Improper \prevdepth with bigfoot package

Question

In my book I use bigfoot package for footnotes. I want to add the continuation marks, and manual tells that I need to redefine the \FN@beforebreak command. But, when I do it, I get and error. MWE:

\documentclass{article}
\usepackage{blindtext}
\usepackage{bigfoot}
\DeclareNewFootnote{default}

% fix bug in bigfoot 2015/08/30 2.1
% see https://tex.stackexchange.com/questions/471379/footnote-marks-missplaced-with-bigfoot/
\usepackage{xpatch}
\makeatletter
\patchcmd\FN@allmarks{266}{256}{}{\fail}
%% error
\renewcommand\FN@beforebreak{...}
\makeatother

\begin{document}
\Blindtext[2][1]\blindtext[1]\footnote{\Blindtext[2][1]}
\end{document}

This gives me an error

! Improper \prevdepth.
\FN@returnbest ...\maxdimen \fi \ifdim \prevdepth 
                                                  <\splitmaxdepth \hrule \@h...
l.20 \end{document}

It seams like bug in bigfoot, but I can't figure it out?

Answer 1

I believe that \FN@beforebreak should contain vertical mode material. More precisely, nothing that starts a paragraph.

\documentclass{article}
\usepackage{blindtext}
\usepackage{bigfoot}
\DeclareNewFootnote{default}

% fix bug in bigfoot 2015/08/30 2.1
% see https://tex.stackexchange.com/questions/471379/footnote-marks-missplaced-with-bigfoot/
\usepackage{xpatch}
\makeatletter
\patchcmd\FN@allmarks{266}{256}{}{\fail}
%% no error
\renewcommand\FN@beforebreak{\hbox{...}}
\makeatother

\begin{document}
\Blindtext[2][1]\blindtext[1]\footnote{\Blindtext[2][1]}
\end{document}

To get the ellipsis at the end of the line, you could try something like

\renewcommand\FN@beforebreak{%
  \vbox to 0pt{\vss\hbox to\hsize{\hss\rlap{\dots}}\vskip\baselineskip}%
}