%%
%% footnotenosplit.sty
%% ===================
%% Suppress orphan footnote rules when footnotes are not allowed to split.
%%
%% 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.
%%
%% Background
%%   Setting \interfootnotelinepenalty=\@M keeps footnote text from being
%%   split across pages: a footnote that does not fit on the current page
%%   is moved to the next page as a whole.  When the footnote insertion
%%   begins with vertical material such as a leading \kern -- as
%%   \@makefntext does in many book-production classes -- TeX's page
%%   builder then leaves an "empty" \box\footins (one that contains only
%%   that leading \kern) on the original page, so that
%%     (1) the original page ends with a lone \footnoterule (plus the
%%         \skip\footins space) with no footnote text below it, and
%%     (2) the footnote moved to the next page gets only
%%         \splittopskip (= \footnotesep) above its first line, i.e. it
%%         sits closer to the rule than a normal footnote does, by the
%%         amount of the leading \kern.
%%
%% What this package does
%%   (1) If \ht\footins < \footnotesep (i.e. \box\footins holds no actual
%%       footnote line), \box\footins is discarded, so that neither
%%       \footnoterule nor \skip\footins is emitted; the footnote itself
%%       is typeset normally on the next page.  The implementation
%%       differs by engine, so this file dispatches to one of:
%%         * footnotenosplit-ptex.sty  : (u)pLaTeX; patches the \@makecol
%%                                       of plcore.ltx
%%         * footnotenosplit-latex.sty : LaTeX with the socket-based
%%                                       \@makecol (LaTeX2e 2025-06-01 or
%%                                       later; pdfLaTeX, LuaLaTeX,
%%                                       XeLaTeX, ...); uses the
%%                                       build/column/before hook
%%   (2) \splittopskip inside \@footnotetext (\H@@footnotetext when
%%       hyperref is loaded) is patched to
%%       \footnotesep + \footnotetopkern.  This is engine-independent
%%       and done in this file.
%%
%% Usage
%%   \usepackage{footnotenosplit}
%%   \footnotetopkern=2.6pt   %% the \kern used at the top of
%%                            %% \@makefntext (default: 0pt)
%%   \renewcommand\@makefntext[1]{\kern\footnotetopkern ... #1}
%%   If your class's \@makefntext starts with "\kern <dimen>", set
%%   \footnotetopkern to that dimension and replace the \kern with
%%   \kern\footnotetopkern.
%%
%% Option
%%   nopenalty : do not touch \interfootnotelinepenalty (by default this
%%               package sets it to \@M)
%%
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{footnotenosplit}
  [2026/10/20 v1.0 suppress orphan footnote rule when footnotes are not split]

\RequirePackage{etoolbox}

\newif\if@fns@penalty \@fns@penaltytrue
\DeclareOption{nopenalty}{\@fns@penaltyfalse}
\ProcessOptions\relax

\if@fns@penalty
  \interfootnotelinepenalty\@M\relax
\fi

\newdimen\footnotetopkern \footnotetopkern\z@

\def\fns@warning{\PackageWarningNoLine{footnotenosplit}}

%% (1) Discard an "empty" \box\footins (implementation is per-engine)
\def\fns@discard@emptyfootins{\setbox\footins\box\voidb@x}
\ifdefined\ptexversion
  \def\fns@engine{ptex}%%<= pTeX family ((u)pLaTeX)
\else\ifdefined\@outputbox@appendfootnotes
  \def\fns@engine{latex}%%<= socket-based \@makecol (LaTeX2e 2025-06-01+)
\else
  \let\fns@engine\relax
  \fns@warning{Neither pTeX's \string\@makecol\space nor socket-based
    \string\@makecol\space found\MessageBreak
    (pLaTeX2e or LaTeX2e 2025-06-01 or later required);\MessageBreak
    orphan footnote rules will not be suppressed}%
\fi\fi
\ifx\fns@engine\relax\else
  \RequirePackage{footnotenosplit-\fns@engine}%
\fi

%% (2) Align the space above a moved footnote with that of a normal one
\AtBeginDocument{%
  \@ifundefined{H@@footnotetext}{%
    \patchcmd{\@footnotetext}{\splittopskip\footnotesep}%
      {\splittopskip\dimexpr\footnotesep+\footnotetopkern\relax}%
      {}{\fns@warning{Failed to patch \string\@footnotetext}}%
  }{%
    \patchcmd{\H@@footnotetext}{\splittopskip\footnotesep}%
      {\splittopskip\dimexpr\footnotesep+\footnotetopkern\relax}%
      {}{\fns@warning{Failed to patch \string\H@@footnotetext}}%
  }}

\endinput