%%
%% subcaptionlite.sty
%% ==================
%% Minimal subfigure/subtable environments, \subcaption, \subcaptionbox
%% and \subref without the caption package.
%%
%% Copyright (c) 2026 Munehiro Yamamoto <munepixyz@gmail.com>
%%
%% This package is licensed 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
%%
%% This work has the LPPL maintenance status `maintained'.
%% The Current Maintainer of this work is Munehiro Yamamoto.
%%
%% What this package does
%%   The subcaption package needs the caption package, which redefines
%%   \@makecaption of the class.  Thus it cannot be used with a class
%%   that has its own design of captions.  This package provides the
%%   subfigure and subtable environments, \subcaption, \subcaptionbox
%%   and \subref without touching \@makecaption of the class; \caption
%%   is only wrapped for the numbering (see below).
%%
%% What it provides (<type> is figure or table)
%%   * The counter sub<type>, reset by <type>.  \thesub<type> is (a),
%%     (b), ...; \p@sub<type> is \the<type>, so that \ref gives "4.2(a)"
%%     (and \Cref of cleveref "Figure 4.2(a)").  \label works through
%%     \refstepcounter (with hyperref, the anchor is \theHsub<type>).
%%   * \begin{subfigure}[<pos>]{<width>} ... \end{subfigure}, and the
%%     subtable environment
%%       A minipage (<pos> is b by default, as in the subcaption
%%       package), inside which \caption and \caption* mean \subcaption
%%       and \subcaption*.
%%   * \subcaption{<text>} and \subcaption*{<text>}
%%       Numbered with the counter of the float it is in: subfigure in a
%%       figure, subtable in a table (also in a subfigure environment).
%%   * \subcaptionbox{<caption>}[<width>]{<contents>}
%%       Puts <contents> centered in a minipage of <width>, followed by
%%       \subcaption{<caption>}.  Without <width>, the natural width of
%%       <contents> is used; with <width>, \linewidth in <contents> is
%%       <width>.  If <contents> is wider than <width>, the minipage
%%       keeps <width>.
%%   * \subref{<label>} and \subref*{<label>} (no link with hyperref)
%%       Only the label of the subfigure/subtable, e.g. "(a)": after a
%%       numbered \subcaption, \label{<label>} also writes the label
%%       sub@<label>, as the subcaption package does.
%%   * \captionsetup[..]{..}: a no-op, so that the settings for the
%%     caption package can be left in the document.
%%
%% Numbering
%%   When a \subcaption comes before the \caption of its float (the
%%   usual way for figures), the first \subcaption steps the counter of
%%   the float in advance, and the \caption that follows does not step
%%   it again (as the subcaption package does; otherwise the subfigures
%%   would get the number of the previous figure).  When the \caption
%%   comes first (the usual way for tables), the \subcaption uses its
%%   number.
%%
%% Errors
%%   \subcaption (and \subcaptionbox) outside a float, or in a float
%%   other than figure and table: the subcaption is typeset without a
%%   number.
%%
%% Customization (redefine in the class or a local style)
%%   \subcaption@font   the font of a subcaption (default: \small)
%%   \subcaption@sep    the space between the label (a) and the text
%%                      (default: \hspace{.5zw} with pTeX, .5\zw with
%%                      LuaTeX-ja and the classes that define \zw,
%%                      .5em otherwise)
%%   \subcaption@skip   the space between the subfigure and its
%%                      subcaption (default: \vskip.25\baselineskip)
%%
%% Supported formats/engines
%%   * pdfLaTeX, XeLaTeX, LuaLaTeX (with or without LuaTeX-ja)
%%   * pLaTeX, upLaTeX (+ dvipdfmx)
%%
%% Limitations
%%   * Subcaptions are for figures and tables only.
%%   * The package cannot be used together with the caption or
%%     subcaption package.
%%
\NeedsTeXFormat{LaTeX2e}[2020-10-01]
\ProvidesPackage{subcaptionlite}
  [2026/10/26 v1.0 minimal subfigures/subtables without the caption package]

\RequirePackage{etoolbox}%% \AtBeginEnvironment

\newbox\subcaption@box
\newdimen\subcaption@dim

\newcommand*\subcaption@Error[1]{%
  \PackageError{subcaptionlite}{#1}{%
    \string\subcaption\space and \string\subcaptionbox\space can be used
    in a figure or a table.\MessageBreak
    The subcaption is typeset without a number.}}

%% \subcaption@declare{<type>}: the counter sub<type>, reset by <type>,
%% and the environment sub<type>; for figure and table
\def\subcaption@declare#1{%
  \newcounter{sub#1}[#1]%
  \@namedef{thesub#1}{(\alph{sub#1})}%
  \@namedef{p@sub#1}{\csname the#1\endcsname}%
  \@namedef{theHsub#1}{\csname theH#1\endcsname.\arabic{sub#1}}%
  \newenvironment{sub#1}[2][b]{%
    \begin{minipage}[##1]{##2}%
      \let\caption\subcaption
  }{\end{minipage}}%
  \AtBeginEnvironment{#1}{\subcaption@reset{#1}}%
  \AtBeginEnvironment{#1*}{\subcaption@reset{#1}}}

