:nolink} which can be
used to suppress the unwanted link area:
\documentclass[a4paper]{article}
\usepackage{fancyhdr}
\pagestyle{fancy}
\cfoot{some longer text that should not be linked}
\usepackage{ifxetex}
\ifxetex
%\cfoot{\special{pdf:nolink}some longer text that should not be
linked\special{pdf:link}}
\fi
\usepackage{hyperref}
\begin{document}
\vspace*{48\baselineskip}
xxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxx
\href{xxxxx}{link link link link }
\end{document}
Would it be possible to add to luatex something similar?
--
Ulrike Fischer
http://www.troubleshooting-tex.de/
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