% \iffalse meta-comment
%
% Copyright (c) 2025 by Michael Ummels <michael@ummels.de>
%
% This work may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either version 1.3c
% of this license or (at your option) any later version.
% The latest version of this license is in
%   https://www.latex-project.org/lppl.txt
% and version 1.3c or later is part of all distributions of LaTeX
% version 2008 or later.
%
% This work has the LPPL maintenance status `maintained'.
%
% The Current Maintainer of this work is Michael Ummels.
%
% This work consists of the files figureversions.dtx, figureversions.ins and
% the derived files figureversions.sty and figureversions.pdf.
%
%<*driver>
\documentclass[a4paper,onlydoc]{l3doc}

\usepackage[nottoc]{tocbibind}
\usepackage{figureversions}
\usepackage[toc,enum,bib]{tabfigures}
\usepackage[scale=0.95]{cantarell}
\usepackage[narrow]{inconsolata}
\usepackage{microtype}

\hypersetup{
  bookmarksnumbered,
  colorlinks=false,
  pdfborder={0 0 0}
}

% Hack in order to get quotes in verbatim mode right
\DeclareEncodingSubset{TS1}{zi4}{1}

\renewcommand{\sfdefault}{cantarell-OsF}
\renewcommand{\familydefault}{\sfdefault}
\renewcommand{\MacroLongFont}{\fontfamily{zi4}\scriptsize}
\renewcommand{\baselinestretch}{1.1}
\makeatletter
\renewcommand{\meta@font@select}{\sffamily\itshape}
\makeatother

\EnableCrossrefs
\CodelineIndex
\RecordChanges

\begin{document}
  \DocInput{figureversions.dtx}
\end{document}
%</driver>
%<*package>
\ProvidesExplPackage {figureversions} {2025-04-05} {1.0} {Figure versions}
%</package>
% \fi
%
% \changes{v1.0}{2025-04-05}{Initial version}
%
% \GetFileInfo{figureversions.sty}
%
% \title{How Do You Like Your Figures?}
% \author{Michael Ummels}
% \date{\fileversion\quad\filedate}
% \maketitle
%
% \begin{abstract}
% The \pkg{figureversions} package defines several commands to switch between
% figure versions, which determine the appearance of numbers in your
% document. The package works with many font packages available on CTAN
% as well as with most OpenType fonts under \XeTeX\ and \LuaTeX\ in combination
% with \pkg{fontspec}.
% \end{abstract}
%
% \begin{documentation}
%
% \tableofcontents
%
% \section{Introduction}
%
% While basic fonts only have \emph{lining} figures (aka numbers), which extend
% from the base line to the height of capital letters, advanced fonts may come
% with several other \emph{figure versions}, the most prominent being
% \emph{old-style} or \emph{text} figures which look more like lowercase letters
% and therefore fit nicely into a block of lower/mixed-case text: compare
% \liningfigures{1234567890} to \textfigures{1234567890}.%
% \marginpar{%
%   \raggedleft\LARGE
%   \begin{tabular}{r}
%     \liningfigures{1234567890} \\
%     \textfigures{1234567890}
%   \end{tabular}
% }
%
% Since \LaTeX's font selection system \cite{nfss} has no support
% for figure versions, font package authors have resorted to define one
% \LaTeX\ font family for each figure version, so you can switch between
% different figure versions by invoking the low-level \cs{fontfamily} command,
% followed by a call to \cs{selectfont}. This is not only cumbersome, but also
% ties the font family to the figure version, so you cannot change them
% independently.
%
% The \pkg{figureversions} package not only makes it easier to switch figure
% versions, but it also lets you change the two dimensions of a figure version
% separately: \emph{figure style} and \emph{figure alignment}. While figure
% style is solely about the the appearance of figures, figure alignment
% is concerned with the width of figures. In particular, \emph{tabular}
% figures all have the same width, so multiple-digit numbers nicely line up
% when stacked on top of each other.%
% \marginpar{%
%   \raggedleft\LARGE
%   \begin{tabular}{rr}
%     12345 & \tbfigures{12345} \\
%     67890 & \tbfigures{67890}
%   \end{tabular}
% }
%
% \subsection{History}
%
% Most commands defined by this package first appeared in the
% \pkg{MinionPro} package\footnote{\url{https://ctan.org/pkg/minionpro}} by
% Achim Blumensath et al., a package that made the professional
% Minion\texttrademark\ Pro font family by Adobe accessible to all
% \LaTeX\ users (i.e.\ not only when using \XeTeX\ or \LuaTeX).
% Since the concept of figure versions is not specific to Minion Pro, the
% corresponding functionality was then incorporated by Andreas Bühmann into a
% separate package called \pkg{fontaxes}.\kern-0.15em%
% \footnote{\url{https://ctan.org/pkg/fontaxes}} The \pkg{fontaxes}
% package does not only support different figure versions, but has also split
% the \emph{shape} of a font into two dimensions (`axes'), which can be
% changed independently of each other. For instance, \cs{itshape} operates on
% the first dimension, while \cs{scshape} operates on the second. With
% \LaTeX\ release 2020-02-02, that functionality was integrated into the
% kernel \cite{ltnews31}, so -- with the exception of the functionality
% dealing with figure versions -- the \pkg{fontaxes} package has been made
% redundant. Hence, its current maintainer decided to undertake a modern
% rewrite and strip off all functionality that has been integrated into the
% kernel, thereby adding support for
% \pkg{fontspec}\footnote{\url{https://ctan.org/pkg/fontspec}} under
% \XeTeX\ and \LuaTeX.
