Why does \everydisplay conflict with gather and multline

Question

When gather* is used together with \everydisplay an error is produced. Is there a possibility to make these work together?

Minimal working example:

\documentclass{ctexart}
\usepackage{amsmath,color}
\everydisplay{\color{blue}}
\begin{document}
\begin{gather*}
1+\cos x
\end{gather*}
\end{document}

Possibly related: Modifying \everydisplay causes the align* environment to stop working. — Hendrik Vogt, Mar 16 '11 at 08:55
Please consider accepting some answers of your other questions by clicking on the tickmark below their vote count. This shows which answer helped you most, and it assigns reputation points to the author of the answer (and to you!). — Martin Scharrer, Apr 15 '11 at 13:51

score 3 · Answer 1 · answered Mar 16 '11 at 11:45

Instead of \everydisplay, \everymath could be used. This applies to gather as well. To avoid coloring of inline math, you could check if you are within gather or align similar to amsmath's own checks.

Complete example:

\documentclass{article}
\usepackage{amsmath,color}
\newcommand*{\eqcolor}{\color{blue}}
\makeatletter
\everymath{%
  \ifingather@ \eqcolor%
    \else \ifinalign@ \eqcolor
      \fi
  \fi
}
\makeatother
\begin{document}
\begin{gather*}
1+\cos x
\end{gather*}
\begin{align*}
1+\cos x
\end{align*}
\centering $1 + \cos x$
\end{document}

enter image description here

As you can see, inline math is not colored. Regarding other displayed math: instead of equation or \[ ... \] you could use gather or gather*, respectively. This could be done in the preamble, without changes to equation environments in the text, such as

\let\equation\gather
\let\endequation\endgather

score 0 · Answer 2 · answered Mar 16 '11 at 12:00

0

If you just say \everydisplay{\color{blue}}, then the previous content of it gets erased and you will have these kind of problems. The right way to use \everydisplay is:

\everydisplay\expandafter{\the\everydisplay \color{blue}}

Then no problem should happen.

answered Mar 16 '11 at 12:00

IRAN

2,338

2

With gather and this definition the same error occurs (! Improper \halign inside $$'s.) – Stefan Kottwitz Mar 16 '11 at 12:05
1

Also doesn't work with align – xotix Jul 14 '21 at 13:50

Why does \everydisplay conflict with gather and multline

2 Answers2

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