Roll HarfBuzz to 1.2.6

third_party/harfbuzz-ng/src/hb-ot-layout-gsub-table.hh

 /*
  * Copyright © 2007,2008,2009,2010  Red Hat, Inc.
  * Copyright © 2010,2012,2013  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 1270 matching lines @@
 };
 
 
 void
 GSUB::substitute_start (hb_font_t *font, hb_buffer_t *buffer)
 {
   _hb_buffer_assert_gsubgpos_vars (buffer);
 
   const GDEF &gdef = *hb_ot_layout_from_face (font->face)->gdef;
   unsigned int count = buffer->len;
+  hb_glyph_info_t *info = buffer->info;
   for (unsigned int i = 0; i < count; i++)
   {
-    _hb_glyph_info_set_glyph_props (&buffer->info[i], gdef.get_glyph_props (buffer->info[i].codepoint));
-    _hb_glyph_info_clear_lig_props (&buffer->info[i]);
+    unsigned int props = gdef.get_glyph_props (info[i].codepoint);
+    if (!props)
+    {
+      /* Never mark default-ignorables as marks.
+       * They won't get in the way of lookups anyway,
+       * but having them as mark will cause them to be skipped
+       * over if the lookup-flag says so, but at least for the
+       * Mongolian variation selectors, looks like Uniscribe
+       * marks them as non-mark.  Some Mongolian fonts without
+       * GDEF rely on this.  Another notable character that
+       * this applies to is COMBINING GRAPHEME JOINER. */
+      props = (_hb_glyph_info_get_general_category (&info[i]) !=
+               HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK ||
+               _hb_glyph_info_is_default_ignorable (&info[i])) ?
+              HB_OT_LAYOUT_GLYPH_PROPS_BASE_GLYPH :
+              HB_OT_LAYOUT_GLYPH_PROPS_MARK;
+    }
+    _hb_glyph_info_set_glyph_props (&info[i], props);
+    _hb_glyph_info_clear_lig_props (&info[i]);
     buffer->info[i].syllable() = 0;
   }
 }
 
 
 /* Out-of-class implementation for methods recursing */
 
 /*static*/ inline bool ExtensionSubst::is_reverse (void) const
 {
   unsigned int type = get_type ();
@@ skipping 22 matching lines @@
   c->set_lookup_index (saved_lookup_index);
   c->set_lookup_props (saved_lookup_props);
   return ret;
 }
 
 
 } /* namespace OT */
 
 
 #endif /* HB_OT_LAYOUT_GSUB_TABLE_HH */