LMTX incompatbility: don't use fixed strings for \meaning

[leahneukirchen]

Brief outline of the bug

Some TikZ libraries (e.g. quotes) use keys which include the string given by \meaning, e.g.

\pgfkeyssetvalue{/handlers/first char syntax/the character "}{\tikz@quote@parser}%

However, in LMTX, \meaning" expands to

the character U+0022 'quotation mark'

and they don't intent to change that.

In my experiments, it seems sufficient to instead write

\pgfkeyssetvalue{/handlers/first char syntax/\meaning"}{\tikz@quote@parser}%

which uses whatever string the current TeX implementation uses.

This is related to #990.

Minimal working example (MWE)

(this is ConTeXt)

\usemodule[tikz]
\usetikzlibrary[quotes,angles]

\starttext

\meaning"

\starttikzpicture
  \node ["abc" draw] {node};
\stoptikzpicture

\stoptext

[hmenke]

I think we need \expandafter\meaning\string" here, just in case " is active at that point.

[leahneukirchen]

Also in

pgf/tex/generic/pgf/frontendlayer/tikz/libraries/tikzlibraryanimations.code.tex

Line 597 in 0280303

\expandafter\let\csname tikz@anim@test@the character 0\endcsname\pgfutil@empty

Thanks for the quick fixing!