% \iffalse meta-comment
% SPDX-FileCopyrightText: Copyright (c) 2021-2026 Yegor Bugayenko
% SPDX-License-Identifier: MIT
% \fi

% \CheckSum{0}
%
% \CharacterTable
%  {Upper-case    \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
%   Lower-case    \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
%   Digits        \0\1\2\3\4\5\6\7\8\9
%   Exclamation   \!     Double quote  \"     Hash (number) \#
%   Dollar        \$     Percent       \%     Ampersand     \&
%   Acute accent  \'     Left paren    \(     Right paren   \)
%   Asterisk      \*     Plus          \+     Comma         \,
%   Minus         \-     Point         \.     Solidus       \/
%   Colon         \:     Semicolon     \;     Less than     \<
%   Equals        \=     Greater than  \>     Question mark \?
%   Commercial at \@     Left bracket  \[     Backslash     \\
%   Right bracket \]     Circumflex    \^     Underscore    \_
%   Grave accent  \`     Left brace    \{     Vertical bar  \|
%   Right brace   \}     Tilde         \~}

% \GetFileInfo{ffcode.dtx}
% \DoNotIndex{\endgroup,\begingroup,\let,\else,\fi,\newcommand,\newenvironment}

% \iffalse
%<*driver>
\ProvidesFile{ffcode.dtx}
%</driver>
%<package>\NeedsTeXFormat{LaTeX2e}
%<package>\ProvidesPackage{ffcode}
%<*package>
[2026-07-10 0.13.0 Fixed Font Code]
%</package>
%<*driver>
\documentclass{ltxdoc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{microtype}
\AddToHook{env/verbatim/begin}{\microtypesetup{protrusion=false}}
\usepackage{href-ul}
\usepackage{ffcode}
\usepackage{amsmath}
\usepackage{multicol}
\usepackage{xcolor}
\usepackage[dtx,runs=2]{docshots}
\PageIndex
\EnableCrossrefs
\CodelineIndex
\RecordChanges
\begin{document}
	\DocInput{ffcode.dtx}
	\PrintChanges
	\PrintIndex
\end{document}
%</driver>
% \fi

% \title{|ffcode|: \LaTeX{} Package \\ for Fixed-Font Code Blocks\thanks{The sources are in GitHub at \href{https://github.com/yegor256/ffcode}{yegor256/ffcode}}}
% \author{Yegor Bugayenko \\ \texttt{yegor256@gmail.com}}
% \date{\filedate, \fileversion}
%
% \maketitle
%
% \section{Introduction}
%
% This package typesets source code within articles
% and ensures a tidy, consistent appearance. Following installation from
% CTAN, the typical usage proceeds as follows (note the |\ff| command
% and the |ffcode| environment):
% \begin{docshot}
% \documentclass{article}
% \usepackage{ffcode}
% \pagestyle{empty}
% \begin{document}
% The function |fibo()| is recursive:
% \begin{ffcode}
% int fibo(int n) {
%   if (n < 2) {
%     return n; (*@ \label{ln:ret} @*)
%   }
%   return fibo(n-1)+fibo(n-2);
% }
% \end{ffcode}
% Line no.~\ref{ln:ret} returns \ff{n}
% and terminates it.
% \end{document}
% \end{docshot}

% \DescribeMacro{\ffinput}
% An |\ffinput| command is also provided, which reads content from a file
% and inserts it into the document, formatted in precisely the manner that
% would result from the |ffcode| environment. The |ffsave|
% environment may be employed beforehand; it behaves as the |ffcode|
% environment, save that the content is written to a file rather than
% printed, whence it may subsequently be retrieved by the |\ffinput| command.

% \section{Package Options}

% \DescribeMacro{samepage}
% The |samepage| package option prevents page breaks inside |ffcode| blocks.

% \DescribeMacro{noframes}
% The |noframes| package option omits the light gray frames around |\ff|
% texts.

% \DescribeMacro{nobars}
% The |nobars| package option omits the vertical gray bar at the left side
% of each snippet.

% \DescribeMacro{nonumbers}
% The |nonumbers| package option omits the line numbers.