%
% \section{Usage}
%
% You can load this package by adding
% \begin{quote}
%   |\usepackage{figureversions}|
% \end{quote}
% to the preamble of your document.
%
% \subsection{High-level document commands}
%
% \begin{function}{\lnfigures,\txfigures,\liningfigures,\textfigures}
% \begin{syntax}
%    \cs{lnfigures}
%    \cs{txfigures}
%    \cs{liningfigures}\marg{text}
%    \cs{textfigures}\marg{text}
% \end{syntax}
% By default, the \pkg{figureversions} package knows two figure styles, `text'
% and `lining', which can be accessed using the commands \cs{txfigures} and
% \cs{lnfigures} respectively. Similar to commands like \cs{itshape},
% these commands are \emph{declarations} and remain in effect until the end of
% the current group or environment. If you only want to change the figure
% style for a short amount of text, you can use the corresponding \emph{text
% font commands} \cs{liningfigures} and \cs{textfigures}, which take as
% argument the text to which the figure style should apply.
% \end{function}
%
% \begin{function}{\prfigures,\tbfigures,\proportionalfigures,\tabularfigures}
% \begin{syntax}
%    \cs{prfigures}
%    \cs{tbfigures}
%    \cs{proportionalfigures}\marg{text}
%    \cs{tabularfigures}\marg{text}
% \end{syntax}
% For changing the figure alignment, use the commands \cs{prfigures} and
% \cs{tbfigures}: while \cs{prfigures} changes to proportional figures, which
% vary in width, \cs{tbfigures} changes to tabular or \emph{monospaced} figures.
% As for \cs{linfigures} and \cs{txfigures}, the selected figure
% alignment remains in effect until the end of the current group or environment;
% the corresponding text font commands are \cs{proportionalfigures} and
% \cs{tabularfigures}.
% \end{function}
%
% \begin{function}{\boldmath,\unboldmath,\tabularmath,\proportionalmath}
% \begin{syntax}
%    \cs{boldmath}
%    \cs{unboldmath}
%    \cs{tabularmath}
%    \cs{proportionalmath}
% \end{syntax}
% By default, \LaTeX\ provides two \emph{math versions}, `normal' and `bold',
% as well as commands \cs{boldmath} and \cs{unboldmath} for switching between
% them. The \pkg{figureversions} packages redefines these commands to only
% change the math font's weight and provides commands \cs{tabularmath} and
% \cs{proportionalmath} to switch between tabular and proportional figures
% in math mode.\footnote{Note that these commands have to be executed outside
% of math mode.} This functionality assumes the presence of additional math
% versions `tabular' and `boldtabular'; the package will copy the setups of math
% versions `normal' and `bold' if you do not provide your own declarations.
% \end{function}
%
% \begin{function}{\figureversion}
% \begin{syntax}
%   \cs{figureversion}\marg{comma-separated list}
% \end{syntax}
% The \cs{figureversion} command can be used to change the figure version by a
% single command. It takes as argument a comma-separated list of one or more
% of the following options:\footnote{More options can be added by package
% authors; see Section~\ref{sect:code-interface}.}
% \begin{quote}
% \begin{tabular}{@{}ll}
% |text|, |osf| & for text figures,\\
% |lining|, |lf| & for lining figures,\\
% |tabular|, |tab| & for tabular figures (also in math mode),\\
% |proportional|, |prop| & for proportional figures (also in math mode).
% \end{tabular}
% \end{quote}
% \end{function}
%
% \subsection{Low-level document commands}
%
% The low-level commands described in this section are mostly relevant for
% package authors. They are meant to be be combined with other low-level font
% selection commands like \cs{fontshape} and \cs{fontseries} and a subsequent
% call to \cs{selectfont}.
% Finally, since they rely on the classical \LaTeXe\ font selection scheme --
% with the exception of \cs{mathweight}  and \cs{mathfigurealignment} -- they
% would normally not work with \pkg{fontspec}.
%
% \begin{function}{\fontfigurestyle}
% \begin{syntax}
%   \cs{fontfigurestyle}\marg{figure style}
% \end{syntax}
% By default, the \pkg{figureversions} package knows two figure styles: `text'
% and `lining', but package authors can define additional figure styles; see
% Section~\ref{sect:code-interface}.
% \end{function}
%
% \begin{function}{\fontfigurealignment}
% \begin{syntax}
%   \cs{fontfigurealignment}\marg{figure alignment}
% \end{syntax}
% Using this command, you can choose either `proportional' or `tabular' figures.
% \end{function}
%
% \begin{function}{\fontbasefamily}
% \begin{syntax}
%   \cs{fontbasefamily}\marg{family name}
% \end{syntax}
% Recall that figure versions are implemented on top of the \LaTeXe\ font
% selection scheme by amending the family name. For instance,
% |\fontfamily{cantarell-TLF}| selects \emph{Cantarell} with tabular lining
% figures.
% The \cs{fontbasefamily} command thus allows you to select the
% font family independently of the figure version. Hence,
% |\fontbasefamily{cantarell}| switches to Cantarell, but does not change the
% current figure style or alignment.
% \end{function}
%
% \begin{function}{\mathweight}
% \begin{syntax}
%   \cs{mathweight}\marg{font weight}
% \end{syntax}
% The package knows two different math weights `normal' and `bold', which can
% be accessed by this command. Note that -- like \cs{mathversion} -- this
% command does \emph{not} work in math mode and takes effect immediately,
% i.e.\ for all following invocations of math mode.
