[Tex/LaTex] ‘\pdfendlink ended up in different nesting level than \pdfstartlink’ error with current version of hyperref

errorshyperrefpdftex

I am experiencing the hyperref split-link issue described in previous questions. I tried to update the hyperref package as recommended as well as the oberdiek package which also seems to have some hyperref-related files.

My hyperref.sty is now at v6.83m, hobsub-hyperref.sty at v1.13. The MWE in @Michael's question compiles without problems, but my document still generates the same error. My documentclass is elsarticle (version 1.2.0).

The following suffices to produce the problem:

\documentclass[5p]{elsarticle}

\usepackage{kantlipsum}
\usepackage{hyperref}

\begin{document}

\begin{frontmatter}
\end{frontmatter} 

\kant*[1-4]
\kant[5]
\href{http://tex.stackexchange.com}{This is a very very
  very very very very very very very very very very very very very
  very very very very very very very very long link.}
\end{document}

Both the 5p option and frontmatter seem to be required, though the latter may be empty.

Best Answer

The MWE is a good starting point. From there I could simplify it further. frontmatter sets the title in the optional argument of \twocolumn. Thus \twocolumn[] is sufficient. The text can be replaced by vertical spaces. The class can be replaced by the standard article class.

MWE:

\documentclass{article}

\usepackage{hyperref}

\begin{document}
\twocolumn[]   

\null\vfill\newpage
\null\kern.95\textheight

\href{http://tex.stackexchange.com}{This is a very very
  very very very very very very very very very very very very very
  very very very very very very very very long link.}
\end{document}

If \twocolumn is called with the optional argument, then macro \@topnewpage is called, which puts the stuff of the optional argument in a double column float object for the top of the page. Thus also the following triggers the problem instead of \twocolumn[]:

\twocolumn
\begin{figure*}\end{figure*}

At some later time in the output routine, macro \@combinedblfloats combines the top double float object with the normal page contents:

\setbox\@outputbox \vbox to\textheight{%
  \unvbox\@tempboxa
  \vskip-\dblfloatsep
  \ifnum \@dbltopnum>\m@ne
    \dblfigrule
  \fi
  \vskip \dbltextfloatsep
  \box\@outputbox
}%

As can be seen, \@outputbox is boxed again in an additional \vbox. Thus the box level of the first part of the link is higher by one in comparison to the second page without the double float object.

The following workaround increases the boxing level except for the first page:

\documentclass{article}

\usepackage{hyperref}

\AtBeginShipout{%
  \ifnum\value{page}>1 %
    \typeout{* Additional boxing of page `\thepage'}%
    \setbox\AtBeginShipoutBox=\hbox{\copy\AtBeginShipoutBox}%
  \fi
}

\begin{document}
\twocolumn[]

\null\vfill\newpage
\null\kern.95\textheight

\href{http://tex.stackexchange.com}{This is a very very
  very very very very very very very very very very very very very
  very very very very very very very very long link.}
\end{document}

The workaround also works with the original MWE of the question. In real documents, it is not trivial to know, which pages would need how many additional box levels.

A manual way would be using the following snippet, the first two lines quite early, even before \documentclass, the remaining part should be executed late, here via \AtBeginDocument.

\RequirePackage{atbegshi}
\AtBeginShipoutInit

\AtBeginDocument{%
  \AtBeginShipout{%
    \begingroup
      \showboxdepth=\maxdimen
      \showboxbreadth=\maxdimen
      \tracingonline=1 %
      \edef\restoreinteractionmode{\interactionmode=\the\interactionmode}%
      \nonstopmode
      \showbox\AtBeginShipoutBox
      \restoreinteractionmode
    \endgroup
  }%
}

Then the box listings of the output pages can be analyzed to identify the start part of the link and the end part on the next page. Then the number of dots at the line starts need to be compared.

The next example tries a more automatic solution:

\documentclass[5p]{elsarticle}

\usepackage{kantlipsum}
\usepackage{hyperref}  

\usepackage{etoolbox}
\makeatletter
\newcount\c@additionalboxlevel
\setcounter{additionalboxlevel}{0}
\newcount\c@maxboxlevel
\setcounter{maxboxlevel}{1}
\patchcmd\@combinedblfloats{\box\@outputbox}{%
  \stepcounter{additionalboxlevel}%
  \box\@outputbox
}{}{\errmessage{\noexpand\@combinedblfloats could not be patched}}

\AtBeginShipout{%
  \ifnum\value{additionalboxlevel}>\value{maxboxlevel}%
    \typeout{Warning: maxboxlevel might be too small, increase to %
      \the\value{additionalboxlevel}%
    }%
  \fi 
  \@whilenum\value{additionalboxlevel}<\value{maxboxlevel}\do{%
    \typeout{* Additional boxing of page `\thepage'}%
    \setbox\AtBeginShipoutBox=\hbox{\copy\AtBeginShipoutBox}%
    \stepcounter{additionalboxlevel}%
  }%
  \setcounter{additionalboxlevel}{0}%
}
\makeatother

\begin{document}

\begin{frontmatter}
\end{frontmatter}  

\kant*[1-4]
\kant[5]   
\href{http://tex.stackexchange.com}{This is a very very
  very very very very very very very very very very very very very
  very very very very very very very very long link.}
\end{document}

Maybe this issue could also be fixed by replacing \box\@outputbox by \unvbox\@outputbox in macro \@combinedblfloats (maybe the vertical glue assignments might change):

\usepackage{etoolbox}
\makeatletter
\patchcmd\@combinedblfloats{\box\@outputbox}{\unvbox\@outputbox}{}{%
  \errmessage{\noexpand\@combinedblfloats could not be patched}%
}%
\makeatother
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