Ignore a static composition that starts before the current checking position in redisplay.

src/ChangeLog

+2011-07-07  Kenichi Handa  <handa@m17n.org>
+
+	* composite.c (composition_compute_stop_pos): Ignore a static
+	composition starting before CHARPOS (Bug#8915).
+
+	* xdisp.c (handle_composition_prop): Likewise.
+
 2011-06-18  YAMAMOTO Mitsuharu  <mituharu@math.s.chiba-u.ac.jp>
 	* dispnew.c (scrolling_window): Before scrolling, turn off a

src/composite.c

@@ -1042,6 +1042,7 @@ composition_compute_stop_pos (cmp_it, charpos, bytepos, endpos, string)
   cmp_it->id = -1;
   cmp_it->ch = -2;
   if (find_composition (charpos, endpos, &start, &end, &prop, string)
+      && start >= charpos
       && COMPOSITION_VALID_P (start, end, prop))
     {
       cmp_it->stop_pos = endpos = start;

src/xdisp.c

@@ -4641,6 +4641,11 @@ handle_composition_prop (it)
       && COMPOSITION_VALID_P (start, end, prop)
       && (STRINGP (it->string) || (PT <= start || PT >= end)))
     {
+      if (start < pos)
+	/* As we can't handle this situation (perhaps, font-lock added
+	   a new composition), we just return here hoping that next
+	   redisplay will detect this composition much earlier.  */
+	return HANDLED_NORMALLY;
       if (start != pos)
 	{
 	  if (STRINGP (it->string))