Strange line break with varwidth and microtype

[Virgil121]

This is based on this question: https://tex.stackexchange.com/questions/749756/strange-line-break-in-tabularrays-latest-version

Some tables seem to be broken when compiling with the varwidth library and microtype, using tabularray's latest version: This code:

\documentclass{article}
\usepackage{tabularray}
\UseTblrLibrary{varwidth}
\usepackage{microtype}

\begin{document}

\begin{tblr}{
    hlines,
    vlines,
    colspec={c},
}
hello ($hello$)
\end{tblr}

\begin{tblr}{
    hlines,
    vlines,
    colspec={ccc},
}
& $g_0 > 0$ & $g_0 < 0$ \\
$q > 1$ & AAAAAAAAAAAAA & AAAAAAAAAAAAA \\
$0 < q < 1$ & AAAAAAAAAAAAA & AAAAAAAAAAAAA \\
\end{tblr}
\end{document}

Compiles to this, using lualatex (and an updated miktex distribution):

Aside from disabling microtype or varwidth, either using the previous version of tabularray or changing the measure specification to hbox or vstore fixes the issue. As mentioned by a user in the original question, adding \let\MT@varwidth@setup\relax also works as a workaround.

[lvjr]

Basically tabularray uses varwidth to measure cell widths and use the widths to create some \vboxes for cells.

I doubt it is a proper solution to \let\MT@varwidth@setup\relax. Please also report the issue to microtype developer.

[schlcht]

(microtype developer here) I don't think microtype is to blame. What I imagine happening is something like this:

tabularray uses varwidth to measure the cell; because of microtype's varwidth patch, protrusion will be applied, resulting in a narrower cell width than without protrusion;
tabularray then sets the cell with the measured width again, but in a context where protrusion is not enabled (for example in \hboxes, there's no protrusion); the text doesn't fit, so a line break will occur;
(and at some later point, somehow a \vbox must be involved again, because in the actually typeset table, protrusion is indeed applied).

What I have a hard time understanding is why this happens with lualatex only, but works as expected with pdflatex.

The suggestion to disable microtype's varwidth patch was only meant as a workaround, it's of course not the proper solution. But this would have to fixed in tabularray I believe.

[lvjr]

Thanks for the reply. Maybe later I need to produce an example with minimal tabularray code, hoping to locate the actual problem with luatex and find a proper solution.

[schlcht]

Ah yes, sorry, I wanted to add one but forgot, here's a minimal tabularray (preamble from the OP):

\begin{tblr}{l}
  H )
\end{tblr}

It only needs a space to allow for a line break and a char that protrudes on the right hand side.

[lvjr]

@schlcht I made the following example without tabularray. It seems \raggedright affects microtype (with lualatex only). Do you know the reason?

\documentclass{article}
\usepackage{varwidth}
\usepackage{microtype}
\begin{document}

\newcommand\mytext{H )}
\newlength\mylen
\settowidth\mylen{\begin{varwidth}{\textwidth}\mytext\end{varwidth}}
\setlength\parindent{0pt}

Default:
\fbox{\begin{minipage}{\mylen}\mytext\end{minipage}}
\fbox{\vbox{\hsize=\mylen\mytext}}

Raggedright:
\fbox{\begin{minipage}{\mylen}\raggedright\mytext\end{minipage}}
\fbox{\vbox{\hsize=\mylen\raggedright\mytext}}

\end{document}

[ponte-vecchio]

This is based on this question: https://tex.stackexchange.com/questions/749756/strange-line-break-in-tabularrays-latest-version

Some tables seem to be broken when compiling with the varwidth library and microtype, using tabularray's latest version: This code:

\documentclass{article}
\usepackage{tabularray}
\UseTblrLibrary{varwidth}
\usepackage{microtype}

\begin{document}

\begin{tblr}{
    hlines,
    vlines,
    colspec={c},
}
hello ($hello$)
\end{tblr}

\begin{tblr}{
    hlines,
    vlines,
    colspec={ccc},
}
& $g_0 > 0$ & $g_0 < 0$ \\
$q > 1$ & AAAAAAAAAAAAA & AAAAAAAAAAAAA \\
$0 < q < 1$ & AAAAAAAAAAAAA & AAAAAAAAAAAAA \\
\end{tblr}
\end{document}

Compiles to this, using lualatex (and an updated miktex distribution):

Aside from disabling microtype or varwidth, either using the previous version of tabularray or changing the measure specification to hbox or vstore fixes the issue. As mentioned by a user in the original question, adding \let\MT@varwidth@setup\relax also works as a workaround.

Interestingly this behaviour disappears when tabularray also loads the tikz module:

\documentclass{article}
\usepackage{tabularray}
- \UseTblrLibrary{varwidth}
+ \UseTblrLibrary{varwidth, tikz}
\usepackage{microtype}

\begin{document}

\begin{tblr}{
    hlines,
    vlines,
    colspec={c},
}
hello ($hello$)
\end{tblr}

\begin{tblr}{
    hlines,
    vlines,
    colspec={ccc},
}
& $g_0 > 0$ & $g_0 < 0$ \\
$q > 1$ & AAAAAAAAAAAAA & AAAAAAAAAAAAA \\
$0 < q < 1$ & AAAAAAAAAAAAA & AAAAAAAAAAAAA \\
\end{tblr}
\end{document}

[peaR-red]

After further investigation, we conclude that the issue does not reside with tabularray; rather, it is the result of a flawed assumption in the microtype sources. We have thus closed this issue.

For further information (and a more robust patch), see #66.