No output with radialshading in RTL context (lualatex)

[seloumi]

Brief outline of the bug

In RTL context (lualatex engine) radialshading do not produce result (example was taken from tikz manual)

Minimal working example (MWE)

% lualatex
\documentclass{article}
\usepackage{tikz}
\usepackage[bidi=basic,nil]{babel}
\babelprovide[import,main]{arabic}
            
\fboxsep=0pt            
\parindent=0pt
            
\begin{document}

% TRT

\fbox{%
\pgfdeclareradialshading{sphere}{\pgfpoint{0.5cm}{0.5cm}}%
{rgb(0cm)=(0.9,0,0);
rgb(0.7cm)=(0.7,0,0);
rgb(1cm)=(0.5,0,0);
rgb(1.05cm)=(1,1,1)}
\pgfuseshading{sphere}
}

\selectlanguage{nil}

% TLT

\fbox{%
\pgfdeclareradialshading{sphere}{\pgfpoint{0.5cm}{0.5cm}}%
{rgb(0cm)=(0.9,0,0);
rgb(0.7cm)=(0.7,0,0);
rgb(1cm)=(0.5,0,0);
rgb(1.05cm)=(1,1,1)}
\pgfuseshading{sphere}
}

\end{document}

[hmenke]

Is this a regression or does this also happen with older versions of PGF (and older versions of LaTeX)?

[seloumi]

I noticed the issue mid 2019, before that I don't know .

[muzimuzhi]

bidi option is added from babel v3.14, 2017/10/03 (see doc of babel v3.49, sec. 1.23 and relevant lines in changes-old.txt).

Quick tests show that both texlive 2019 and 2018 on Overleaf.com give the same, wrong output.

[seloumi]

Remarque: if we add \bodydir TLT the result appears, but the position where to place \bodydir TLT differs if we use \pgfdeclareradialshading with optional argument or not.

% lualatex
% Notice position of \bodydir TLT with those two cases
\documentclass{article}
\usepackage{tikz}
\usepackage[bidi=basic,nil]{babel}
\babelprovide[import,main]{arabic}
            
\fboxsep=0pt            
\parindent=0pt
           
\begin{document}

% TRT

\makeatletter
\pgfutil@colorlet{tikz@ball}{red}
\pgfdeclareradialshading[tikz@ball]{ball}{\pgfqpoint{-10bp}{10bp}}{%
 color(0bp)=(tikz@ball!15!white);
 color(9bp)=(tikz@ball!75!white);
 color(18bp)=(tikz@ball!70!black);
 color(25bp)=(tikz@ball!50!black);
 color(50bp)=(black)}%
\makeatother 

{\bodydir TLT
\pgfuseshading{ball} 
}

{\bodydir TLT
\pgfdeclareradialshading{sphere}{\pgfpoint{-10bp}{10bp}}{%
color(0bp)=(red!15!white);
 color(9bp)=(red!75!white);
 color(18bp)=(red!70!black);
 color(25bp)=(red!50!black);
 color(50bp)=(black)}
}

\pgfuseshading{sphere} 

\end{document}

[seloumi]

This work fine

% lualatex
\documentclass{article}
\usepackage{tikz}
\usepackage[bidi=basic,nil]{babel}
\babelprovide[import,main]{arabic}
                     
\makeatletter
\def\pgfsys@radialshading#1#2#3{%
  {%
    \pgf@parsefunc{#3}%
    \setbox\pgfutil@tempboxa=\hbox dir TLT to2\pgf@max{\vbox to2\pgf@max{\vfil\pgfsys@invoke{/Sh sh}}\hfil}%
    \pgf@process{#2}%
    \pgf@xa=\pgf@x%
    \pgf@ya=\pgf@y%
    \pgf@process{\pgfpoint{\pgf@max}{\pgf@max}}%
    \advance\pgf@xa by \pgf@x%
    \advance\pgf@ya by \pgf@y%
    \pgf@sys@bp@correct{\pgf@x}%
    \pgf@sys@bp@correct{\pgf@y}%
    \pgf@sys@bp@correct{\pgf@xa}%
    \pgf@sys@bp@correct{\pgf@ya}%
    \immediate\saveboxresource resources {%
      /Shading << /Sh << /ShadingType 3
      /ColorSpace \pgf@shading@device\space
      /Domain [\pgf@pdfparseddomain]
      /Coords [\pgf@sys@tonumber{\pgf@xa} \pgf@sys@tonumber{\pgf@ya} \pgf@doma\space \pgf@sys@tonumber{\pgf@x} \pgf@sys@tonumber{\pgf@y} \pgf@domb]
      /Function \pgf@pdfparsedfunction
      /Extend [true false] >> >>}\pgfutil@tempboxa% <<
    \xdef\pgfutil@tempa{\hbox{\noexpand\useboxresource\the\lastsavedboxresourceindex}}%
  }%
  \global\expandafter\let\csname @pgfshading#1!\endcsname=\pgfutil@tempa
}%
\makeatother
           
\begin{document}

% TRT

\makeatletter
\pgfutil@colorlet{tikz@ball}{red}
\pgfdeclareradialshading[tikz@ball]{ball}{\pgfqpoint{-10bp}{10bp}}{%
 color(0bp)=(tikz@ball!15!white);
 color(9bp)=(tikz@ball!75!white);
 color(18bp)=(tikz@ball!70!black);
 color(25bp)=(tikz@ball!50!black);
 color(50bp)=(black)}%
\makeatother 

\pgfuseshading{ball} 

\pgfdeclareradialshading{sphere}{\pgfpoint{-10bp}{10bp}}{%
color(0bp)=(red!15!white);
 color(9bp)=(red!75!white);
 color(18bp)=(red!70!black);
 color(25bp)=(red!50!black);
 color(50bp)=(black)}

\pgfuseshading{sphere} 

\end{document}

[hmenke]

Thank you very much for finding a fix!