Pandoc Lua filter: How can I check in function Str if argument comes from a title (of a chapter or section)

Question

actually, i do some filtering for the markdown to LaTeX transformation. I use lua filters for this. Now i'd need to do something like this:

function Str (el)
  if is_in_a_title(el) then
    -- do this
  else
    -- do that
  end
end

meaning that inside Str i want to check if the argument belongs to a chapter/section title. Is there any way to do this?

Answer 1

Re-posting what I wrote on the mailing list:

This is best done by running sub-filters:

local header_filter = {
  Str = function (el)
    -- do this
  end
}

function Header (h)
  return pandoc.util.walk_block(h, header_filter)
end

The header_filter is just like a normal Lua filter. The walk_block function applies that filter to all elements below the Header, and those elements only.