Issue with align* environment in TRT pagedir (lualatex)

[seloumi]

Brief outline of the bug

I have this example with align* environment in TRT pagedir (lualatex engine), The result is aligned to the right even though the environment is placed in left to right context (with \bodydir TLT \pardir TLT \textdir TLT)

https://tex.stackexchange.com/q/621820/54817

Minimal example showing the bug

\RequirePackage{latexbug}       
\documentclass{article}
\usepackage[showframe]{geometry}
\usepackage{amsmath}

\pagedir TRT\bodydir TRT \pardir TRT \textdir TRT
\begin{document}

\begin{align*}
f(x)&=1+\dfrac{1}{x+2}\\
    &=1+k(x+2) 
\end{align*}

{%
\bodydir TLT \pardir TLT \textdir TLT
\begin{align*}
f(x)&=1+\dfrac{1}{x+2}\\
    &=1+k(x+2) 
\end{align*}
 }

 \newpage

\pagedir TLT \bodydir TLT \pardir TLT \textdir TLT

\begin{align*}
f(x)&=1+\dfrac{1}{x+2}\\
    &=1+k(x+2) 
\end{align*}

\end{document}

Log file (required) and possibly PDF file

image1.log image1.pdf

[muzimuzhi]

Some casual tests show

• equation*, align, gather, gather*, multline, and multline* all work well
• align* always aligned to the right , as reported
• equation puts the equation number to the left, not right

[FrankMittelbach]

In his talk at TUG online conference 2021 Vafa Khaligi mentions this problem with basic $$ ... $$ math (which is what equation is using underneath as a bug in the luatex engine (that he reported long time ago), see near the end of the talk:

I guess that accounts for your third bullet point, but obviously not for the initially reported issue.

[seloumi]

@FrankMittelbach Thanks for the guidance, the confusing thing is why the issue appears only with align* environment and It does not appear in similar environments as mentioned by @muzimuzhi !