% \end{function}
%
% \begin{function}{\mathfigurealignment}
% \begin{syntax}
%   \cs{mathfigurealignment}\marg{figure alignment}
% \end{syntax}
% To change the math figure alignment, use this command. As for
% \cs{fontfigurealignment}, valid arguments are `proportional` and `tabular`.
% Like \cs{mathweight}, this command does not work  in math mode and takes
% effect immediately.
% \end{function}
%
% \subsection{Code-level interface}\label{sect:code-interface}
%
% Like other packages implemented in \LaTeX3, this package defines several
% commands at \emph{code level}, i.e.\ with \cs{ExplSyntaxOn}, which can be
% used to extend the functionality of this package.
%
% \begin{function}{\figureversions_new_figurestyle:nnn,\figureversions_new_figurestyle:Vnn}
% \begin{syntax}
%   \cs{figureversions_new_figurestyle:nnn} \marg{name} \marg{proportional suffixes} \marg{tabular suffixes}
% \end{syntax}
% Defines a new figure style named \meta{name} with corresponding font family
% suffixes (given as comma-separated lists, maybe empty) for proportional and
% tabular figure alignment. For instance, the existing figure style `text'
% is defined by
% \begin{quote}
% |\figureversions_new_figurestyle:nnn {text} {OsF} {TOsF}|
% \end{quote}
% \end{function}
%
% \begin{function}{\figureversions_new_figureversion:nn}
% \begin{syntax}
%   \cs{figureversions_new_figureversion:nn} \marg{option} \marg{code}
% \end{syntax}
% Defines a new option for the \cs{figureversion} command: Expands to
% \meta{code} when \cs{figureversion} is called with \meta{option} among
% its arguments.
% \end{function}
%
% \section{Compatibility}
%
% \subsection{Font support}
%
% Within the \LaTeXe\ font selection scheme, the package supports the two most
% common naming schemes for font families:
% \begin{enumerate}
%  \item \meta{family}|-|\meta{suffix} where the suffix is e.g. |OsF| for
%    proportional text figures or |TLF| for tabular lining figures.
%  \item \meta{family}\meta{style} where the family is given by a
%    three-letter lowercase identifier and and \emph{style} is either
%    |j| for text figures or |x| for lining figures.\footnote{Note that
%    this scheme does not support different figure alignments.}
% \end{enumerate}
% Almost all of the many font packages available on CTAN adhere to one of these
% conventions, so \pkg{figureversions} works with all of them.
%
% Even more fonts are supported with \pkg{fontspec}: Since the
% \pkg{figureversions} package simply maps commands like \cs{tbfigures} to the
% corresponding OpenType feature, the package works with any OpenType font that
% implements one or more of these features.
%
% \subsection{Interplay with other packages}
%
% Since this package defines the \cs{tbfigures} command to switch to tabular
% figures, this package plays well and -- in some sense -- enables the
% \pkg{tabfigures} package\footnote{https://ctan.org/pkg/tabfigures}, which
% patches several \LaTeX\ commands and environments to use tabular figures. If
% you are a document author who uses a font with proportional figures by
% default, the \pkg{tabfigures} package is warmly recommended (also used in
% this document for e.g.\ the table of contents).
%
% As mentioned in the introduction, this package replaces the \pkg{fontaxes}
% package, which -- as of version~1.1 -- is just a wrapper around
% this package, adding some internal commands that
% have historically been used by package authors to define new figure styles.
% If you are the author of a package that depends on \pkg{fontaxes}, please
% consider updating you package to depend on this package instead, using the
% commands described in Section~\ref{sect:code-interface} to define additional
% figure styles if necessary.
%
% \end{documentation}
%
% \begin{implementation}
% \AddToHook{sffamily}{\fontfigurealignment{tabular}}
%
% \section{Implementation}
%
%    \begin{macrocode}
%<*package>
%<@@=figureversions>
%    \end{macrocode}
%
% \subsection{Variables and Constants}
%
% First, some constants.
%    \begin{macrocode}
\str_const:Nn \c_@@_text_str {text}
\str_const:Nn \c_@@_lining_str {lining}
\str_const:Nn \c_@@_proportional_str {proportional}
\str_const:Nn \c_@@_tabular_str {tabular}
\str_const:Nn \c_@@_normal_str {normal}
\str_const:Nn \c_@@_bold_str {bold}
\str_const:Nn \c_@@_lf_str {LF}
\str_const:Nn \c_@@_osf_str {OsF}
\str_const:Nn \c_@@_tlf_str {TLF}
\str_const:Nn \c_@@_tosf_str {TOsF}
%    \end{macrocode}
% This global boolean is set to true when \pkg{fontspec} is loaded.
%    \begin{macrocode}
\bool_new:N \g_@@_fontspec_bool
%    \end{macrocode}
% The following string variables will hold the current value of the font base
% family, the font figure style, and the figure alignment, respectively. We
% initialize them with default values, although these will almost surely be
% overwritten once a figure style selection command is executed.
%    \begin{macrocode}
\str_new:N \l_@@_fontbasefamily_str
\str_new:N \l_@@_fontfigurestyle_str
\str_new:N \l_@@_fontfigurealignment_str
\str_set:Nn \l_@@_fontbasefamily_str {cmr}
\str_set_eq:NN \l_@@_fontfigurestyle_str \c_@@_lining_str
\str_set_eq:NN \l_@@_fontfigurealignment_str \c_@@_proportional_str
%    \end{macrocode}
% The defined figure styles are held in two maps, one each for the two
% supported figure alignments `proportional' and `tabular'. Those
% maps take as key the name of the figure style and as value the corresponding
% suffix of the font family (think |OsF| or |TOsF|).
