Furigana is misaligned in simple centered tabular cell

Question

Furigana seems misaligned in a simple tabular environment. Ruby hacks in MWE are from this answer.

\documentclass{article}
\usepackage{xeCJK}
\setCJKmainfont{ipaexm.ttf}
\usepackage{ruby}
\renewcommand\rubysep{.05ex}
\renewcommand\rubysize{.4}
\let\oldruby\ruby
\def\ruby#1#2{\oldruby{#1}{#2}\futurelet\next\addCJKglue}
\def\addCJKglue{\ifx\next\ruby \CJKglue \fi}
\usepackage{array}
\begin{document}
\ruby{一}{いち}\ruby{日}{にち}%Correct
\begin{tabular}{|c|}
\hline
\ruby{一}{いち}\ruby{日}{にち}\%Furigana misaligned
\hline
\end{tabular}
\begin{tabular}{|m{10mm}|}
\hline
\ruby{一}{いち}\ruby{日}{にち}\%Correct
\hline
\end{tabular}
\end{document}

I would like to understand why the most natural approach with \begin{tabular}{|c|} fails, and how to fix it (as I don't want to manually set up the column width).

Answer 1

The ruby macro is basing its height on \baselineskip which is 0 in a c column, but you can set it using the array package > declaration.

\documentclass{article}
\usepackage{xeCJK}
\setCJKmainfont{ipaexm.ttf}
\usepackage{ruby}
\renewcommand\rubysep{.05ex}
\renewcommand\rubysize{.4}
\let\oldruby\ruby
\def\ruby#1#2{\oldruby{#1}{#2}\futurelet\next\addCJKglue}
\def\addCJKglue{\ifx\next\ruby \CJKglue \fi}
\usepackage{array}
\begin{document}
\ruby{一}{いち}\ruby{日}{にち}%Correct
\begin{tabular}{|>{\baselineskip\normalbaselineskip}c|}
\hline
\ruby{一}{いち}\ruby{日}{にち}\%Furigana misaligned
\hline
\end{tabular}
\begin{tabular}{|m{10mm}|}
\hline
\ruby{一}{いち}\ruby{日}{にち}\%Correct
\hline
\end{tabular}
\end{document}