[pango] [HB] Add comment

[Behdad Esfahbod <behdad src gnome org>]

commit 07bb283c9f2d5a1403964dc083c981d9b2e4919f
Author: Behdad Esfahbod <behdad behdad org>
Date:   Mon Sep 21 13:58:56 2009 -0400

    [HB] Add comment

 pango/opentype/hb-ot-layout-gsubgpos-private.hh |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/pango/opentype/hb-ot-layout-gsubgpos-private.hh b/pango/opentype/hb-ot-layout-gsubgpos-private.hh
index fd9c783..8b9b1cd 100644
--- a/pango/opentype/hb-ot-layout-gsubgpos-private.hh
+++ b/pango/opentype/hb-ot-layout-gsubgpos-private.hh
@@ -219,6 +219,11 @@ static inline bool apply_lookup (APPLY_ARG_DEF,
 
   /* TODO We don't support lookupRecord arrays that are not increasing:
    *      Should be easy for in_place ones at least. */
+
+  /* Note: If sublookup is reverse, i will underflow after the first loop
+   * and we jump out of it.  Not entirely disastrous.  So we don't check
+   * for reverse lookup here.
+   */
   for (unsigned int i = 0; i < count; /* NOP */)
   {
     while (_hb_ot_layout_skip_mark (context->face, IN_CURINFO (), lookup_flag, NULL))