CTAN sync 202207210300

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diff --git a/macros/latex/contrib/wrapstuff/README.md b/macros/latex/contrib/wrapstuff/README.md
new file mode 100644
index 0000000000..017a8bf27c
--- /dev/null
+++ b/macros/latex/contrib/wrapstuff/README.md
@@ -0,0 +1,50 @@
+wrapstuff
+=========
+
+The `wrapstuff` package provides another implementation of text wrapping.
+Its implementation benefits from the paragraph hooks available since
+LaTeX 2021-06-01.
+
+Basic Usage
+-----------
+The package only provides a user environment `wrapstuff`.
+
+    \begin{wrapstuff}[<options>]
+      <wrapping stuff>
+    \end{wrapstuff}
+    <main text>
+
+You can read the package manual (in Chinese) for some explanations.
+
+Contributing
+------------
+The package is still highly experimental and not fully tested.
+[Issues](https://github.com/qinglee/wrapstuff/issues) and
+[pull requests](https://github.com/qinglee/wrapstuff/pulls)
+are always welcome.
+
+Copyright and Licence
+---------------------
+
+    Copyright (C) 2022 by Qing Lee <sobenlee@gmail.com>
+    -----------------------------------------------------------------
+
+    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. This version of this license is in
+       http://www.latex-project.org/lppl/lppl-1-3c.txt
+    and the latest version of this license is in
+       http://www.latex-project.org/lppl.txt
+    and version 1.3 or later is part of all distributions of
+    LaTeX version 2005/12/01 or later.
+
+    This work has the LPPL maintenance status "maintained".
+
+    The Current Maintainer of this work is Qing Lee.
+
+    This package consists of the file  wrapstuff.dtx,
+                 and the derived files wrapstuff.pdf,
+                                       wrapstuff.sty,
+                                       wrapstuff.ins and
+                                       README.md (this file).
diff --git a/macros/latex/contrib/wrapstuff/wrapstuff.dtx b/macros/latex/contrib/wrapstuff/wrapstuff.dtx
new file mode 100644
index 0000000000..5b8c03ec03
--- /dev/null
+++ b/macros/latex/contrib/wrapstuff/wrapstuff.dtx
@@ -0,0 +1,3011 @@
+% \iffalse meta-comment
+% !TeX program  = XeLaTeX
+% !TeX encoding = UTF-8
+%<*internal>
+\iffalse
+%</internal>
+%<*readme>
+wrapstuff
+=========
+
+The `wrapstuff` package provides another implementation of text wrapping.
+Its implementation benefits from the paragraph hooks available since
+LaTeX 2021-06-01.
+
+Basic Usage
+-----------
+The package only provides a user environment `wrapstuff`.
+
+    \begin{wrapstuff}[<options>]
+      <wrapping stuff>
+    \end{wrapstuff}
+    <main text>
+
+You can read the package manual (in Chinese) for some explanations.
+
+Contributing
+------------
+The package is still highly experimental and not fully tested.
+[Issues](https://github.com/qinglee/wrapstuff/issues) and
+[pull requests](https://github.com/qinglee/wrapstuff/pulls)
+are always welcome.
+
+Copyright and Licence
+---------------------
+
+    Copyright (C) 2022 by Qing Lee <sobenlee@gmail.com>
+    -----------------------------------------------------------------
+
+    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. This version of this license is in
+       http://www.latex-project.org/lppl/lppl-1-3c.txt
+    and the latest version of this license is in
+       http://www.latex-project.org/lppl.txt
+    and version 1.3 or later is part of all distributions of
+    LaTeX version 2005/12/01 or later.
+
+    This work has the LPPL maintenance status "maintained".
+
+    The Current Maintainer of this work is Qing Lee.
+
+    This package consists of the file  wrapstuff.dtx,
+                 and the derived files wrapstuff.pdf,
+                                       wrapstuff.sty,
+                                       wrapstuff.ins and
+                                       README.md (this file).
+%</readme>
+%<*internal>
+\fi
+\begingroup
+  \def\temp{LaTeX2e}
+\expandafter\endgroup\ifx\temp\fmtname\else
+\csname fi\endcsname
+%</internal>
+%<*install>
+
+\input ctxdocstrip %
+
+\preamble
+
+    Copyright (C) 2022 by Qing Lee <sobenlee@gmail.com>
+-----------------------------------------------------------------
+
+    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. This version of this license is in
+       http://www.latex-project.org/lppl/lppl-1-3c.txt
+    and the latest version of this license is in
+       http://www.latex-project.org/lppl.txt
+    and version 1.3 or later is part of all distributions of
+    LaTeX version 2005/12/01 or later.
+
+    This work has the LPPL maintenance status "maintained".
+
+    The Current Maintainer of this work is Qing Lee.
+
+-----------------------------------------------------------------
+
+\endpreamble
+
+\postamble
+
+    This work consists of the file  wrapstuff.dtx,
+              and the derived files wrapstuff.pdf,
+                                    wrapstuff.sty,
+                                    wrapstuff.ins and
+                                    README.md.
+\endpostamble
+
+\generate
+  {
+%</install>
+%<*internal>
+    \usedir{source/latex/wrapstuff}
+    \file{wrapstuff.ins} {\from{\jobname.dtx}{install}}
+%</internal>
+%<*install>
+    \usedir{tex/latex/wrapstuff}
+    \file{wrapstuff.sty} {\from{\jobname.dtx}{package}}
+    \nopreamble\nopostamble
+    \usedir{doc/latex/wrapstuff}
+    \file{README.md}     {\from{\jobname.dtx}{readme}}
+  }
+
+\endbatchfile
+%</install>
+%<*internal>
+\fi
+%</internal>
+%<package>\NeedsTeXFormat{LaTeX2e}
+%<package>\@ifundefined{ExplLoaderFileDate}{\RequirePackage{expl3}}{}
+%<+package>\GetIdInfo$Id: wrapstuff.dtx 564fe9d 2022-07-20 19:55:58 +0800 Qing Lee <sobenlee@gmail.com> $
+%<package>  {Wrapping text around stuff}
+%<package>\ProvidesExplPackage{\ExplFileName}
+%<package>  {\ExplFileDate}{0.1}{\ExplFileDescription}
+%<*driver>
+\documentclass{ctxdoc}
+\usepackage{wrapstuff}
+\usepackage{graphicx}
+\usepackage{zhlipsum}
+\ExplSyntaxOn
+\makeatletter
+\DeclareDocumentCommand \gitsha { m }
+  {
+    \href { https \c_colon_str //github.com/qinglee/wrapstuff/commit/#1 }
+          { rev. ~ \texttt{#1} }
+  }
+\DeclareDocumentCommand \QIANZIWEN { }
+  {
+    天地玄黄宇宙洪荒日月盈昃辰宿列张
+    寒来暑往秋收冬藏闰馀成岁律召调阳 \par
+    云腾致雨露结为霜金生丽水玉出昆冈 \par
+  }
+\DeclareDocumentCommand \ADDSPECEIALKEY { m }
+  {
+    \cs_gset_eq:NN \@@_codedoc_names_typeset_save:
+                   \__codedoc_names_typeset:
+    \cs_gset_protected:Npn \__codedoc_names_typeset:
+      {
+        \cs_gset_eq:NN \__codedoc_names_typeset:
+                       \@@_codedoc_names_typeset_save:
+        \__codedoc_names_typeset:
+        #1 \\
+      }
+  }
+\DeclareDocumentCommand \IMAGE { m m }
+  { \includegraphics [ width = \dim_eval:n {#1} ] { example-image-#2.pdf } }
+\tl_put_left:Nn \Example
+  { \trivlist \item \relax }
+\tl_put_right:Nn \endExample
+  { \endtrivlist }
+\SideBySideExampleSet { numbers = none }
+\makeatother
+\ExplSyntaxOff
+\begin{document}
+  \DocInput{\jobname.dtx}
+  \IndexLayout
+  \PrintChanges
+  \PrintIndex
+\end{document}
+%</driver>
+% \fi
+%
+% \CheckSum{2923}
+%
+% \changes{v0.1}{2022/07/05}{初始版本。}
+% \changes{v0.1}{2022/07/20}{首次提交到 CTAN 发布。}
+%
+% \GetFileId{wrapstuff.sty}
+%
+% \title{\bfseries\pkg{wrapstuff} 宏包}
+% \author{李清}
+% \date{\filedate\qquad\fileversion\thanks{\gitsha{\ExplFileVersion}.}}
+% \maketitle
+%
+% \begin{documentation}
+%
+% \section{基本用法}
+%
+% \pkg{wrapstuff} 宏包提供了图文绕排的另一种实现。
+% \pkg{wrapstuff} 的实现依赖 \LaTeX\ 2021-06-01 开始提供的段落钩子，
+% 并依赖 \LaTeXiii\ 2022-04-10 之后的版本。
+%
+% \begin{function}{wrapstuff}
+%   \begin{syntax}
+%     \tn{begin}\{wrapstuff\}\oarg{选项}
+%       <绕排内容>
+%     \tn{end}\{wrapstuff\}
+%     <正文>
+%   \end{syntax}
+%   \pkg{wrapstuff} 只提供了一个用户环境 \env{wrapstuff}，
+%   会在环境之后的段落开始绕排。例如
+%   \begin{Example}[frame=single,numbers=none,gobble=5]
+%     \begin{wrapstuff}[c,top=1]
+%       \includegraphics[width=\dimeval{\linewidth/3}]{example-image.pdf}
+%     \end{wrapstuff}
+%     \zhlipsum[1][name=zhufu]
+%   \end{Example}
+% \end{function}
+%
+% \begin{function}{\wrapstuffset}
+%   \begin{syntax}
+%     \tn{wrapstuffset} \Arg{选项列表}
+%   \end{syntax}
+%   \pkg{wrapstuff} 的选项可以在调用宏包时设置，也可以通过 \tn{wrapstuffset} 设置。
+%   选项将在下面描述。
+% \end{function}
+%
+% \ADDSPECEIALKEY{\textrm{\meta{n}}}
+% \begin{function}{top}
+%   \begin{syntax}
+%     top = <非负整数>
+%   \end{syntax}
+%   设置在正文段落的第几行之后开始绕排，可以设置为非负整数。
+%   非负整数选项 \meta{n} 是设置选项 \opt{top} 为 \meta{n} 的缩写形式。
+%   初始值是 \num{0}。
+% \end{function}
+%
+% \begin{function}{width}
+%   \begin{syntax}
+%     width = <宽度>
+%   \end{syntax}
+%   设置绕排内容的宽度，初始值为 \qty{0}{pt}，代表自然宽度。
+% \end{function}
+%
+% \begin{function}{height}
+%   \begin{syntax}
+%     height = <高度>
+%   \end{syntax}
+%   设置绕排内容的高度，初始值为 \qty{0}{pt}，代表自然高度。
+% \end{function}
+%
+% \begin{function}{leftsep,rightsep,hsep}
+%   \begin{syntax}
+%     leftsep  = <长度>
+%     rightsep = <长度>
+%     hsep     = <长度>
+%   \end{syntax}
+%   设置绕排内容与正文的左/右间距，选项 \opt{hsep} 同时设置 \opt{leftsep} 和 \opt{rightsep}。
+%   初始值是 \qty{1}{em}。
+% \end{function}
+%
+% \begin{function}{abovesep,belowsep,vsep}
+%   \begin{syntax}
+%     abovesep = <长度>
+%     belowsep = <长度>
+%     vsep     = <长度>
+%   \end{syntax}
+%   设置绕排内容与正文的上/下间距，选项 \opt{vsep} 同时设置 \opt{abovesep} 和 \opt{belowsep}。
+%   初始值是 \qty{0}{pt}。
+% \end{function}
+%
+% \begin{function}{l,r,c,i,o,ratio}
+%   \begin{syntax}
+%     l/r/c/i/o
+%     ratio = <实数>
+%   \end{syntax}
+%   这些选项用于设置绕排内容位于正文中的位置。
+%   选项 \opt{l/r/c/i/o} 分别设置绕排内容位于正文的左侧、右侧、中间、内侧、外侧。
+%   选项 \opt{ratio} 设置绕排内容左侧的正文占据行宽的比例，可以设置为 $[0,1]$ 区间中的合理实数。
+%   选项 \opt{i/o} 可以与 \opt{ratio} 一起使用，这时设置的是内/外侧正文的行宽比例。
+%   初始设置为 |r|，即位于正文的右侧。
+% \end{function}
+%
+% \begin{function}{column}
+%   \begin{syntax}
+%     column = <(true)|false|par>
+%   \end{syntax}
+%   控制是否将绕排内容两侧的正文分栏显示，只有设置 |c| 选项或者
+%   设置 \opt{ratio} 不等于 $0$ 或者 $1$ 时才有效。
+%   \opt{false} 表示不分栏，正文文字方向始终保持从左到右的顺序；
+%   \opt{par} 表示以段落为单位进行分栏，如下示例。
+%   \begin{SideBySideExample}[xrightmargin=\dimeval{20em+5mm}]
+%     \begin{wrapstuff}[c,1]
+%       \IMAGE{2em}{a}
+%     \end{wrapstuff}
+%     \QIANZIWEN
+%     \begin{wrapstuff}[c,1,column=par]
+%       \IMAGE{2em}{b}
+%     \end{wrapstuff}
+%     \QIANZIWEN
+%     \begin{wrapstuff}[c,0,column=false]
+%       \IMAGE{2em}{c}
+%     \end{wrapstuff}
+%     \QIANZIWEN
+%   \end{SideBySideExample}
+% \end{function}
+%
+% \begin{function}{hoffset}
+%   \begin{syntax}
+%     hoffset = <长度>
+%   \end{syntax}
+%   设置绕排内容伸出正文版心的长度。
+%   当设置了选项 \opt{c} 或者选项 \opt{ratio} 的值位于 $(0,1)$ 时，本选项无效。
+%   一个特殊值 \tn{width} 用于表示绕排内容和相应间距的总宽度，
+%   可以将 \opt{hoffset} 设置为 \tn{width}，完全伸出版心。
+%   初始值为 \qty{0}{pt}。
+% \end{function}
+%
+% \begin{function}{voffset}
+%   \begin{syntax}
+%     voffset = <长度>
+%   \end{syntax}
+%   用于调整绕排内容的竖直位置，初始值为 \qty{0}{pt}。
+% \end{function}
+%
+% \begin{function}{type}
+%   \begin{syntax}
+%     type = <浮动体类型>
+%   \end{syntax}
+%   设置绕排内容的浮动体类型，初始值为空。
+%   如果需要在 \env{wrapstuff} 环境中使用 \tn{caption} 命令，
+%   则需要设置 \opt{type} 为 \opt{figure} 或 \opt{table} 等类型，
+%   并需要同时设置 \opt{width} 指定宽度。
+%   \begin{SideBySideExample}[xrightmargin=\dimeval{18em+5mm}]
+%     \begin{wrapstuff}[type=figure,width=5em]
+%       \centering
+%       \IMAGE{4em}{plain}
+%       \caption{示例}
+%     \end{wrapstuff}
+%     \QIANZIWEN
+%   \end{SideBySideExample}
+% \end{function}
+%
+% \begin{function}{lines}
+%   \begin{syntax}
+%     lines = <正整数>
+%   \end{syntax}
+%   设置绕排内容占据正文的行数，可以设置正整数。
+%   初始值为空，根据绕排内容的高度自动计算行数。
+% \end{function}
+%
+% \begin{function}{linewidth}
+%   \begin{syntax}
+%     linewidth = <宽度>
+%   \end{syntax}
+%   设置正文段落的行宽，初始设置为 |\linewidth|，一般不需要调整。
+% \end{function}
+%
+% \begin{function}{\wrapstuffclear}
+%   如果当前正文段落的行数不够，\pkg{wrapstuff} 的作用会延续到下一段。
+%   这可能会导致某些意外结果，可以在下一段之前启用命令 \tn{wrapstuffclear} 消除影响。
+% \end{function}
+%
+% \end{documentation}
+%
+%
+% \StopEventually{}
+%
+%
+%\begin{implementation}
+%
+% \section{代码实现}
+%
+%    \begin{macrocode}
+%<*package>
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%<@@=wstf>
+%    \end{macrocode}
+%
+% \pkg{wrapstuff} 的实现依赖 \LaTeX\ 2021-06-01 开始提供的段落钩子。
+%    \begin{macrocode}
+\@ifl@t@r \fmtversion { 2021-06-01 }
+  { }
+  {
+    \msg_new:nnn { wrapstuff } { latex-too-old }
+      {
+        You~need~to~update~your~LaTeX~to~the~latest~release. \\
+        Loading~wrapstuff~will~abort!
