\ProvidesPackage{showhyphens}[2016/02/19 v0.5c Show hyphenation points (PGU)]
\RequirePackage{ifluatex,luatexbase}
% License: MIT style license

% Copyright (c) 2011-2016 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.

\def\lua@SHcolor{1 0 0}% red
\DeclareOption{blue}{\def\lua@SHcolor{0 0 1 }}% must be a rgb color
\ProcessOptions

\ifluatex
\directlua{
local show_hyph
local hlist_node = node.id("hlist")
local vlist_node = node.id("vlist")
local disc_node = node.id("disc")
local glyph_node = node.id("glyph")

local function round(num)
  return math.floor(num * 10^3 + 0.5) / 10^3
end

show_hyph = function(head)
  while head do
    if head.id == hlist_node or head.id == vlist_node then
      show_hyph(head.list)
    elseif head.id == disc_node then
      if head.replace and head.replace.id == glyph_node and head.replace.components then
        local wd = round(head.replace.width / 65781)  or 0
        local ht = round(head.replace.height / 65781) + 0.5  or 0
        local r = node.new("whatsit","pdf_literal")
        r.data = "q 0.3 w 0 " .. tostring(ht) .. " m " .. tostring(-wd) .. " " .. tostring(ht) ..  "  l S Q"
        node.insert_after(head.replace,head.replace,r)
      else
        local n = node.new("whatsit","pdf_literal")
        n.mode = 0
        n.data = "q \lua@SHcolor RG 0.3 w 0 2 m 0 7 l S Q"
        n.next = head.next
        head.next.prev = n
        n.prev = head
        head.next = n
        head = n
      end
    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