[Dev-luatex] Re: user_defined node clears \lastskip

30 May 2024

      With attributes it is difficult to know when marked contend is really 
finished
because when attribute removed (set to -"7FFFFFFF) it just stops adding 
new attributes.
If latest written node with some current attribute would get some 
meaningful
value that this is a final node with that attribute that would  be perfect.

For example
\setbox0=\hbox {very long}

\attribute2=5
Section \unhbox0 title
\attribute2=-"7FFFFFFF

And if I say that everything with  attributes (2=5)  is semantic section 
in this document
than I'll get two "sections" in this case because when I'll be scanning 
nodes I will not know
that this box without attributes is part of the section and I need to 
seek for other node without attribute
which should mean ending.

On 5/30/2024 11:25 AM, Max Chernoff wrote:
...
Hi Linas,
On Thu, 2024-05-30 at 10:39 +0300, Linas Stonys wrote:
...
For example  if there would be few primitives which could add an
attribute or/and properties
to next (yet to be created) non discardable item like
\luaAddFeaturesNodeNext {{attr=1, properties={"<section>}}}
\section{foo}
\luaAddFeaturesNodePrev{{attr=1, properties={"</section>}}}
The primitive \attribute is pretty close. You just need a little bit of
Lua to make it behave exactly like you want:
\attributedef\myattribute=1234 % or use \newattribute
     \newcount\mycount
     \def\addattribute#1{%
         \advance\mycount by 1
         \global\myattribute=\mycount
         \global\expandafter\def\csname myattribute\the\mycount\endcsname{#1}%
     }
\catcode`\~=12
     \directlua{%
         attribute_number = token.create("myattribute").index
         local function recurse(head)
             for n in node.traverse(head) do
                 if n.list then
                     recurse(n.list)
                 end
local attr = node.get_attribute(n, attribute_number)
                 local value
                 if attr and
                    n.id ~= node.id("glue") and
                    n.id ~= node.id("local_par")
                 then
                     value = token.get_macro("myattribute" .. attr)
                     token.set_macro("myattribute" .. attr, nil, "global")
                 end
if value and value ~= "" then
                     local colour = node.new("whatsit", "pdf_literal")
                     node.unset_attribute(colour, attribute_number)
                     colour.mode = 2
                     colour.data = value
                     node.insert_before(head, n, colour)
                 end
             end
             return head
         end
         callback.register("pre_output_filter", recurse)
     }
\addattribute{1 0 0 rg} abc
     \addattribute{0 1 0 rg} def
     \addattribute{0 0 1 rg} ghi
\bye
-- Max