%    \begin{macrocode}
\prop_new:N \g_@@_figurestyles_proportional_prop
\prop_new:N \g_@@_figurestyles_tabular_prop
%    \end{macrocode}
% The possible inputs for the \cs{figureversion} commands and their meanings are
% held in a map as well.
%    \begin{macrocode}
\prop_new:N \g_@@_figureversions_prop
%    \end{macrocode}
% For math fonts, we only support changing the weight or the figure alignment.
% The following two variables will hold the current value of each axis.
%    \begin{macrocode}
\str_new:N \l_@@_mathweight_str
\str_new:N \l_@@_mathalign_str
%    \end{macrocode}
%
% \subsection{Messages}
%
%    \begin{macrocode}
\msg_new:nnn { figureversions } { unknown-figurestyle }
  { Ignoring~unknown~figure~style~`#1'~\msg_line_context: }
\msg_new:nnn { figureversions } { unknown-figurealignment }
  { Ignoring~unknown~figure~alignment~`#1'~\msg_line_context: }
\msg_new:nnn { figureversions } { unknown-mathweight }
  { Ignoring~unknown~math~weight~`#1'~\msg_line_context: }
\msg_new:nnn { figureversions } { unknown-mathfigurealignment }
  { Ignoring~unknown~math~figure~alignment~`#1'~\msg_line_context: }
\msg_new:nnn { figureversions } { unknown-figureversion }
  { Ignoring~unknown~figure~version~`#1'~\msg_line_context: }
%    \end{macrocode}
% \subsection{Utility functions}
%
% \begin{macro}{\@@_warning:nn}
% Issues a warning.
%    \begin{macrocode}
\cs_new:Nn \@@_warning:nn
  { \msg_warning:nnn {figureversions} {#1} {#2} }
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\@@_if_family_exists:nTF}
% Used to test whether a given font family exists or not.
%    \begin{macrocode}
\prg_new_protected_conditional:Nnn \@@_if_family_exists:n { TF }
  {
    \group_begin:
    \fontfamily {#1}
    \try@load@fontshape
    \cs_if_eq:cNTF \curr@fontshape \relax
      { \group_insert_after:N \prg_return_false: }
      { \group_insert_after:N \prg_return_true: }
    \group_end:
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_split_family:nNNTF,
%               \@@_split_family:VNNTF,
%               \@@_split_family_aux:w}
% Tries to split the font family name given by the \meta{token list}~|#1|
% into the base name and a variant suffix, delimited by |-|. Sets
% \meta{string variable}~|#2| to the base name and \meta{string variable}~|#3|
% to the suffix if the split succeeds.
%    \begin{macrocode}
\prg_new_protected_conditional:Nnn \@@_split_family:nNN { TF }
  { \@@_split_family_aux:w #1 - - \q_stop #2 #3 }
\prg_generate_conditional_variant:Nnn \@@_split_family:nNN { V } { TF }
%    \end{macrocode}
%    \begin{macrocode}
\cs_new_protected:Npn \@@_split_family_aux:w #1-#2-#3 \q_stop #4 #5
  {
    \tl_if_empty:nTF {#2}
      { \prg_return_false: }
      {
        \str_set:Nn #4 {#1}
        \str_set:Nn #5 {#2}
        \prg_return_true:
      }
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_copy_mathversion_if_undefined:nn}
% Declare math version |#1| to be a copy of math version |#2| if |#1| does not
% exist already. To accomplish this, we have to know that a math version's
% configuration is basically stored in a macro |\mv@|\meta{name}.
%    \begin{macrocode}
\cs_new_protected:Nn \@@_copy_mathversion_if_undefined:nn
  {
    \cs_if_exist:cF {mv@#1}
      {
        \DeclareMathVersion {#1}
        \cs_set_eq:cc {mv@#1} {mv@#2}
      }
  }
%    \end{macrocode}
% \end{macro}
%
% \subsection{Encoding}
%
% \begin{macro}{\@@_encode_suffix_proportional:N}
% Determines the possible proportional font family suffixes for the
% current figure style and places the result in the given \meta{seq variable}
% |#1|. Since some figure styles may only exist in a tabular version, use that
% as a fallback. Finally, fall back to |LF|, |OsF|, |TLF| and |TOsF| (in that
% order).
%    \begin{macrocode}
\cs_new_protected:Nn \@@_encode_suffix_proportional:N
  {
    \prop_get:NVNF \g_@@_figurestyles_proportional_prop
      \l_@@_fontfigurestyle_str \l_tmpa_str
      {
        \prop_get:NVNF \g_@@_figurestyles_tabular_prop
          \l_@@_fontfigurestyle_str \l_tmpa_str
      }
      \tl_if_eq:NNTF \l_tmpa_str \q_no_value
        { \seq_set_eq:NN #1 \c_empty_seq }
        { \seq_set_from_clist:NN #1 \l_tmpa_str }
%    \end{macrocode}
% Since any given font family might have only a restricted number of figure
% versions (maybe even only tabular ones), we add the well-known suffixes
% |LF|, |OsF|, |TLF| and |TOsF| to the end of the seq.
%    \begin{macrocode}
      \seq_if_in:NVF #1 \c_@@_lf_str { \seq_put_right:NV #1 \c_@@_lf_str }
      \seq_if_in:NVF #1 \c_@@_osf_str { \seq_put_right:NV #1 \c_@@_osf_str }
      \seq_if_in:NVF #1 \c_@@_tlf_str { \seq_put_right:NV #1 \c_@@_tlf_str }
      \seq_if_in:NVF #1 \c_@@_tosf_str { \seq_put_right:NV #1 \c_@@_tosf_str }
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_encode_suffix_tabular:N}
% Determines the possible tabular font family suffixes for the current figure
% style and places the result in the given \meta{seq variable} |#1|.
