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在 LuaTeX 中粘合节点何时具有类型“xspaceskip”？

tag-icon • tag-icon spacing luatex glue
在 LuaTeX 中粘合节点何时具有类型“xspaceskip”？

我正在使用 TeX Live 2017，并且当前 luatex 的 glue 节点文档表示subtype粘合节点的字段具有以下可能的值：

0 = userskip, 1 = lineskip, 2 = baselineskip, 3 = parskip, 4 = abovedisplayskip, 5 = belowdisplayskip, 6 = abovedisplayshortskip, 7 = belowdisplayshortskip, 8 = leftskip, 9 = rightskip, 10 = topskip, 11 = splittopskip, 12 = tabskip, 13 = spaceskip, 14 = xspaceskip, 15 = parfillskip, 16 = mathskip, 17 = thinmuskip, 18 = medmuskip, 19 = thickmuskip, 98 = conditionalmathskip, 99 = muglue, 100 = leaders, 101 = cleaders, 102 = xleaders, 103 = gleaders

我尝试了解 LuaTeX，并编写了以下简单代码来输出有关每个段落的一些信息输出：

\documentclass{article}
\directlua{dofile("parinfo.lua")}
\begin{document}

Word1, word2 office. Word3. End.
\end{document}

哪里parinfo.lua：

function traverse_paragraph(head)
   while head do
      print(string.format('In paragraph: %s %s', node.type(head.id), debugstr_node(head)))
      head = head.next
   end
  return true
end
luatexbase.add_to_callback('pre_linebreak_filter', traverse_paragraph, 'Info for debugging')

function debugstr_node(n)
   if node.type(n.id) == "glue" then
      return debugstr_glue(n)
   elseif node.type(n.id) == "glyph" then
      return n.char < 128 and string.char(n.char) or string.format('[char %s]', n.char)
   elseif node.type(n.id) == "kern" then
      return string.format('%s', n.kern)
   elseif node.type(n.id) == "penalty" then
      return string.format('%s', n.penalty)
   else
      return ''
   end
end

function debugstr_glue(n)
   if n.subtype == 13 then
      subtype = 'spaceskip'
   elseif n.subtype == 14 then
      subtype = 'xspaceskip'
   elseif n.subtype == 15 then
      subtype = 'parfillskip'
   else
      subtype = '' .. n.subtype
   end
   return string.format('<%s: %s plus %s(%s) minus %s(%s)', subtype, n.width, n.stretch, n.stretch_order, n.shrink, n.shrink_order)
end

因此，当.tex使用 编译文件时lualatex，我们会得到如下输出：

In paragraph: local_par 
In paragraph: hlist 
In paragraph: glyph W
In paragraph: kern -54395
In paragraph: glyph o
In paragraph: glyph r
In paragraph: glyph d
In paragraph: glyph 1
In paragraph: glyph ,
In paragraph: glue <spaceskip: 218235 plus 136396(0) minus 58196(0)
In paragraph: glyph w
In paragraph: kern -18350
In paragraph: glyph o
In paragraph: glyph r
In paragraph: glyph d
In paragraph: glyph 2
In paragraph: glue <spaceskip: 218235 plus 109117(0) minus 72745(0)
In paragraph: glyph o
In paragraph: glyph [char 64259]
In paragraph: glyph c
In paragraph: glyph e
In paragraph: glyph .
In paragraph: glue <spaceskip: 290980 plus 327351(0) minus 24248(0)
In paragraph: glyph W
In paragraph: kern -54395
In paragraph: glyph o
In paragraph: glyph r
In paragraph: glyph d
In paragraph: glyph 3
In paragraph: glyph .
In paragraph: glue <spaceskip: 290980 plus 327351(0) minus 24248(0)
In paragraph: glyph E
In paragraph: glyph n
In paragraph: glyph d
In paragraph: glyph .
In paragraph: penalty 10000
In paragraph: glue <parfillskip: 0 plus 65536(2) minus 0(0)

请注意，逗号后的粘连（具有较大的延伸）和 后的粘连.（具有较大的宽度和较大的延伸）仍然都显示为具有子类型spaceskip，而不是xspaceskip。 （段落末尾的粘连具有子类型parfillskip，正如预期的那样。）

这是预料之中的吗？我们什么时候会看到具有 类型的粘连xspaceskip？除了跟踪最近看到的单词间粘连并比较差异之外，pre_linebreak 过滤器中还有其他方法可以检测标点符号或句末（带有\nonfrenchspacing）后面的较大粘连吗？

我不完全理解这些工作原理，即使对于非 LuaTeX，所以我可能会感到困惑 :-) 以防万一，luatex --version说

这是 LuaTeX，版本 1.0.4 (TeX Live 2017)

答案1

当你设置\xspaceskip

\documentclass{article}
\directlua{dofile("parinfo.lua")}
\setlength\xspaceskip{10pt}
\begin{document}

Word1, word2 office. Word3. End.
\end{document}

In paragraph: glyph 3
In paragraph: glyph .
In paragraph: glue <xspaceskip: 655360 plus 0(0) minus 0(0)
In paragraph: glyph E

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