表格与 makeindex 结合时垂直间距错误

Question

tabularx我在垂直空白出现在我不希望的环境中时遇到了一些麻烦。考虑以下 MWE：

\documentclass{article}
\usepackage{tabularx}

\makeindex % removing this line also removes the 

\newcommand{\loc}[1]{\index{#1@\emph{#1} (location)}\emph{#1}}

\begin{document}

\begin{tabular}{|l|}
  \hline
  foo \\
  \hline
  \loc{bar} \\
  \hline
  baz \\
  \hline
\end{tabular}

And now for something completely different:

\begin{tabularx}{\textwidth}{|X|}
  \hline
  foo \\
  \hline
  \loc{bar} \\
  \hline
  baz \\
  \hline
\end{tabularx}

\end{document}

两个表格的主体相同。由于某些原因，第二个表格中存在垂直间隙：

如果我注释掉该\makeindex命令，空格就会消失，但显然这不是我实际文档中的选项。空格从何而来？我该如何避免它？

Answer 1

tabularx与此无关；甚至

xxx\parbox[t]{5cm}{\loc{bar} blah}

也会出现同样的问题，即“酒吧”在“xxx”下面一行。

问题在于用“whatsit”启动 parbox。添加\leavevmode，这在其他情况下不会造成任何有害影响：

\newcommand{\loc}[1]{\leavevmode\index{#1@\emph{#1} (location)}\emph{#1}}

完整示例

\documentclass{article}
\usepackage{makeidx}
\usepackage{tabularx}

\makeindex % removing this line also removes the 

\newcommand{\loc}[1]{\leavevmode\index{#1@\emph{#1} (location)}\emph{#1}}

\begin{document}

xxx\parbox[t]{5cm}{\loc{bar} blah}

\begin{tabular}{|p{10cm}|}
  \hline
  foo \\
  \hline
  \loc{bar} \\
  \hline
  baz \\
  \hline
\end{tabular}

And now for something completely different:

\begin{tabularx}{\textwidth}{|X|}
  \hline
  foo \\
  \hline
  \loc{bar} \\
  \hline
  baz \\
  \hline
\end{tabularx}

\end{document}