+      }
+    \msg_critical:nn { wrapstuff } { latex-too-old }
+  }
+%    \end{macrocode}
+%
+% 由于使用了 \cs{keys_precompile:nnN}，需要比较新的 \LaTeXiii。
+%    \begin{macrocode}
+\@ifl@t@r \ExplLoaderFileDate { 2022-04-10 }
+  { }
+  {
+    \msg_new:nnn { wrapstuff } { latex3-too-old }
+      {
+        You~need~to~update~your~installation~of~the~bundles~
+        "l3kernel"~and~"l3packages". \\
+        Loading~wrapstuff~will~abort!
+      }
+    \msg_critical:nn { wrapstuff } { latex3-too-old }
+  }
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+\prop_gput:Nnn \g_msg_module_name_prop { wstf } { wrapstuff }
+%    \end{macrocode}
+%
+% \begin{macro}[TF]{
+%   \@@_if_last_none:,
+%   \@@_if_last_hlist:,
+%   \@@_if_last_whatsit:,
+%   \@@_if_last_glue:,
+%   \@@_if_last_kern:,
+%   \@@_if_last_penalty:}
+% 一些 \hologo{eTeX} 结点判定函数。
+%    \begin{macrocode}
+\group_begin:
+\cs_set:Npn \@@_tmp:nn #1
+  {
+    \group_begin:
+      \exp_args:Ncc \@@_tmp_aux:NNn
+        { @@_if_last_ #1 : }
+        { c_@@_ #1 _node }
+  }
+\cs_set:Npn \@@_tmp_aux:NNn #1#2#3
+  {
+    \group_end:
+    \int_const:Nn #2 {#3}
+    \prg_new_conditional:Npnn #1 { T , F , TF }
+      {
+        \if_int_compare:w \tex_lastnodetype:D = #2
+          \prg_return_true: \else: \prg_return_false: \fi:
+      }
+  }
+\@@_tmp:nn { none }    { -1 }
+\@@_tmp:nn { hlist }   {  1 }
+\@@_tmp:nn { whatsit } {  9 }
+\@@_tmp:nn { glue }    { 11 }
+\@@_tmp:nn { kern }    { 12 }
+\@@_tmp:nn { penalty } { 13 }
+\group_end:
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_gadd_hook:nn, \@@_package_hook:nn}
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_gadd_hook:nn #1
+  { \hook_gput_code:nnn {#1} { wrapstuff } }
+\cs_new_protected:Npn \@@_package_hook:nn #1
+  { \hook_gput_code:nnn { package/#1/after } { wrapstuff } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{wrapstuff}
+% 主要功能环境接口。
+%    \begin{macrocode}
+\NewDocumentEnvironment { wrapstuff } { O { } }
+  {
+    \@@_clear:
+    \int_set:Nn \l_@@_top_int { -1 }
+    \tl_if_blank:nTF {#1}
+      { \tl_clear:N \l_@@_main_kv_tl }
+      {
+        \keys_set_filter:nnnN { wrapstuff }
+          { main , ratio }
+          {#1} \l_@@_main_kv_tl
+      }
+    \tl_set:Nx \l_@@_type_tl { \l_@@_type_tl }
+    \dim_set:Nn \l_@@_width_dim { \l_@@_width_tl }
+    \dim_set:Nn \l_@@_height_dim { \l_@@_height_tl }
+    \hbox_gset:Nw \g_@@_stuff_box
+      \dim_compare:nNnTF \l_@@_width_dim > \c_zero_dim
+        { \@@_minipage_begin: }
+        { \@@_hbox_begin: }
+  }
+  {
+    \dim_compare:nNnTF \l_@@_width_dim > \c_zero_dim
+      { \@@_minipage_end: }
+      { \@@_hbox_end: }
+    \@@_set_vsep:
+    \@@_attach_label:
+    \tl_if_empty:NTF \l_@@_main_kv_tl
+      { \tl_gclear:N \g_@@_main_setting_tl }
+      { \@@_save_main_setting: }
+    \@@_set_top_line:
+    \dim_gset:Nn \g_@@_stuff_wd_dim
+      { \box_wd:N \g_@@_stuff_box }
+    \dim_gset:Nn \g_@@_stuff_ht_dim
+      { \box_ht_plus_dp:N \g_@@_stuff_box }
+    \dim_gset_eq:NN
+      \g_@@_remaining_dim
+      \g_@@_stuff_ht_dim
+    \@@_next_para:
+  }
+\@@_gadd_hook:nn { env/wrapstuff/before } { \par }
+\cs_new_protected_nopar:Npn \@@_minipage_begin:
+  {
+    \@@_floatrow_hook:
+    \dim_compare:nNnTF \l_@@_height_dim > \c_zero_dim
+      { \begin { minipage } [b] [ \l_@@_height_dim ] [c] { \l_@@_width_dim } }
+      { \begin { minipage } [b] { \l_@@_width_dim } }
+    \tl_if_empty:NF \l_@@_type_tl
+      { \@@_set_float: }
+  }
+\cs_new_protected_nopar:Npn \@@_minipage_end:
+  {
+      \end { minipage }
+    \hbox_gset_end:
+    \@@_float_pos_hook:
+  }
+\cs_new_protected_nopar:Npn \@@_hbox_begin:
+  { \tex_ignorespaces:D }
+\cs_new_protected_nopar:Npn \@@_hbox_end:
+  {
+      \tex_unskip:D
+    \hbox_gset_end:
+    \dim_compare:nNnT \l_@@_height_dim > \c_zero_dim
+      { \@@_gset_height: }
+  }
+\cs_new_protected_nopar:Npn \@@_gset_height:
+  {
+    \hbox_gset:Nn \g_@@_stuff_box
+      {
+        \box_move_up:nn
+          {
+            (   \l_@@_height_dim
+              - \box_ht:N \g_@@_stuff_box
+              + \box_dp:N \g_@@_stuff_box
+            ) / 2
+          }
+          { \box_use_drop:N \g_@@_stuff_box }
+      }
+    \box_gset_ht:Nn \g_@@_stuff_box { \l_@@_height_dim }
+    \box_gset_dp:Nn \g_@@_stuff_box { \c_zero_dim }
+  }
+\cs_new_protected_nopar:Npn \@@_set_vsep:
+  {
+    \@@_gadd_ht:Nn \g_@@_stuff_box { \l_@@_abovesep_tl }
+    \dim_set:Nn \l_@@_shift_dim { \l_@@_belowsep_tl }
+    \dim_compare:nNnF \l_@@_shift_dim = \c_zero_dim
+      { \@@_set_belowsep: }
+  }
+\cs_new_protected_nopar:Npn \@@_set_belowsep:
+  {
+    \hbox_gset:Nn \g_@@_stuff_box
+      {
+        \box_move_up:nn
+          { \l_@@_shift_dim + \box_dp:N \g_@@_stuff_box }
+          { \box_use_drop:N \g_@@_stuff_box }
+      }
+    \box_gset_dp:Nn \g_@@_stuff_box { \c_zero_dim }
+  }
+\tl_new:N \l_@@_main_kv_tl
+\tl_new:N \g_@@_main_setting_tl
+\box_new:N \g_@@_stuff_box
+\dim_new:N \g_@@_stuff_ht_dim
+\dim_new:N \g_@@_stuff_wd_dim
+\dim_new:N \l_@@_shift_dim
+\dim_new:N \l_@@_width_dim
+\dim_new:N \l_@@_height_dim
+\dim_new:N \g_@@_prevdepth_dim
+\dim_new:N \g_@@_remaining_dim
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_attach_label:, \@@_write_label:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_attach_label:
+  {
+    \stepcounter { wrapstuff }
+    \hbox_gset:Nn \g_@@_stuff_box
+      {
+        \@@_write_label:
+        \box_use_drop:N \g_@@_stuff_box
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_write_label:
+  {
+    \iow_shipout_x:Nx \@auxout
+      {
+        \c_backslash_str wrapstuff@label
+          { \@@_counter:n { wrapstuff } }
+          { \exp_not:N \wrapstuff@counter { page } }
+      }
+  }
+\cs_new:Npn \@@_counter:n #1
+  { \int_value:w \value {#1} }
+\cs_new_eq:NN \wrapstuff@counter \@@_counter:n
+\cs_new_protected_nopar:Npn \wrapstuff@label
+  { \@newl@bel { wrapstuff@label } }
+\tl_const:Nn \c_@@_label_tl
+  { wrapstuff@label@ \int_value:w \value { wrapstuff } }
+\@@_gadd_hook:nn { begindocument }
+  {
+    \legacy_if:nTF { @filesw }
+      {
+        \iow_now:Nx \@mainaux
+          {
+            \c_backslash_str providecommand
+            \c_backslash_str wrapstuff@label [2] { }
+          }
+      }
+      { \cs_gset_eq:NN \@@_write_label: \@@_empty: }
+  }
+\newcounter { wrapstuff }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_save_main_setting:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_save_main_setting:
+  {
+    \exp_args:Nnno
+    \keys_set_filter:nnnN { wrapstuff }
+      { main }
+      { \l_@@_main_kv_tl } \l_@@_main_kv_tl
+    \bool_if:NTF \l_@@_swap_bool
+      { \@@_swap_ratio: }
+      { \@@_set_ratio:N \l_@@_ratio_fp }
+    \tl_if_empty:NF \l_@@_main_kv_tl
+      { \@@_save_main_setting_aux: }
+  }
+\cs_new_protected:Npn \@@_set_ratio:N #1
+  {
+    \tl_gset:Nx \g_@@_main_setting_tl
+      { \fp_set:Nn \exp_not:N \l_@@_ratio_fp { \fp_use:N #1 } }
+  }
+\cs_new_protected:Npn \@@_set_ratio:n #1
+  {
+    \tl_gset:Nx \g_@@_main_setting_tl
+      { \fp_set:Nn \exp_not:N \l_@@_ratio_fp { \fp_eval:n {#1} } }
+  }
+\cs_new_protected_nopar:Npn \@@_save_main_setting_aux:
+  {
+    \exp_args:Nno
+    \keys_precompile:nnN
+      { wrapstuff }
+      { \l_@@_main_kv_tl } \l_@@_main_kv_tl
+    \tl_gconcat:NNN \g_@@_main_setting_tl
+      \g_@@_main_setting_tl \l_@@_main_kv_tl
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_set_top_line:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_set_top_line:
+  {
+    \int_compare:nNnF \l_@@_top_int < \c_zero_int
+      {
+        \tl_gput_right:Nx \g_@@_main_setting_tl
+          {
+            \int_set:Nn \l_@@_top_int
+              { \int_use:N \l_@@_top_int }
+          }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_swap_ratio:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_swap_ratio:
+  {
+    \fp_compare:nF
+      { \c_zero_fp < \l_@@_ratio_fp < \c_one_fp }
+      { \fp_zero:N \l_@@_ratio_fp }
+    \int_if_odd:nTF
+      {
+        \exp_args:Ne \cs_if_exist_use:cF
+          { \c_@@_label_tl }
+          { \@@_counter:n { page } }
+      }
+      { \bool_if:NTF \l_@@_inner_bool }
+      { \bool_if:NTF \l_@@_outer_bool }
+      { \@@_set_ratio:N \l_@@_ratio_fp }
+      { \@@_set_ratio:n { \c_one_fp - \l_@@_ratio_fp } }
+  }
+\bool_new:N \l_@@_swap_bool
+\bool_new:N \l_@@_inner_bool
+\bool_new:N \l_@@_outer_bool
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_gadd_ht:Nn,\@@_gsub_ht:Nn}
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_gadd_ht:Nn #1#2
+  { \box_gset_ht:Nn #1 { \box_ht:N #1 + \dim_eval:n {#2} } }
+\cs_new_protected:Npn \@@_gsub_ht:Nn #1#2
+  { \box_gset_ht:Nn #1 { \box_ht:N #1 - \dim_eval:n {#2} } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_clear:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_clear:
+  {
+    \@@_clear_para_hook:
+    \@@_clear_kludge:
+    \@@_clear_variable:
+  }
+\cs_new_protected_nopar:Npn \@@_clear_variable:
+  {
+    \int_gset:Nn \g_@@_top_int { -1 }
+    \int_gzero:N \g_@@_window_int
+    \dim_gzero:N \g_@@_total_ht_dim
+    \dim_gzero:N \g_@@_column_left_dim
+    \tl_gclear:N \g_@@_main_setting_tl
+    \bool_gset_false:N \g_@@_next_bool
+    \bool_gset_false:N \g_@@_hoffset_bool
+    \bool_gset_false:N \g_@@_next_hang_bool
+    \bool_gset_false:N \g_@@_first_save_bool
+    \bool_gset_false:N \g_@@_right_move_bool
+    \bool_gset_false:N \g_@@_column_right_bool
+  }
+\cs_new_protected_nopar:Npn \@@_clear_kludge:
+  {
+    \bool_if:NTF \g_@@_next_bool
+      {
+        \box_gclear:N \g_@@_stuff_box
+        \skip_vertical:n
+          { \tex_baselineskip:D * \g_@@_window_int }
+      }
+      {
+        \box_if_empty:NF \g_@@_stuff_box
+          { \@@_clear_stuff_box: }
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_clear_stuff_box:
+  {
+    \@@_ignore_depth:
+    \skip_set:Nn \l_@@_last_skip
+      { \box_dp:N \strutbox }
+    \skip_vertical:N \l_@@_last_skip
+    \box_use_drop:N \g_@@_stuff_box
+    \skip_vertical:N \l_@@_last_skip
+    \@@_ignore_depth:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_next_para:}
+% 将 \env{wrapstuff} 环境之后的段落放入内部环境 \env{wrapstuff@par} 中。
+% 为了控制钩子执行顺序，需要使用 |wrapstuff| 标签，
+% 而不用更为方便的 \cs{hook_gput_next_code:nn} 实现。
+%    \begin{macrocode}
+\@@_gadd_hook:nn { para/before } { \@@_para_before: }
+\@@_gadd_hook:nn { para/begin }  { \@@_para_begin: }
+\@@_gadd_hook:nn { para/end }    { \@@_para_end: }
+\cs_new_protected_nopar:Npn \@@_next_para:
+  {
+    \cs_gset_eq:NN \@@_para_before: \@@_env_before:
+    \cs_gset_eq:NN \@@_para_begin:  \@@_env_begin:
+    \cs_gset_eq:NN \@@_para_end:    \@@_env_end:
+  }
+\cs_new_protected_nopar:Npn \@@_env_before:
+  { \dim_gset_eq:NN \g_@@_prevdepth_dim \tex_prevdepth:D }
+\cs_new_protected_nopar:Npn \@@_env_begin:
+  { \begin { wrapstuff@par } }
+\cs_new_protected_nopar:Npn \@@_env_end:
+  { \end { wrapstuff@par } }
+\cs_new_protected_nopar:Npn \@@_clear_para_hook:
+  {
+    \cs_gset_eq:NN \@@_para_before: \@@_empty:
+    \cs_gset_eq:NN \@@_para_begin:  \@@_empty:
+    \cs_gset_eq:NN \@@_para_end:    \@@_empty:
+  }
+\cs_new_protected_nopar:Npn \@@_empty:
+  { }
+\cs_new_eq:NN \@@_para_before: \@@_empty:
+\cs_new_eq:NN \@@_para_begin:  \@@_empty:
+\cs_new_eq:NN \@@_para_end:    \@@_empty:
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}[int]{wrapstuff@par}
+% 内部环境，实现主要功能。
+%    \begin{macrocode}
+\NewDocumentEnvironment { wrapstuff@par } { }
+  {
