Re: post_linebreak_filter in context

[Hans Hagen <pragma@wxs.nl>]

On 25-2-2011 12:28, Patrick Gundlach wrote:
> Hi,
>
> how do I install a custom post_linebreak_filter in ConTeXt? I have this LaTeX file:
>
> ------------------------------------------------------------------------------------
> \documentclass[12pt,a4paper]{scrartcl}
> \usepackage[english]{babel}
> \usepackage{blindtext}
> \usepackage{fontspec}
> \directlua{
> show_hyph = function(head)
>    while head do
>      if head.id == 0 or head.id == 1 then % hlist, vlist
>        show_hyph(head.list) % should be head.head in a newer luatex than 0.64
>      elseif head.id == 7 then             % disc
>        local n = node.new("whatsit","pdf_literal")
>        n.mode = 0
>        n.data = "q 0.3 w 0 2 m 0 7 l S Q"
>        n.next = head.next
>        n.prev = head
>        head.next = n
>        head = n
>      end
>    head = head.next
>    end
>    return true
> end
> luatexbase.add_to_callback("post_linebreak_filter",show_hyph,"show_hyph")
>
> }
>
> \begin{document}
> \begin{minipage}{5cm}
> \blindtext
> \end{minipage}
> \end{document}
> ------------------------------------------------------------------------------------
>
> which registers a function "show_hyph" as the post_linebreak_filter (the rest is not really interesting). How would I do this in ConTeXt?

first put the function in some namespace, like:

moduledata.mystuff = { }
moduledata.mystuff.show_hyph = show_hyph

then register it in the finalizer group (which is the post_linebreak stuff)

nodes.tasks.appendaction("finalizers","after","moduledata.mystuff.show_hyph")

(before and after are subgroups that can be used by users if needed; of 
course one never know to what extent it will influence other processes, 
so "shipouts","after" might be a better choice)

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                                           Hans Hagen | PRAGMA ADE
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                                              | www.pragma-pod.nl
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