% \DescribeMacro{nocn}
% By default, line numbering is continuous: numbers commence at the
% first snippet and increment until the end of the document. The |nocn|
% package option (an abbreviation for ``no continuous numbering'') causes
% the numbering to restart from one in each snippet.

% \DescribeMacro{tmpfile}
% Every |ffcode| block is captured verbatim to a scratch file before it
% is typeset (this is what makes |\ffcolumnbreak| possible). The name of
% that file defaults to |\jobname.ffcode| and may be changed with the
% |tmpfile| package option, for instance
% |\usepackage[tmpfile=build/ffcode.tmp]{ffcode}|.

% \DescribeMacro{bold}
% The |\ff| fragments may be rendered in a heavier weight than the default, which proves convenient for certain document classes
% (note the use of the \href{https://ctan.org/pkg/lmodern}{lmodern} package: without it, boldface fails to operate, as explained \href{https://tex.stackexchange.com/a/215489/1449}{here}):
% \docshotOptions{firstline=4,lastline=10}
% \begin{docshot}
% \documentclass{article}
% \usepackage[paperwidth=3in]{geometry}
% \pagestyle{empty}
% \usepackage{lmodern}
% \usepackage[bold,noframes]{ffcode}
% \begin{document}
% Sometimes it's necessary to make
% code pieces look bolder, like
% the |fibo()| function in this text.
% \end{document}
% \end{docshot}

% \DescribeMacro{sf}
% The font family of |\ff| fragments may be altered to |\sffamily|:
% \docshotOptions{firstline=4,lastline=10}
% \begin{docshot}
% \documentclass{article}
% \usepackage[paperwidth=3in]{geometry}
% \pagestyle{empty}
% \usepackage[sf,bold,noframes]{ffcode}
% \begin{document}
% Sometimes a less strictly fixed-width,
% more elegant look may be preferred,
% like the \emph{|fibo()|} here.
% \end{document}
% \end{docshot}

% \section{Typesetting}

% The package handles low-height text correctly, for instance a solitary
% dot: \ff{.}

% A pair of vertical bars decorates a \TeX{} command within a snippet.
% A single vertical bar may be produced by means of
% ``\verb+|\char`\\vert|+''.

% The |\ff| command behaves differently in math mode---it adds no
% grey frames:
% \docshotOptions{firstline=6,lastline=8}
% \begin{docshot}
% \documentclass{article}
% \usepackage{ffcode}
% \usepackage{mathtools}
% \pagestyle{empty}
% \begin{document}
% \begin{equation*}
% x = \int_{|home|}^{\ff{N}} f(x).
% \end{equation*}
% \end{document}
% \end{docshot}

% Lines within the |ffcode| environment may be highlighted,
% and any further configuration parameters from
% the |listings| package may likewise be supplied:
% \docshotOptions{firstline=6,lastline=13}
% \begin{docshot}
% \documentclass{article}
% \usepackage[paperwidth=3in]{geometry}
% \usepackage{ffcode}
% \pagestyle{empty}
% \begin{document}
% \begin{ffcode}[backgroundcolor=\color{gray!20}]
% while (true) {
%   (*@\textcolor{red}{print("Hi!")}@*)
%   print("Enter your name:")
%   scan(x)
%   print("Your name | " + x)
% }
% \end{ffcode}
% \end{document}
% \end{docshot}

% \DescribeMacro{\ffcolumnbreak}
% A snippet may be split into two or more side-by-side columns by
% placing |\ffcolumnbreak| on a line of its own, wrapped in an escape so
% that |listings| does not print it. Line numbering runs continuously
% across the columns, which is handy for a listing too tall for the
% page. Each further |\ffcolumnbreak| adds one more column. By default
% the columns share the line equally; a column whose longest line does
% not fit in its equal share is widened just enough to hold it, and the
% extra space is taken from the columns that have room to spare:
% \docshotOptions{firstline=6,lastline=14}
% \begin{docshot}
% \documentclass{article}
% \usepackage[paperwidth=4in]{geometry}
% \usepackage{ffcode}
% \pagestyle{empty}
% \begin{document}
% \begin{ffcode}
% int fibo(int n) {
%   if (n < 2) {
% (*@ \ffcolumnbreak @*)
%     return n;
%   }
%   return fibo(n-1)+fibo(n-2);
% }
% \end{ffcode}
% \end{document}
% \end{docshot}

% By means of the optional argument of |ffcode|,
% any other options from the |listings| package may be conveyed to the
% snippet.

