计算行内字符数

Question

_{（来源：bankfotek.pl）}

我有章节，在每一行的末尾我会写上字符的计数器，并在文本行之前写一行字符数的大小。

请使用 LuaTeX 解决方案。我的 LaTeX 代码

\begin{document}
\begin{minipage}{5cm}
\blindtext
\end{minipage}
\end{document}

Answer 1

这是一个概念证明：

\documentclass{article}
\usepackage{luacode,luatexbase}
\begin{document}

\begin{luacode*}
function countchars(head)
  while head do
    if head.id == 0 then
      -- a hbox
      local c = 0
      local first_font
      for n in node.traverse_id(37,head.head) do
        c = c + 1
        first_font = first_font or n.font
      end

      local glue = node.new("glue")
      glue.spec = node.new("glue_spec")
      glue.spec.stretch = 2^16
      glue.spec.stretch_order = 3
      local rule = node.new("rule")
      rule.width = 1 * c * 2^16
      rule.height = 2 * 2^16
      while c > 0 do
        local digit = math.mod(c,10)
        local glyf = node.new("glyph")
        glyf.font = first_font
        glyf.char = 48 + digit
        node.insert_after(glue,glue,glyf)
        c = c - digit
        c = c / 10
      end
      local llap_glue = node.new("glue")
      llap_glue.spec = node.new("glue_spec")
      llap_glue.spec.stretch = 2^16
      llap_glue.spec.stretch_order = 2
      llap_glue.spec.shrink = 2^16
      llap_glue.spec.shrink_order = 2
      node.insert_after(llap_glue, llap_glue, rule)
      llap_hbox = node.hpack(llap_glue,0,"exactly")
      local marker = node.insert_before(glue,glue,llap_hbox)
      local h = node.hpack(marker,head.width + 14*2^16,"exactly")
      h.width = 0
      head.head = node.insert_before(head.head,head.head,h)
    end
    head = head.next
  end
  return true
end

luatexbase.add_to_callback("post_linebreak_filter",countchars,"countchars")
\end{luacode*}

A \emph{wonderful} serenity has taken {\large possession} of my entire soul, like these
\textsl{sweet}
\textbf{mornings} of spring which I enjoy with my whole heart. I am alone, and feel the
charm of existence in this spot, \textbf{which} was created for the bliss of souls like
mine. I am so happy, my dear friend, so absorbed in the exquisite sense of
mere tranquil existence, that I neglect my talents. I should be incapable of
drawing a single stroke at the present moment; and yet I feel that I never was
a greater artist than now.

\end{document}