% Since some figure styles may only exist in a proportional version, use that
% as a fallback.
%    \begin{macrocode}
\cs_new_protected:Nn \@@_encode_suffix_tabular:N
  {
    \prop_get:NVNF \g_@@_figurestyles_tabular_prop
      \l_@@_fontfigurestyle_str \l_tmpa_str
      {
        \prop_get:NVN \g_@@_figurestyles_proportional_prop
          \l_@@_fontfigurestyle_str \l_tmpa_str
      }
      \tl_if_eq:NNTF \l_tmpa_str \q_no_value
        { \seq_set_eq:NN #1 \c_empty_seq }
        { \seq_set_from_clist:NN #1 \l_tmpa_str }
%    \end{macrocode}
% Since any given font family might have only a restricted number of figure
% versions (maybe even only proportional ones), we add the well-known suffixes
% |TLF|, |TOsF|, |LF| and |OsF| to the end of the seq.
%    \begin{macrocode}
      \seq_if_in:NVF #1 \c_@@_tlf_str { \seq_put_right:NV #1 \c_@@_tlf_str }
      \seq_if_in:NVF #1 \c_@@_tosf_str { \seq_put_right:NV #1 \c_@@_tosf_str }
      \seq_if_in:NVF #1 \c_@@_lf_str { \seq_put_right:NV #1 \c_@@_lf_str }
      \seq_if_in:NVF #1 \c_@@_osf_str { \seq_put_right:NV #1 \c_@@_osf_str }
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_encode_suffix:N}
% Determines the possible font family suffixes corresponding to the current
% figure style/alignment and places the result in the given
% \meta{seq variable} |#1|.
%    \begin{macrocode}
\cs_new_protected:Nn \@@_encode_suffix:N
  {
    \str_if_eq:NNTF \l_@@_fontfigurealignment_str \c_@@_tabular_str
      { \@@_encode_suffix_tabular:N #1 }
      { \@@_encode_suffix_proportional:N #1 }
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_encode_suffix_alt:N}
% Determines the alternate one-letter suffix for the current
% figure style and places the result in the given \meta{string variable}
% |#1|. Note that the suffix only depends on the current figure style
% and not on the current figure alignment.
%    \begin{macrocode}
\cs_new_protected:Nn \@@_encode_suffix_alt:N
  {
    \str_if_eq:NNTF \l_@@_fontfigurestyle_str \c_@@_text_str
      { \str_set:Nn #1 {j} }
      { \str_set:Nn #1 {x} }
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_set_fontfamily:}
% Sets the font family accoding to the current figure style, figure alignment
% and base family.
%    \begin{macrocode}
\cs_new_protected:Nn \@@_set_fontfamily:
  {
    \bool_set_false:N \l_tmpa_bool
    \@@_encode_suffix:N \l_tmpa_seq
    \seq_map_inline:Nn \l_tmpa_seq
      {
        \@@_if_family_exists:nTF { \l_@@_fontbasefamily_str-##1 }
          {
            \fontfamily { \l_@@_fontbasefamily_str-##1 }
            \seq_map_break:n { \bool_set_true:N \l_tmpa_bool }
          }
      }
%    \end{macrocode}
% If no suffix could be applied, try the alternate scheme.
%    \begin{macrocode}
    \bool_if:NF \l_tmpa_bool
      {
        \@@_encode_suffix_alt:N \l_tmpa_str
        \@@_if_family_exists:nTF { \l_@@_fontbasefamily_str\l_tmpa_str }
          { \fontfamily { \l_@@_fontbasefamily_str\l_tmpa_str } }
          { \fontfamily \l_@@_fontbasefamily_str }
      }
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_set_mathversion:}
% Sets the math version according to the current math weight and figure
% alignment.
%    \begin{macrocode}
\cs_new_protected:Nn \@@_set_mathversion:
  {
    \str_clear:N \l_tmpa_str
    \str_if_eq:NNT \l_@@_mathweight_str \c_@@_bold_str
      { \str_put_right:Nn \l_tmpa_str { bold } }
    \str_if_eq:NNT \l_@@_mathalign_str \c_@@_tabular_str
      { \str_put_right:Nn \l_tmpa_str { tabular } }
    \str_if_empty:NTF \l_tmpa_str
      { \mathversion { normal } }
      { \mathversion { \l_tmpa_str } }
  }
%    \end{macrocode}
% \end{macro}
%
% \subsection{Decoding}
%
% \begin{macro}{\@@_decode_suffix:n,\@@_decode_suffix:V}
% Takes a font family suffix like |TOsF| and sets the current font
% figure style and figure alignment accordingly. Iterates through all
% suffixes corresponding to the proportional version of a figure style
% before it iterates through all suffixes corresponding to the tabular
% versions until the given suffix is found. Does not alter the current
% figure alignment if a figure style has no tabular version or the suffix
% is ambiguous.