+    \tl_use:N \g_@@_main_setting_tl
+    \dim_set:Nn \l_@@_leftsep_dim { \l_@@_leftsep_tl }
+    \dim_set:Nn \l_@@_rightsep_dim { \l_@@_rightsep_tl }
+    \dim_set:Nn \l_@@_voffset_dim { \l_@@_voffset_tl }
+    \dim_set:Nn \l_@@_line_dim { \l_@@_linewidth_tl }
+    \dim_set:Nn \l_@@_min_dim { \box_dp:N \strutbox }
+    \dim_set_eq:NN \l_@@_main_width_dim \l_@@_line_dim
+    \dim_sub:Nn \l_@@_line_dim
+      { \tex_leftskip:D + \tex_rightskip:D }
+    \dim_set:Nn \l_@@_window_dim
+      { \l_@@_line_dim - \g_@@_stuff_wd_dim }
+    \fp_compare:nNnTF \l_@@_ratio_fp > \c_zero_fp
+      {
+        \fp_compare:nNnTF \l_@@_ratio_fp < \c_one_fp
+          { \@@_set_window: }
+          { \@@_set_hang_right: }
+      }
+      { \@@_set_hang_left: }
+    \int_compare:nNnTF \g_@@_window_int > \c_zero_int
+      {
+        \int_set_eq:NN \l_@@_window_int \g_@@_window_int
+        \int_zero:N \l_@@_top_int
+      }
+      { \@@_set_lines: }
+    \bool_if:NTF \l_@@_hang_bool
+      {
+        \dim_set_eq:NN \l_@@_display_dim \l_@@_window_dim
+        \int_set_eq:NN \l_@@_window_line_int \l_@@_window_int
+      }
+      {
+        \dim_set_eq:NN \l_@@_display_dim \l_@@_l_dim
+        \int_set:Nn \l_@@_window_int { \l_@@_window_int * 2 }
+        \int_set:Nn \l_@@_window_line_int
+          {
+            \bool_if:NTF \g_@@_column_right_bool
+              { \l_@@_window_int / 2 + \g_@@_column_window_int }
+              { \l_@@_window_int }
+          }
+      }
+    \cs_gset_eq:NN \@@_para_before: \@@_empty:
+    \cs_gset_eq:NN \@@_para_begin:  \@@_empty:
+    \@@_save_parshape:
+    \vbox_set:Nw \l_@@_body_box
+      \@@_set_prevdepth:N \g_@@_prevdepth_dim
+      \@@_save_tex_skip:
+      \@@_tex_parameter:
+      \@@_restore_parshape:
+      \@@_display_parameter:
+      \@@_make_main_parshape:
+      \para_raw_noindent:
+  }
+  {
+      \@@_save_hangfrom:
+      \@@_save_tex_skip:
+      \@@_group_kludge:
+      \@@_tex_parameter:
+      \@@_make_main_parshape:
+      \para_raw_end:
+      \int_gset_eq:NN \g_@@_line_int \tex_prevgraf:D
+    \vbox_set_end:
+    \@@_adjust_tex_skip:
+    \cs_gset_eq:NN \@@_para_end: \@@_empty:
+    \int_compare:nNnTF \g_@@_line_int > \l_@@_top_int
+      { \@@_build_par: }
+      { \@@_put_par: }
+  }
+\box_new:N \l_@@_body_box
+\box_new:N \l_@@_window_box
+\int_new:N \l_@@_window_int
+\int_new:N \g_@@_window_int
+\int_new:N \g_@@_line_int
+\int_new:N \l_@@_window_line_int
+\int_new:N \g_@@_column_window_int
+\dim_new:N \l_@@_l_dim
+\dim_new:N \l_@@_r_dim
+\dim_new:N \l_@@_min_dim
+\dim_new:N \l_@@_line_dim
+\dim_new:N \l_@@_window_dim
+\dim_new:N \l_@@_display_dim
+\dim_new:N \l_@@_voffset_dim
+\dim_new:N \l_@@_leftsep_dim
+\dim_new:N \l_@@_rightsep_dim
+\dim_new:N \g_@@_window_ht_dim
+\dim_new:N \l_@@_main_width_dim
+\int_new:N \g_@@_top_int
+\int_gdecr:N \g_@@_top_int
+\bool_new:N \l_@@_hang_bool
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_set_hang_left:, \@@_set_hang_right:, \@@_set_window:,}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_set_hang_left:
+  {
+    \bool_set_true:N \l_@@_hang_bool
+    \bool_if:NF \g_@@_hoffset_bool
+      { \@@_set_hoffset:NN \l_@@_rightsep_dim \use:nn }
+    \dim_sub:Nn \l_@@_window_dim { \l_@@_rightsep_dim }
+    \dim_zero:N \l_@@_l_dim
+    \dim_set_eq:NN \l_@@_r_dim \l_@@_window_dim
+    \cs_set_eq:NN \@@_build_box: \@@_build_hang:
+  }
+\cs_new_protected_nopar:Npn \@@_set_hang_right:
+  {
+    \bool_set_true:N \l_@@_hang_bool
+    \bool_if:NF \g_@@_hoffset_bool
+      { \@@_set_hoffset:NN \l_@@_leftsep_dim \use_ii_i:nn }
+    \dim_sub:Nn \l_@@_window_dim { \l_@@_leftsep_dim }
+    \dim_zero:N \l_@@_r_dim
+    \dim_set_eq:NN \l_@@_l_dim \l_@@_window_dim
+    \cs_set_eq:NN \@@_build_box: \@@_build_hang:
+  }
+\cs_new_protected_nopar:Npn \@@_set_window:
+  {
+    \bool_set_false:N \l_@@_hang_bool
+    \dim_sub:Nn \l_@@_window_dim
+      { \l_@@_leftsep_dim + \l_@@_rightsep_dim }
+    \dim_set:Nn \l_@@_l_dim
+      { \@@_ratio:Nn \l_@@_ratio_fp { \l_@@_window_dim } }
+    \dim_set:Nn \l_@@_r_dim
+      { \l_@@_window_dim - \l_@@_l_dim }
+    \bool_if:NTF \l_@@_column_bool
+      { \cs_set_eq:NN \@@_build_box: \@@_build_column: }
+      { \cs_set_eq:NN \@@_build_box: \@@_build_block: }
+  }
+\cs_new_protected:Npn \@@_set_hoffset:NN #1#2
+  {
+    \bool_gset_true:N \g_@@_hoffset_bool
+    \dim_set:Nn \l_@@_hoffset_width_dim
+      { #1 + \g_@@_stuff_wd_dim }
+    \group_begin:
+      \cs_set_eq:NN \width \l_@@_hoffset_width_dim
+      \dim_gset:Nn \g_@@_hoffset_dim { \l_@@_hoffset_tl }
+    \group_end:
+    \int_compare:nNnF \g_@@_hoffset_dim = \c_zero_dim
+      {
+        \hbox_gset:Nn \g_@@_stuff_box
+          {
+            #2 { \tex_kern:D - \g_@@_hoffset_dim }
+               { \box_use_drop:N \g_@@_stuff_box }
+          }
+        \dim_add:Nn \l_@@_window_dim { \g_@@_hoffset_dim }
+      }
+  }
+\dim_new:N \g_@@_hoffset_dim
+\dim_new:N \l_@@_hoffset_width_dim
+\bool_new:N \g_@@_hoffset_bool
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_set_lines:, \@@_window_init:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_set_lines:
+  {
+    \bool_if:NTF \g_@@_next_bool
+      { \tl_clear:N \l_@@_lines_tl }
+      { \tl_set:Nx \l_@@_lines_tl { \l_@@_lines_tl } }
+    \int_set:Nn \l_@@_window_int
+      {
+        \tl_if_empty:NTF \l_@@_lines_tl
+          { \@@_unit:n { \g_@@_remaining_dim + \l_@@_min_dim } }
+          { \l_@@_lines_tl }
+      }
+    \bool_if:NF \g_@@_next_bool
+      { \@@_window_init: }
+    \int_compare:nNnTF \g_@@_top_int < \c_zero_int
+      {
+        \int_compare:nNnT \l_@@_top_int < \c_zero_int
+          { \int_zero:N \l_@@_top_int }
+      }
+      { \int_set_eq:NN \l_@@_top_int \g_@@_top_int }
+  }
+\cs_new_protected_nopar:Npn \@@_window_init:
+  {
+    \int_gset_eq:NN \g_@@_column_window_int \l_@@_window_int
+    \dim_gset:Nn \g_@@_window_ht_dim
+      { \tex_baselineskip:D * \g_@@_column_window_int }
+    \tl_if_empty:NF \l_@@_lines_tl
+      {
+        \dim_gset:Nn \g_@@_remaining_dim
+          { \g_@@_window_ht_dim - \box_ht:N \strutbox }
+        \dim_gset_eq:NN \g_@@_stuff_ht_dim \g_@@_remaining_dim
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_make_main_parshape:}
+% 主要处理用于标题悬挂的 \tn{@hangfrom} 和用于列表环境的 \tn{parshape}。
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_make_main_parshape:
+  {
+    \dim_compare:nNnTF \g_@@_hangindent_dim > \c_zero_dim
+      {
+        \int_compare:nNnTF \g_@@_hangafter_int = \c_one_int
+          { \@@_make_hangfrom: }
+          { \@@_make_main_parshape_aux: }
+      }
+      { \@@_make_main_parshape_aux: }
+  }
+\cs_new_protected_nopar:Npn \@@_make_main_parshape_aux:
+  {
+    \bool_gset_false:N \g_@@_hangfrom_bool
+    \tex_parshape:D
+      \int_eval:n { \l_@@_top_int + 1 } ~
+      \prg_replicate:nn
+        { \l_@@_top_int }
+        { \g_@@_parshape_indent_dim \g_@@_parshape_length_dim }
+      \c_zero_dim \c_max_dim
+  }
+\cs_new_protected_nopar:Npn \@@_save_parshape:
+  {
+    \int_gset_eq:NN \g_@@_parshape_int \tex_parshape:D
+    \int_compare:nNnTF \g_@@_parshape_int = \c_one_int
+      {
+        \dim_gset:Nn \g_@@_parshape_indent_dim
+          { \tex_parshapeindent:D \c_one_int }
+        \dim_gset:Nn \g_@@_parshape_length_dim
+          { \tex_parshapelength:D \c_one_int }
+      }
+      {
+        \int_gzero:N \g_@@_parshape_int
+        \dim_gzero:N \g_@@_parshape_indent_dim
+        \dim_gset_eq:NN \g_@@_parshape_length_dim \l_@@_main_width_dim
+        \int_gset_eq:NN \g_@@_hangafter_int  \tex_hangafter:D
+        \dim_gset_eq:NN \g_@@_hangindent_dim \tex_hangindent:D
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_restore_parshape:
+  {
+    \int_compare:nNnTF \g_@@_parshape_int = \c_one_int
+      {
+        \tex_parshape:D \g_@@_parshape_int
+          \g_@@_parshape_indent_dim \g_@@_parshape_length_dim
+      }
+      { \@@_restore_hangfrom: }
+  }
+\cs_new_protected_nopar:Npn \@@_parshape_kern:
+  {
+    \dim_compare:nNnT \l_@@_l_dim = \c_zero_dim
+      {
+        \dim_compare:nNnF \g_@@_parshape_indent_dim = \c_zero_dim
+          { \tex_kern:D - \g_@@_parshape_indent_dim }
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_make_hangfrom:
+  {
+    \bool_if:NTF \l_@@_hang_bool
+      { \@@_make_hangfrom_aux: }
+      { \@@_make_main_parshape_aux: }
+  }
+\cs_new_protected_nopar:Npn \@@_make_hangfrom_aux:
+  {
+    \@@_restore_hangfrom:
+    \int_zero:N \tex_parshape:D
+    \bool_gset_true:N \g_@@_hangfrom_bool
+    \dim_set_eq:NN \tex_hsize:D \l_@@_window_dim
+  }
+\cs_new_protected_nopar:Npn \@@_save_hangfrom:
+  {
+    \int_gset_eq:NN \g_@@_hangafter_int  \tex_hangafter:D
+    \dim_gset_eq:NN \g_@@_hangindent_dim \tex_hangindent:D
+  }
+\cs_new_protected_nopar:Npn \@@_restore_hangfrom:
+  {
+    \int_set_eq:NN \tex_hangafter:D  \g_@@_hangafter_int
+    \dim_set_eq:NN \tex_hangindent:D \g_@@_hangindent_dim
+  }
+\bool_new:N \g_@@_hangfrom_bool
+\int_new:N \g_@@_parshape_int
+\int_new:N \g_@@_hangafter_int
+\dim_new:N \g_@@_hangindent_dim
+\dim_new:N \g_@@_parshape_indent_dim
+\dim_new:N \g_@@_parshape_length_dim
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_group_kludge:}
+% \LaTeX\ 的 \tn{list} 环境中，为了保持 \tn{parshape}，\tn{par} 被重定义为 |{\@@par}|。
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_group_kludge:
+  {
+    \scan_stop:
+    \int_compare:nNnTF \tex_currentgrouptype:D = \c_one_int
+      {
+        \c_group_end_token
+        \cs_gset_eq:NN \@@_group_begin: \c_group_begin_token
+      }
+      { \cs_gset_eq:NN \@@_group_begin: \@@_empty: }
+    \legacy_if:nTF { @noitemarg }
+      { \cs_gset_eq:NN \@@_set_itemarg: \@noitemargtrue }
+      { \cs_gset_eq:NN \@@_set_itemarg: \@@_empty: }
+  }
+\cs_new_eq:NN \@@_set_itemarg: \@@_empty:
+\cs_new_eq:NN \@@_group_begin: \@@_empty:
+\@@_gadd_hook:nn { env/wrapstuff@par/after }
+  {
+    \@@_set_itemarg:
+    \@@_group_begin:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_ratio:Nn, \@@_unit:n}
+%    \begin{macrocode}
+\cs_new:Npn \@@_ratio:Nn #1#2
+  { \fp_to_dim:n { #1 \dim_to_fp:n {#2} } }
+\cs_new:Npn \@@_unit:n #1
+  {
+    \fp_eval:n
+      {
+        ceil
+          (
+            \dim_to_decimal_in_unit:nn
+              {#1}
+              { \tex_baselineskip:D }
+          )
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_save_tex_skip:,\@@_tex_parameter:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_save_tex_skip:
+  {
+    \skip_gset_eq:NN \g_@@_left_skip \tex_leftskip:D
+    \skip_gset_eq:NN \g_@@_right_skip \tex_rightskip:D
+    \skip_gset_eq:NN \g_@@_parfill_skip \tex_parfillskip:D
+    \skip_gset_eq:NN \g_@@_baseline_skip \tex_baselineskip:D
+    \skip_gset:Nn \g_@@_main_left_skip { - \tex_leftskip:D }
+  }
+\cs_new_protected_nopar:Npn \@@_adjust_tex_skip:
+  {
+    \@@_adjust_skip:N \g_@@_left_skip
+    \@@_adjust_skip:N \g_@@_right_skip
+    \@@_adjust_skip:N \g_@@_parfill_skip
+  }
+\cs_new_protected:Npn \@@_adjust_skip:N #1
+  { \skip_gsub:Nn #1 { \dim_eval:n {#1} } }
+\cs_new_protected_nopar:Npn \@@_tex_parameter:
+  {
+    \int_zero:N \tex_clubpenalty:D
+    \int_zero:N \tex_widowpenalty:D
+    \int_zero:N \tex_interlinepenalty:D
+    \int_zero:N \tex_displaywidowpenalty:D
+    \int_zero:N \tex_clubpenalties:D
+    \int_zero:N \tex_widowpenalties:D
+    \int_zero:N \tex_interlinepenalties:D
+    \int_zero:N \tex_displaywidowpenalties:D
+    \skip_set_eq:NN \tex_leftskip:D \g_@@_left_skip