% The |\lstset| command of the |listings| package may also be employed
% to establish defaults for the |ffcode| environment.
% In contrast to the optional argument, which applies solely to a single
% snippet, |\lstset| acts globally: every subsequent code listing in the
% document inherits the new settings, including any further |ffcode|
% blocks thereafter.
% To confine the change to a single |ffcode| block, the call should be
% wrapped within a |\begingroup|\ldots|\endgroup| pair:
% \docshotOptions{firstline=6,lastline=12}
% \begin{docshot}
% \documentclass{article}
% \usepackage[paperwidth=3in]{geometry}
% \usepackage{ffcode}
% \pagestyle{empty}
% \begin{document}
% \begingroup
% \lstset{backgroundcolor=\color{yellow!30}}
% \begin{ffcode}
% print("Hi!")
% \end{ffcode}
% \endgroup
% \end{document}
% \end{docshot}

% A snippet may be rendered in ``condensed'' mode, with reduced spacing
% between letters, by supplying |columns=fixed| together with a narrower
% |basewidth| from the |listings| package:
% \docshotOptions{firstline=6,lastline=12}
% \begin{docshot}
% \documentclass{article}
% \usepackage[paperwidth=3in]{geometry}
% \usepackage{ffcode}
% \pagestyle{empty}
% \begin{document}
% \begin{ffcode}[columns=fixed,basewidth=0.4em]
% while (true) {
%   print("Enter your name:")
%   scan(x)
%   print("Hello, " + x)
% }
% \end{ffcode}
% \end{document}
% \end{docshot}

% \StopEventually{}

% \section{Implementation}
% \changes{v0.1.0}{2021/06/10}{Initial version}

% First, we parse package options with the help of
% \href{https://ctan.org/pkg/pgfopts}{pgfopts} package:
% \changes{v0.2.0}{2021/06/13}{Package options \texttt{nonumbers} and \texttt{noframes} added.}
% \changes{v0.3.0}{2021/09/07}{Package option \texttt{nocn} added.}
% \changes{v0.4.0}{2022/01/09}{Package option \texttt{nobars} added.}
% \changes{v0.6.0}{2022/11/16}{We use \texttt{pgfopts} instead of \texttt{xkeyval}.}
% \changes{v0.6.0}{2022/11/16}{Package option \texttt{novert} added, to disable the redefinition of the vertical bar.}
% \changes{v0.7.0}{2022/11/28}{Package option \texttt{bold} added, to make all \texttt{\char`\\ff} pieces look bolder than usual.}
% \changes{v0.7.0}{2022/11/28}{Package option \texttt{sf} added, to print all \texttt{\char`\\ff} pieces with \texttt{\char`\\sffamily}.}
% \changes{v0.9.2}{2024/02/04}{All lengths and sizes are in "em" instead of "pt".}
% \changes{v0.10.0}{2025/01/02}{Package option \texttt{samepage} added, to prevent each \texttt{ffcode} block from breaking across pages.}
% \changes{v0.11.1}{2026/05/01}{Reserve \texttt{xleftmargin} for line numbers so they sit inside the column instead of protruding into the page margin.}
% \changes{v0.13.0}{2026/07/10}{Package option \texttt{tmpfile} added, to configure the scratch file used to capture \texttt{ffcode} bodies.}
%    \begin{macrocode}
\RequirePackage{pgfopts}
\pgfkeys{
  /ff/.cd,
  bold/.store in=\ff@bold,
  sf/.store in=\ff@sf,
  samepage/.store in=\ff@samepage,
  noframes/.store in=\ff@noframes,
  nonumbers/.store in=\ff@nonumbers,
  nobars/.store in=\ff@nobars,
  novert/.store in=\ff@novert,
  nocn/.store in=\ff@nocn,
  tmpfile/.store in=\ff@file,
  tmpfile/.default=\jobname.ffcode,
  tmpfile,
}
\ProcessPgfPackageOptions{/ff}
%    \end{macrocode}

% Then, we include the \href{https://ctan.org/pkg/xcolor}{xcolor} package:
%    \begin{macrocode}
\RequirePackage{xcolor}
%    \end{macrocode}

