[luatex] node missing

[Paul Isambert]

Andreas Matthias <andreas.matthias at gmail.com> a écrit:
> 
> Paul Isambert wrote:
> 
> > Andreas Matthias <andreas.matthias at gmail.com> a écrit:
> >> 
> >> In the following example I expected \mybox to contain `abc'
> >> eventually. Instead it only contains `bc'. Why is the `a'
> >> missing?
> > 
> > You must assign n1 to box.head, as in
> > 
> > [...]
> >       n1.next = box.head
> >       box.head = n1       
> >       tail = node.slide(n1)
> > [...]
> > 
> > otherwise the box still points to its former head as its first node
> > (which has indeed n1 as its prev node, but it is ignored because scanning
> > begins at the former head).
> 
> 
> Hmm. I see it's working now but I still don't understand why.
> 
> Function foo creates and returns an hlist `h' and I thought this
> hlist would be assigned to mybox with
> 
>    tex.setbox(mybox, foo(tex.box.mybox))
> 
> Hlist `h' does not contain the original box but the interior of
> the box, does it? Then why do I have to set box.head?

Sorry, I didn't pay enough attention. I thought it was the usual error
(forgetting to reassign to a list's head being quite common).

Actually, 

    tex.setbox(mybox, foo(tex.box.mybox))

doesn't mean anything, it should be:

    tex.setbox("mybox", foo(tex.box.mybox))

Consequently:

      n1.next = box.head

should be:

      n1.next = node.copy_list(box.head)

Otherwise LuaTeX will be stuck in a loop (I have no time to investigate
why, but it does so).

Best,
Paul