\ProvidesPackage{showhyphens}[2011/09/12 v0.1 Show hyphenation points (PGU)]
\RequirePackage{ifluatex,luatexbase}
% License: MIT style license

% Copyright (c) 2011 Patrick Gundlach patrick@gundla.ch

% Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the
% "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge,
% publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do
% so, subject to the following conditions:
% 
% The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
% 
% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
% MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
% FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
% WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

\ifluatex
\directlua{
show_hyph = function(head)
  while head do
    if head.id == 0 or head.id == 1 then % hlist, vlist
      show_hyph(head.head)
    elseif head.id == 7 then             % disc
      local n = node.new("whatsit","pdf_literal")
      n.mode = 0
      n.data = "q 1 0 0 RG  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")
}
\else
\errhelp{Please use LuaLaTeX when you require the package 'showhyphens'}
\errmessage{Package showhyphens error: This works only with LuaLaTeX!}
\fi
