witharrows package reverses text in RTL language?

Question

I do my homework in Latex, and I recently learned about the witharrows package which allows me to draw arrows between lines explaining what I did there. I find this very helpful for my homework assignments. However, there is a weird problem when I try to use the package. I do my homework in our native language, Hebrew, an RTL language. I use the polyglossia and fontspec packages to configure the language settings and fonts of the document.

When I tried to use the witharrows package with this simple example:

דוגמה לחישוב:
\begin{DispWithArrows*}
A &= (a + b)^2 \Arrow{נפתח את הסוגריים בביטוי} \\
&= a^2 + 2ab + b^2
\end{DispWithArrows*}

I got this output:

As you can see, the text next to the arrow is reversed. It looks like it's trying to write it in an LTR setting for some reason. After reading this question, I tried to use the option font=\selectlanguage{hebrew} like so:

\tikzset{
    WithArrows/arrow/.append style = {
        font = \selectlanguage{hebrew},
    }
}

However, it didn't work. I got the same output. Note that I did it in tikzset so it applies to all arrows, but doing it inside the arrow itself: \Arrow[tikz={font={\selectlanguage{hebrew}}}]{נפתח את הסוגריים בביטוי} doesn't work either.

I did some more experiments and I found something very weird: If I add another setting to the font such as changing the color:

\tikzset{
    WithArrows/arrow/.append style = {
        color=blue,
        font = \selectlanguage{hebrew},
    }
}

It suddenly works and renders correctly from right to left, and that's extremely weird. Another solution that I found to work is using \texthebrew:

דוגמה לחישוב:
\begin{DispWithArrows*}
A &= (a + b)^2 \Arrow{\texthebrew{נפתח את הסוגריים בביטוי}} \\
&= a^2 + 2ab + b^2
\end{DispWithArrows*}

which also renders correctly. The first solution is just weird and I'd like to know why adding the color option suddenly fixes it (of course I can use color=black so the color doesn't change but this feels like a dirty hack and not a real solution), and while the second solution makes sense, I don't want to always have to surround the text in my arrows with a \texthebrew command and I couldn't find a way to apply it globally.

Does anyone know how I can fix these issues and get Hebrew text to render correctly in arrows?

Full example code (Note I use the font Assistant):

% !TeX spellcheck = he_HE
\documentclass{article}

\usepackage{witharrows}

% Font and language settings
\usepackage[no-math]{fontspec}
\usepackage{polyglossia}

\newfontfamily\hebrewfont[
    Script=Hebrew,
    ItalicFont=*-Regular,
    ItalicFeatures={FakeSlant=0.3},
]{Assistant}

\setmainlanguage{hebrew}
\setotherlanguage{english}
\setsansfont{Assistant}
\setmonofont{Assistant}

\WithArrowsOptions{displaystyle}
\tikzset{
    WithArrows/arrow/.append style = {
        font = \selectlanguage{hebrew},
    }
}

\begin{document}
דוגמה לחישוב:
\begin{DispWithArrows*}
A &= (a + b)^2 \Arrow{נפתח את הסוגריים בביטוי} \\
&= a^2 + 2ab + b^2
\end{DispWithArrows*}
\end{document}

Answer 1

That problem is not specific to witharrows. It's a problem of the PGF/Tikz nodes (in conjunction with polyglossia and xelatex).

I think that the best solution is to put a command \tikzset{text=.} in the preamble of the document ("." will be the current color at the time of creation of the Tikz node).

\documentclass{article}

\usepackage{witharrows}

% Font and language settings
\usepackage[no-math]{fontspec}
\usepackage{polyglossia}

\newfontfamily\hebrewfont[
    Script=Hebrew,
    ItalicFont=*-Regular,
    ItalicFeatures={FakeSlant=0.3},
]{Assistant}

\setmainlanguage{hebrew}
\setotherlanguage{english}
\setsansfont{Assistant}
\setmonofont{Assistant}


\tikzset{text=.}  % "." is the current color

\WithArrowsOptions{displaystyle,tikz={font=}}

\begin{document}


דוגמה לחישוב:
\begin{DispWithArrows*}
A &= (a + b)^2 \Arrow{נפתח את הסוגריים בביטוי} \\
&= a^2 + 2ab + b^2
\end{DispWithArrows*}
\end{document}

I think that the origin of the problem is that PGF uses \hbox to construct the boxes containing the contents of its nodes (at least when text width is not used). That command \hbox, which is a primitive of TeX, is not ''color-safe'' (whereas the commands of constructions of boxes of LaTeX, such as \mbox are all ''color-safe''). With a box which is not ``color-safe'', the commands to pop the color from the stack are in fact after the box (inserted with a \aftergroup) and may have bad consequences.

By putting \tikzset{text=.} in the preamble, instructions to put color are inserted at each PGF node, and the protection added (to avoid color links) has probably an action to prevent also problems with RTL mode (I assume the command \hbox is not ''RTL-safe'').