(concat): Be sure to avoid putting the same `composition'

property on the adjacent regions.

diff --git a/src/fns.c b/src/fns.c
index fd06513a0b434feb729c98a2de004df4dbc3561c..4656c41a9f3a9e771d2dc14a1e375146611c861d 100644 (file)
--- a/src/fns.c
+++ b/src/fns.c
@@ -830,6 +830,7 @@ concat (nargs, args, target_type, last_special)
   if (num_textprops > 0)
     {
       Lisp_Object props;
+      int last_to_end = -1;
 
       for (argnum = 0; argnum < num_textprops; argnum++)
        {
@@ -840,11 +841,11 @@ concat (nargs, args, target_type, last_special)
                                      Qnil);
          /* If successive arguments have properites, be sure that the
             value of `composition' property be the copy.  */
-         if (argnum > 0
-             && textprops[argnum - 1].argnum + 1 == textprops[argnum].argnum)
+         if (last_to_end == textprops[argnum].to)
            make_composition_value_copy (props);
          add_text_properties_from_list (val, props,
                                         make_number (textprops[argnum].to));
+         last_to_end = textprops[argnum].to + XSTRING (this)->size;
        }
     }
   return val;