load-unicode-xetex-classes.tex が xetex.ini によってのみロードされるのはなぜですか (xelatex.ini によってロードされるのではありません)?

Question

TeX LiveとMiKTeXで使用されるファイル.iniは、DVIを扱うための単純な方法として始まりました。対PDF出力:latex.iniおよびpdflatex.ini。しかし、それらは時間の経過とともに、特にプレーンTeXのような形式のものが増えました。その理由は、プレーンの場合、Knuthは（慣例により）他の人が変更できないファイル内の元のTeX（TeX90）のみをサポートしているためです。したがって、XeTeX、LuaTeX、およびLuaTeXの主要な機能をサポートするには、等ファイルにコードを追加する.ini必要がありました。

しばらくの間、にも変更が加えられずlatex.ltx、にさまざまなものが蓄積されxelatex.ini、等しばらく前に、チームは XeTeX と LuaTeX を積極的にサポートすることを決定し、多くのコードがファイルからに戻されまし.iniたlatex.ltx。

ltfinal.dtx（の最後の部分の出典）を見てlatex.ltxみると、load-unicode-xetex-classes は読む：現在のソース部分は

% \changes{v2.0a}{2015/01/03}{Unicode data loading added}
% \changes{v2.0c}{2015/01/24}{Skip T1-code entirely with Unicode engines}
% \changes{v2.0d}{2015/03/26}{Use renamed 
%   \texttt{unicode-letters.def}}
% \changes{v2.0i}{2015/12/10}{Use new common Unicode data loaders}
% \changes{v2.0j}{2016/01/04}{Do not set up inter character classes for
%   XeTeX}
%  \changes{v2.0l}{2016/01/05}{Correct \textsf{latexrelease} guards}
%  \changes{v2.0l}{2016/01/05}{Ensure old definitions for inter-character
%    class toks are available using \textsf{latexrelease}}
%  \changes{v2.0m}{2016/01/05}{Undefine XeTeX classes when using patching
%    an older kernel}
%  \changes{v2.0l}{2016/01/05}{Missing brace}
%  \changes{v2.0p}{2016/01/05}{Only apply XeTeX change if XeTeX is in use}
%  For $7$- and $8$-bit engines the assumption of T1 encodings is the
%  basis for the hyphenation patterns. That's not the case for the Unicode
%  engines, where the assumption is engine-native working. The common
%  loader system provides access to data from the Unicode Consortium
%  covering not only |\lccode| but also other related data. The
%  |\lccode| part of that at least needs to be loaded before hyphenation is
%  tackled: Xe\TeX{} follows the standard \TeX{} route of building patterns
%  into the format. Lua\TeX{} doesn't require this data be loaded \emph{here}
%  but it does need to be loaded somewhere. Rather than test for the Unicode
%  engines by name, the approach here is to look for the extended math mode
%  handling both provide: any other engine developed in this area will
%  presumably also provide |\Umathcode|.
%    \begin{macrocode}
\ifnum 0%
  \ifx\Umathcode\@undefined\else 1\fi
  \ifx\XeTeXmathcode\@undefined\else 1\fi
  >\z@
  \message{ Unicode character data,}
  \input{load-unicode-data}
%</2ekernel>
%<latexrelease>\IncludeInRelease{2016/02/01}%
%<latexrelease>  {\XeTeXintercharclasses}{XeTeX character classes}%
%<latexrelease>  \ifx\XeTeXinterchartoks\undefined
%<latexrelease>  \else
%<latexrelease>    \begingroup
%<latexrelease>      \chardef\XeTeXcharclassID = 0 %
%<latexrelease>      \chardef\XeTeXcharclassOP = 0 %
%<latexrelease>      \chardef\XeTeXcharclassCL = 0 %
%<latexrelease>      \chardef\XeTeXcharclassEX = 0 %
%<latexrelease>      \chardef\XeTeXcharclassIS = 0 %
%<latexrelease>      \chardef\XeTeXcharclassNS = 0 %
%<latexrelease>      \chardef\XeTeXcharclassCM = 0 %
%<latexrelease>      \input{load-unicode-xetex-classes}
