使用 XeTeXinterchartoks 时如何知道两个字符之间的宽度并填充粘合空间

Question

我正在尝试使用 Xetexinterchartoks 将粘连空间替换为 Xetex 中字形的拉伸版本。以下是示例：

\documentclass[10pt,a4paper]{article}
\usepackage{graphicx}
\newcommand \stretchit{
    \makeatletter   
    \XeTeXinterchartokenstate 1%
    \newXeTeXintercharclass \mycharclassA%
    \newXeTeXintercharclass \mycharclassB%
    \XeTeXcharclass `\A \mycharclassA
    \XeTeXcharclass `\B \mycharclassB   
    \chardef\mylinechar=`= %
    \def\mystretchedchar{%
    \nobreak%
    \leavevmode%
        %MainScenario 
        %\dimen0=\XeTeXglyphbounds2 \the\XeTeXcharglyph\mylinechar%"0640%
        %\dimen1=\XeTeXglyphbounds4 \the\XeTeXcharglyph\mylinechar%"0640
        %\leaders\hrule height \dimen0 depth \dimen1 \hskip 0pt plus 05.em%
        %Alternative Scenario #1 
        \hskip 0pt plus 05.em %
        \dimen0=\lastskip%
        \unskip   
        \typeout{DIMEN2= \the\dimen0***and last skip=\the\lastskip }%
        %Alternative Scenario #2
        \setbox0=\hbox{\leaders\hrule height \dimen0 depth \dimen1 \hskip 0pt plus 05.em} %testing: hfil,   
        \dimen0=\wd0%      
        %The actual drawing
        \typeout{DIMEN2= \the\dimen0***and last skip=\the\lastskip }%
        \resizebox{\dimen0}{\height}{\mylinechar}% this: \clipbox{0pt}{\mylinechar} might clip some strange whitespaces around the glyph
    \makeatother
    }
    \XeTeXinterchartoks \mycharclassA \mycharclassB = {\mystretchedchar}

}
\begin{document}
\stretchit{}
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\end{document}

但是胶水宽度总是报告为零，而输出中当然不为零。我猜这可能是因为我在计算胶水宽度时它仍然为零。

可以\hrule用多个字符（或像 MainScenario 中那样的一行）填充空间，但我想要的是字形的拉伸版本。

PS：实际上我需要用一个字形（Kashida）来填补空白，它看起来与水平线相同，MainScenario 会画一条线来代替，但这样一来，这条标尺/线与其他字形的连接处就会出现凹痕。我注意到拉伸的字形没有这个问题（可能是由于字体提示）。这就是为什么我想找到一种解决方案来像胶水一样拉伸字形。

谢谢

Answer 1

您需要在段落被分成几行之后测量拉伸宽度，而不是在插入 chardef 标记时测量。这意味着您需要运行两次 latex 才能使其工作。

\documentclass[10pt,a4paper]{article}
\usepackage{graphicx}

\makeatletter   %would do nothing inside `\newcommand`
\newcount\zzcount
% don't do new... allocations inside another macro
    \newXeTeXintercharclass \mycharclassA%
    \newXeTeXintercharclass \mycharclassB%
    \XeTeXcharclass `\A \mycharclassA
    \XeTeXcharclass `\B \mycharclassB   
    \chardef\mylinechar=`= %
    \def\mystretchedchar{%
    \leavevmode
    \global\advance\zzcount\@ne
     \pdfsavepos
     \edef\tmp{\write\@auxout{\gdef\expandafter\string\csname TESTA\romannumeral\zzcount\endcsname{\noexpand\the\pdflastxpos}}}%
     \tmp
     \hspace{0pt plus 5em}%
     \pdfsavepos
     \edef\tmp{\write\@auxout{\gdef\expandafter\string\csname TESTB\romannumeral\zzcount\endcsname{\noexpand\the\pdflastxpos}}}%
     \tmp
     \expandafter\ifx\csname TESTA\romannumeral\zzcount\endcsname\relax\else
     \llap{\resizebox{\dimexpr
\csname TESTA\romannumeral\zzcount\endcsname sp - 
\csname TESTB\romannumeral\zzcount\endcsname sp
\relax}{\height}{\mylinechar}}%
     \fi
    }
    \makeatother

\newcommand \stretchit{%%%%
    \XeTeXinterchartokenstate 1 %%% leave space after 1
    \XeTeXinterchartoks \mycharclassA \mycharclassB = {\mystretchedchar}%%%
}
\begin{document}
\stretchit{}
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\end{document}