I intend to use the sidenote package along with David Carlisle's implementation of \marginpar based on \pdfsavedpos from the answer here: https://tex.stackexchange.com/a/52436/44160. I've simplified the \sidenote command a little, this is not the full version.
The basic idea behind the code below is to offer an alternative implementation of \marginpar, which uses the saved position of the marginpar, rather than using the regular \c@page-related macros (which don't always use the correct page number).
The code below produces an "Underfull \vbox while \output is active (badness 10000)" message, and I'm unsure where the problem lies.
What can I do to make the error go away?
PS: The code below requires two LaTeX runs to show the errors.
\documentclass[twoside]{article}
\usepackage{xparse}
\makeatletter
\NewDocumentCommand \sidenote { +m }
{
\marginpar{#1}
}
%\let\sidenote\marginpar
\newbox\@mpbox
\global\setbox\@mpbox\vbox{}
\def\savedpos#1#2#3#4{%
\begingroup
\let\@positions\relax
\expandafter\xdef\csname sp@#1-#2\endcsname{%
\expandafter\ifx\csname sp@#1-#2\endcsname\relax
\else
\csname sp@#1-#2\endcsname
\fi
\@positions{#3}{#4}}%
\endgroup}
\def\marginpar#1{%
\saveposition{mpar}%
\global\setbox\@mpbox\vbox{\unvbox\@mpbox\hbox{%
\hbox{\parbox{\marginparwidth}{\@marginparreset#1}}%
\hbox{\parbox{\marginparwidth}{\@marginparreset#1}}%
}\break}}
\def\saveposition#1{%
\pdfsavepos\write\@auxout{%
\noexpand\savedpos
{#1}{\the\c@page}{\the\pdflastxpos}{\the\pdflastypos}}}
\def\@oddfoot{%
\hss\thepage\hss\rlap{\hskip\marginparsep\mcolumn}}
\def\@evenfoot{%
\llap{\mcolumn\hskip\marginparsep}\hss\thepage\hss\saveposition{foot}}
\def\mcolumn{%
\saveposition{foot}%
\expandafter\ifx\csname sp@foot-\the\c@page\endcsname\relax
\else
\let\@positions\origin@positions
\csname sp@foot-\the\c@page\endcsname
\smash{\raise\footskip\vbox to \textheight{\hsize\marginparwidth
\hrule\@height\z@
\let\@positions\mp@positions
\csname sp@mpar-\the\c@page\endcsname
\vskip\z@\@plus\textheight% not here
\hrule\@height\z@}}%
\fi}
\def\origin@positions#1#2{%
\@tempdima\z@
\dimen@\textheight
\advance\dimen@\headsep
\advance\dimen@ #2sp
}
\def\mp@positions#1#2{%
\setbox\tw@=\vsplit\@mpbox to \maxdimen
\setbox\tw@\vbox{%
\unvbox\tw@
\setbox\tw@\lastbox
\setbox\tw@\hbox{%
\unhbox\tw@
\ifodd\c@page
\global\setbox1\lastbox
\fi
\global\setbox1\lastbox
}}%
\@tempdimb\dimen@
\advance\@tempdimb-#2sp
\ifdim\@tempdimb<2\p@
\@tempdimb2\p@
\fi
\vskip\@tempdimb\@minus\@tempdimb% not here either apparently
\advance\dimen@-\@tempdimb
\advance\dimen@-\ht\@ne
\advance\dimen@-\dp\@ne
\hrule\@height\z@
\box\@ne
\hrule\@height\z@
}
\makeatother
% just some filler text, equations, etc.
\def\someequation{%
\begin{equation}
\left[\frac{\hat p^2}{2m}+V(r)\right]\psi(r)=E\psi(r).
\end{equation}
}
\def\elementarytext{%
One two three four, united states marine core.
}
\def\sometext{%
\elementarytext\elementarytext\elementarytext\elementarytext\par
\elementarytext\elementarytext\elementarytext\elementarytext\par
\elementarytext\elementarytext\elementarytext\elementarytext\par
}
\begin{document}
\sometext
\elementarytext
\someequation
\elementarytext
\someequation
\elementarytext
\someequation
\elementarytext
\someequation
\elementarytext
\someequation
\elementarytext
\someequation
\elementarytext\sidenote{Here is a side note with some text.}
\someequation
\elementarytext\sidenote{Here is a side note with some text.}
\end{document}