% Then, we configure the \href{https://ctan.org/pkg/listings}{listings} package.
% The defaults are applied here, at package load, so that a user may override
% them globally with \texttt{\char`\\lstset} after \texttt{\char`\\usepackage\{ffcode\}}:
% \changes{v0.9.0}{2024/01/09}{The \texttt{minted} package is replaced by the \texttt{listings} package.}
% \changes{v0.10.2}{2025/07/06}{We started to use \texttt{keepspaces} in order to guarantee correct visual rendering of multi-spaced content.}
% \changes{v0.12.0}{2026/05/05}{Static \texttt{\char`\\lstset} defaults moved from the per-environment hook to the preamble, so that user-supplied \texttt{\char`\\lstset} calls are no longer overwritten on every \texttt{ffcode} usage.}
% \changes{v0.12.2}{2026/07/10}{Restore the original \texttt{\char`\\@vspace} inside listings, so \texttt{acmart} no longer warns about the vertical spacing that \texttt{listings} emits around every block.}
%    \begin{macrocode}
\RequirePackage{listings}
\makeatletter
% See \href{https://tex.stackexchange.com/questions/706858}{the explanation}:
\lst@AddToHook{Init}{\setlength{\lineskip}{0pt}}
% \texttt{acmart} warns about the \texttt{\char`\\@vspace}
% that \texttt{listings} emits around displays;
% restore its saved originals during typesetting:
\ifdefined\@vspace@orig
  \lst@AddToHook{DisplayStyle}{%
    \let\@vspace\@vspace@orig
    \ifdefined\@vspacer@orig\let\@vspacer\@vspacer@orig\fi}
\fi
\lstset{breaklines}
\lstset{escapeinside={(*@}{@*)}}
\lstset{basicstyle={\ttfamily}}
\lstset{columns=fullflexible}
\lstset{keepspaces=true}
\ifdefined\ff@nonumbers\else
  \lstset{numbers=left,numbersep=.8em,
    numberstyle={\tiny\sffamily\color{gray}},
    xleftmargin=2.5em}
\fi
\ifdefined\ff@nobars\else
  \lstset{frame=leftline,framerule=.05em,rulecolor={\color{gray}}}
\fi
\ifdefined\ff@nocn\else
  \lstset{firstnumber=last}
\fi
\makeatother
%    \end{macrocode}

