Dirtree pagebreak issue

Question

I have a (rather long-ish) hierarchical structure, typeset with the dirtree package. However, I have some issues when breaking the tree over to a new page -- the line may protrude up to the very top of the sheet writeable area, extending into the headings area.

Note that I used the headings here only to better illustrate the issue, they are not necessary to exemplify the problem. But I do have a similar page setup, and it looks particularly unpleasant with the horizontal rule being intersected by the tree lines.

Here's an example:

\documentclass{article}
\usepackage{lipsum}
\usepackage{dirtree}
\usepackage{fancyhdr}

\fancyhf{}
\fancyhead[C]{\emph{\nouppercase{\rightmark}}}
\fancyfoot[C]{\thepage}
\renewcommand{\headrulewidth}{0.4pt}
\renewcommand{\footrulewidth}{0.4pt}
\pagestyle{fancy}
\renewcommand{\sectionmark}[1]{\markright{#1}}
\renewcommand{\subsectionmark}[1]{\markright{#1}}

\begin{document}
\lipsum[1-4]
\dirtree{%
.1 spam.
.2 eggs.
.2 ham.
.3 circus.
.3 parrot.
.4 knights.
.3 spamalot.
.4 ni.
.5 brian.
.5 vikings.
.2 meaning.
}
\end{document}

Now, the package documentation says that a command \DTsplittree is in the To-Do list, that will allow splitting the tree over several pages. Any ideas for a dirty hack or a workaround that I might be able to use in the meantime?

I've used some other tricks from the book, like reducing the line spacing and playing with font size, and I guess I could split it in two a few smaller parts (which I will have to fit again between pages!) if I can't find another way of doing it. But I'm more interested in a TeXnical solution.

Update Let's see if this will get answered if some 100 bonus rep is thrown at it.

Answer 1

The dirtree package is neat! Below is a slight modification of the package to page break sanely. It requires LaTeX and the zref package, so I don't claim it's the right solution, but it does seem to work (at least with extremely limited testing). As this modification uses references, it takes multiple runs of LaTeX to see the new page breaking behavior.

