Issues with vertical spacing and \addcontentsline

Question

The code \vskip\baselineskip\addvspace{0.5\baselineskip} produces a vertical space equal to \baselineskip, as it should. However, when I add \addcontentsline in the middle, I get a bigger space:

\vskip\baselineskip%
\addcontentsline{toc}{section}{}%
\addvspace{0.5\baselineskip}

How can I fix this?

Full MWE:

\documentclass{article}
\usepackage{hyperref}
\setlength{\parskip}{0mm}
\begin{document}
\begin{minipage}{0.5cm}
    A
\vskip\baselineskip
\addvspace{0.5\baselineskip}
b


\end{minipage}%
\begin{minipage}{0.5cm}
    A
\vskip\baselineskip%
\addcontentsline{toc}{section}{}%
\addvspace{0.5\baselineskip}
b


\end{minipage}%
\begin{minipage}{0.5cm}
    A
\vspace{\baselineskip}
b


\end{minipage}
\end{document}

Does this answer your question? \addtocontents in TeXLive 2022 vs 2021 and previous releases — Marijn, Mar 17 '23 at 13:32
@Marijn I've tried using the \addtocontents{toc}{\protect\contentsline{section}{SomethingA}{SomethingB}{}}%, but nothing changed — Michael Fraiman, Mar 17 '23 at 13:37
I retracted my close vote, it is a different issue. I think what is happening is that in the leftmost minipage the \addvspace is actually ignored (commenting it out doesn't change the output, effectively turning it into the rightmost minipage) but in the middle one \addcontentsline introduces all kinds of grouping and phantomsections etc. that allows \addvspace to take effect. — Marijn, Mar 17 '23 at 13:43

score 1 · Answer 1 · answered Mar 25 '23 at 18:59

\addvspace probes \lastskip. But the \addcontentsline adds a special which causes TeX to report it as zero.

from

\documentclass{article}
\usepackage{hyperref}
\setlength{\parskip}{0mm}
\begin{document}
\begin{minipage}[t]{2cm}
    A
\vskip\baselineskip
\the\lastskip
b


\end{minipage}%
\begin{minipage}[t]{2cm}
    A
\vskip\baselineskip%
\addcontentsline{toc}{section}{}%
\the\lastskip
b


\end{minipage}%
\begin{minipage}[t]{2cm}
    A
\the\lastskip
b


\end{minipage}
\end{document}

I do not know off-hand apart from hacking \addcontentsline how to modify this state of affairs.

Issues with vertical spacing and \addcontentsline

1 Answers1