Roll HarfBuzz to 1.4.6

third_party/harfbuzz-ng/src/hb-ot-layout-gsubgpos-private.hh

 /*
  * Copyright © 2007,2008,2009,2010  Red Hat, Inc.
  * Copyright © 2010,2012  Google, Inc.
  *
  *  This is part of HarfBuzz, a text shaping library.
  *
  * Permission is hereby granted, without written agreement and without
  * license or royalty fees, to use, copy, modify, and distribute this
  * software and its documentation for any purpose, provided that the
  * above copyright notice and the following two paragraphs appear in
@@ skipping 324 matching lines @@
     uint8_t syllable;
     match_func_t match_func;
     const void *match_data;
   };
 
   struct skipping_iterator_t
   {
     inline void init (hb_apply_context_t *c_, bool context_match = false)
     {
       c = c_;
-      match_glyph_data = NULL,
+      match_glyph_data = NULL;
       matcher.set_match_func (NULL, NULL);
       matcher.set_lookup_props (c->lookup_props);
       /* Ignore ZWNJ if we are matching GSUB context, or matching GPOS. */
       matcher.set_ignore_zwnj (context_match || c->table_index == 1);
       /* Ignore ZWJ if we are matching GSUB context, or matching GPOS, or if asked to. */
       matcher.set_ignore_zwj (context_match || c->table_index == 1 || c->auto_zwj);
       matcher.set_mask (context_match ? -1 : c->lookup_mask);
     }
     inline void set_lookup_props (unsigned int lookup_props)
     {
@@ skipping 596 matching lines @@
 static inline bool apply_lookup (hb_apply_context_t *c,
                                  unsigned int count, /* Including the first glyph */
                                  unsigned int match_positions[HB_MAX_CONTEXT_LENGTH], /* Including the first glyph */
                                  unsigned int lookupCount,
                                  const LookupRecord lookupRecord[], /* Array of LookupRecords--in design order */
                                  unsigned int match_length)
 {
   TRACE_APPLY (NULL);
 
   hb_buffer_t *buffer = c->buffer;
-  unsigned int end;
+  int end;
 
   /* All positions are distance from beginning of *output* buffer.
    * Adjust. */
   {
     unsigned int bl = buffer->backtrack_len ();
     end = bl + match_length;
 
     int delta = bl - buffer->idx;
     /* Convert positions to new indexing. */
     for (unsigned int j = 0; j < count; j++)
@@ skipping 16 matching lines @@
     unsigned int orig_len = buffer->backtrack_len () + buffer->lookahead_len ();
     if (!c->recurse (lookupRecord[i].lookupListIndex))
       continue;
 
     unsigned int new_len = buffer->backtrack_len () + buffer->lookahead_len ();
     int delta = new_len - orig_len;
 
     if (!delta)
         continue;
 
-    /* Recursed lookup changed buffer len.  Adjust. */
+    /* Recursed lookup changed buffer len.  Adjust.
+     *
+     * TODO:
+     *
+     * Right now, if buffer length increased by n, we assume n new glyphs
+     * were added right after the current position, and if buffer length
+     * was decreased by n, we assume n match positions after the current
+     * one where removed.  The former (buffer length increased) case is
+     * fine, but the decrease case can be improved in at least two ways,
+     * both of which are significant:
+     *
+     *   - If recursed-to lookup is MultipleSubst and buffer length
+     *     decreased, then it's current match position that was deleted,
+     *     NOT the one after it.
+     *
+     *   - If buffer length was decreased by n, it does not necessarily
+     *     mean that n match positions where removed, as there might
+     *     have been marks and default-ignorables in the sequence.  We
+     *     should instead drop match positions between current-position
+     *     and current-position + n instead.
+     *
+     * It should be possible to construct tests for both of these cases.
+     */
 
-    end = int (end) + delta;
-    if (end <= match_positions[idx])
+    end += delta;
+    if (end <= int (match_positions[idx]))
     {
       /* End might end up being smaller than match_positions[idx] if the recursed
        * lookup ended up removing many items, more than we have had matched.
        * Just never rewind end back and get out of here.
        * https://bugs.chromium.org/p/chromium/issues/detail?id=659496 */
       end = match_positions[idx];
       /* There can't be any further changes. */
       break;
     }
 
@@ skipping 1307 matching lines @@
                                  * in version 0x00010001. */
   public:
   DEFINE_SIZE_MIN (10);
 };
 
 
 } /* namespace OT */
 
 
 #endif /* HB_OT_LAYOUT_GSUBGPOS_PRIVATE_HH */