[luatex] Luatex tutorial

[Paul Isambert]

Mikoláš Štrajt <strajt9 at seznam.cz> a écrit:
> If someone can post some easy simple and/or practical example it 
> will be nice. 

I've just remembered the following code. The motivation is that last
lines whose width is smaller than the paragraph's indentation are
unpleasant. The code adds an infinite penalty before each space (starting
at the end of the paragraph) if the following material isn't large
enough to make a proper last line, thus making that space unbreakable.
In other words, a paragraph ending with e.g.:

    ... bigword a b.

becomes

    ... bigword~a~b.

(The ~ is the unbreakable space in TeX.)

Note that "node.dimensions(a, b)" measures from "a" to the node
preceding "b".

Best,
Paul

\directlua{
local GLYF = node.id"glyph"
local GLUE = node.id"glue"
local function gluelastword (head)
  % Get the last node of the list.
  local last = node.slide(head)
  % Skip the \parfillskip glue and associated penalty.
  while last and not(last.id == GLYF) do
    last = last.prev
  end
  if last then
    local prev, last = last.prev, last.next
    while prev do
      if prev.id == GLUE then
        if node.dimensions(prev.next, last) <= tex.parindent then
          local p = node.new"penalty"
          p.penalty = 10000
          head = node.insert_before(head, prev, p)
        else
          break
        end
      end
      prev = prev.prev
    end
  end
  return head
end

callback.register("pre_linebreak_filter", gluelastword)
}