%<latexrelease>    \endgroup
%<latexrelease>    \global\let\xtxHanGlue\undefined
%<latexrelease>    \global\let\xtxHanSpace\undefined
%<latexrelease>    \global\XeTeXinterchartoks 0 1 = {}
%<latexrelease>    \global\XeTeXinterchartoks 0 2 = {}
%<latexrelease>    \global\XeTeXinterchartoks 0 3 = {}
%<latexrelease>    \global\XeTeXinterchartoks 1 0 = {}
%<latexrelease>    \global\XeTeXinterchartoks 2 0 = {}
%<latexrelease>    \global\XeTeXinterchartoks 3 0 = {}
%<latexrelease>    \global\XeTeXinterchartoks 1 1 = {}
%<latexrelease>    \global\XeTeXinterchartoks 1 2 = {}
%<latexrelease>    \global\XeTeXinterchartoks 1 3 = {}
%<latexrelease>    \global\XeTeXinterchartoks 2 1 = {}
%<latexrelease>    \global\XeTeXinterchartoks 2 2 = {}
%<latexrelease>    \global\XeTeXinterchartoks 2 3 = {}
%<latexrelease>    \global\XeTeXinterchartoks 3 1 = {}
%<latexrelease>    \global\XeTeXinterchartoks 3 2 = {}
%<latexrelease>    \global\XeTeXinterchartoks 3 3 = {}
%<latexrelease>  \fi
%<latexrelease>\EndIncludeInRelease
%<latexrelease>\IncludeInRelease{0000/00/00}%
%<latexrelease>  {\XeTeXintercharclasses}{XeTeX character classes}%
%<latexrelease>  \ifx\XeTeXinterchartoks\undefined
%<latexrelease>  \else
%<latexrelease>   \input{load-unicode-xetex-classes}
%<latexrelease>   \gdef\xtxHanGlue{\hskip0pt plus 0.1em\relax}
%<latexrelease>   \gdef\xtxHanSpace{\hskip0.2em plus 0.2em minus 0.1em\relax}
%<latexrelease>   \global\XeTeXinterchartoks 0 1 = {\xtxHanSpace}
%<latexrelease>   \global\XeTeXinterchartoks 0 2 = {\xtxHanSpace}
%<latexrelease>   \global\XeTeXinterchartoks 0 3 = {\nobreak\xtxHanSpace}
%<latexrelease>   \global\XeTeXinterchartoks 1 0 = {\xtxHanSpace}
%<latexrelease>   \global\XeTeXinterchartoks 2 0 = {\nobreak\xtxHanSpace}
%<latexrelease>   \global\XeTeXinterchartoks 3 0 = {\xtxHanSpace}
%<latexrelease>   \global\XeTeXinterchartoks 1 1 = {\xtxHanGlue}
%<latexrelease>   \global\XeTeXinterchartoks 1 2 = {\xtxHanGlue}
%<latexrelease>   \global\XeTeXinterchartoks 1 3 = {\nobreak\xtxHanGlue}
%<latexrelease>   \global\XeTeXinterchartoks 2 1 = {\nobreak\xtxHanGlue}
%<latexrelease>   \global\XeTeXinterchartoks 2 2 = {\nobreak\xtxHanGlue}
%<latexrelease>   \global\XeTeXinterchartoks 2 3 = {\xtxHanGlue}
%<latexrelease>   \global\XeTeXinterchartoks 3 1 = {\xtxHanGlue}
%<latexrelease>   \global\XeTeXinterchartoks 3 2 = {\xtxHanGlue}
%<latexrelease>   \global\XeTeXinterchartoks 3 3 = {\nobreak\xtxHanGlue}
%<latexrelease>  \fi
%<latexrelease>\EndIncludeInRelease
%<*2ekernel>
%    \end{macrocode}
% \changes{v2.0d}{2015/02/03}{Set \cs{lccode} for \texttt{-} with Unicode
%   engines}
% There is one over-ride that makes sense here (see below for the same for
% $8$-bit engines): setting the lccode for |-| to itself.
%    \begin{macrocode}
  \lccode`\- =`\- % default hyphen char
%    \end{macrocode}

XeTeXクラスの読み込みには2つのバージョンがあることがわかります。これは.iniファイルの変更を反映したもので、等

プレーンTeXの場合、のみUnicode データをフォーマットにロードする方法はファイル内にあります.ini。したがって、ローダーは他のもの (Unicode 基本データや Unicode 数学モード情報など) とともにそこにあります。

Answer 1