设置动态脚注边距（基于页面上的脚注编号）

Question

这是一个后续问题是否可以声明脚注编号右对齐但使用动态宽度？。

我尝试在 LaTeX 而不是 TeX 中实现 @wipet 针对原始问题给出的解决方案。据我所知，我理解了原理，但无法让它工作：似乎信息aux正确地写入了文件，因为

\@namedef{page@of@footnote@0}{1} \@namedef{max@footnote@on@page@1}{0} 
\@namedef{page@of@footnote@1}{1} \@namedef{max@footnote@on@page@1}{1} 
\@namedef{page@of@footnote@2}{2} \@namedef{max@footnote@on@page@2}{2} 
\@namedef{page@of@footnote@100}{3} \@namedef{max@footnote@on@page@3}{100}

但我无法访问它

\csuse{max@footnote@on@page@\csuse{page@of@footnote@\thefootnote}}

（结果为空字符串）。

完整代码

\documentclass{scrbook}

\usepackage{etoolbox}

\newlength{\fnotemargin}
\setlength{\fnotemargin}{4.5mm}
\deffootnote{\fnotemargin}{1em}{%
   \makebox[\fnotemargin][l]{\thefootnotemark}%
}

\makeatletter

\preto{\footnote}{%
   \protected@write\@auxout{}{%
      \string\@namedef{page@of@footnote@\thefootnote}{\thepage}
      \string\@namedef{max@footnote@on@page@\thepage}{\thefootnote}
   }%
   \def\thispagesmaxfootnote{%
      \csuse{max@footnote@on@page@\csuse{page@of@footnote@\thefootnote}}%
   }%
   (max. fnote on this page = \thispagesmaxfootnote)% FOR TESTING
   \ifnum\thispagesmaxfootnote>99\relax
      \setlength{\fnotemargin}{4.5mm}
   \fi
}

\makeatother

\begin{document}
   Test\footnote{Test}\par
   Test\footnote{Test}
   \newpage
   Test\footnote{Test}
   \newpage
   \setcounter{footnote}{100}
   Test\footnote{Test}
\end{document}

问题
所以问题是，为什么虽然信息写在文件中，但我却得到了错误的结果aux？

Answer 1

完整代码应如下所示（我在 MWE 本身添加了一些注释/解释）：

\documentclass{scrbook}

\usepackage{etoolbox}

% a new length for the footnote margin
\newlength{\fnotemargin}
% the "normal" (narrow) value should be 4.5mm
\setlength{\fnotemargin}{4.5mm}

% now we define how the footnotes look
% - first argument: margin for footnotes = the above defined length
% - second argument: the par intent for footnotes = 1em
% - third argument: how the number should be printed in the apparatus
%       = a box of with \fnotemargin containing the mark left aligned
\deffootnote{\fnotemargin}{1em}{%
   \makebox[\fnotemargin][l]{\thefootnotemark}%
}

% make @ available as part of macro names
\makeatletter

% with \preto we prepend some code to \footnote, it will be executed every time \footnote is used
\preto{\footnote}{%
   % wirte the following (third argument) to the *.aux file (this will be used later)
   \protected@write\@auxout{}{%
      % \string protects the following macro to be written verbatim in the file
      % The first line defines a macro named page@of@footnote@n where n is the current
      % (at time of writing to file) footnote value. This the definition is the current
      % page number.
      \string\csgdef{page@of@footnote@\the\value{footnote}}{\thepage}
      % the second line defines a macro named max@footnote@on@page@m (m = current page
      % number) to be the current footnote number.
      \string\csgdef{max@footnote@on@page@\thepage}{\the\value{footnote}}
      % When later (second/further TeX run) the auxfile is read all these defenition will be
      % executed. Then we have one macro for every footnote (\page@of@footnote@n)
      % containing the info on which page it appears and multiple definitions
      % for each page -- where the last one wins -- max@footnote@on@page@m containing
      % the information about the highest footnote number on that page.
      % (Note: The use of \csname (variants of it) allows us to use numbers as part of
      % macro names which is prohibited normally.)
   }%
   % now we define the macro \thispagesmaxfootnote to contain the value of the
   % highes footnote on this page. Ths information is taken from the definitions
   % written to the *.aus file in the previous TeX run.
   \edef\thispagesmaxfootnote{%
      0\csuse{max@footnote@on@page@\csuse{page@of@footnote@\the\value{footnote}}}%
   }%
%   (max. fnote on this page = \thispagesmaxfootnote)% FOR TESTING
   % lastly we test wether the footnote value is grater than 99 (the couter is off by
   % one at this pointcompared with the printed value; thus <98 instead of <99).
   \ifnum\thispagesmaxfootnote>98\relax
      % if TRUE we set the wide margin
%      (set wide margin)% FOR TESTING
      \setlength{\fnotemargin}{7.5mm}%
   \else
      % if FALSE we set the narrow margin
%      (set norrow margin)% FOR TESTING
      \setlength{\fnotemargin}{4.5mm}%
   \fi
}

% for cases where the footnote number is reset in each chapter for instance the
% above definition must be expaned to make the information macro cotain 
% the chapter number too. I.e. page@of@footnote@\the\value{footnote}
% could be changed to page@of@footnote@\the\value{chapter}@\the\value{footnote}

% deactivate @ as part of macro names
\makeatother

\begin{document}
   Test\footnote{Test}\par
   Test\footnote{Test}
   \newpage
   Test\footnote{Test}
   \newpage
   \setcounter{footnote}{100}
   Test\footnote{Test}
\end{document}

笔记：如果每个章节的脚注计数器都重置为 1，则必须向辅助宏添加章节标识符，如下所示：

   \preto{\footnote}{%
      \protected@write\@auxout{}{%
         \string\csgdef{page@of@footnote@chap\the\value{chapter}@fn\the\value{footnote}}{\thepage}
         \string\csgdef{max@footnote@on@page@\thepage}{\the\value{footnote}}
      }%
      \edef\thispagesmaxfootnote{%
         0\csuse{max@footnote@on@page@\csuse{page@of@footnote@chap\the\value{chapter}@fn\the\value{footnote}}}%
      }%
      \ifnum\thispagesmaxfootnote>98\relax
         \setlength{\fnotemargin}{1.75em}%
      \else
         \setlength{\fnotemargin}{1.25em}%
      \fi
   }