% \begin{macro}{\ffcolumnbreak}
% Then, we define the |\ffcolumnbreak| marker and the machinery that
% splits an |ffcode| block into side-by-side columns. Because |listings|
% typesets a single line-by-line stream, a block is first captured
% verbatim to a temporary file; that file is then scanned for
% |\ffcolumnbreak| markers, which cut it into segments. Each segment is
% measured before it is printed: it is typeset once into a discarded box,
% so that |listings| records the width of its longest line in
% |\lst@maxwidth|, and that width (plus the gutter reserved for line
% numbers) becomes the natural width of the column. The available width
% is then shared by a water-filling pass in |\ff@computelevel|: it seeks
% the common level such that every column narrower than the level takes
% the level, while a column wider than the level keeps its natural width,
% and the two together fill |\linewidth|. Thus equal-sized columns split
% the line evenly, and only a column too wide for its share claims more,
% at the expense of the columns that have room to spare. When even the
% natural widths overflow |\linewidth|, the widths are scaled down in
% proportion to fit. A block without any marker is rendered as one
% listing, exactly as before:
% \changes{v0.13.0}{2026/07/10}{The \texttt{\char`\\ffcolumnbreak} marker added, to split an \texttt{ffcode} block into two or more side-by-side columns.}
% \changes{v0.13.0}{2026/07/10}{Columns split by \texttt{\char`\\ffcolumnbreak} are now sized by the longest line in each, instead of splitting \texttt{\char`\\linewidth} evenly.}
% \changes{v0.13.0}{2026/07/10}{Restore the original \texttt{\char`\\@vspace} inside every \texttt{\char`\\ffcolumnbreak} column, so \texttt{acmart} no longer warns about the top-alignment strut in each column box.}
% \changes{v0.15.0}{2026/07/10}{Columns split by \texttt{\char`\\ffcolumnbreak} now share the line equally by default, widening only a column that does not fit its equal share.}
%    \begin{macrocode}
\RequirePackage{fancyvrb}
\makeatletter
\newcommand\ffcolumnbreak{}
\edef\ff@cbmarker{\string\ffcolumnbreak}
\newread\ff@read
\newcount\ff@nlines
\newcount\ff@nbreaks
\newcount\ff@ncols
\newcount\ff@prev
\newdimen\ff@colwd
\newdimen\ff@sepwd
\newdimen\ff@total
\newdimen\ff@avail
\newdimen\ff@natwd
\newdimen\ff@gutter
\newdimen\ff@level
\newdimen\ff@fixedsum
\newcount\ff@fixedcnt
\newcount\ff@denom
\newcount\ff@prevcnt
\newsavebox\ff@mbox
\let\ff@grab\relax
\lst@AddToHook{Init}{\ff@grab}
\def\ff@colsep{\hspace{0.4em}{\color{gray}\vrule width 0.3pt}%
  \hspace{0.4em}}
\def\ff@allother{%
  \count@=\z@
  \loop\catcode\count@=12 \ifnum\count@<255 \advance\count@\@ne\repeat
  \catcode`\ =10 \endlinechar=-1 }
\def\ff@readloop{%
  \read\ff@read to\ff@line
  \ifeof\ff@read
    \let\ff@next\relax
  \else
    \global\advance\ff@nlines\@ne
    \edef\ff@call{\noexpand\in@{\ff@cbmarker}{\ff@line}}\ff@call
    \ifin@
      \global\advance\ff@nbreaks\@ne
      \xdef\ff@segs{\unexpanded\expandafter{\ff@segs}\noexpand\ff@seg
        {\the\numexpr\ff@prev+\@ne\relax}{\the\numexpr\ff@nlines-\@ne\relax}}%
      \global\ff@prev=\ff@nlines
    \fi
    \let\ff@next\ff@readloop
  \fi
  \ff@next}
\def\ff@scan{%
  \global\ff@nlines=\z@ \global\ff@nbreaks=\z@
  \global\ff@prev=\z@ \gdef\ff@segs{}%
  \openin\ff@read=\ff@file\relax
  \begingroup\ff@allother\ff@readloop\endgroup
  \closein\ff@read
  \ifnum\ff@nbreaks>\z@
    \xdef\ff@segs{\unexpanded\expandafter{\ff@segs}\noexpand\ff@seg
      {\the\numexpr\ff@prev+\@ne\relax}{\the\ff@nlines}}%
  \fi}
\def\ff@measure#1#2{%
  \setbox\ff@mbox=\vbox{\hfuzz\maxdimen
    \lstinputlisting[numbers=none,breaklines=false,%
      firstline=#1,lastline=#2]{\ff@file}}%
  \ff@natwd=\dimexpr\lst@maxwidth+\ff@gutter\relax
  \global\advance\ff@total\ff@natwd
  \xdef\ff@cols{\unexpanded\expandafter{\ff@cols}%
    \noexpand\ff@col{#1}{#2}{\the\ff@natwd}}}
\def\ff@onepass{%
  \global\ff@fixedsum=\z@ \global\ff@fixedcnt=\z@
  \begingroup
    \def\ff@col##1##2##3{%
      \ifdim##3>\ff@level
        \global\advance\ff@fixedsum##3\relax
        \global\advance\ff@fixedcnt\@ne
      \fi}%
    \ff@cols
  \endgroup
  \ifnum\ff@fixedcnt<\ff@ncols
    \ff@denom=\numexpr\ff@ncols-\ff@fixedcnt\relax
    \ff@level=\dimexpr(\ff@avail-\ff@fixedsum)/\ff@denom\relax
  \fi}
\def\ff@computelevel{%
  \ff@level=\dimexpr\ff@avail/\ff@ncols\relax
  \ff@prevcnt=\z@
  \loop
    \ff@onepass
  \ifnum\ff@fixedcnt>\ff@prevcnt
    \ff@prevcnt=\ff@fixedcnt
  \repeat}
\def\ff@col#1#2#3{%
  \ifnum\ff@prev=\z@\else\ff@colsep\fi
  \ifdim\ff@total>\ff@avail
    \ff@colwd=\dimexpr#3*\number\ff@avail/\number\ff@total\relax
  \else
    \ifdim#3>\ff@level\ff@colwd=#3\relax\else\ff@colwd=\ff@level\fi
  \fi
  \parbox[t]{\ff@colwd}{%
    \ifdefined\@vspace@orig
      \let\@vspace\@vspace@orig
      \ifdefined\@vspacer@orig\let\@vspacer\@vspacer@orig\fi
    \fi
    \vspace{0pt}%
    \lstinputlisting[firstline=#1,lastline=#2]{\ff@file}}%
  \ff@prev=\@ne}
\def\ff@render{%
  \ff@scan
  \begingroup
  \expandafter\lstset\expandafter{\ff@opts}%
  \ifnum\ff@nbreaks=\z@
    \lstinputlisting{\ff@file}%
  \else
    \ff@ncols=\ff@nbreaks \advance\ff@ncols\@ne
    \ff@sepwd=0.8em \advance\ff@sepwd0.3pt
    \ff@avail=\dimexpr\linewidth-\ff@sepwd*\ff@ncols+\ff@sepwd\relax
    \global\ff@total=\z@ \gdef\ff@cols{}%
    \edef\ff@savednum{\the\c@lstnumber}%
    \def\ff@grab{\global\ff@gutter\@totalleftmargin}%
    \let\ff@seg\ff@measure \ff@segs
    \let\ff@grab\relax
    \global\c@lstnumber=\ff@savednum\relax
    \ff@computelevel
    \par\addvspace\topsep
    \noindent\hbox{\ff@prev=\z@ \ff@cols}%
    \par\addvspace\topsep
  \fi
  \endgroup}
\makeatother
%    \end{macrocode}
% \end{macro}