%    \begin{macrocode}
\cs_new_protected:Nn \@@_decode_suffix:n
  {
    \str_set:Nn \l_tmpa_str {#1}
    \bool_set_false:N \l_tmpa_bool
    \prop_map_inline:Nn \g_@@_figurestyles_proportional_prop
      {
        \seq_set_from_clist:Nn \l_tmpa_seq {##2}
        \seq_if_in:NVT \l_tmpa_seq \l_tmpa_str
          {
            \str_set:Nn \l_@@_fontfigurestyle_str {##1}
            \prop_get:NnNT \g_@@_figurestyles_tabular_prop {##1} \l_tmpb_str
              {
                \seq_set_from_clist:NN \l_tmpa_seq \l_tmpb_str
                \seq_if_in:NVF \l_tmpa_seq \l_tmpa_str
                  {
                    \str_set_eq:NN \l_@@_fontfigurealignment_str
                      \c_@@_proportional_str
                  }
              }
            \prop_map_break:n { \bool_set_true:N \l_tmpa_bool }
          }
      }
    \bool_if:NF \l_tmpa_bool
      {
        \prop_map_inline:Nn \g_@@_figurestyles_tabular_prop
          {
            \seq_set_from_clist:Nn \l_tmpa_seq {##2}
            \seq_if_in:NVT \l_tmpa_seq \l_tmpa_str
              {
                \str_set:Nn \l_@@_fontfigurestyle_str {##1}
                \str_set_eq:NN \l_@@_fontfigurealignment_str
                  \c_@@_tabular_str
                \prop_map_break:
              }
          }
      }
  }
\cs_generate_variant:Nn \@@_decode_suffix:n { V }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_decode_fontfamily_alt:n,
%               \@@_decode_fontfamily_alt:V,
%               \@@_decode_fontfamily_alt_aux:w}
% Tries to decode the given font family name using the \emph{alternate}
% four-letter scheme where the last letter is either |x| for lining or
% |j| for text and sets the font base family and figure style accordingly.
% Note that the current figure alignment is not altered by this command.
%    \begin{macrocode}
\cs_new_protected:Nn \@@_decode_fontfamily_alt:n
  {
    \str_set:Nn \l_@@_fontbasefamily_str {#1}
    \@@_decode_fontfamily_alt_aux:w #1 \q_stop
  }
\cs_generate_variant:Nn \@@_decode_fontfamily_alt:n { V }
%    \end{macrocode}
%    \begin{macrocode}
\cs_new_protected:Npn \@@_decode_fontfamily_alt_aux:w #1#2#3#4 \q_stop
  {
    \str_if_eq:nnT {#4} {x}
      {
        \str_set:Nn \l_@@_fontbasefamily_str { #1#2#3 }
        \str_set_eq:NN \l_@@_fontfigurestyle_str \c_@@_lining_str
      }
    \str_if_eq:nnT {#4} {j}
      {
        \str_set:Nn \l_@@_fontbasefamily_str { #1#2#3 }
        \str_set_eq:NN \l_@@_fontfigurestyle_str \c_@@_text_str
      }  
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_get_fontfamily:}
% Evaluates the current font family and infers the current figure
% style, figure alignment and base family.
%    \begin{macrocode}
\cs_new_protected:Nn \@@_get_fontfamily:
  {
    \@@_split_family:VNNTF \f@family \l_@@_fontbasefamily_str \l_tmpa_str
      { \@@_decode_suffix:V \l_tmpa_str }
      { \@@_decode_fontfamily_alt:V \f@family }
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_get_mathversion:}
% Evaluates the current math version and infers the current math weight
% and figure alignment.
%    \begin{macrocode}
\cs_new_protected:Nn \@@_get_mathversion:
  {
    \str_if_in:NnTF \math@version { bold }
      { \str_set_eq:NN \l_@@_mathweight_str \c_@@_bold_str }
      { \str_set_eq:NN \l_@@_mathweight_str \c_@@_normal_str }
    \str_if_in:NnTF \math@version { tabular }
      { \str_set_eq:NN \l_@@_mathalign_str \c_@@_tabular_str }
      { \str_set_eq:NN \l_@@_mathalign_str \c_@@_proportional_str }
  }
%    \end{macrocode}
% \end{macro}
%
% \subsection{User functions}
%
% \begin{macro}{\fontfigurestyle,\@@_fontfigurestyle:n,\@@_fontfigurestyle:e}
% Sets the font figure style.
%    \begin{macrocode}
\ProvideDocumentCommand \fontfigurestyle {m}
  { \@@_fontfigurestyle:e {#1} }
%    \end{macrocode}
%    \begin{macrocode}
\cs_new_protected:Nn \@@_fontfigurestyle:n
  {
    \bool_if:nTF
      {
        \prop_if_in_p:Nn \g_@@_figurestyles_proportional_prop {#1} ||
        \prop_if_in_p:Nn \g_@@_figurestyles_tabular_prop {#1}
      }
      {
        \@@_get_fontfamily:
        \str_set:Nn \l_@@_fontfigurestyle_str {#1}
        \@@_set_fontfamily:
      }
      {
        \@@_warning:nn { unknown-figurestyle } {#1}
      }
  }
\cs_generate_variant:Nn \@@_fontfigurestyle:n { e }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\fontfigurealignment,
%               \@@_fontfigurealignment:n,
%               \@@_fontfigurealignment:e}
% Sets the font figure alignment.
%    \begin{macrocode}
\ProvideDocumentCommand \fontfigurealignment {m}
  { \@@_fontfigurealignment:e {#1} }
%    \end{macrocode}
%    \begin{macrocode}
\cs_new_protected:Nn \@@_fontfigurealignment:n
  {
    \bool_if:nTF
      {
        \str_if_eq_p:Vn \c_@@_proportional_str {#1} ||
        \str_if_eq_p:Vn \c_@@_tabular_str {#1}
      }
      {
        \@@_get_fontfamily:
        \str_set:Nn \l_@@_fontfigurealignment_str {#1}
        \@@_set_fontfamily:
      }
      {
        \@@_warning:nn { unknown-figurealignment } {#1}
      }
  }
\cs_generate_variant:Nn \@@_fontfigurealignment:n { e }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\fontbasefamily}
% Sets the base font family.