+    \skip_set_eq:NN \tex_rightskip:D \g_@@_right_skip
+    \skip_set_eq:NN \tex_parfillskip:D \g_@@_parfill_skip
+  }
+\skip_new:N \g_@@_left_skip
+\skip_new:N \g_@@_right_skip
+\skip_new:N \g_@@_parfill_skip
+\skip_new:N \g_@@_baseline_skip
+\skip_new:N \g_@@_main_left_skip
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_display_parameter:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_display_parameter:
+  {
+    \bool_gset_false:N \g_@@_display_bool
+    \tex_everydisplay:D \exp_after:wN
+      {
+        \tex_the:D \tex_everydisplay:D
+        \@@_test_leqno:
+        \dim_compare:nNnF \tex_displaywidth:D < \c_max_dim
+          {
+            \bool_gset_true:N \g_@@_display_bool
+            \dim_set_eq:NN \tex_displaywidth:D \l_@@_display_dim
+          }
+      }
+  }
+\cs_new_eq:NN \@@_test_leqno: \@@_empty:
+\bool_new:N \g_@@_display_bool
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_build_par:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_build_par:
+  {
+    \bool_if:NTF \g_@@_hangfrom_bool
+      { \@@_build_box: }
+      { \@@_build_par_aux: }
+    \box_if_empty:NTF \l_@@_window_box
+      { \@@_put_next_par: }
+      { \@@_put_box: }
+  }
+\cs_new_protected_nopar:Npn \@@_build_par_aux:
+  {
+    \@@_extract_display_hbox:NN \l_@@_body_box \l_@@_bottom_box
+    \int_compare:nNnT \l_@@_top_int > \c_zero_int
+      { \@@_put_body_box: }
+    \box_if_empty:NTF \l_@@_bottom_box
+      {
+        \box_if_empty:NF \g_@@_display_box
+          { \@@_build_display_box: }
+      }
+      { \@@_build_body_box: }
+  }
+\box_new:N \l_@@_bottom_box
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_put_par:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_put_par:
+  {
+    \int_gset:Nn \g_@@_top_int
+      { \l_@@_top_int - \g_@@_line_int }
+    \int_gzero:N \g_@@_window_int
+    \@@_put_body_box:
+    \skip_zero:N \tex_parskip:D
+    \para_raw_noindent:
+    \@@_next_para:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_put_body_box:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_put_body_box:
+  {
+    \para_raw_end:
+    \dim_compare:nNnTF { \box_wd:N \l_@@_body_box } < \c_max_dim
+      { \@@_put_body_aux:N \l_@@_body_box }
+      {
+        \@@_extract_hbox:NN \l_@@_body_box \l_@@_bottom_box
+        \@@_put_body_aux:N \l_@@_body_box
+        \box_set_eq_drop:NN \l_@@_body_box \l_@@_bottom_box
+      }
+    \para_raw_end:
+  }
+\cs_new_protected_nopar:Npn \@@_put_body_aux:N #1
+  {
+    \dim_gset:Nn \g_@@_prevdepth_dim { \box_dp:N #1 }
+    \vbox_unpack_drop:N #1
+    \@@_set_prevdepth:N \g_@@_prevdepth_dim
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_put_next_par:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_put_next_par:
+  {
+    \int_gzero:N \g_@@_top_int
+    \int_gzero:N \g_@@_window_int
+    \skip_zero:N \tex_parskip:D
+    \para_raw_noindent:
+    \@@_next_para:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_build_display_box:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_build_display_box:
+  {
+    \bool_set_true:N \l_@@_display_bool
+    \bool_if:NTF \g_@@_amsmath_bool
+      { \@@_build_display_amsmath: }
+      { \@@_build_display_normal: }
+    \box_if_empty:NTF \l_@@_body_box
+      { \@@_build_display_auxi: }
+      { \@@_build_display_auxii: }
+  }
+\cs_new_protected_nopar:Npn \@@_build_display_amsmath:
+  {
+    \vbox_gset:Nn \g_@@_equation_box
+      {
+        \skip_vertical:n { - \g_@@_display_pre_skip }
+        \vbox_unpack_drop:N \g_@@_display_box
+        \skip_gset_eq:NN \g_@@_pos_skip \tex_lastskip:D
+        \tex_unskip:D
+        \int_gset_eq:NN \g_@@_pos_int \tex_lastpenalty:D
+        \tex_unpenalty:D
+        \skip_gadd:Nn \g_@@_pos_skip { \tex_lastskip:D }
+        \tex_unskip:D
+        \tex_unpenalty:D
+      }
+    \box_gset_wd:Nn \g_@@_equation_box
+      { \l_@@_display_dim }
+    \vbox_gset:Nn \g_@@_display_box
+      {
+        \tex_penalty:D \g_@@_display_pre_int
+        \skip_vertical:N \g_@@_display_pre_skip
+      }
+    \skip_gset_eq:NN \g_@@_pre_skip \g_@@_display_pre_skip
+  }
+\cs_new_protected_nopar:Npn \@@_build_display_normal:
+  {
+    \vbox_gset:Nn \g_@@_display_box
+      {
+        \vbox_unpack_drop:N \g_@@_display_box
+        \skip_gset_eq:NN \g_@@_pos_skip \tex_lastskip:D
+        \tex_unskip:D
+        \int_gset_eq:NN \g_@@_pos_int \tex_lastpenalty:D
+        \tex_unpenalty:D
+        \box_gset_to_last:N \g_@@_equation_box
+        \skip_gset_eq:NN \g_@@_pre_skip \tex_lastskip:D
+        \tex_unskip:D
+        \skip_gadd:Nn \g_@@_pre_skip { \tex_lastskip:D }
+        \tex_unskip:D
+        \skip_vertical:N \g_@@_pre_skip
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_build_display_auxi:
+  {
+    \bool_if:NTF \g_@@_amsmath_bool
+      { \box_set_eq_drop:NN \l_@@_window_box \g_@@_equation_box }
+      {
+        \hbox_set_to_wd:Nnn \l_@@_window_box
+          { \l_@@_display_dim }
+          {
+            \tex_hss:D
+              \@@_adjust_equation:
+              \box_use_drop:N \g_@@_equation_box
+            \tex_hss:D
+          }
+      }
+    \dim_gset:Nn \g_@@_ht_dim { \box_ht:N \l_@@_window_box }
+    \dim_add:Nn \l_@@_voffset_dim
+      { \box_ht:N \g_@@_display_box / 2 }
+  }
+\cs_new_protected_nopar:Npn \@@_build_display_auxii:
+  {
+    \box_if_horizontal:NTF \l_@@_body_box
+      {
+        \box_set_eq:NN \l_@@_bottom_box \l_@@_body_box
+        \@@_build_display_auxiii:
+      }
+      {
+        \@@_extract_hbox:NN \l_@@_body_box \l_@@_bottom_box
+        \str_if_eq:eeTF
+          {
+            \dim_eval:n { \box_ht:N \l_@@_body_box }
+            \dim_eval:n { \box_dp:N \l_@@_body_box }
+            \dim_eval:n { \box_ht:N \l_@@_bottom_box }
+            \dim_eval:n { \box_dp:N \l_@@_bottom_box }
+          }
+          { \c_@@_zero_pt_str }
+          {
+            \vbox_unpack_drop:N \l_@@_body_box
+            \box_clear:N \l_@@_bottom_box
+            \@@_build_display_auxi:
+          }
+          { \@@_build_display_auxiii: }
+      }
+  }
+\str_const:Nx \c_@@_zero_pt_str
+  {
+    \dim_use:N \c_zero_dim
+    \dim_use:N \c_zero_dim
+    \dim_use:N \c_zero_dim
+    \dim_use:N \c_zero_dim
+  }
+\cs_new_protected_nopar:Npn \@@_build_display_auxiii:
+  {
+    \bool_set_true:N \l_@@_attach_equation_bool
+    \bool_if:NTF \g_@@_amsmath_bool
+      { \box_set_eq_drop:NN \l_@@_display_box \g_@@_display_box }
+      {
+        \box_gclear:N \g_@@_display_box
+        \@@_adjust_equation:
+      }
+    \@@_build_body_box:
+  }
+\cs_new_protected_nopar:Npn \@@_attach_equation:N
+  {
+    \bool_if:NTF \g_@@_amsmath_bool
+      { \@@_attach_equation_amsmath:N }
+      { \@@_attach_equation_normal:N }
+  }
+\cs_new_protected:Npn \@@_attach_equation_amsmath:N #1
+  {
+    \vbox_set:Nn #1
+      {
+        \box_use:N #1
+        \@@_ignore_depth:
+        \vbox_unpack_drop:N \l_@@_display_box
+        \skip_vertical:n
+          { \g_@@_display_pre_dim - \box_dp:N #1 }
+        \box_use_drop:N \g_@@_equation_box
+      }
+  }
+\cs_new_protected:Npn \@@_attach_equation_normal:N #1
+  {
+    \vbox_set:Nn #1
+      {
+        \@@_tex_parameter:
+        \dim_set_eq:NN \tex_hsize:D \l_@@_display_dim
+        \para_raw_noindent:
+          \hbox_unpack_drop:N #1 \tex_unskip:D
+          \@@_insert_equation:
+        \para_raw_end:
+        \skip_gset_eq:NN \g_@@_pos_skip \tex_lastskip:D
+        \tex_unskip:D
+        \int_gset_eq:NN \g_@@_pos_int \tex_lastpenalty:D
+        \tex_unpenalty:D
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_insert_equation:
+  {
+    \c_math_toggle_token \c_math_toggle_token
+      \dim_compare:nNnTF \tex_displaywidth:D = \l_@@_display_dim
+        { \box_use_drop:N \g_@@_equation_box }
+        {
+          \bool_if:NTF \g_@@_eqnum_bool
+            { \@@_repack_equation: }
+            { \box_use_drop:N \g_@@_equation_box }
+        }
+    \c_math_toggle_token \c_math_toggle_token
+  }
+\cs_new_protected_nopar:Npn \@@_repack_equation:
+  {
+    \box_gclear:N \g_@@_equation_box
+    \box_use_drop:N \g_@@_eqbody_box
+    \bool_if:NTF \g_@@_leqno_bool
+      { \tex_leqno:D }
+      { \tex_eqno:D }
+    \box_use_drop:N \g_@@_eqnum_box
+  }
+\cs_new_protected_nopar:Npn \@@_adjust_equation:
+  {
+    \@@_test_eqnum:
+    \bool_if:NT \g_@@_eqnum_bool
+      { \@@_adjust_equation_width: }
+  }
+\cs_new_protected_nopar:Npn \@@_test_eqnum:
+  {
+    \hbox_set:Nn \l_@@_last_box
+      {
+        \bool_gset_false:N \g_@@_eqnum_bool
+        \hbox_unpack:N \g_@@_equation_box
+        \@@_if_last_hlist:F { \use_none_delimit_by_q_stop:w }
+        \box_gset_to_last:N \g_@@_eqnum_box
+        \@@_if_last_kern:F  { \use_none_delimit_by_q_stop:w }
+        \tex_unkern:D
+        \@@_if_last_hlist:F { \use_none_delimit_by_q_stop:w }
+        \box_gset_to_last:N \g_@@_eqbody_box
+        \@@_if_last_none:F  { \use_none_delimit_by_q_stop:w }
+        \bool_gset_true:N \g_@@_eqnum_bool
+        \use_none_delimit_by_q_stop:w \q_stop
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_adjust_equation_width:
+  {
+    \bool_if:NTF \g_@@_leqno_bool
+      { \@@_adjust_leqno: }
+      {
+        \box_gset_wd:Nn \g_@@_equation_box
+          { \box_wd:N \g_@@_eqbody_box }
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_adjust_leqno:
+  {
+    \box_set_eq_drop:NN \l_@@_last_box \g_@@_eqnum_box
+    \box_gset_eq_drop:NN \g_@@_eqnum_box \g_@@_eqbody_box
+    \box_gset_eq_drop:NN \g_@@_eqbody_box \l_@@_last_box
+    \hbox_gset:Nn \g_@@_equation_box
+      {
+        \skip_horizontal:n
+          {
+              \box_wd:N \g_@@_eqbody_box
+            - \box_wd:N \g_@@_equation_box
+          }
+        \box_use_drop:N \g_@@_equation_box
+      }
+  }
+\box_new:N \g_@@_eqbody_box
+\box_new:N \g_@@_eqnum_box
+\box_new:N \g_@@_equation_box
+\box_new:N \l_@@_display_box
+\int_new:N \g_@@_pos_int
+\skip_new:N \g_@@_pos_skip
+\bool_new:N \g_@@_eqnum_bool
+\bool_new:N \g_@@_leqno_bool
+\bool_new:N \l_@@_display_bool
+\bool_new:N \l_@@_attach_equation_bool
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_add_pos_skip:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_add_pos_skip:
+  {
+    \bool_lazy_or:nnTF
+      { \g_@@_right_move_bool }
+      { \int_compare_p:nNn \g_@@_window_int > \c_zero_int }
+      {
+        \tex_vadjust:D
+          {
+            \tex_penalty:D \c_@@_nobreak_int
+            \bool_if:NT \l_@@_display_bool
+              { \skip_vertical:N \g_@@_pos_skip }
+          }
+      }
+      {
+        \bool_if:NT \l_@@_display_bool
+          {
+            \tex_vadjust:D
+              {
+                \tex_penalty:D \g_@@_pos_int
+                \skip_vertical:N \g_@@_pos_skip
+              }
+          }
+      }
+    \int_gzero:N \g_@@_pos_int
+    \skip_gzero:N \g_@@_pos_skip
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_build_body_box:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_build_body_box:
+  {
+    \box_set_eq:NN \l_@@_save_body_box \l_@@_bottom_box
+    \@@_build_window:
+    \int_compare:nNnTF \g_@@_line_int > \l_@@_window_line_int
+      { \@@_extract_hbox:NN \l_@@_body_box \l_@@_bottom_box }
+      { \box_clear:N \l_@@_bottom_box }
+    \box_if_empty:NF \l_@@_bottom_box
+      { \bool_set_false:N \l_@@_attach_equation_bool }
+    \box_clear:N \l_@@_window_box
+    \@@_build_box:
+  }
+\box_new:N \l_@@_save_body_box
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_build_body_box:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_build_window:
+  {
+    \vbox_set:Nn \l_@@_body_box
+      {
+        \@@_tex_parameter:
+        \@@_make_parshape:
+        \@@_column_penalties:
+        \dim_zero:N \tex_emergencystretch:D
+        \dim_set_eq:NN \tex_hfuzz:D \c_max_dim
+        \dim_set_eq:NN \tex_vfuzz:D \c_max_dim
+        \int_set_eq:NN \tex_hbadness:D \c_max_int
+        \int_set_eq:NN \tex_vbadness:D \c_max_int
+        \int_set:Nn \tex_tolerance:D { 1000 }
+        \para_raw_noindent:
+          \hbox_unpack_drop:N \l_@@_bottom_box
+        \para_raw_end:
+        \int_gset_eq:NN \g_@@_line_int \tex_prevgraf:D
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_make_parshape:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_make_parshape:
+  {
+    \tex_parshape:D
+      \int_eval:n { \l_@@_window_line_int + 1 } ~
+      \bool_if:NTF \l_@@_hang_bool
+        {
+          \prg_replicate:nn
+            { \l_@@_window_int }
+            { \c_zero_dim \l_@@_window_dim }
+        }
+        {
+          \bool_if:NTF \l_@@_column_bool
+            {
+              \prg_replicate:nn
+                { \l_@@_window_int / 2 }
+                { \c_zero_dim \l_@@_l_dim }
+              \prg_replicate:nn
+                {
+                  \bool_if:NTF \g_@@_column_right_bool
+                    { \g_@@_column_window_int }
+                    { \l_@@_window_int / 2 }
+                }
+                { \c_zero_dim \l_@@_r_dim }
+            }
+            {
+              \prg_replicate:nn
+                { \l_@@_window_int / 2 }
+                {
+                  \c_zero_dim \l_@@_l_dim
+                  \c_zero_dim \l_@@_r_dim
+                }
+            }
+        }
+      \c_zero_dim \c_max_dim
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_column_penalties:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_column_penalties:
+  {
+    \bool_if:NF \l_@@_hang_bool
+      {
+        \bool_if:NT \l_@@_column_bool
+          { \@@_column_penalties_aux: }
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_column_penalties_aux:
+  {
+    \tex_interlinepenalties:D
+      \int_eval:n { \l_@@_window_int / 2 + \c_one_int } ~
+      \prg_replicate:nn
+        { \l_@@_window_int / 2 - \c_one_int }
+        { \c_@@_nobreak_int }
+      \c_@@_break_int
+      \c_zero_int
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_build_box:, \@@_build_block:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_build_block:
+  {
+    \@@_build_block_auxi:
+    \vbox_set:Nn \l_@@_window_box
+      {
+        \@@_tex_parameter:
+        \dim_set_eq:NN \tex_hsize:D \l_@@_line_dim
+        \para_raw_noindent:
+          \hbox_unpack_drop:N \g_@@_line_box
+        \para_raw_end:
+      }
+    \bool_if:NT \l_@@_attach_equation_bool
+      {
+        \box_set_ht:Nn \l_@@_window_box
+          { \box_ht_plus_dp:N \l_@@_window_box - \g_@@_dp_dim }
+        \box_set_dp:Nn \l_@@_window_box { \g_@@_dp_dim }
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_build_block_auxi:
+  {
+    \vbox_set:Nn \l_@@_body_box
+      {
+        \vbox_unpack_drop:N \l_@@_body_box
+        \bool_lazy_and:nnTF
+          { \box_if_empty_p:N \l_@@_bottom_box }
+          { \int_if_odd_p:n { \g_@@_line_int } }
+          { \box_set_eq:NN \l_@@_r_box \l_@@_empty_box }
+          {
+            \box_set_to_last:N \l_@@_r_box
+            \tex_unskip:D \tex_unpenalty:D
+          }
+        \box_set_to_last:N \l_@@_l_box
+        \tex_unskip:D \tex_unpenalty:D
+        \hbox_gset:Nn \g_@@_line_box
+          {
+            \bool_if:NT \l_@@_attach_equation_bool
+              { \@@_build_block_attach: }
+            \box_use:N \l_@@_l_box
+            \tex_hfill:D
+            \box_use:N \l_@@_r_box
+          }
+        \@@_build_block_auxii:
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_build_block_auxii:
+  {
+    \int_case:nnTF
+      { \tex_lastnodetype:D }
+      {
+        { \c_@@_none_node }    { }
+        { \c_@@_whatsit_node } { }
+      }
+      { \@@_build_block_finalise: }
+      { \@@_build_block_auxiii: }
+  }
+\cs_new_protected_nopar:Npn \@@_build_block_auxiii:
+  {
+    \box_set_to_last:N \l_@@_r_box
+    \tex_unskip:D \tex_unpenalty:D
+    \box_set_to_last:N \l_@@_l_box
+    \tex_unskip:D \tex_unpenalty:D
+    \hbox_gset:Nn \g_@@_line_box
+      {
+        \box_use:N \l_@@_l_box
+        \tex_hfill:D
+        \box_use:N \l_@@_r_box
+        \tex_penalty:D \c_@@_break_int
+        \hbox_unpack_drop:N \g_@@_line_box
+      }
+    \@@_build_block_auxii:
+  }
+\cs_new_protected_nopar:Npn \@@_build_block_attach:
+  {
+    \box_set_eq:NN \l_@@_last_box \l_@@_l_box
+    \@@_attach_equation:N \l_@@_last_box
+    \dim_gset:Nn \g_@@_dp_dim { \box_dp:N \l_@@_last_box }
+    \hbox_set:Nn \l_@@_l_box
+      {
+        \box_move_down:nn
+          { \box_ht:N \l_@@_last_box - \box_ht:N \l_@@_l_box }
+          { \box_use_drop:N \l_@@_last_box }
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_build_block_finalise:
+  {
+    \dim_gset:Nn \g_@@_ht_dim
+      {
+        \dim_max:nn
+          { \box_ht:N \l_@@_l_box }
+          { \box_ht:N \l_@@_r_box }
+      }
+  }
+\dim_new:N \g_@@_dp_dim
+\dim_new:N \g_@@_ht_dim
+\box_new:N \l_@@_l_box
+\box_new:N \l_@@_r_box
+\box_new:N \g_@@_line_box
+\box_new:N \l_@@_empty_box
+\hbox_set:Nn \l_@@_empty_box { }
+\int_const:Nn \c_@@_break_int { -10000 }
+\int_const:Nn \c_@@_nobreak_int { 10000 }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_build_column_fuzzy:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_build_column_fuzzy:
+  {
+    \hbox_set_to_wd:Nnn \l_@@_window_box
+      { \l_@@_line_dim }
+      {
+        \skip_zero:N \tex_splittopskip:D
+        \dim_set_eq:NN \tex_vfuzz:D \c_max_dim
+        \int_set_eq:NN \tex_vbadness:D \c_max_int
+        \@@_build_column_aux:
+        \box_if_empty:NT \l_@@_bottom_box
+          { \@@_build_column_fuzzy_aux: }
+        \dim_gset:Nn \g_@@_ht_dim { \box_ht:N \l_@@_l_box }
+        \vbox_set:Nn \l_@@_l_box
+          {
+            \vbox_unpack_drop:N \l_@@_l_box
+            \bool_if:NT \l_@@_attach_equation_bool
+              {
+                \box_set_to_last:N \l_@@_last_box
+                \@@_attach_equation:N \l_@@_last_box
+                \vbox_unpack_drop:N \l_@@_last_box
+              }
+          }
+        \box_use:N \l_@@_l_box
+        \tex_hfil:D
+        \box_move_up:nn
+          { \box_ht:N \l_@@_l_box - \box_ht:N \l_@@_r_box }
+          { \box_use_drop:N \l_@@_r_box }
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_build_column_aux:
+  {
+    \vbox_set_split_to_ht:NNn \l_@@_l_box \l_@@_body_box
+      { \c_zero_dim }
+    \vbox_set_top:Nn \l_@@_l_box
+      { \vbox_unpack_drop:N \l_@@_l_box }
+    \box_set_eq_drop:NN \l_@@_r_box \l_@@_body_box
+  }
+\cs_new_protected_nopar:Npn \@@_build_column_fuzzy_aux:
+  {
+    \dim_compare:nNnTF
+      {
+        \box_ht_plus_dp:N \l_@@_r_box -
+        \box_ht_plus_dp:N \l_@@_l_box
+      }
+      >
+      { \l_@@_min_dim }
+      {
+        \box_if_empty:NF \l_@@_last_l_box
+          {
+            \box_set_eq_drop:NN \l_@@_l_box \l_@@_last_l_box
+            \box_set_eq_drop:NN \l_@@_r_box \l_@@_last_r_box
+          }
+      }
+      { \@@_rebuild_window: }
+  }
+\cs_new_protected_nopar:Npn \@@_rebuild_window:
+  {
+    \int_compare:nNnT \l_@@_window_int > { 2 }
+      {
+        \int_sub:Nn \l_@@_window_int { 2 }
+        \box_set_eq_drop:NN \l_@@_last_l_box \l_@@_l_box
+        \box_set_eq_drop:NN \l_@@_last_r_box \l_@@_r_box
+        \box_set_eq:NN \l_@@_bottom_box \l_@@_save_body_box
+        \int_set_eq:NN \l_@@_window_line_int \l_@@_window_int
+        \@@_build_window:
+        \@@_build_column_aux:
+        \@@_build_column_fuzzy_aux:
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_build_column_strict:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_build_column_strict:
+  {
+    \group_begin:
+      \skip_zero:N \tex_splittopskip:D
+      \dim_set_eq:NN \tex_vfuzz:D \c_max_dim
+      \int_set_eq:NN \tex_vbadness:D \c_max_int
+      \@@_build_column_aux:
+      \box_if_empty:NTF \l_@@_r_box
+        { \@@_build_column_strict_auxi: }
+        {
+          \box_if_empty:NTF \l_@@_bottom_box
+            { \@@_build_column_strict_auxii: }
+            {
+              \bool_if:NTF \g_@@_column_right_bool
+                { \@@_build_column_strict_auxiii: }
+                { \@@_build_column_strict_auxiv: }
+            }
+        }
+    \group_end:
+    \box_set_eq_drop:NN \l_@@_window_box \g_@@_window_box
+  }
+\cs_new_protected_nopar:Npn \@@_build_column_strict_auxi:
+  {
+    \@@_repack_left_box:
+    \bool_if:NT \l_@@_attach_equation_bool
+      { \@@_column_attach:N \l_@@_l_box }
+    \box_gset_eq_drop:NN \g_@@_window_box \l_@@_l_box
+    \bool_gset_true:N \g_@@_column_right_bool
+    \bool_if:NF \g_@@_first_save_bool
+      {
+        \bool_gset_true:N \g_@@_first_save_bool
+        \dim_gset:Nn \g_@@_first_sep_dim
+          { \tex_baselineskip:D - \g_@@_ht_dim }
+        \dim_gset_eq:NN \g_@@_first_dp_dim \g_@@_prevdepth_dim
+      }
+    \int_case:nnT { \g_@@_window_int }
+      {
+        { \c_zero_int } { }
+        { \g_@@_line_int } { }
+      }
+      { \@@_column_move_entire_aux: }
+  }
+\cs_new_protected_nopar:Npn \@@_column_move_entire_aux:
+  {
+    \bool_gset_true:N \g_@@_entire_bool
+    \bool_gset_true:N \g_@@_next_hang_bool
+  }
+\cs_new_protected_nopar:Npn \@@_column_move_entire:
+  {
+    \dim_gsub:Nn \g_@@_first_sep_dim
+      { \box_dp:N \l_@@_window_box }
+    \bool_gset_false:N \g_@@_entire_bool
+    \dim_gzero:N \g_@@_column_right_ht_dim
+    \dim_gset_eq:NN \g_@@_prevdepth_dim \g_@@_first_dp_dim
+    \@@_column_right_move_set:nn
+      { \g_@@_stuff_ht_dim }
+      { \g_@@_window_ht_dim }
+    \int_gset_eq:NN \g_@@_window_int \g_@@_column_window_int
+  }
+\cs_new_protected:Npn \@@_column_right_move_set:nn #1#2
+  {
+    \bool_gset_true:N \g_@@_right_move_bool
+    \bool_gset_true:N \g_@@_first_set_bool
+    \tl_gput_right:Nn \g_@@_main_setting_tl
+      {
+        \bool_if:NTF \g_@@_first_set_bool
+          {
+            \bool_gset_false:N \g_@@_first_set_bool
+            \bool_set_true:N \l_@@_first_move_bool
+          }
+          { \bool_set_false:N \l_@@_first_move_bool }
+        \fp_zero:N \l_@@_ratio_fp
+      }
+    \@@_make_next_stuff:nn
+      { \l_@@_line_dim - \l_@@_r_dim - \l_@@_rightsep_dim }
+      {#1}
+    \dim_gset:Nn \g_@@_column_left_dim {#2}
+    \int_gzero:N \g_@@_top_int
+  }
+\cs_new_protected_nopar:Npn \@@_build_column_strict_auxii:
+  {
+    \bool_gset_false:N \g_@@_entire_bool
+    \@@_repack_left_box:
+    \bool_if:NT \l_@@_attach_equation_bool
+      { \@@_column_attach:N \l_@@_r_box }
+    \dim_gset:Nn \g_@@_hang_ht_dim
+      {
+        \g_@@_stuff_ht_dim - \tex_baselineskip:D *
+          \@@_unit:n { \box_ht_plus_dp:N \l_@@_r_box }
+        - \g_@@_pos_skip
+      }
+    \dim_compare:nNnTF \g_@@_hang_ht_dim > \c_zero_dim
+      { \@@_column_move_right: }
+      { \@@_column_put_right: }
+    \box_gset_ht:Nn \g_@@_window_box { \box_ht:N \l_@@_l_box }
+    \box_gset_dp:Nn \g_@@_window_box { \box_dp:N \l_@@_l_box }
+  }
+\cs_new_protected_nopar:Npn \@@_column_move_right:
+  {
+    \int_compare:nNnTF \g_@@_window_int > \c_zero_int
+      {
+        \dim_gset:Nn \g_@@_column_left_dim
+          {
+              \g_@@_window_ht_dim
+            - \g_@@_first_sep_dim
