From 279a85109de091df32665fa854c6764a19ab21d2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marcel=20Fabian=20Kr=C3=BCger?= <zauguin@gmail.com>
Date: Wed, 3 Jun 2020 23:59:59 +0200
Subject: [PATCH] Better handle duplicate destinations

---
 luametalatex-back-pdf.lua | 6 +++++-
 luametalatex-pdf.lua      | 8 ++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/luametalatex-back-pdf.lua b/luametalatex-back-pdf.lua
index f1cfec5..a4e490c 100644
--- a/luametalatex-back-pdf.lua
+++ b/luametalatex-back-pdf.lua
@@ -142,7 +142,11 @@ local function do_dest(prop, p, n, x, y)
   elseif dest_type == "fitbv" then
     data = string.format("[%i 0 R/FitBV %.5f]", cur_page, sp2bp(x))
   end
-  dests[id] = pfile:indirect(dests[id], data)
+  if pfile:written(dests[id]) then
+    texio.write_nl(string.format("Duplicate destination %q", id))
+  else
+    dests[id] = pfile:indirect(dests[id], data)
+  end
 end
 local function do_refobj(prop, p, n, x, y)
   pfile:reference(prop.obj)
diff --git a/luametalatex-pdf.lua b/luametalatex-pdf.lua
index 1b35f6e..bb067cc 100644
--- a/luametalatex-pdf.lua
+++ b/luametalatex-pdf.lua
@@ -7,6 +7,13 @@ local pairs = pairs
 local setmetatable = setmetatable
 local assigned = {}
 local delayed = {}
+-- slightly tricky interface: No/nil return means that the objects content
+-- isn't known yet, while false indicates a delayed object.
+local function written(pdf, num)
+  num = pdf[num]
+  if not num or num == assigned then return end
+  return num ~= delayed
+end
 local function stream(pdf, num, dict, content, isfile)
   if not num then num = pdf:getobj() end
   if pdf[num] ~= assigned then
@@ -117,6 +124,7 @@ local pdfmeta = {
   delayed = delayed,
   delayedstream = delayedstream,
   reference = reference,
+  written = written,
 }
 pdfmeta.__index = pdfmeta
 local function open(filename)