%    \begin{macrocode}
\ProvideDocumentCommand \fontbasefamily {m}
  {
    \@@_get_fontfamily:
    \str_set:Ne \l_@@_fontbasefamily_str {#1}
    \@@_set_fontfamily:
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\mathweight,\@@_mathweight:n,\@@_mathweight:e}
% Sets the math weight.
%    \begin{macrocode}
\ProvideDocumentCommand \mathweight {m}
  { \@@_mathweight:e {#1} }
%    \end{macrocode}
%    \begin{macrocode}
\cs_new_protected:Nn \@@_mathweight:n
  {
    \bool_if:nTF
      {
        \str_if_eq_p:Vn \c_@@_normal_str {#1} ||
        \str_if_eq_p:Vn \c_@@_bold_str {#1}
      }
      {
        \@@_get_mathversion:
        \str_set:Nn \l_@@_mathweight_str {#1}
        \@@_set_mathversion:
      }
      {
        \@@_warning:nn { unknown-mathweight } {#1}
      }
  }
\cs_generate_variant:Nn \@@_mathweight:n { e }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\mathfigurealignment,
%               \@@_mathfigurealignment:n,
%               \@@_mathfigurealignment:e}
% Sets the math figure alignment.
%    \begin{macrocode}
\ProvideDocumentCommand \mathfigurealignment {m}
  { \@@_mathfigurealignment:e {#1} }
%    \end{macrocode}
%    \begin{macrocode}
\cs_new_protected:Nn \@@_mathfigurealignment:n
  {
    \bool_if:nTF
      {
        \str_if_eq_p:Vn \c_@@_proportional_str {#1} ||
        \str_if_eq_p:Vn \c_@@_tabular_str {#1}
      }
      {
        \@@_get_mathversion:
        \str_set:Nn \l_@@_mathalign_str {#1}
        \@@_set_mathversion:
      }
      {
        \@@_warning:nn { unknown-mathfigurealignment } {#1}
      }
  }
\cs_generate_variant:Nn \@@_mathfigurealignment:n { e }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\txfigures,\lnfigures}
% Higher-level commands for choosing the font figure style.
%    \begin{macrocode}
\ProvideDocumentCommand \txfigures {}
  {
    \@nomath \txfigures
    \bool_if:NTF \g_@@_fontspec_bool
      { \addfontfeature{ Numbers = OldStyle } }
      {
        \fontfigurestyle { \c_@@_text_str }
        \selectfont
      }
  }
\ProvideDocumentCommand \lnfigures {}
  {
    \@nomath \lnfigures
    \bool_if:NTF \g_@@_fontspec_bool
      { \addfontfeature{ Numbers = Lining } }
      {
        \fontfigurestyle { \c_@@_lining_str }
        \selectfont
      }
  }
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\prfigures,\tbfigures}
% Higher-level commands for choosing the font figure alignment.
%    \begin{macrocode}
\ProvideDocumentCommand \prfigures {}
  {
    \@nomath\prfigures
    \bool_if:NTF \g_@@_fontspec_bool
      { \addfontfeature{ Numbers = Proportional } }
      {
        \fontfigurealignment { \c_@@_proportional_str }
        \selectfont
      }
  }
\ProvideDocumentCommand \tbfigures {}
  {
    \@nomath\tbfigures
    \bool_if:NTF \g_@@_fontspec_bool
      { \addfontfeature{ Numbers = Monospaced } }
      {
        \fontfigurealignment { \c_@@_tabular_str }
        \selectfont
      }
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\boldmath,\unboldmath}
% Reimplementation of \cs{boldmath} and \cs{unboldmath} to only change the
% math weight.
%    \begin{macrocode}
\RenewDocumentCommand \boldmath {}
  {
    \@nomath \boldmath
    \mathweight { \c_@@_bold_str }
  }
\RenewDocumentCommand \unboldmath {}
  {
    \@nomath \unboldmath
    \mathweight { \c_@@_normal_str }
  }
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\tabularmath,\proportionalmath}
% Higher-level commands to change the math figure alignment.
%    \begin{macrocode}
\ProvideDocumentCommand \proportionalmath {}
  {
    \@nomath \proportionalmath
    \mathfigurealignment { \c_@@_proportional_str }
  }
\ProvideDocumentCommand \tabularmath {}
  {
    \@nomath \tabularmath
    \mathfigurealignment { \c_@@_tabular_str }
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\textfigures,\liningfigures,
%               \tabularfigures,\proportionalfigures}
% Text font commands which apply a certain figure style or figure alignment
% to their argument.
%    \begin{macrocode}
\DeclareTextFontCommand {\textfigures} {\txfigures}
\DeclareTextFontCommand {\liningfigures }{\lnfigures}
\DeclareTextFontCommand {\tabularfigures} {\tbfigures\tabularmath}
\DeclareTextFontCommand {\proportionalfigures} {\prfigures\proportionalmath}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\figureversion}
% Convenience macro for setting font figure style and alignment simultaneously.
