This question led to a new feature in a package:

One rule in French typography is that the last line of a paragraph should not be shorter than the double of the indentation of the next paragraph.

Is it possible to specify that, or least considering that all paragraphs are indented of the same value, to make sure the last line is longer than twice this value?

A LuaTeX-specific solution is welcome, too.

  • 2
    The more I read about french typography, the more I think they have some really odd conventions…
    – Seamus
    Commented Jan 17, 2012 at 22:22
  • The requirement that the last line of a paragraph should not be shorter than the indent of the next one is also common in german typography. Commented Jul 18, 2012 at 17:21
  • @StephanLehmke: then you can also use this option in impnattypo in German :-)
    – raphink
    Commented Jul 19, 2012 at 5:31
  • @Raphink I'm very seldomly writing documents with LaTeX, but I've just fixed a bug in the respective configuration option of DocScape to enable this ;-) Commented Jul 19, 2012 at 6:40

2 Answers 2


You asked for a LuaTeX solution and you get one:


local PENALTY=node.id("penalty")
last_line_twice_parindent = function (head)
  while head do
    local _w,_h,_d = node.dimensions(head)
    if head.id == PENALTY and head.subtype ~= 15 and (_w < 2 * tex.parindent) then

        -- we are at a glue and have less than 2*\parindent to go
        local p = node.new("penalty")
        p.penalty = 10000
        p.next = head
        head.prev.next = p
        p.prev = head.prev
        head.prev = p

    head = head.next
  return true


\parindent = 2cm
\emergencystretch = \hsize

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What it does is it adds ties (~) between the words at the end of a paragraph, when the distance to the end is less then 2*\parindent. If the \parindent is large enough, the paragraphs will get ugly.

ugly paragraph

Note: this does not prevent hyphenation. So the minimal amount is not enforced by an hbox or so. This is an exercise left to the ambitious reader.

Edit: do not hardcode glyph ids...

  • Thanks. I've very interesting to see what can be done with LuaTeX. I'll favor the native, more portable solution, but I'm still interested in the LuaTeX one.
    – raphink
    Commented Sep 13, 2011 at 20:59
  • I understand, but I have slight feeling that a native solution based on parfillskip will not handle all situations (see my example in my comment to egreg's solution).
    – topskip
    Commented Sep 13, 2011 at 21:07
  • I actually found some other examples in a book of mine where your Lua code worked and not @egreg's setting.
    – raphink
    Commented Sep 13, 2011 at 22:00

At the end of each paragraph, TeX usually adds infinitely stretchable glue, since the usual setting of \parfillskip is equivalent to

\setlength{\parfillskip}{0pt plus 1fill}

One way might be to set

\setlength{\parfillskip}{0pt plus\dimexpr\textwidth-2\parindent}

but this would work only for normal paragraphs. In lists one should reset the \parfillskip with \linewidth instead of \textwidth: its value stated as before is not dynamically computed, but rather it's fixed. If \parfillskip had been a macro, instead of a skip parameter (or if Knuth had provided an \everyendofpar token parameter), things would be different. One might redefine \par, of course, but LaTeX already does it in some cases.

Note that glue can always stretch more than the stated value, but in this case the badness of the line would increase, usually producing an Underfull \hbox message. In general I'm inclined not to be overly confident in automatic adjustments like this: no automated system will be able to do this as well as you, writes Knuth about page breaking, but paragraph breaking is very much alike, particularly with respect to the final line.

  • The \setlength solution works well :-)
    – raphink
    Commented Sep 13, 2011 at 20:26
  • @egreg somehow this solution doesn't work with the extreme settings (and the example) from the example I have chosen (see my answer). Perhaps I have made a mistake!?!
    – topskip
    Commented Sep 13, 2011 at 20:41
  • @Patrick: your text works for me. It doesn't if I say \frenchspacing; that's why I said that "automated" adjustments are risky. Your tie might not work either, because TeX might choose to hyphenate in the preceding line.
    – egreg
    Commented Sep 13, 2011 at 20:52
  • 1
    Alright, I'm convinced, too :-) Well, both answers are right in normal conditions, and I'm actually going to use both for my package (the LuaTeX implementation when LuaTeX is used, and @egreg's as default). I'll choose Patrick's implementation as the answer because it's more precise.
    – raphink
    Commented Sep 13, 2011 at 21:24
  • 1
    Just for the record, I'd like to note that the TeX-only possibilities are further discussed in another question. Commented Jul 18, 2012 at 17:19

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