[Dev-luatex] \lastnodetype not working as expected in LuaTeX

Hans Hagen pragma at wxs.nl
Mon Jun 11 18:55:07 CEST 2012


On 11-6-2012 17:43, Frank Mittelbach wrote:
> Hans,
>
> my fluency in the linebreak algorithm is a little bit rusty. Are you
> saying that there are other points and stuff in that space that is not
> updated or more on the page builder side of the house?

More in the pagebuilder area where we have this insert stuff (which for 
that reason I mostly left for the future). In your case setting the 
prevdepth and prevgraf is indeed needed. Actually, you need:

\def\partest {%
     \directlua {%
         function hpackparagraph  (head)
             local h = node.hpack(head)
             tex.nest[tex.nest.level].prevgraf = 1
             tex.nest[tex.nest.level].prevdepth = h.depth
             return h
         end
         callback.register("linebreak_filter", hpackparagraph)
     }%
     \par
}

btw, Internally the linebreaker is somewhat complicated by the fact that 
hz and protrusion play a role. I have a (lua) parbuilder prototype that 
gets rid of a lot of that code but Harmut needs time to implement a few 
things in the backend (will happen later this year) and that in turn 
will make the parbuilder cleaner. We also want systematic usage of 
left/rightskip nodes in broken lines so that we can have a more 
predictable model of a broken line.

> Or asked differently is there more that needs updating to make my little
> example work, and if so could that be already done through a workaround
> like I did with
>
> tex.nest[tex.nest.ptr].tail = node.tail(head)
>
> or would it absolutely need fixes in the program itself?

Sort of. The returned -1 is now a signal that prevdepth has not been set 
and that is not something deliberate.

However, the fact that you need to set prevdepth and prefgraf (maybe 
more) explicitly gives the possibility to manipulate those depth and 
graf parameters. So, in any code that uses the callback one needs to 
take care of these variables anyway.

Hans

p.s I remember that there has been some fixes to lastnode(type) so it 
might as well that at that time some buglet crept in.

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