%% Half of the full-width character: zw is a unit of pTeX; LuaTeX-ja
%% (and some classes) define \zw.  Decided when used, so that LuaTeX-ja
%% may be loaded after this package.
\def\subcaption@halfzw{%
  \ifdefined\ptexversion .5zw\else\ifdefined\zw .5\zw\else .5em\fi\fi}
\providecommand*\subcaption@font{\small}
\providecommand*\subcaption@sep{\hspace{\subcaption@halfzw}}
\providecommand*\subcaption@skip{\vskip.25\baselineskip}

%% With hyperref, step the counter of the float in advance with
%% \H@refstepcounter, which makes no anchor
\def\subcaption@precount{%
  \@ifundefined{H@refstepcounter}{\refstepcounter}{\H@refstepcounter}{\@captype}}

%% precounted: a \subcaption has stepped the counter of the float in
%%             advance;
%% captioned:  the \caption of the float has been given
\newif\if@subcaption@precounted
\newif\if@subcaption@captioned
%% The counter sub<type> is reset here too: it is reset by the counter
%% <type>, which is not stepped before the first \subcaption
\def\subcaption@reset#1{%
  \global\@subcaption@precountedfalse
  \global\@subcaption@captionedfalse
  \setcounter{sub#1}{0}}
\@ifundefined{c@figure}{}{\subcaption@declare{figure}}
\@ifundefined{c@table}{}{\subcaption@declare{table}}

%% \caption is wrapped at the end of \begin{document}, after hyperref and
%% the like have defined it
\AddToHook{begindocument/end}{%
  \let\subcaption@saved@caption\caption
  \def\caption{%
    \if@subcaption@precounted
      \global\@subcaption@precountedfalse
      \addtocounter{\@captype}{\m@ne}%
    \fi
    \global\@subcaption@captionedtrue
    \ifx\label\subcaption@label \let\label\subcaption@ORI@label \fi
    \subcaption@saved@caption}}

\newcommand*\subcaption{\@ifstar\subcaption@star\subcaption@nostar}
\newcommand\subcaption@nostar{\subcaption@iftype\subcaption@numbered\subcaption@star}
\newcommand\subcaption@numbered[1]{%
  \if@subcaption@precounted\else\if@subcaption@captioned\else
    \global\@subcaption@precountedtrue
    \subcaption@precount
  \fi\fi
  \refstepcounter{sub\@captype}%
  \ifx\label\subcaption@label \else
    \let\subcaption@ORI@label\label
    \let\label\subcaption@label
  \fi
  \subcaption@typeset{\csname thesub\@captype\endcsname\subcaption@sep}{#1}}
%% \subcaption@iftype{<true>}{<false>}: in a float that has subcaptions?
\def\subcaption@iftype{%
  \ifx\@captype\@undefined
    \subcaption@Error{\string\subcaption\space outside float}%
    \expandafter\@secondoftwo
  \else
    \expandafter\subcaption@iftype@
  \fi}
\def\subcaption@iftype@{%
  \@ifundefined{c@sub\@captype}%
    {\subcaption@Error{Float type `\@captype' has no subcaptions}%
     \@secondoftwo}%
    {\@firstoftwo}}
\newcommand\subcaption@star[1]{\subcaption@typeset{}{#1}}
\newcommand\subcaption@typeset[2]{%
  \par\subcaption@skip
  {\centering\subcaption@font\ifdefined\inhibitglue\inhibitglue\fi#1#2\par}}

%% After a numbered \subcaption, \label also writes the label
%% sub@<label> with \thesub<type> only, for \subref (as the subcaption
%% package does).  #1 is the optional argument of cleveref, if any.
\def\subcaption@label#1#{\subcaption@@label{#1}}
\def\subcaption@@label#1#2{%
  \@bsphack\begingroup
    \let\@bsphack\relax
    \let\@esphack\relax
    \subcaption@ORI@label#1{#2}%
    \let\SK@\@gobbletwo%% showkeys
    \protected@edef\@currentlabel{\csname thesub\@captype\endcsname}%
    \subcaption@ORI@label{sub@#2}%
  \endgroup\@esphack}
\DeclareRobustCommand*\subref{\@ifstar\subcaption@ref@star\subcaption@ref}
\def\subcaption@ref#1{\ref{sub@#1}}
\def\subcaption@ref@star#1{%
  \@ifundefined{hyperref}{\ref{sub@#1}}{\ref*{sub@#1}}}

%% \subcaptionbox{caption}[width]{contents}
\NewDocumentCommand\subcaptionbox{ m O{} m }{%
  \begingroup
    \if\relax\detokenize{#2}\relax
      \setbox\subcaption@box\hbox{#3}%
      \subcaption@dim\wd\subcaption@box
    \else
      %% with a width, \linewidth in contents is the width (as in the
      %% subcaption package)
      \subcaption@dim#2\relax
      \setbox\subcaption@box\hbox{\linewidth\subcaption@dim #3}%
    \fi
    \begin{minipage}[b]{\subcaption@dim}%
      %% put contents in an \hsize-wide hbox, so that the minipage does
      %% not get wider than its width
      \hb@xt@\hsize{\hss\box\subcaption@box\hss}\par
      \subcaption{#1}%
    \end{minipage}%
  \endgroup}

%% \captionsetup of the caption package is ignored
\NewDocumentCommand\captionsetup{ o m }{}

\endinput