From e1cbd4539f392034899353f55daffa32e6d62c87 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 20 Nov 2021 11:46:48 -0700
Subject: [PATCH] [unsafe-to-concat] Add annotations to GPOS and kern

Failures from 13 to 14.
---
 src/hb-kern.hh                 |  4 +++-
 src/hb-ot-layout-gpos-table.hh | 43 +++++++++++++++++++++++++++++-----
 2 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/src/hb-kern.hh b/src/hb-kern.hh
index 3f952fe7f..4e1a35bbc 100644
--- a/src/hb-kern.hh
+++ b/src/hb-kern.hh
@@ -67,8 +67,10 @@ struct hb_kern_machine_t
       }
 
       skippy_iter.reset (idx, 1);
-      if (!skippy_iter.next ())
+      unsigned unsafe_to;
+      if (!skippy_iter.next (&unsafe_to))
       {
+        buffer->unsafe_to_concat (idx, unsafe_to);
 	idx++;
 	continue;
       }
diff --git a/src/hb-ot-layout-gpos-table.hh b/src/hb-ot-layout-gpos-table.hh
index be341fb44..8dd4cf4de 100644
--- a/src/hb-ot-layout-gpos-table.hh
+++ b/src/hb-ot-layout-gpos-table.hh
@@ -1362,7 +1362,12 @@ struct PairPosFormat1
 
     hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c->iter_input;
     skippy_iter.reset (buffer->idx, 1);
-    if (!skippy_iter.next ()) return_trace (false);
+    unsigned unsafe_to;
+    if (!skippy_iter.next (&unsafe_to))
+    {
+      buffer->unsafe_to_concat (buffer->idx, unsafe_to);
+      return_trace (false);
+    }
 
     return_trace ((this+pairSet[index]).apply (c, valueFormat, skippy_iter.idx));
   }
@@ -1555,7 +1560,12 @@ struct PairPosFormat2
 
     hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c->iter_input;
     skippy_iter.reset (buffer->idx, 1);
-    if (!skippy_iter.next ()) return_trace (false);
+    unsigned unsafe_to;
+    if (!skippy_iter.next (&unsafe_to))
+    {
+      buffer->unsafe_to_concat (buffer->idx, unsafe_to);
+      return_trace (false);
+    }
 
     unsigned int len1 = valueFormat1.get_len ();
     unsigned int len2 = valueFormat2.get_len ();
@@ -1861,7 +1871,12 @@ struct CursivePosFormat1
 
     hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c->iter_input;
     skippy_iter.reset (buffer->idx, 1);
-    if (!skippy_iter.prev ()) return_trace (false);
+    unsigned unsafe_from;
+    if (!skippy_iter.prev (&unsafe_from))
+    {
+      buffer->unsafe_to_concat_from_outbuffer (unsafe_from, buffer->idx);
+      return_trace (false);
+    }
 
     const EntryExitRecord &prev_record = entryExitRecord[(this+coverage).get_coverage  (buffer->info[skippy_iter.idx].codepoint)];
     if (!prev_record.exitAnchor) return_trace (false);
@@ -2128,7 +2143,13 @@ struct MarkBasePosFormat1
     skippy_iter.reset (buffer->idx, 1);
     skippy_iter.set_lookup_props (LookupFlag::IgnoreMarks);
     do {
-      if (!skippy_iter.prev ()) return_trace (false);
+      unsigned unsafe_from;
+      if (!skippy_iter.prev (&unsafe_from))
+      {
+	buffer->unsafe_to_concat_from_outbuffer (unsafe_from, buffer->idx);
+	return_trace (false);
+      }
+
       /* We only want to attach to the first of a MultipleSubst sequence.
        * https://github.com/harfbuzz/harfbuzz/issues/740
        * Reject others...
@@ -2382,7 +2403,12 @@ struct MarkLigPosFormat1
     hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c->iter_input;
     skippy_iter.reset (buffer->idx, 1);
     skippy_iter.set_lookup_props (LookupFlag::IgnoreMarks);
-    if (!skippy_iter.prev ()) return_trace (false);
+    unsigned unsafe_from;
+    if (!skippy_iter.prev (&unsafe_from))
+    {
+      buffer->unsafe_to_concat_from_outbuffer (unsafe_from, buffer->idx);
+      return_trace (false);
+    }
 
     /* Checking that matched glyph is actually a ligature by GDEF is too strong; disabled */
     //if (!_hb_glyph_info_is_ligature (&buffer->info[skippy_iter.idx])) { return_trace (false); }
@@ -2579,7 +2605,12 @@ struct MarkMarkPosFormat1
     hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c->iter_input;
     skippy_iter.reset (buffer->idx, 1);
     skippy_iter.set_lookup_props (c->lookup_props & ~LookupFlag::IgnoreFlags);
-    if (!skippy_iter.prev ()) return_trace (false);
+    unsigned unsafe_from;
+    if (!skippy_iter.prev (&unsafe_from))
+    {
+      buffer->unsafe_to_concat_from_outbuffer (unsafe_from, buffer->idx);
+      return_trace (false);
+    }
 
     if (!_hb_glyph_info_is_mark (&buffer->info[skippy_iter.idx])) { return_trace (false); }