[Dev-luatex] How to insert at start of hlist/vlist?

[Hans Hagen]

Heiko Oberdiek wrote:
> Hello,
> 
> I have some trouble to insert something at the start
> of a list.
> 

weird message indeed; this works

   do
     local hlist = tex.box[0]
     local pdf_literal = node.new(8,8)% \pdfliteral
     pdf_literal.mode = 2 % direct
     pdf_literal.data = "1 0 0 rg 1 0 0 RG"
     pdf_literal.next = hlist.list
     hlist.list = pdf_literal
   end

current assigning to a box (or operating on box related lists are 
somewhat tricky, internal invisible pointers and such; this interface 
will probably change a bit; it helps to copy the list, work on the copy 
and hpack the result


> Example (complete example file after PS):
> 
> \setbox0=\hbox{XY}
> \directlua0{
>   do
>     local hlist = tex.box[0]
>     local pdf_literal = node.new(8,8)% \pdfliteral
>     pdf_literal.mode = 2 % direct
>     pdf_literal.data = "1 0 0 rg 1 0 0 RG"
>     local head = hlist.list
>     % local current = hlist.list.next % works
>     local current = hlist.list % fails  
>     hlist.list = node.insert_before(head, current, pdf_literal)  
>   end
> }
> 
> ! LuaTeX error Attempt to node.insert_before() a non-existing node.
> 
> Have I misunderstood node.insert_before()?
> 
> Yours sincerely
>   Heiko <oberdiek at uni-freiburg.de>
> 
> PS: Complete example file that can be used with
>     iniTeX, plain-TeX and LaTeX:
> 
> \ifnum\catcode`\{=1
> \else
>   \catcode`\{=1
>   \catcode`\}=2
>   \hsize=6.5in
>   \vsize=8.9in
>   \parfillskip=0pt plus 1fil
> \fi
> \font\f=cmr10
> \f
> \pdfoutput=1
> 
> \setbox0=\hbox{XY}
> \directlua0{
>   do
>     local hlist = tex.box[0]
>     local pdf_literal = node.new(8,8)% \pdfliteral
>     pdf_literal.mode = 2 % direct
>     pdf_literal.data = "1 0 0 rg 1 0 0 RG"
>     local head = hlist.list
>     % local current = hlist.list.next % works
>     local current = hlist.list % fails  
>     hlist.list = node.insert_before(head, current, pdf_literal)  
>   end
> }
> \shipout\hbox{[\box0]}
> 
> \csname @@end\endcsname
> \end
> _______________________________________________
> dev-luatex mailing list
> dev-luatex at ntg.nl
> http://www.ntg.nl/mailman/listinfo/dev-luatex


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