% babelbidi-onchar.def
%
% BabelBidi: bidirectional support for LaTeX.
%
% This file is part of the BabelBidi package.
%
% This work is free software: you may redistribute it and/or modify
% it under the terms of the LaTeX Project Public License as published
% by the LaTeX Project, either version 1.3c of the License, or
% (at your option) any later version.
%
% This work is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
%
% The full license text is available at:
% https://www.latex-project.org/lppl/

\ProvidesFile{babelbidi-onchar.def}
[2026/10/11 v0.2.0 Cache for Babel font mappings]

\makeatletter

% Keep the upstream implementation as a compatibility guard. If Babel or
% another package changes it, retain the upstream behaviour automatically.
\def\bbd@fontcache@expected@mapdir#1{%
  \begingroup
  \setbox\z@\hbox{% Force text mode
    \def\languagename{#1}%
    \let\bbl@ifrestoring\@firstoftwo % To avoid font warning
    \bbl@switchfont
    \ifnum\fontid\font>\z@ % A hack, for the pgf nullfont hack
      \directlua{
        Babel.locale_props[\the\csname bbl@id@@#1\endcsname]%
          ['/\bbl@prefontid'] = \fontid\font\space}%
    \fi}%
  \endgroup}%

\directlua{
  babelbidi_font_cache = {entries = {}, hits = 0, misses = 0, size = 0}
  function babelbidi_font_cache.restore(key, locale, source)
  local cache = babelbidi_font_cache
  local target = cache.entries[key]
  if target then
  cache.hits = cache.hits + 1
  Babel.locale_props[locale]['/' .. source] = target
  token.set_macro('bbd@fontcache@hit', '1')
  else
  cache.misses = cache.misses + 1
  token.set_macro('bbd@fontcache@hit', '0')
  end
  end
  function babelbidi_font_cache.store(key, locale, source, target)
  local cache = babelbidi_font_cache
  if not cache.entries[key] then cache.size = cache.size + 1 end
  cache.entries[key] = target
  Babel.locale_props[locale]['/' .. source] = target
  end
}



\def\bbd@fontcache@mapdir#1{%
  \begingroup
  % A physical font ID alone is insufficient: NFSS can select the same
  % physical font for different requested sizes or family contexts.
  \edef\bbd@fontcache@key{#1/\bbl@prefontid/\f@encoding/\f@family/%
    \f@series/\f@shape/\f@size/\bbl@font@fams}%
  \bbl@foreach\bbl@font@fams{%
    \edef\bbd@fontcache@key{\bbd@fontcache@key/%
      \csname##1default\endcsname/%
      \expandafter\meaning\csname bbl@##1dflt@#1\endcsname/%
      \expandafter\meaning\csname bbl@famrst@##1\endcsname}%
  }%
  \directlua{babelbidi_font_cache.restore(
    "\luaescapestring{\bbd@fontcache@key}",
    \the\csname bbl@id@@#1\endcsname, \bbl@prefontid)}%
  \ifnum\bbd@fontcache@hit=0\relax
    \setbox\z@\hbox{%
      \def\languagename{#1}%
      \let\bbl@ifrestoring\@firstoftwo
      \bbl@switchfont
      \ifnum\fontid\font>\z@
        \directlua{babelbidi_font_cache.store(
          "\luaescapestring{\bbd@fontcache@key}",
          \the\csname bbl@id@@#1\endcsname,
          \bbl@prefontid, \fontid\font)}%
      \fi}%
  \fi
  \endgroup
}

% Install after font/language setup; preamble font configuration is untouched.
% This only wraps Babel's mapper; it does not enable onchar processing.
\AddToHook{begindocument/end}[babelbidi/font-cache]{%
  \ifbbd@font@cache
    \ifx\bbl@mapdir\bbd@fontcache@expected@mapdir
      \let\bbl@mapdir\bbd@fontcache@mapdir
    \else
      \PackageWarningNoLine{babelbidi}{%
        Unsupported Babel font mapper; font cache disabled}%
    \fi
  \fi
}

\makeatother
\endinput