% \begin{macro}{ffcode}
% Then, we (re)define the |ffcode| environment. Its body is written
% verbatim to the temporary file and handed to |\ff@render|. The
% optional |[...]| argument is parsed the same way |fancyvrb| does it,
% by turning the end-of-line active before looking ahead, so that the
% newline after |\begin{ffcode}| is not swallowed when no options are
% supplied:
%    \begin{macrocode}
\makeatletter
\newenvironment{ffcode}
  {\catcode`\^^M=\active
   \@ifnextchar[\ff@begin{\ff@begin[]}}
  {\end{VerbatimOut}%
   \ff@render
   \ifdefined\ff@samepage\endminipage\fi}
\def\ff@begin[#1]{%
  \catcode`\^^M=5\relax
  \def\ff@opts{#1}%
  \ifdefined\ff@samepage\noindent\minipage{\linewidth}\fi
  \VerbatimEnvironment\begin{VerbatimOut}{\ff@file}}
\makeatother
%    \end{macrocode}
% \end{macro}

% \begin{macro}{ffinput}
% Then, we define the \texttt{\char`\\ffinput} command:
% \changes{v0.10.0}{2024/12/29}{The \texttt{\char`\\ffinput} command added.}
% \changes{v0.12.0}{2026/05/26}{Stopped \texttt{\char`\\ffinput} options from leaking into later listings.}
%    \begin{macrocode}
\makeatletter
\newcommand\ffinput[2][]{%
  \ifdefined\ff@samepage\noindent\minipage{\linewidth}\fi%
  \lstinputlisting[#1]{#2}%
  \ifdefined\ff@samepage\endminipage\fi%
}
\makeatother
%    \end{macrocode}
% \end{macro}

