Ticket #3984: patch-src_diffviewer_ydiff_c_proposal

--- src/diffviewer/ydiff.c.orig Fri Dec 28 20:35:25 2018
+++ src/diffviewer/ydiff.c      Sun May  5 23:41:00 2019
@@ -619,7 +619,7 @@
         return length;
 
     if (g_utf8_validate (text, -1, NULL))
-        result = g_utf8_offset_to_pointer (text, length) - text;
+       result =  g_utf8_strlen (text, length);
     else
     {
         gunichar uni;
@@ -637,10 +637,10 @@
                 tmpbuf++;
             }
         }
-        result = g_utf8_offset_to_pointer (tmpbuf, length) - tmpbuf;
+       result =  g_utf8_strlen (tmpbuf, length);
         g_free (buffer);
     }
-    return MAX (length, (size_t) result);
+       return 2 * length - result;
 }
 #endif /*HAVE_CHARSET */