siunitx-formatting.tex

\documentclass{article}

\usepackage{siunitx}
\usepackage{booktabs}
\usepackage[table]{xcolor}

\usepackage{etoolbox}

% Individual \itshape or \bfseries work without this.
% Combinations of both need the robustified version
\robustify\itshape
\robustify\bfseries

\begin{document}

% Required so that siunitx can detect \bfseries, \itshape, etc
\sisetup{detect-all = true}

\begin{table}[t]
    \centering
    \caption{\texttt{siunitx S} columns require a special treatment to format them correctly.}

    \begin{tabular}{SS}
        \toprule
        % Non-number headings require braces:
        {Heading A} & {Heading B} \\
        % Fails with an error: Heading A & Heading B \\
        \midrule
        1.00 & 2.00 \\
        % This is the only way to correctly color and format cells for siunitx:
        {\cellcolor[gray]{0.8}} \bfseries 10.0 & \bfseries\itshape 20.0\\
        100.000 & 200.000 \\
        % color 
        \color{red} 1000.00 & \color{green} \bfseries 2000.00\\
        \multicolumn{2}{c}{(Cells aligned at decimal dot)}\\
        \midrule
        10.0 & 20.0 \\
        % \cellcolor does not work without enclosing braces: Wrong alignment
        \cellcolor[gray]{0.8} \textbf 10.0 & \bfseries \itshape 20.0 \\
        \multicolumn{2}{c}{(Second 10.0 is wrongly aligned,}\\
        \multicolumn{2}{c}{formatting is only applied to first digit.)}\\
        \midrule
        10.0 & 20.0 \\
        % \textbf and \textit do not work: Wrong alignment
        {\cellcolor[gray]{0.8}} \textbf{10.0} & \textit{20.0}\\
        \multicolumn{2}{c}{(Second 10.0 and 20.0 are wrongly aligned)}\\
        \bottomrule
    \end{tabular}
\end{table}

\begin{table}[t]
    \centering
    \caption{Formatting also works with regular \texttt{c} columns}

    \begin{tabular}{cc}
        \toprule
        % Non-number headings require braces:
        {Heading A} & {Heading B} \\
        % Fails with an error: Heading A & Heading B \\
        \midrule
        1.00 & 2.00 \\
        % This is the only way to correctly color and format cells for siunitx:
        {\cellcolor[gray]{0.8}} \bfseries 10.0 & \bfseries \itshape 20.0\\
        100.000 & 200.000 \\
        \color{red} 1000.00 & \color{green} \bfseries 2000.00\\
        \bottomrule
    \end{tabular}
\end{table}

\end{document}

I don't think there would be any benefit. Apart from "italic correction" (done by \textit but not needed in the context of tables) there shouldn't be any difference (see e.g. here). As my example shows, the combination of bold and italic also works in both cases.

OK so it seems like \itshape and \bfseries play nicely together in the default case, and with siunitx they need robusity preamble which needs to be documented.

I needed to add \sisetup{detect-all = true}

We can document this also.

The only thing left is the automatic choice of the S column type. As far as I can see, the siunitx parameter influences nothing else apart from the column format.

Yes it seems the same braces formatting that is compatible with siunitx is also capable of rendering without it, so this should be the default in the CSS converter.

I agree 👍

Pull requests 40422 and 40721 are now actively submitted. feel free to review them and to encourage core devs to go through them to get them approved.

Great!

#40721 is likely spelling mistake. Which one do you really mean?

40731

Thanks! I subscribed to the pull requests. Is there anything I can do to speed up the review process?