%    \begin{macrocode}
\ProvideDocumentCommand \figureversion {m}
  {
    \clist_set:Ne \l_tmpa_clist {#1}
    \clist_map_inline:Nn \l_tmpa_clist
      { 
        \prop_get:NnNTF \g_@@_figureversions_prop {##1} \l_tmpa_tl
          { \tl_use:N \l_tmpa_tl }
          { \@@_warning:nn { unknown-figureversion } {##1} }
      }
  }
%    \end{macrocode}
% \end{macro}
%
% \subsection{Public code-level functions}
%
% \begin{macro}{\figureversions_new_figurestyle:nnn,
%              \figureversions_new_figurestyle:Vnn,
%              \@@_new_figurestyle_proportional:nn,
%              \@@_new_figurestyle_tabular:nn}
% Defines the figure style |#1| with the corresponding font family suffixes
% listed in the \meta{comma lists} |#2| for proportional figures and |#3| for
% tabular figures. Does nothing if |#1| is already defined as a figure style.
%    \begin{macrocode}
\cs_new_protected:Nn \@@_new_figurestyle_proportional:nn
  {
    \prop_gput_if_not_in:Nne \g_@@_figurestyles_proportional_prop {#1}
      { \tl_to_str:n {#2} }
  }
\cs_new_protected:Nn \@@_new_figurestyle_tabular:nn
  {
    \prop_gput_if_not_in:Nne \g_@@_figurestyles_tabular_prop {#1}
      { \tl_to_str:n {#2} }
  }
\cs_new_protected:Nn \figureversions_new_figurestyle:nnn
  {
    \@@_new_figurestyle_proportional:nn {#1} {#2}
    \@@_new_figurestyle_tabular:nn {#1} {#3}
  }
\cs_generate_variant:Nn \figureversions_new_figurestyle:nnn { V }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\figureversions_new_figureversion:nn}
% Defines the figure version |#1| and assigns the code |#2| to it.
% Does nothing if |#1| is already defined as a figure version.
%    \begin{macrocode}
\cs_new_protected:Nn \figureversions_new_figureversion:nn
  { \prop_gput_if_not_in:Nnn \g_@@_figureversions_prop {#1} {#2} }
%    \end{macrocode}
% \end{macro}
%
% \subsection{Initialization}
%
% Finally, we declare the pre-defined figure styles `text' and `lining' and the
% initial keys for the  \cs{figureversion} command.
%    \begin{macrocode}
\figureversions_new_figurestyle:Vnn \c_@@_text_str { OsF  } { TOsF }
\figureversions_new_figurestyle:Vnn \c_@@_lining_str { LF } { TLF }
%    \end{macrocode}
%    \begin{macrocode}
\figureversions_new_figureversion:nn { text } { \txfigures }
\figureversions_new_figureversion:nn { osf } { \txfigures }
\figureversions_new_figureversion:nn { lining } { \lnfigures }
\figureversions_new_figureversion:nn { lf } { \lnfigures }
\figureversions_new_figureversion:nn { tabular }
  { \tbfigures \tabularmath }
\figureversions_new_figureversion:nn { tab }
  { \tbfigures \tabularmath }
\figureversions_new_figureversion:nn { proportional }
  { \prfigures \proportionalmath }
\figureversions_new_figureversion:nn { prop }
  { \prfigures \proportionalmath }
%    \end{macrocode}
%
% \subsection{Hooks}
%
% At the start of the document, we check whether math versions `tabular' and
% `boldtabular' have been defined. If not, we provide a default by copying the
% state of `normal' respectively `bold'.
%    \begin{macrocode}
\AtBeginDocument
  {
    \@@_copy_mathversion_if_undefined:nn { tabular } { normal }
    \@@_copy_mathversion_if_undefined:nn { boldtabular } { bold }
%    \end{macrocode}
% Test for \pkg{fontspec}.
%    \begin{macrocode}
    \IfPackageLoadedT { fontspec }
      { \bool_gset_true:N \g_@@_fontspec_bool }
%    \end{macrocode}     
% Finally, we redefine some commands for use in PDF strings.
%    \begin{macrocode}
    \IfPackageLoadedT { hyperref }
      {
        \pdfstringdefDisableCommands
          {
            \cs_set_eq:NN \figureversion \use_none:n
            \cs_set_eq:NN \fontfigurestyle \use_none:n
            \cs_set_eq:NN \fontfigurealignment \use_none:n
            \cs_set_eq:NN \fontbasefamily \use_none:n
            \cs_set_eq:NN \mathweight \use_none:n
            \cs_set_eq:NN \mathfigurealignment \use_none:n
            \cs_set_eq:NN \txfigures \relax
            \cs_set_eq:NN \lnfigures \relax
            \cs_set_eq:NN \prfigures \relax
            \cs_set_eq:NN \tbfigures \relax
            \cs_set_eq:NN \proportionalmath \relax
            \cs_set_eq:NN \tabularmath \relax
            \cs_set_eq:NN \textfigures \use:n
            \cs_set_eq:NN \liningfigures \use:n
            \cs_set_eq:NN \tabularfigures \use:n
            \cs_set_eq:NN \proportionalfigures \use:n
          }
      }
  }
%</package>
%    \end{macrocode}
%
% \RemoveFromHook{sffamily}
% \end{implementation}
%
% \begin{thebibliography}{9}
%
% \bibitem{nfss}
% \LaTeX\ Project Team:
% \LaTeXe\ font selection.
% \url{https://www.latex-project.org/help/documentation/fntguide.pdf}
%
% \bibitem{ltnews31}
% \LaTeX\ News. Issue 31, February 2020.
% \url{https://www.latex-project.org/news/latex2e-news/ltnews31.pdf}
%
% \end{thebibliography}
%
% \Finale