2012/3/4 Pablo Rodríguez <oinos@web.de>

> On 03/04/2012 12:04 PM, Wolfgang Schuster wrote:
> > Am 04.03.2012 um 11:20 schrieb Pablo Rodríguez:
> >>
> >> I wanted to be able to have in the headers the first and last line
> >> number from page. This feature is extremely useful when typesetting some
> >> kinds of poetry.
> >> [...]
> >> Is that possible to achieve with ConTeXt?
> >
> > Yes but it’s not usable because the numbers are always shown on the next
> page.
>
> Many thanks for your reply, Wolfgang.
>
> If you allow me one more question: is showing the numbers on the same
> page they refer to beyond the limits of TeX/LuaTeX?
>

Absolutely no. As Hans said, a quick/dirty trick is possible: just mark the
object
with \pagereference[<unique id>]. The data is stored into the *tuc file,
which can be read
from  the second pass.
Then always run with
$>context --purgeall ; context <yourfile>.mkiv
Of course, "it's possible " doesn't mean "it's the right context way".

\startluacode
document.my_name_space = document.my_name_space or {}
document.my_name_space.pages = document.my_name_space.pages or {}
local f =  io.open(file.addsuffix(tex.jobname,"tuc") )
print('>>>>> ',f)
if f==nil then
 --[=[ do nothin ]=]
else
 f:close()
 local tuc = dofile(file.addsuffix(tex.jobname,"tuc"))
 local data =  tuc.structures.references.collected[""]
 local  w
 local pages = document.my_name_space.pages
 local realpage,ref
 for k, v in  pairs(data) do
   w=string.gmatch(k,'LIN:(\%d+):\%d+')
   ref = tonumber(w())
   realpage = tostring(v.references.realpage)
   pages[realpage]= pages[realpage] or {}
   table.insert(pages[realpage],ref)
 end
 for page,array in pairs(pages) do
   table.sort(array)
 end
end
\stopluacode


\definemarking[linenumber]
\define\LinenumberCommand
 {\normalexpanded{\setmarking[linenumber]{\linenumber}}\pagereference[LIN:\linenumber:\currentpage]}

\setuplinenumbering[command=\LinenumberCommand]

\startsetups linenumber
%       \doiftext {
%               \getmarking[linenumber]
%       }
%       {
%               \getmarking[linenumber][first] –
\getmarking[linenumber][last]
%       }
 \startluacode
 local l=0;
 if document.my_name_space == nil then return end;
 if document.my_name_space.pages == nil then return end;
 local pages = document.my_name_space.pages;
 for _,_ in  pairs(pages) do l=l+1 end;
 if l== 0 then return end;
 --[=[ OK, we have some data to print ]=]
 local array = pages[tostring(tex.count.realpageno)]
 l=0;
 if array ==nil then return end;
 for _,_ in  pairs(array) do l=l+1 end;
 if l>0 then context(" nr. "..array[1].." --- "..array[l]) end;
 \stopluacode
\stopsetups

\setupheadertexts[\texsetup{linenumber}]

\starttext

\dorecurse{6}{\input tufte\par}

\startlinenumbering
\dorecurse{20}{\input knuth\par}
\stoplinenumbering

\resetmarking[linenumber]

\dorecurse{6}{\input tufte\par}

\stoptext

--
luigi