% \begin{macro}{ffsave}
% Then, we define the \texttt{ffsave} environment. Before opening the
% output stream, its missing parent directory is created, so that
% \texttt{\char`\\begin\char`\{ffsave\char`\}[foo/bar.txt]}
% works even when \texttt{foo/} is absent (this needs shell escape enabled):
% \changes{v0.11.0}{2025/07/06}{The \texttt{ffsave} environment added.}
% \changes{v0.12.1}{2026/07/10}{The \texttt{ffsave} environment now creates the missing parent directory of its target file.}
%    \begin{macrocode}
\RequirePackage{fancyvrb}
\RequirePackage{shellesc}
\makeatletter
\ExplSyntaxOn
\cs_new_protected:cpn { ff@mkdir } #1
  {
    \str_set:Nn \l_tmpa_str {#1}
    \sys_if_platform_windows:TF
      {
        \str_replace_all:Nnn \l_tmpa_str { / } { \c_backslash_str }
        \ShellEscape { if~not~exist~"\l_tmpa_str"~mkdir~"\l_tmpa_str" }
      }
      { \ShellEscape { mkdir~-p~"\l_tmpa_str" } }
  }
\ExplSyntaxOff
\newenvironment{ffsave}[1][ffsave.txt]
  {\filename@parse{#1}%
   \ifx\filename@area\@empty\else
     \expandafter\ff@mkdir\expandafter{\filename@area}%
   \fi
   \VerbatimEnvironment\begin{VerbatimOut}{#1}}
  {\end{VerbatimOut}}
\makeatother
%    \end{macrocode}
% \end{macro}

% \begin{macro}{\ff@print}
% Then, we define a supplementary macro |\ff@print|:
% \changes{v0.5.1}{2022/10/30}{Now, the command \texttt{ff} ignores italic and bold and always prints \texttt{\char`\\texttt} as it should be.}
%    \begin{macrocode}
\makeatletter
\newcommand\ff@print[1]{%
  \textnormal{%
    \ifdefined\ff@sf\sffamily\else\ttfamily\fi%
    \ifdefined\ff@bold\fontseries{b}\selectfont\fi%
    #1%
  }%
}
\makeatother
%    \end{macrocode}
% \end{macro}

% \begin{macro}{\ff@rule}
% Then, we define a supplementary command |\ff@rule|:
%    \begin{macrocode}
\makeatletter\newcommand\ff@rule
  {\vrule height 0.6em depth 0.1em width 0em}
\makeatother
%    \end{macrocode}
% \end{macro}

% \begin{macro}{\ff@box}
% Then, we use \href{https://ctan.org/pkg/tcolorbox}{tcolorbox} to define the |\ff@box|
% command for a gray box around a verbatim text block:
%    \begin{macrocode}
\makeatletter
\ifdefined\ff@noframes\else
  \RequirePackage{tcolorbox}
  \newtcbox\ff@box{nobeforeafter,colframe=gray!80!white,
    colback=gray!5!white,boxrule=0.01em,arc=0.1em,
    boxsep=0.12em,left=0.05em,right=0.05em,top=0.02em,bottom=0.02em,
    tcbox raise base}
\fi
\makeatother
%    \end{macrocode}
% \end{macro}

% \begin{macro}{\ff@x}
% Then, we define the internal |\ff@x| command for printing a piece of fixed-width-font text:
%    \begin{macrocode}
\makeatletter
\NewDocumentCommand\ff@x{v}{\ff{#1}}
\makeatother
%    \end{macrocode}
% \end{macro}

% \begin{macro}{\ff}
% \changes{v0.8.0}{2022/12/01}{The \texttt{\char`\\ff} command is now a normal command, not verbatim.}
% Then, we define |\ff| macro:
%    \begin{macrocode}
\makeatletter
\newcommand\ff[1]{%
  \ifdefined\ff@noframes%
    \ff@rule\ff@print{#1}%
  \else%
    \relax\ifmmode%
      \ff@rule\ff@print{#1}%
    \else%
      \ff@box{\ff@rule\ff@print{#1}}%
    \fi%
  \fi%
}
\makeatother
%    \end{macrocode}
% \end{macro}

% \begin{macro}{novert}
% Finally, we let vertical bars work similarly to |\ff|, as suggested
% \href{https://tex.stackexchange.com/a/665105/1449}{here}
% and \href{https://tex.stackexchange.com/a/665303/1449}{here}
% (unless the |novert| package option is used):
%    \begin{macrocode}
\makeatletter\ifdefined\ff@novert\else
  \catcode`\|\active
  \AtBeginDocument{\catcode`\|\active\protected\def|{\ff@x|}}
  \catcode`\| 12 %
\fi\makeatother
%    \end{macrocode}
% \end{macro}

%    \begin{macrocode}
\endinput
%    \end{macrocode}

% \Finale

%\clearpage
%
%\PrintChanges
%\clearpage
%\PrintIndex