Baffling interaction of Asymptote and Transparency

Question

Context: I'm trying to use Asymptote to draw explanatory arrows and comments atop a semitransparent lstlisting environment. In the course of doing so I've encountered a bizarre interaction between Asymptote and the package transparency that I've reduced to a minimal working example. I'm using LuaLaTeX but can reproduce in pdfLaTeX too.

For reasons not understood to me, an Asymptote asy environment will sometimes, though not always, almost completely disable transparency inside and outside and both fore and aft of the \begin{asy} ... \end{asy} block. Here's the MCVE example.

\documentclass{article}
\usepackage{asymptote}
\usepackage{transparent}

\begin{document}
\section{Before Asymptote}
{\transparent{0.1}Ghost X}
\section{In Asymptote}
\begin{asy}
if(false){                 //TOGGLE THIS
    label("x");
}else{
    draw((0cm,0)--(1cm,0));
}
\end{asy}
\section{After Asymptote}
{\transparent{0.1}Ghost X}
\end{document}

There is an if statement with a toggle inside, currently false. When it is set to false, I get ghostly text before and after the asy drawing:

However, if I set the toggle to true, I don't:

Note how both the text before and after is no longer transparent.

Variants I've tested:

• The contents of the label are irrelevant.
• Wrapping asy in a figure or minipage does not contain the disease.
• Nor does adding \pdfpageattr{/Group <</S /Transparency /I true /CS /DeviceRGB>>} in the preamble or any other incantations as suggested here.
• Both TeXStudio's embedded viewer and KDE's Okular show this, so it's not a peculiarity of the PDF viewer.
• I've also just tried texpreamble("\usepackage{transparent}"); and label("{\transparent{0.1}x}"); and got the same results for both toggles, and $x$ was not transparent.
• When you set the toggle to true and do both label("x"); and draw((0cm,0)--(1cm,0), opacity(0.1)); in the if-side of the branch, you get the same result (transparency disabled fore and aft), but the drawn line is transparent.

Why do only some Asymptote figures trigger spooky-action-at-a-distance and blow up everything else like this? And how can I work around it?

Answer 1

I still don't know why it's happening, but here's a workaround for the MCVE:

1. Use asypictureB package instead of asymptote. (Correspondingly, change all asy environments to asypicture, both \begin and \end, and make sure to add the mandatory argument after \begin{asypicture}.
2. Add the line settings.outformat="pdf"; to the beginning of your asypictures. Otherwise it will get compiled to eps, which can cause peculiar spacing.

Here's the code:

\documentclass{article}
\usepackage{asypictureB}
\usepackage{transparent}

\begin{document}
\section{Before Asymptote}
{\transparent{0.1}Ghost X}
\section{In Asymptote}
\begin{asypicture}{name=foo}
settings.outformat = "pdf";
if(true){                 //TOGGLE THIS
    label("x");
}else{
    draw((0cm,0)--(1cm,0));
}
\end{asypicture}
\section{After Asymptote}
{\transparent{0.1}Ghost X}
\end{document}

and the result:

The only clue I have as to the reason is that the asymptote package has tighter interaction with the LaTeX code than the asypictureB package. This allows the asymptote package to automatically copy the fonts and packages used in the main document, but apparently it also allows for issues like this.