% This file was dirtree.tex. It was modified by TH. to support
% splitting the tree at pagebreaks sanely. It has been renamed to
% durtree.sty. It will now only work with LaTeX. It is meant as a
% quick hack to solve the problem at hand. Any bugs in it are my own,
% please don't blame M. Charpentier for them!
%
%%
%% This is file `dirtree.tex',
%% generated with the docstrip utility.
%%
%% The original source files were:
%%
%% dirtree.dtx  (with options: `tex')
%% 
%% IMPORTANT NOTICE:
%% 
%% For the copyright see the source file.
%% 
%% Any modified versions of this file must be renamed
%% with new filenames distinct from dirtree.tex.
%% 
%% For distribution of the original source see the terms
%% for copying and modification in the file dirtree.dtx.
%% 
%% This generated file may be distributed as long as the
%% original source files, as listed above, are part of the
%% same distribution. (The sources need not necessarily be
%% in the same archive or directory.)
%%
%% Package `dirtree.dtx'
%% -----------------------------------------------
%% Copyright (C) 2004-2006 Jean-C\^ome Charpentier
%% -----------------------------------------------
%%
%% This work may be distributed and/or modified under the
%% conditions of the LaTeX Project Public License, either version 1.3
%% of this license or (at your option) any later version.
%% The latest version of this license is in
%%   http://www.latex-project.org/lppl.txt
%% and version 1.3 or later is part of all distributions of LaTeX
%% version 2003/12/01 or later.
%%
%% See CTAN archives in directory macros/latex/base/lppl.txt.
%%
%% CONTENTS:
%%   This work consists of the files dirtree.ins and dirtree.dtx.
%%   Derived files are dirtree.tex and dirtree.sty.
%%
%% DESCRIPTION:
%%   dirtree is a package displaying directory trees.
%%
\def\fileversion{0.1}
\def\filedate{2010/12/04}
\NeedsTeXFormat{LaTeX2e}[1995/06/01]
\ProvidesPackage{durtree}[\filedate\space v\fileversion]
\RequirePackage{zref-abspage}
\long\def\LOOP#1\REPEAT{%
  \def\ITERATE{#1\relax\expandafter\ITERATE\fi}%
  \ITERATE
  \let\ITERATE\relax
}
\let\REPEAT=\fi
\def\@nameedef#1{\expandafter\edef\csname #1\endcsname}
\newdimen\DT@offset \DT@offset=0.2em
\newdimen\DT@width \DT@width=1em
\newdimen\DT@sep \DT@sep=0.2em
\newdimen\DT@all
\DT@all=\DT@offset
\advance\DT@all \DT@width
\advance\DT@all \DT@sep
\newdimen\DT@rulewidth \DT@rulewidth=0.4pt
\newdimen\DT@dotwidth \DT@dotwidth=1.6pt
\newdimen\DTbaselineskip \DTbaselineskip=\baselineskip
\newcount\DT@counti
\newcount\DT@countii
\newcount\DT@countiii
\newcount\DT@countiv
\newcount\DT@treenum \DT@treenum=0
\newif\ifDT@split
\def\DTsetlength#1#2#3#4#5{%
  \DT@offset=#1\relax
  \DT@width=#2\relax
  \DT@sep=#3\relax
  \DT@all=\DT@offset
  \advance\DT@all by\DT@width
  \advance\DT@all by\DT@sep
  \DT@rulewidth=#4\relax
  \DT@dotwidth=#5\relax
}
\def\DTstyle{\ttfamily}
\def\DTstylecomment{\rmfamily}
\def\DTcomment#1{%
  \kern\parindent\dotfill
  {\DTstylecomment{#1}}%
}
\def\dirtree#1{%
  \global\advance\DT@treenum by\@ne
  \let\DT@indent=\parindent
  \parindent=\z@
  \let\DT@parskip=\parskip
  \parskip=\z@
  \let\DT@baselineskip=\baselineskip
  \baselineskip=\DTbaselineskip
  \let\DT@strut=\strut
  \def\strut{\vrule width\z@ height0.7\baselineskip depth0.3\baselineskip}%
  \DT@counti=\z@
  \let\next\DT@readarg
  \next#1\@nil
  \dimen@=\hsize
  \advance\dimen@ -\DT@offset
  \advance\dimen@ -\DT@width
  \setbox\z@=\hbox to\dimen@{%
    \hsize=\dimen@
    \vbox{\@nameuse{DT@body@1}}%
  }%
  \dimen@=\ht\z@
  \advance\dimen@ by\dp\z@
  \advance\dimen@ by-0.7\baselineskip
  \ht\z@=0.7\baselineskip
  \dp\z@=\dimen@
  \par\leavevmode
  \kern\DT@offset
  \kern\DT@width
  \box\z@
  \endgraf
  \DT@countii=\@ne
  \DT@countiii=\z@
  \dimen3=\dimen@
  \@namedef{DT@lastlevel@1}{-0.7\baselineskip}%
  \loop
  \ifnum\DT@countii<\DT@counti
    \advance\DT@countii \@ne
    \advance\DT@countiii \@ne
    \dimen@=\@nameuse{DT@level@\the\DT@countii}\DT@all
    \advance\dimen@ by\DT@offset
    \advance\dimen@ by-\DT@all
    \leavevmode
    \kern\dimen@
    \DT@countiv=\DT@countii
    \count@=\z@
    \DT@splitfalse
    \LOOP
      \advance\DT@countiv \m@ne
      \ifnum\@nameuse{DT@level@\the\DT@countiv} >
        \@nameuse{DT@level@\the\DT@countii}\relax
      \else
        \count@=\@ne
      \fi
      \ifnum0\zref@extract{DT\the\DT@treenum.\the\DT@countiv}{abspage} =
        0\zref@extract{DT\the\DT@treenum.\the\DT@countii}{abspage}\relax
      \else
        \advance\DT@countiv\@ne
        \count@=\@ne
        \DT@splittrue
      \fi
    \ifnum\count@=\z@
    \REPEAT
    \edef\DT@hsize{\the\hsize}%
    \count@=\@nameuse{DT@level@\the\DT@countii}\relax
    \dimen@=\count@\DT@all
    \advance\hsize by-\dimen@
    \setbox\z@=\vbox{\@nameuse{DT@body@\the\DT@countii}}%
    \hsize=\DT@hsize
    \dimen@=\ht\z@
    \advance\dimen@ by\dp\z@
    \advance\dimen@ by-0.7\baselineskip
    \ht\z@=0.7\baselineskip
    \dp\z@=\dimen@
    \@nameedef{DT@lastlevel@\the\DT@countii}{\the\dimen3}%
    \advance\dimen3 by\dimen@
    \advance\dimen3 by0.7\baselineskip
    \dimen@=\@nameuse{DT@lastlevel@\the\DT@countii}\relax
    \advance\dimen@ by-\@nameuse{DT@lastlevel@\the\DT@countiv}\relax
    \advance\dimen@ by0.3\baselineskip
    \ifnum\@nameuse{DT@level@\the\DT@countiv} <
        \@nameuse{DT@level@\the\DT@countii}\relax
      \advance\dimen@ by-0.5\baselineskip
    \fi
    \ifDT@split
      \advance\dimen@ by.4\baselineskip
    \fi
    \kern-0.5\DT@rulewidth
    \hbox{\vbox to\z@{\vss\hrule width\DT@rulewidth height\dimen@}}%
    \kern-0.5\DT@rulewidth
    \kern-0.5\DT@dotwidth
    \vrule width\DT@dotwidth height0.5\DT@dotwidth depth0.5\DT@dotwidth
    \kern-0.5\DT@dotwidth
    \vrule width\DT@width height0.5\DT@rulewidth depth0.5\DT@rulewidth
    \kern\DT@sep
    \box\z@
    \endgraf
  \repeat
  \parindent=\DT@indent
  \parskip=\DT@parskip
  \DT@baselineskip=\baselineskip
  \let\strut\DT@strut
}
\def\DT@readarg.#1 #2. #3\@nil{%
  \advance\DT@counti \@ne
  \@namedef{DT@level@\the\DT@counti}{#1}%
  \edef\DT@label{DT\the\DT@treenum.\the\DT@counti}%
  \expandafter\def\csname DT@body@\the\DT@counti\expandafter\endcsname
      \expandafter{\expandafter\strut\expandafter\zref@label\expandafter{%
      \DT@label}%
    {\DTstyle{#2}\strut}%
  }
  \ifx\relax#3\relax
    \let\next\@gobble
  \fi
  \next#3\@nil
}
\endinput
%%
%% End of file `durtree.sty'.

It might be instructive to diff this file with dirtree.tex to see what I changed in detail. Basically, I added an absolute page ref after the first \strut that gets added around each entry. Then, when typesetting, it checks if the page number of the current entry matches the previous entry at that level. If they match, nothing different happens (\ifDT@split is false). Otherwise, it only draws the vertical rule to the top of the first entry on the current page.

I also changed the \dimen\z@ and \dimen0 to \dimen@. I guess this is technically slightly faster, but mostly it was annoying me.