From 71aaeaf020340412b8d012fe23a556c0420eda5f Mon Sep 17 00:00:00 2001
From: Matthias Clasen <mclasen@redhat.com>
Date: Fri, 17 Aug 2018 22:29:36 -0400
Subject: [PATCH] Prevent an assertion with invalid Unicode sequences

Invalid Unicode sequences, such as 0x2665 0xfe0e 0xfe0f,
can trick the Emoji iter code into returning an empty
segment, which then triggers an assertion in the itemizer.

Prevent this by ensuring that we make progress.

This issue was reported by Jeffrey M.
---
 pango/pango-emoji.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/pango/pango-emoji.c b/pango/pango-emoji.c
index 0e332dff..29472452 100644
--- a/pango/pango-emoji.c
+++ b/pango/pango-emoji.c
@@ -253,6 +253,12 @@ _pango_emoji_iter_next (PangoEmojiIter *iter)
     if (iter->is_emoji == PANGO_EMOJI_TYPE_IS_EMOJI (current_emoji_type))
     {
       iter->is_emoji = !PANGO_EMOJI_TYPE_IS_EMOJI (current_emoji_type);
+
+      /* Make sure we make progress.  Weird sequences, like a VC15 followed
+       * by VC16, can trick us into stalling otherwise. */
+      if (iter->start == iter->end)
+        iter->end = g_utf8_next_char (iter->end);
+
       return TRUE;
     }
   }
-- 
2.17.1