Margin note beside heading

Question

I would like to insert a hyperlink or two for each heading and I would like to have them inserted into the margin such that they are aligned with the header. I was hoping to create a command which would do this automatically, but this is proving to be harder than I expected.

So to begin with, I simply had

\documentclass{article}

\usepackage{marginnote}

\newcommand\Hlink[1]{%
    \marginnote{#1}[-1.9\baselineskip]%
    \noindent}

\reversemarginpar

\begin{document}

\section{Section 1}

\Hlink{Sec 1 Link}
Lorem Ipsum

\subsection{Subsection 1.1}

\Hlink{Subsec 2 Link}
Lorem Ipsum

\end{document}

Where the -1.9\baselineskip was chosen by trial and error, but this no longer works for other headings (e.g. \subsection). Is there a command which defines the spacing after a heading?

The \noindent preserves the un-indented paragraph, but requires that no lines separate \Hlink and the start of the text. Though this is a relatively minor issue, surely there is a way around it.

This command has the additional problem that if the header is near the end of a page, it will most most likely cause a page break. I have tried inserting \nobreak before and after the command, but to no avail.

An additional problem with this is that the margin changes sides depending on the page, though in print it probably looks better, in a PDF this may not be desirable (and the links are meant to be hyperlinks). Is it possible to modify \Hlink to always use the left side?

Answer 1

If you're willing to call macro on a as-needed basis to insert content to the left of the sectional unit heading, then using \sectionlink as defined below is sufficient:

\documentclass{article}
\makeatletter
\def\sectionlink#1{\def\@sectionlink{#1}}% User interface macro for defining section link
\let\@sectionlink\@empty% Default value for \@sectionlink
\def\@seccntformat#1{% Update sectional unit formatting macro
  \ifx\@sectionlink\@empty\else% If a section link exists...
    \llap{\normalfont\normalsize\@sectionlink\hspace*{\marginparsep}}\fi% ...print it in left margin.
  \csname the#1\endcsname\quad}
\let\old@xsect\@xsect
\def\@xsect{\let\@sectionlink\@empty\old@xsect}% Erase old section link
\makeatother

\begin{document}

\sectionlink{Sec 1 Link}
\section{Section 1} Lorem Ipsum

\sectionlink{Subsec 2 Link}
\subsection{Subsection 1.1} Lorem Ipsum

\subsection{Subsection 1.2} Lorem Ipsum

\end{document}

The intent would be to call \sectionlink{<stuff>} before a call to \section and friends.

It would be possible to incorporate this as part of the sectioning macro, although that would require more work. Additionally, more work is required if the "section link" is too wide to fit in the margin (allowing, for example, to place it in a \parbox).

---

For allowing line breaks in the sectional link, you can set it in the tabular. In the example below, the code has been updated to store the link in a tabular (default is right- and [t]op-aligned, and then stored in a box. This box is then \smashed to not impede any overflow below the line that it's called in.

\documentclass{article}
\makeatletter
\newsavebox\@sectionlinkbox
% User interface macro for defining section link
\newcommand{\sectionlink}[2][r]{% ***
  \savebox{\@sectionlinkbox}{%
    \tabular[t]{@{}#1@{}}#2\endtabular}}
\def\@seccntformat#1{% Update sectional unit formatting macro
    \llap{\normalfont\normalsize\smash{\usebox\@sectionlinkbox}\hspace*{\marginparsep}}% ...print it in left margin.
  \csname the#1\endcsname\quad}
\let\old@xsect\@xsect
\def\@xsect{\savebox{\@sectionlinkbox}{\@empty}\old@xsect}% Erase old section link
\makeatother

\begin{document}

\sectionlink{Sec 1 Link}
\section{Section 1} Lorem Ipsum

\sectionlink{Subsec 1 \\ Link}
\subsection{Subsection 1.1} Lorem Ipsum

\subsection{Subsection 1.2} Lorem Ipsum

\sectionlink[l]{Subsec 3 \\ Link}
\subsection{Subsection 1.3} Lorem Ipsum

\end{document}

If you have more paragraph-style sectional links, you can modify the line of code marked *** to read

\newcommand{\sectionlink}[2][p{\marginparwidth}]{%

or, experiment with the regular tabular settings contained within the definition of \sectionlink.