+            - \box_ht:N \l_@@_r_box
+          }
+        \@@_next_hang_para:
+      }
+      {
+        \dim_gset:Nn \g_@@_column_left_dim
+          {
+              \box_ht:N \l_@@_l_box
+            - \box_ht:N \l_@@_r_box
+          }
+        \dim_gset:Nn \g_@@_first_sep_dim
+          { \tex_baselineskip:D - \g_@@_ht_dim }
+        \bool_gset_true:N \g_@@_right_move_bool
+        \bool_gset_true:N \g_@@_next_hang_bool
+      }
+    \hbox_gset_to_wd:Nnn \g_@@_window_box
+      { \l_@@_line_dim }
+      {
+        \box_use:N \l_@@_l_box
+        \tex_hfil:D
+        \box_move_up:nn
+          { \g_@@_column_left_dim }
+          { \box_use:N \l_@@_r_box }
+      }
+    \dim_gset:Nn \g_@@_column_right_ht_dim
+      { \box_ht:N \l_@@_r_box + \g_@@_pos_skip }
+  }
+\cs_new_protected_nopar:Npn \@@_column_put_right:
+  {
+    \hbox_gset_to_wd:Nnn \g_@@_window_box
+      { \l_@@_line_dim }
+      {
+        \box_use:N \l_@@_l_box
+        \tex_hfil:D
+        \box_move_up:nn
+          {
+            \int_compare:nNnTF \g_@@_window_int > \c_zero_int
+              { \g_@@_window_ht_dim - \g_@@_first_sep_dim }
+              { \box_ht:N \l_@@_l_box }
+            - \box_ht:N \l_@@_r_box
+          }
+          { \box_use:N \l_@@_r_box }
+      }
+    \skip_gzero:N \g_@@_pos_skip
+  }
+\cs_new_protected_nopar:Npn \@@_next_hang_para:
+  {
+    \bool_if:NTF \g_@@_entire_bool
+      { \@@_column_move_entire: }
+      {
+        \@@_column_right_move_set:nn
+          { \g_@@_hang_ht_dim }
+          { \g_@@_column_left_dim }
+        \int_gzero:N \g_@@_window_int
+      }
+    \bool_gset_false:N \g_@@_next_hang_bool
+  }
+\cs_new_protected_nopar:Npn \@@_build_column_strict_auxiii:
+  {
+    \bool_gset_false:N \g_@@_column_right_bool
+    \@@_repack_left_box:
+    \hbox_gset_to_wd:Nnn \g_@@_window_box
+      { \l_@@_line_dim }
+      {
+        \box_use:N \l_@@_l_box
+        \tex_hfil:D
+        \box_use:N \l_@@_r_box
+      }
+    \box_gset_ht:Nn \g_@@_window_box
+      { \box_ht:N \l_@@_l_box }
+  }
+\cs_new_protected_nopar:Npn \@@_build_column_strict_auxiv:
+  {
+    \@@_repack_left_box:
+    \hbox_gset_to_wd:Nnn \g_@@_window_box
+      { \l_@@_line_dim }
+      {
+        \box_use:N \l_@@_l_box
+        \tex_hfil:D
+        \box_move_up:nn
+          { \box_ht:N \l_@@_l_box - \box_ht:N \l_@@_r_box }
+          { \box_use_drop:N \l_@@_r_box }
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_repack_left_box:
+  {
+    \dim_gset:Nn \g_@@_ht_dim { \box_ht:N \l_@@_l_box }
+    \vbox_set:Nn \l_@@_l_box
+      { \vbox_unpack_drop:N \l_@@_l_box }
+  }
+\cs_new_protected_nopar:Npn \@@_column_attach:N #1
+  {
+    \vbox_set:Nn #1
+      {
+        \vbox_unpack_drop:N #1
+        \box_set_to_last:N \l_@@_last_box
+        \@@_attach_equation:N \l_@@_last_box
+        \vbox_unpack_drop:N \l_@@_last_box
+      }
+  }
+\box_new:N \l_@@_last_l_box
+\box_new:N \l_@@_last_r_box
+\box_new:N \g_@@_window_box
+\dim_new:N \g_@@_fake_wd_dim
+\dim_new:N \g_@@_first_dp_dim
+\dim_new:N \g_@@_first_sep_dim
+\dim_new:N \g_@@_column_left_dim
+\dim_new:N \g_@@_column_right_ht_dim
+\bool_new:N \g_@@_entire_bool
+\bool_new:N \g_@@_next_hang_bool
+\bool_new:N \g_@@_first_save_bool
+\bool_new:N \g_@@_column_right_bool
+\bool_new:N \l_@@_column_strict_bool
+\bool_new:N \g_@@_first_set_bool
+\bool_new:N \l_@@_first_move_bool
+\bool_new:N \g_@@_right_move_bool
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_build_box:,\@@_build_column:}
+%    \begin{macrocode}
+\bool_new:N \l_@@_column_bool
+\cs_new_eq:NN \@@_build_column: \@@_build_column_strict:
+\cs_new_eq:NN \@@_build_box:    \@@_build_column:
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_build_hang:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_build_hang:
+  {
+    \bool_if:NTF \g_@@_hangfrom_bool
+      { \@@_build_hangfrom: }
+      {
+        \vbox_set_top:Nn \l_@@_window_box
+          { \vbox_unpack:N \l_@@_body_box }
+        \dim_gset:Nn \g_@@_ht_dim { \box_ht:N \l_@@_window_box }
+      }
+    \bool_if:NTF \l_@@_attach_equation_bool
+      {
+        \vbox_set:Nn \l_@@_window_box
+          {
+            \vbox_unpack_drop:N \l_@@_window_box
+            \box_set_to_last:N \l_@@_last_box
+            \@@_attach_equation:N \l_@@_last_box
+            \vbox_unpack_drop:N \l_@@_last_box
+          }
+      }
+      { \box_set_eq_drop:NN \l_@@_window_box \l_@@_body_box }
+    \dim_compare:nNnTF \g_@@_column_left_dim > \c_zero_dim
+      { \@@_build_hang_aux: }
+      { \bool_gset_false:N \g_@@_move_hang_bool }
+  }
+\cs_new_protected_nopar:Npn \@@_build_hang_aux:
+  {
+    \dim_set:Nn \l_@@_shift_dim
+      {
+        \dim_max:nn
+          { \box_ht:N \l_@@_window_box }
+          { \tex_baselineskip:D * \g_@@_line_int }
+        + \tex_parskip:D
+      }
+    \dim_gsub:Nn \g_@@_column_left_dim { \l_@@_shift_dim }
+    \dim_compare:nNnTF \g_@@_column_left_dim > \c_zero_dim
+      {
+        \box_if_empty:NTF \l_@@_bottom_box
+          { \bool_if:NT \g_@@_right_move_bool { \@@_set_next_hang: } }
+          { \bool_gset_false:N \g_@@_move_hang_bool }
+      }
+      { \bool_gset_false:N \g_@@_move_hang_bool }
+  }
+\cs_new_protected_nopar:Npn \@@_set_next_hang:
+  {
+    \bool_if:NF \g_@@_move_hang_bool
+      {
+        \bool_gset_true:N \g_@@_move_hang_bool
+        \dim_gset_eq:NN \g_@@_hang_ht_dim \g_@@_remaining_dim
+      }
+    \dim_gsub:Nn \g_@@_hang_ht_dim { \l_@@_shift_dim }
+    \dim_gset:Nn \g_@@_dp_dim { \box_dp:N \l_@@_window_box }
+    \@@_column_right_move_set:nn
+      { \g_@@_hang_ht_dim }
+      { \g_@@_column_left_dim }
+    \int_gzero:N \g_@@_window_int
+  }
+\dim_new:N \g_@@_hang_ht_dim
+\bool_new:N \g_@@_move_hang_bool
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_build_hangfrom:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_build_hangfrom:
+  {
+    \dim_compare:nNnTF \g_@@_prevdepth_dim > \c_@@_ignore_depth_dim
+      { \@@_build_hangfrom_aux: }
+      { \dim_gzero:N \g_@@_ht_dim }
+  }
+\cs_new_protected_nopar:Npn \@@_build_hangfrom_aux:
+  {
+    \group_begin:
+      \skip_zero:N \tex_splittopskip:D
+      \vbox_gset:Nn \g_@@_line_box
+        {
+          \tex_penalty:D \c_@@_break_int
+          \vbox_unpack:N \l_@@_body_box
+        }
+      \vbox_set_split_to_ht:NNn \l_@@_last_box \g_@@_line_box
+        { \c_zero_dim }
+      \dim_gset:Nn \g_@@_ht_dim
+        {
+            \g_@@_baseline_skip
+          - \g_@@_prevdepth_dim
+          - \l_@@_shift_dim
+          - \box_ht:N \l_@@_body_box
+          + \box_ht:N \g_@@_line_box
+        }
+    \group_end:
+    \box_set_eq_drop:NN \l_@@_body_box \g_@@_line_box
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_put_box:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_put_box:
+  {
+    \para_raw_end:
+    \dim_compare:nNnTF \g_@@_prevdepth_dim > \c_@@_ignore_depth_dim
+      { \@@_add_vskip: }
+      { \skip_gzero:N \g_@@_pre_skip }
+    \skip_set_eq:NN \l_@@_par_skip \tex_parskip:D
+    \skip_zero:N \tex_parskip:D
+    \bool_if:NTF \g_@@_right_move_bool
+      { \@@_put_box_aux: }
+      {
+        \box_if_empty:NTF \l_@@_bottom_box
+          {
+            \dim_compare:nNnTF
+              { \g_@@_remaining_dim }
+              >
+              { \box_ht_plus_dp:N \l_@@_window_box }
+              { \@@_set_next: }
+              { \@@_put_box_aux: }
+          }
+          { \@@_put_box_aux: }
+      }
+  }
+\skip_new:N \l_@@_par_skip
+\cs_new_protected_nopar:Npn \@@_put_box_aux:
+  {
+    \int_gzero:N \g_@@_window_int
+    \@@_hbox:n
+      {
+        \@@_put_window_box:
+        \bool_if:NF \g_@@_next_bool
+          { \@@_put_stuff_box: }
+      }
+    \box_if_empty:NTF \l_@@_bottom_box
+      { \@@_put_trailer_box: }
+      { \@@_put_bottom_box: }
+  }
+\cs_new_protected_nopar:Npn \@@_put_trailer_box:
+  {
+    \bool_if:NTF \g_@@_next_hang_bool
+      {
+        \@@_next_hang_para:
+        \@@_next_para_trailer:
+      }
+      {
+        \bool_if:NTF \g_@@_right_move_bool
+          { \@@_next_para_trailer: }
+          {
+            \@@_add_pos_skip:
+            \box_if_empty:NF \g_@@_pos_box
+              {
+                \@@_newline:
+                \hbox_unpack_drop:N \g_@@_pos_box
+              }
+          }
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_put_bottom_box:
+  {
+    \@@_newline:
+    \hbox_unpack_drop:N \l_@@_bottom_box
+    \box_if_empty:NF \g_@@_equation_box
+      { \@@_insert_equation: }
+    \box_if_empty:NF \g_@@_pos_box
+      { \hbox_unpack_drop:N \g_@@_pos_box }
+    \bool_gset_false:N \g_@@_right_move_bool
+    \bool_gset_false:N \g_@@_first_save_bool
+  }
+\cs_new_protected_nopar:Npn \@@_newline:
+  {
+    \tex_penalty:D \c_@@_nobreak_int
+    \tex_hfil:D
+    \tex_penalty:D \c_@@_break_int
+  }
+\cs_new_protected:Npn \@@_hbox:n #1
+  {
+    \para_raw_noindent:
+    \hbox_gset:Nn \g_@@_last_box {#1}
+    \box_gset_wd:Nn \g_@@_last_box { \l_@@_line_dim }
+    \box_use_drop:N \g_@@_last_box
+  }
+\cs_new_protected_nopar:Npn \@@_put_window_box:
+  {
+    \dim_compare:nNnF \l_@@_l_dim > \c_zero_dim
+      { \skip_horizontal:n { \l_@@_line_dim - \l_@@_r_dim } }
+    \box_use:N \l_@@_window_box
+  }
+\cs_new_protected_nopar:Npn \@@_put_stuff_box:
+  {
+    \@@_move_stuff_box:nn { up }
+      {
+          \l_@@_voffset_dim
+        + ( \box_dp:N \g_@@_stuff_box -
+            \box_dp:N \l_@@_window_box )
+        + ( \box_ht_plus_dp:N \l_@@_window_box -
+            \g_@@_stuff_ht_dim ) / 2
+        \box_if_empty:NT \l_@@_bottom_box
+          { - \g_@@_pos_skip / 2 }
+      }
+    \@@_output_stuff_box:
+  }
+\cs_new_protected_nopar:Npn \@@_output_stuff_box:
+  {
+    \skip_horizontal:n
+      {
+        \dim_compare:nNnTF \l_@@_r_dim > \c_zero_dim
+          {
+            \dim_compare:nNnTF
+              { \box_wd:N \l_@@_window_box }
+              <
+              { \l_@@_window_dim }
+              { \l_@@_leftsep_dim }
+              {
+                - \l_@@_r_dim
+                - \l_@@_rightsep_dim
+                - \g_@@_stuff_wd_dim
+              }
+          }
+          { \l_@@_leftsep_dim }
+      }
+    \box_use_drop:N \g_@@_stuff_box
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_move_stuff_box:n}
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_move_stuff_box:nn #1#2
+  {
+    \hbox_gset:Nn \g_@@_stuff_box
+      {
+        \@@_parshape_kern:
+        \use:c { box_move_ #1 :nn }
+          {#2}
+          { \box_use_drop:N \g_@@_stuff_box }
+      }
+    \box_gset_ht:Nn \g_@@_stuff_box { \c_zero_dim }
+    \box_gset_dp:Nn \g_@@_stuff_box { \c_zero_dim }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_add_vskip:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_add_vskip:
+  {
+    \box_if_empty:NTF \g_@@_display_box
+      { \@@_add_vskip_auxi: }
+      { \@@_add_vskip_display: }
+  }
+\cs_new_protected_nopar:Npn \@@_add_vskip_display:
+  {
+    \vbox_unpack_drop:N \g_@@_display_box
+    \@@_ignore_depth:
+  }
+\cs_new_protected_nopar:Npn \@@_add_vskip_auxi:
+  {
+    \dim_compare:nNnTF \tex_pagegoal:D < \c_max_dim
+      { \@@_add_vskip_auxii: }
+      { \@@_add_vskip_auxiii: }
+  }
+\cs_new_protected_nopar:Npn \@@_add_vskip_auxii:
+  {
+    \skip_gset:Nn \g_@@_pre_skip
+      {
+          \g_@@_baseline_skip
+        - \g_@@_prevdepth_dim
+        - \g_@@_ht_dim
+      }
+    \dim_compare:nNnT \g_@@_pre_skip < \tex_lineskiplimit:D
