\newline 有哪些限制？#tabularx, #\newline 换句话说，为什么此示例中的第一个 \newline 不生效？

Question

\documentclass{article}
\usepackage{tabularx}
\begin{document}
\newcolumntype{L}[1]{>{\hsize=#1\hsize\raggedright\small\arraybackslash}X}%
\begin{tabularx}{\textwidth}{ c | L{1.3} | L{1.2} L{1.2} | L{.65} L{.65} }
    Mechanism\newline\ State
  & Initialization\newline\ feh
  & xAV
  & yAV
  & Hard reset (jumper)
  & Hard reset (swap) \\
  \begin{minipage}[t]{20pt}
    Mechanism\\ State
  \end{minipage}
  & Initialization
  & xAV
  & yAV
  & Hard reset (jumper)
  & Hard reset (swap)
\end{tabularx}
\end{document}

输出如下所示：

版本：

Running `LaTeX' on `z1' with ``xelatex  -file-line-error -interaction=nonstopmode "\input" z1.tex''
This is XeTeX, Version 3.14159265-2.6-0.99998 (TeX Live 2017/MacPorts 2017_1) (preloaded format=xelatex)
  restricted \write18 enabled.
entering extended mode
LaTeX2e <2017-04-15>
...

Answer 1

\newline仅适用于段落模式单元格，不适用于标准l,c,r。但对于这些单元格，您可以使用makecell包，它允许换行和通用格式。默认情况下，\makecell或\thead命令的内容在水平和垂直方向上居中：

\documentclass{article}
\usepackage{tabularx, makecell}
\newcolumntype{L}[1]{>{\hsize=#1\hsize\raggedright\small\arraybackslash}X}%
\renewcommand{\theadfont}{\small\bfseries}

\begin{document}

\begin{tabularx}{\textwidth}{ c | L{1.3} | L{1.2} L{1.2} | L{.65} L{.65} }
    \thead[tc]{Mechanism\\ State}
  & Initialization\break\ feh
  & xAV
  & yAV
  & Hard reset (jumper)
  & Hard reset (swap) \\
  \makecell{Mechanism\\ State}
  & Initialization
  & xAV
  & yAV
  & Hard reset (jumper)
  & Hard reset (swap)
\end{tabularx}

\end{document}