为了学习，我尝试使用（并理解）LuaTeX 代码来做边注这里在 LuaLaTeX 中。
因此我做了这个最小设置：
\documentclass{article}
\usepackage{luatexbase}
\directlua{
local HLIST = node.id("hlist")
local RULE = node.id("rule")
local GLUE = node.id("glue")
local KERN = node.id("kern")
local WHAT = node.id("whatsit")
local COL = node.subtype("pdf_colorstack")
mark_lines = function (head)
for mark in node.traverse_id(WHAT, head) do
local attr = node.has_attribute(mark, 100)
if attr then
local item = mark.next
while item do
if item.id == HLIST then
node.set_attribute(item, 100, attr)
item = nil
else
item = item.next
end
end
head = node.remove(head, mark)
end
end
return head
end
process_marginalia = function (head)
local remainingheight, first, item = 0, true, node.slide(head)
while item do
if node.has_field(item, "kern") then
if not first then
remainingheight = remainingheight + item.kern
end
elseif node.has_field(item, "spec") then
if not first then
remainingheight = remainingheight + item.spec.width
end
elseif node.has_field(item, "height") then
if first then
first = false
else
remainingheight = remainingheight + item.depth
end
local attr = node.has_attribute(item, 100)
if attr then
local note = node.copy(tex.box[attr])
local upward = note.depth - node.tail(note.list).depth
if upward > remainingheight then
upward = remainingheight - upward
else
upward = 0
end
local kern = node.new(KERN, 1)
kern.kern = upward - note.height - item.depth
node.insert_before(note.list, note.list, kern)
note.list = kern
note.height, note.depth = 0, 0
node.insert_after(head, item, note)
note.shift = tex.hsize + tex.sp("1em")
first = true
remainingheight = upward
else
remainingheight = remainingheight + item.height
end
end
item = item.prev
end
end
luatexbase.add_to_callback("post_linebreak_filter", mark_lines, "mark_lines")
}
\newcount\notecount
\def\note#1{%
\advance\notecount 1%
\expandafter\newbox\csname marginnote_\the\notecount\endcsname%
\expandafter\setbox\csname marginnote_\the\notecount\endcsname=\vtop{\hsize=4cm\rightskip=0pt plus 1fil\noindent\it #1}%
\bgroup\attribute100=\expandafter\the\csname marginnote_\the\notecount\endcsname\vadjust pre {\pdfliteral{}}\egroup%
}
\begin{document}
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.\note{Please do not fill this with too much text}
\output{\directlua{process_marginalia(tex.box[255].list)}\shipout\box255}
\end{document}
但是 LuaLaTeX 总是在该行抛出错误\setbox（LuaTeX 的修改版本也会出现这种情况）：
! Missing number, treated as zero.
<to be read again>
\marginnote_1
l.85 ...{Please do not fill this with too much text}
?
我不完全理解为什么会出现这种情况以及如何解决它。所以我的问题是：为什么 TeX 不喜欢这样\setbox？
答案1
这是一种明显的“缺失空间综合症”
\def\note#1{%
\advance\notecount 1
\expandafter\newbox\csname marginnote_\the\notecount\endcsname%
\expandafter\setbox\csname marginnote_\the\notecount\endcsname=\vtop{\hsize=4cm\rightskip=0pt plus 1fil\noindent\it #1}%
\bgroup\attribute100=\expandafter\the\csname marginnote_\the\notecount\endcsname\vadjust pre {\pdfliteral{}}\egroup%
}
你有一个%之后1。
你还需要\usepackage{luatex85}。经过这些修复后，我得到了
发生了什么？常量后面缺少的空格1会触发下一个标记的扩展，即\expandafter，这又会触发\csname，因此以前的的值\notecount被使用。
您会得到“缺失数字”，因为盒子寄存器实际上是整数；您的宏分配了\marginnote_0，但\setbox看到的却是\marginnote_1。