+      { \skip_gset_eq:NN \g_@@_pre_skip \tex_lineskip:D }
+    \bool_if:NTF \l_@@_first_move_bool
+      { \@@_first_move_skip: }
+      { \skip_vertical:N \g_@@_pre_skip }
+    \@@_ignore_depth:
+  }
+\cs_new_protected_nopar:Npn \@@_add_vskip_auxiii:
+  {
+    \dim_compare:nNnTF \tex_topskip:D > \g_@@_ht_dim
+      {
+        \tex_hrule:D height \c_zero_dim \scan_stop:
+        \skip_gset:Nn \g_@@_pre_skip
+          { \tex_topskip:D - \g_@@_ht_dim }
+        \skip_vertical:n { \g_@@_pre_skip - \tex_topskip:D }
+      }
+      { \skip_gzero:N \g_@@_pre_skip }
+  }
+\cs_new_protected_nopar:Npn \@@_first_move_skip:
+  {
+    \skip_vertical:n
+      {
+          \g_@@_first_sep_dim
+        - \g_@@_window_ht_dim
+        - \tex_parskip:D
+        \dim_compare:nNnT \g_@@_column_right_ht_dim > \c_zero_dim
+          { + \g_@@_column_right_ht_dim + \g_@@_pre_skip }
+      }
+  }
+\skip_new:N \g_@@_pre_skip
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_ignore_depth:,\@@_set_prevdepth:N}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_ignore_depth:
+  { \dim_set_eq:NN \tex_prevdepth:D \c_@@_ignore_depth_dim }
+\cs_new_protected_nopar:Npn \@@_set_prevdepth:N
+  { \dim_set_eq:NN \tex_prevdepth:D }
+\dim_const:Nn \c_@@_ignore_depth_dim { -1000pt }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_set_next:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_set_next:
+  {
+    \dim_set:Nn \l_@@_height_dim
+      {
+          \g_@@_pre_skip
+        + \g_@@_pos_skip
+        + \box_ht_plus_dp:N \l_@@_window_box
+      }
+    \dim_gadd:Nn \g_@@_total_ht_dim { \l_@@_height_dim }
+    \dim_set:Nn \l_@@_shift_dim
+      { \g_@@_remaining_dim - \l_@@_height_dim }
+    \dim_compare:nNnTF \l_@@_shift_dim > \c_zero_dim
+      { \@@_set_next_auxi: }
+      {
+        \dim_compare:nNnTF
+          { - \l_@@_shift_dim } > \l_@@_min_dim
+          { \@@_set_next_auxii: }
+          { \@@_set_next_auxi: }
+      }
+  }
+\dim_new:N \g_@@_total_ht_dim
+\cs_new_protected_nopar:Npn \@@_set_next_auxi:
+  {
+    \int_gset:Nn \g_@@_window_int
+      {
+        \dim_compare:nNnTF \l_@@_shift_dim > \c_zero_dim
+          { \@@_unit:n { \l_@@_shift_dim } }
+          { \c_one_int }
+      }
+    \@@_set_next_verify:
+    \bool_if:NF \g_@@_next_bool
+      { \@@_move_next_stuff_box: }
+    \@@_set_next_output:
+    \@@_make_next_stuff:nn
+      { \g_@@_stuff_wd_dim }
+      { \l_@@_shift_dim }
+    \int_gzero:N \g_@@_top_int
+    \@@_next_para_trailer:
+  }
+\cs_new_protected_nopar:Npn \@@_move_next_stuff_box:
+  {
+    \@@_move_stuff_box:nn { down }
+      {
+          \box_ht:N \g_@@_stuff_box
+        - \box_ht:N \l_@@_window_box
+        + (   \g_@@_window_ht_dim
+            - \g_@@_stuff_ht_dim
+            - \g_@@_pre_skip
+            + \g_@@_pos_skip
+            + \l_@@_par_skip ) / 2
+        - \l_@@_voffset_dim
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_set_next_auxii:
+  {
+    \int_gzero:N \g_@@_window_int
+    \bool_if:NF \g_@@_next_bool
+      {
+        \@@_move_stuff_box:nn { down }
+          {
+              \box_ht:N \g_@@_stuff_box
+            - \box_ht:N \l_@@_window_box
+            - \l_@@_voffset_dim
+          }
+      }
+    \@@_set_next_output:
+    \@@_add_pos_skip:
+  }
+\cs_new_protected_nopar:Npn \@@_set_next_output:
+  {
+    \@@_hbox:n
+      {
+        \@@_put_window_box:
+        \bool_if:NF \g_@@_next_bool
+          { \@@_output_stuff_box: }
+      }
+  }
+\cs_new_protected_nopar:Npn \@@_set_next_verify:
+  {
+    \dim_set:Nn \l_@@_height_dim
+      { \g_@@_window_ht_dim - \g_@@_total_ht_dim }
+    \dim_until_do:nNnn
+      { \tex_baselineskip:D * \g_@@_window_int + \l_@@_par_skip }
+      >
+      { \l_@@_height_dim }
+      { \int_gincr:N \g_@@_window_int }
+    \dim_gadd:Nn \g_@@_total_ht_dim
+      { \tex_baselineskip:D * \g_@@_window_int + \l_@@_par_skip }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_next_para_trailer:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_next_para_trailer:
+  {
+    \@@_add_pos_skip:
+    \box_if_empty:NTF \g_@@_pos_box
+      { \@@_next_para: }
+      {
+        \@@_env_begin:
+          \hbox_unpack_drop:N \g_@@_pos_box
+        \@@_env_end:
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_make_next_stuff:nn}
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_make_next_stuff:nn #1#2
+  {
+    \bool_gset_true:N \g_@@_next_bool
+    \dim_gset:Nn \g_@@_stuff_wd_dim  {#1}
+    \dim_gset:Nn \g_@@_remaining_dim {#2}
+  }
+\bool_new:N \g_@@_next_bool
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_extract_hbox:NN}
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_extract_display_hbox:NN #1
+  {
+    \box_gclear:N \g_@@_pos_box
+    \vbox_set:Nn #1
+      {
+        \vbox_unpack_drop:N #1
+        \bool_if:NTF \g_@@_display_bool
+          { \@@_test_display_math: }
+          { \box_gclear:N \g_@@_display_box }
+        \box_if_empty:NTF \g_@@_display_box
+          {
+            \bool_gset_false:N \g_@@_amsmath_bool
+            \@@_extract_last_hbox:N \g_@@_last_box
+          }
+          { \box_gclear:N \g_@@_last_box }
+      }
+    \box_if_empty:NF \g_@@_display_box
+      { \dim_gset:Nn \g_@@_display_pre_dim { \box_dp:N #1 } }
+    \@@_extract_hbox_aux:N
+  }
+\cs_new_protected:Npn \@@_extract_hbox:NN #1
+  {
+    \vbox_set:Nn #1
+      {
+        \vbox_unpack_drop:N #1
+        \@@_extract_last_hbox:N \g_@@_last_box
+      }
+    \@@_extract_hbox_aux:N
+  }
+\cs_new_protected:Npn \@@_extract_hbox_aux:N #1
+  {
+    \box_if_empty:NTF \g_@@_last_box
+      { \box_clear:N #1 }
+      { \@@_repack_hbox:N #1 }
+  }
+\cs_new_protected:Npn \@@_repack_hbox:N #1
+  {
+    \hbox_set:Nn #1
+      {
+        \skip_if_eq:nnF
+          { \g_@@_main_left_skip } { \c_zero_skip }
+          { \skip_horizontal:N \g_@@_main_left_skip }
+        \hbox_unpack_drop:N \g_@@_last_box
+        \tex_unskip:D \tex_unskip:D \tex_unpenalty:D
+      }
+  }
+\cs_new_protected:Npn \@@_extract_last_hbox:N #1
+  {
+    \@@_if_last_hlist:TF
+      {
+        \box_gset_to_last:N #1
+        \tex_unskip:D
+      }
+      { \box_gclear:N #1 }
+  }
+\box_new:N \g_@@_last_box
+\box_new:N \g_@@_display_box
+\dim_new:N \g_@@_display_pre_dim
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_test_display_math:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_test_display_math:
+  {
+    \@@_if_last_hlist:T
+      {
+        \box_gset_to_last:N \g_@@_pos_box
+        \tex_unskip:D
+      }
+    \box_clear:N \l_@@_add_box
+    \box_gclear:N \g_@@_display_box
+    \skip_gzero:N \g_@@_last_skip
+    \skip_gzero:N \g_@@_display_pre_skip
+    \bool_gset_false:N \g_@@_amsmath_bool
+    \@@_add_last_skip:w
+    \@@_add_last_penalty:w
+    \@@_add_last_box:w
+    \@@_add_last_skip:w
+    \@@_add_last_skip:w
+    \@@_add_last_penalty:w
+    \@@_add_last_finalise:w \q_stop
+  }
+\box_new:N \l_@@_add_box
+\box_new:N \g_@@_pos_box
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_add_last_stop:w}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_add_last_stop:w
+  {
+    \vbox_unpack_drop:N \l_@@_add_box
+    \use_none_delimit_by_q_stop:w
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_add_last_skip:w}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_add_last_skip:w
+  {
+    \@@_if_last_glue:TF
+      {
+        \skip_set_eq:NN \l_@@_last_skip \tex_lastskip:D
+        \vbox_set:Nn \l_@@_add_box
+          {
+            \skip_vertical:N \l_@@_last_skip
+            \vbox_unpack_drop:N \l_@@_add_box
+          }
+        \tex_unskip:D
+        \skip_gadd:Nn \g_@@_last_skip { \l_@@_last_skip }
+      }
+      { \@@_skip_stop:w }
+  }
+\skip_new:N \l_@@_last_skip
+\skip_new:N \g_@@_last_skip
+\cs_new_eq:NN \@@_skip_stop:w \@@_add_last_stop:w
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_add_last_penalty:w}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_add_last_penalty:w
+  {
+    \@@_if_last_penalty:TF
+      {
+        \int_set_eq:NN \l_@@_last_int \tex_lastpenalty:D
+        \vbox_set:Nn \l_@@_add_box
+          {
+            \tex_penalty:D \l_@@_last_int
+            \vbox_unpack_drop:N \l_@@_add_box
+          }
+        \tex_unpenalty:D
+        \skip_gset_eq:NN \g_@@_pre_skip \g_@@_last_skip
+        \skip_gzero:N \g_@@_last_skip
+      }
+      { \@@_penalty_stop:w }
+  }
+\int_new:N \l_@@_last_int
+\cs_new_eq:NN \@@_penalty_stop:w \@@_add_last_stop:w
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_add_last_box:w}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_add_last_box:w
+  {
+    \@@_if_last_hlist:TF
+      {
+        \skip_gzero:N \g_@@_last_skip
+        \box_set_to_last:N \l_@@_last_box
+        \vbox_set:Nn \l_@@_add_box
+          {
+            \box_use_drop:N \l_@@_last_box
+            \vbox_unpack_drop:N \l_@@_add_box
+          }
+      }
+      { \@@_box_stop:w }
+  }
+\box_new:N \l_@@_last_box
+\cs_new_eq:NN \@@_box_stop:w \@@_add_last_stop:w
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_add_last_finalise:w}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_add_last_finalise:w
+  {
+    \int_gset_eq:NN \g_@@_display_pre_int \l_@@_last_int
+    \skip_gadd:Nn \g_@@_display_pre_skip { \g_@@_pre_skip }
+    \int_case:nnTF { \tex_lastnodetype:D }
+      {
+        { \c_@@_hlist_node }   { }
+        { \c_@@_none_node }    { }
+        { \c_@@_whatsit_node } { }
+      }
+      { \box_gset_eq_drop:NN \g_@@_display_box \l_@@_add_box }
+      { \vbox_unpack_drop:N \l_@@_add_box }
+    \use_none_delimit_by_q_stop:w
+  }
+\int_new:N \g_@@_display_pre_int
+\skip_new:N \g_@@_display_pre_skip
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_amsmath_boot:w,\@@_amsmath_recursion:w,\@@_amsmath_multline:w}
+% \pkg{amsmath} 的 \env{align} 等数学环境内部是一个 \tn{halign} 环境，结构不一样，需要另外处理。
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_amsmath_boot:w
+  {
+    \@@_add_last_skip:w
+    \@@_add_last_penalty:w
+    \cs_set_eq:NN \@@_box_stop:w \@@_add_last_stop:w
+    \@@_add_last_box:w
+    \bool_gset_true:N \g_@@_amsmath_bool
+    \cs_set_eq:NN \@@_skip_stop:w \@@_amsmath_multline:w
+    \cs_set_eq:NN \@@_penalty_stop:w \@@_amsmath_stop:NN
+    \@@_amsmath_recursion:w
+  }
+\cs_new_protected_nopar:Npn \@@_amsmath_recursion:w
+  {
+    \@@_add_last_skip:w
+    \@@_add_last_skip:w
+    \@@_add_last_penalty:w
+    \@@_add_last_box:w
+    \@@_amsmath_recursion:w
+  }
+\cs_new_protected:Npn \@@_amsmath_stop:NN #1#2
+  {
+    \cs_set_eq:NN \@@_skip_stop:w \@@_add_last_stop:w
+    \cs_set_eq:NN \@@_penalty_stop:w \@@_add_last_stop:w
+  }
+\bool_new:N \g_@@_amsmath_bool
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_amsmath_multline:w}
+% \env{multline} 环境的结构与其他环境不一样。\pkg{amsmath} 的 \tn{@display@init} 定义为
+% \begin{verbatim}
+% \def\@display@init#1{%
+%     \global\dt@ptrue \spread@equation
+%     \everycr{%
+%         \noalign{%
+%             #1%
+%             \ifdt@p
+%                 \global\dt@pfalse
+%                 \vskip-\lineskiplimit
+%                 \vskip\normallineskiplimit
+%             \else
+%                 \penalty\@eqpen \global\dspbrk@lvl\m@ne
+%             \fi
+%         }%
+%     }%
+% }
+% \end{verbatim}
+% \env{align} 等环境的开头 \tn{ifdt@p} 为真，会插入两个 \tn{vskip}，
+% 但是 \env{multline} 定义中的 \tn{mmeasure@} 没有重定义 \tn{everycr}，
+% 上述定义中的 \tn{dt@pfalse} 被执行，导致环境开头被加入了 \tn{penalty}，
+% 不确定是有意为之还是疏忽。
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_amsmath_multline:w
+  {
+    \@@_amsmath_stop:NN ? ?
