make fixme notes in displaymath

Question

I am using the fixme package. I observed the use of \fxerror* or \fxnote* inside displaymath yields errors.

I can write

\documentclass[draft]{article}
\usepackage{fixme}
\fxsetup{theme=colorsig}

\begin{document}
\fxerror*{$\forall y \exists x \varphi(x,y)$}
{
\[
\forall y \exists x \varphi(x,z)
\]
}
\end{document}

with the expected result. But I sometimes would like to do something like

\documentclass[draft]{article}
\usepackage{fixme}
\fxsetup{theme=colorsig}

\begin{document}
\[
\forall y \exists x \varphi(x,\fxerror*{y}{z})
\]
\end{document}

which doesn't work. Is it a (non)feature of the fixme package?

Second point, I would like it to work with the align environnement as well as with all the other math environnement provided in amsmath.

Answer 1

fixme uses \marginpar and this prevents using the commands in some places; a possible workaround is to substitute \marginpar for \marginnote from the marginnote package:

\documentclass[draft]{article}
\usepackage{marginnote}
\usepackage{fixme}
\fxsetup{theme=colorsig}

\makeatletter
\renewcommand*\FXLayoutMargin[3]{%
  \marginnote[%
  \raggedleft\@fxuseface{margin}\ignorespaces#3 \fxnotename{#1}: #2]{%
    \raggedright\@fxuseface{margin}\ignorespaces#3 \fxnotename{#1}: #2}}
\renewcommand*\FXLayoutMarginClue[3]{%
  \marginnote[%
  \raggedleft\@fxuseface{margin}\ignorespaces#3 \fxnotename{#1}!]{%
    \raggedright\@fxuseface{margin}\ignorespaces#3 \fxnotename{#1}!}}
\makeatother

\begin{document}
\fxerror*{$\forall y \exists x \varphi(x,y)$}
{
\[
\forall y \exists x \varphi(x,z)
\]
}

\[
\forall y \exists x \varphi(x,\fxerror*{y}{z})
\]
\end{document}