+    \@@_add_last_penalty:w
+    \skip_gset_eq:NN \g_@@_display_pre_skip
+                     \g_@@_pre_skip
+    \@@_add_last_skip:w
+    \@@_add_last_penalty:w
+    \@@_add_last_finalise:w
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_amsmath_leqno:}
+% \pkg{amsmath} 的 \opt{leqno} 是直接用 \cs{tex_leqno:D} 实现的，与 \LaTeX\ 的实现不一样。
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_amsmath_leqno:
+  {
+    \legacy_if:nTF { tagsleft@ }
+      { \bool_gset_true:N  \g_@@_leqno_bool }
+      { \bool_gset_false:N \g_@@_leqno_bool }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+\@@_package_hook:nn { amsmath }
+  {
+    \cs_gset_eq:NN \@@_box_stop:w
+                   \@@_amsmath_boot:w
+    \cs_gset_eq:NN \@@_test_leqno:
+                   \@@_amsmath_leqno:
+  }
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_set_float:}
+%    \begin{macrocode}
+\cs_new_protected_nopar:Npn \@@_set_float:
+  {
+    \cs_set_eq:NN \@captype \l_@@_type_tl
+    \@@_float_pre_hook:
+    \@@_caption_hook:
+    \@floatboxreset
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_float_pre_hook:, \@@_float_pos_hook:}
+%    \begin{macrocode}
+\cs_new_eq:NN \@@_float_pre_hook: \@@_empty:
+\cs_new_eq:NN \@@_float_pos_hook: \@@_empty:
+\@@_package_hook:nn { float }
+  {
+    \bool_new:N \g_@@_float_pos_bool
+    \cs_gset_protected_nopar:Npn \@@_float_pre_hook:
+      { \exp_args:No \@@_float_pre_aux:n { \l_@@_type_tl } }
+    \cs_new_protected:Npn \@@_float_pre_aux:n #1
+      {
+        \cs_if_exist_use:cTF { fst@ #1 }
+          {
+            \@float@setevery {#1}
+            \bool_gset_true:N \g_@@_float_pos_bool
+          }
+          { \bool_gset_false:N \g_@@_float_pos_bool }
+      }
+    \cs_gset_protected_nopar:Npn \@@_float_pos_hook:
+      {
+        \bool_if:NT \g_@@_float_pos_bool
+          { \exp_args:No \@@_float_pos_aux:n { \l_@@_type_tl } }
+      }
+    \cs_new_protected:Npn \@@_float_pos_aux:n #1
+      {
+        \hbox_gset:Nn \g_@@_stuff_box
+          {
+            \use:c { fst@ #1 }
+            \cs_set_eq:NN \@currbox \g_@@_stuff_box
+            \vbox_gset:Nn \g_@@_stuff_box
+              { \box_use_drop:N \g_@@_stuff_box }
+            \exp_args:Ne \float@makebox
+              { \dim_eval:n { \box_wd:N \g_@@_stuff_box } }
+          }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_floatrow_hook:}
+%    \begin{macrocode}
+\cs_new_eq:NN \@@_floatrow_hook: \@@_empty:
+\@@_package_hook:nn { floatrow }
+  {
+    \cs_gset_protected_nopar:Npn \@@_floatrow_hook:
+      {
+        \cs_set_eq:NN \@captype \l_@@_type_tl
+        \killfloatstyle
+        \FR@redefs
+        \dim_zero:N \FBc@wd
+        \exp_args:Ne \flrow@setlist
+          {
+            { \l_@@_type_tl }
+            { wrapfloat }
+            { wrap \l_@@_type_tl }
+          }
+        \FRifFBOX \@@@@setframe \relax \@@@@FStrue
+        \hbox_gset:Nw \g_@@_stuff_box
+          \tl_set:Nx \FBB@wd { \dim_use:N \l_@@_width_dim }
+          \FB@fs@wd
+          \dim_set:Nn \l_@@_width_dim { \FBo@wd }
+      }
+    \cs_gset_protected_nopar:Npn \@@_float_pre_hook:
+      { \the \FR@everyfloat }
+    \cs_gset_protected_nopar:Npn \@@_float_pos_hook:
+      {
+        \legacy_if:nTF { FBbuild }
+          {
+            \cs_set_eq:NN \@currbox \g_@@_stuff_box
+            \vbox_gset:Nn \g_@@_stuff_box
+              { \box_use_drop:N \g_@@_stuff_box }
+            \flrow@FB { \l_@@_width_dim }
+          }
+          {
+            \cs_undefine:N \flrow@typ@tmpset
+            \box_use_drop:N \g_@@_stuff_box
+          }
+        \hbox_gset_end:
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_caption_hook:}
+%    \begin{macrocode}
+\cs_new_eq:NN \@@_caption_hook: \@@_empty:
+\@@_package_hook:nn { caption }
+  {
+    \cs_gset_protected_nopar:Npn \@@_caption_hook:
+      { \exp_args:No \@@_caption_aux:n { \l_@@_type_tl } }
+    \cs_new_protected:Npn \@@_caption_aux:n #1
+      {
+        \caption@settype {#1}
+        \caption@clearmargin
+        \caption@setoptions { wrap #1 }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{top}
+%    \begin{macrocode}
+\keys_define:nn { wrapstuff }
+  {
+    abovesep   .tl_set:N = \l_@@_abovesep_tl ,
+    belowsep   .tl_set:N = \l_@@_belowsep_tl ,
+    leftsep    .tl_set:N = \l_@@_leftsep_tl ,
+    rightsep   .tl_set:N = \l_@@_rightsep_tl ,
+    linewidth  .tl_set:N = \l_@@_linewidth_tl ,
+    lines      .tl_set:N = \l_@@_lines_tl ,
+    width      .tl_set:N = \l_@@_width_tl ,
+    height     .tl_set:N = \l_@@_height_tl ,
+    hoffset    .tl_set:N = \l_@@_hoffset_tl ,
+    voffset    .tl_set:N = \l_@@_voffset_tl ,
+    type       .tl_set:N = \l_@@_type_tl ,
+    ratio      .fp_set:N = \l_@@_ratio_fp ,
+    top       .int_set:N = \l_@@_top_int ,
+    i            .code:n = \@@_swap_true:N \c_true_bool ,
+    o            .code:n = \@@_swap_true:N \c_false_bool ,
+    l            .code:n = \@@_swap_false:N \c_zero_fp ,
+    r            .code:n = \@@_swap_false:N \c_one_fp ,
+    c            .code:n = \@@_swap_false:N \c_@@_c_fp ,
+    column     .choice: ,
+    column/true  .code:n =
+      {
+        \bool_set_true:N \l_@@_column_bool
+        \cs_set_eq:NN \@@_build_column:
+                      \@@_build_column_strict:
+      } ,
+    column/par   .code:n =
+      {
+        \bool_set_true:N \l_@@_column_bool
+        \cs_set_eq:NN \@@_build_column:
+                      \@@_build_column_fuzzy:
+      } ,
+    column/false .code:n =
+      { \bool_set_false:N \l_@@_column_bool } ,
+    hsep         .code:n =
+      {
+        \tl_set:Nn \l_@@_leftsep_tl {#1}
+        \tl_set_eq:NN \l_@@_rightsep_tl
+                      \l_@@_leftsep_tl
+      } ,
+    vsep         .code:n =
+      {
+        \tl_set:Nn \l_@@_abovesep_tl {#1}
+        \tl_set_eq:NN \l_@@_belowsep_tl
+                      \l_@@_abovesep_tl
+      } ,
+    unknown      .code:n =
+      { \exp_args:No \@@_unknown_key:n { \l_keys_key_str } } ,
+    leftsep    .groups:n = main ,
+    rightsep   .groups:n = main ,
+    hsep       .groups:n = main ,
+    linewidth  .groups:n = main ,
+    lines      .groups:n = main ,
+    column     .groups:n = main ,
+    hoffset    .groups:n = main ,
+    voffset    .groups:n = main ,
+    top        .groups:n = stuff ,
+    abovesep   .groups:n = stuff ,
+    belowsep   .groups:n = stuff ,
+    vsep       .groups:n = stuff ,
+    width      .groups:n = stuff ,
+    height     .groups:n = stuff ,
+    float      .groups:n = stuff ,
+    ratio      .groups:n = ratio ,
+    l          .groups:n = ratio ,
+    r          .groups:n = ratio ,
+    c          .groups:n = ratio ,
+    i          .groups:n = ratio ,
+    o          .groups:n = ratio ,
+    column    .default:n = true ,
+    column    .initial:n = true ,
+    abovesep  .initial:n = \c_zero_dim ,
+    belowsep  .initial:n = \c_zero_dim ,
+    leftsep   .initial:n = 1em ,
+    rightsep  .initial:n = 1em ,
+    linewidth .initial:n = \linewidth ,
+    hoffset   .initial:n = \c_zero_dim ,
+    voffset   .initial:n = \c_zero_dim ,
+    width     .initial:n = \c_zero_dim ,
+    height    .initial:n = \c_zero_dim ,
+    ratio     .initial:n = \c_one_fp ,
+    abovesep  .value_required:n = true ,
+    belowsep  .value_required:n = true ,
+    leftsep   .value_required:n = true ,
+    rightsep  .value_required:n = true ,
+    linewidth .value_required:n = true ,
+    width     .value_required:n = true ,
+    height    .value_required:n = true ,
+    hoffset   .value_required:n = true ,
+    voffset   .value_required:n = true ,
+    hsep      .value_required:n = true ,
+    vsep      .value_required:n = true ,
+    l        .value_forbidden:n = true ,
+    r        .value_forbidden:n = true ,
+    c        .value_forbidden:n = true ,
+    i        .value_forbidden:n = true ,
+    o        .value_forbidden:n = true
+  }
+\fp_const:Nn \c_@@_c_fp { 0.5 }
+\cs_new_protected:Npn \@@_swap_true:N #1
+  {
+    \bool_set_true:N \l_@@_swap_bool
+    \bool_set_eq:NN \l_@@_inner_bool #1
+    \bool_if:NTF \l_@@_inner_bool
+      { \bool_set_false:N \l_@@_outer_bool }
+      { \bool_set_true:N  \l_@@_outer_bool }
+  }
+\cs_new_protected_nopar:Npn \@@_swap_false:N
+  {
+    \bool_set_false:N \l_@@_swap_bool
+    \fp_set_eq:NN \l_@@_ratio_fp
+  }
+\cs_new_protected:Npn \@@_unknown_key:n #1
+  {
+    \regex_match:NnTF \c_@@_integer_regex {#1}
+      { \int_set:Nn \l_@@_top_int }
+      { \@@_unknown_key_error:n }
+      {#1}
+  }
+\regex_const:Nn \c_@@_integer_regex { \A \d+ \Z }
+\cs_new_protected_nopar:Npn \@@_unknown_key_error:n
+  { \msg_error:nnn { wrapstuff } { unknown-key } }
+\msg_new:nnnn { wrapstuff } { unknown-key }
+  { The~key~'#1'~is~unknown~and~is~being~ignored. }
+  {
+    The~package~wrapstuff~does~not~have~a~key~called~'#1'.\\
+    Check~that~you~have~spelled~the~key~name~correctly.
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\wrapstuffset}
+%    \begin{macrocode}
+\NewDocumentCommand \wrapstuffset { m }
+  { \keys_set:nn { wrapstuff } {#1} }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\wrapstuffclear}
+% 保险起见，加入 \tn{par} 结束段落，同时结束 \env{wrapstuff@par} 环境。
+%    \begin{macrocode}
+\NewDocumentCommand \wrapstuffclear { }
+  {
+    \par
+    \@@_clear:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+\cs_if_exist:NTF \ProcessKeyOptions
+  { \ProcessKeyOptions [ wrapstuff ] }
+  {
+    \RequirePackage { l3keys2e }
+    \ProcessKeysOptions { wrapstuff }
+  }
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%</package>
+%    \end{macrocode}
+%
+% \end{implementation}
+%
+% \Finale
+%
+\endinput
diff --git a/macros/latex/contrib/wrapstuff/wrapstuff.pdf b/macros/latex/contrib/wrapstuff/wrapstuff.pdf
new file mode 100644
index 0000000000..c9cd89da98
--- /dev/null
+++ b/macros/latex/contrib/wrapstuff/wrapstuff.pdf