harfbuzz-ng roll

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 13 matching lines @@
  *
  * Red Hat Author(s): Behdad Esfahbod
  * Google Author(s): Behdad Esfahbod
  */
 
 #ifndef HB_OT_LAYOUT_GSUBGPOS_PRIVATE_HH
 #define HB_OT_LAYOUT_GSUBGPOS_PRIVATE_HH
 
 #include "hb-buffer-private.hh"
 #include "hb-ot-layout-gdef-table.hh"
+#include "hb-set-private.hh"
 
 
-
-/* unique ligature id */
-/* component number in the ligature (0 = base) */
-static inline void
-set_lig_props (hb_glyph_info_t &info, unsigned int lig_id, unsigned int lig_comp)
-{
-  info.lig_props() = (lig_id << 4) | (lig_comp & 0x0F);
-}
-static inline unsigned int
-get_lig_id (hb_glyph_info_t &info)
-{
-  return info.lig_props() >> 4;
-}
-static inline unsigned int
-get_lig_comp (hb_glyph_info_t &info)
-{
-  return info.lig_props() & 0x0F;
-}
-
-static inline uint8_t allocate_lig_id (hb_buffer_t *buffer) {
-  uint8_t lig_id = buffer->next_serial () & 0x0F;
-  if (unlikely (!lig_id))
-    lig_id = allocate_lig_id (buffer); /* in case of overflow */
-  return lig_id;
-}
-
+namespace OT {
 
 
 #ifndef HB_DEBUG_CLOSURE
 #define HB_DEBUG_CLOSURE (HB_DEBUG+0)
 #endif
 
 #define TRACE_CLOSURE() \
         hb_auto_trace_t<HB_DEBUG_CLOSURE> trace (&c->debug_depth, "CLOSURE", this, HB_FUNC, "");
 
 
-/* TODO Add TRACE_RETURN annotation for would_apply */
-
-
 struct hb_closure_context_t
 {
   hb_face_t *face;
   hb_set_t *glyphs;
   unsigned int nesting_level_left;
   unsigned int debug_depth;
 
 
   hb_closure_context_t (hb_face_t *face_,
                         hb_set_t *glyphs_,
                         unsigned int nesting_level_left_ = MAX_NESTING_LEVEL) :
-                          face (face_), glyphs (glyphs_),
+                          face (face_),
+                          glyphs (glyphs_),
                           nesting_level_left (nesting_level_left_),
                           debug_depth (0) {}
 };
 
 
 
+/* TODO Add TRACE_RETURN annotation to gsub. */
+#ifndef HB_DEBUG_WOULD_APPLY
+#define HB_DEBUG_WOULD_APPLY (HB_DEBUG+0)
+#endif
+
+#define TRACE_WOULD_APPLY() \
+        hb_auto_trace_t<HB_DEBUG_WOULD_APPLY> trace (&c->debug_depth, "WOULD_APPLY", this, HB_FUNC, "%d glyphs", c->len);
+
+
+struct hb_would_apply_context_t
+{
+  hb_face_t *face;
+  const hb_codepoint_t *glyphs;
+  unsigned int len;
+  bool zero_context;
+  unsigned int debug_depth;
+
+  hb_would_apply_context_t (hb_face_t *face_,
+                            const hb_codepoint_t *glyphs_,
+                            unsigned int len_,
+                            bool zero_context_) :
+                              face (face_),
+                              glyphs (glyphs_),
+                              len (len_),
+                              zero_context (zero_context_),
+                              debug_depth (0) {};
+};
+
+
 #ifndef HB_DEBUG_APPLY
 #define HB_DEBUG_APPLY (HB_DEBUG+0)
 #endif
 
 #define TRACE_APPLY() \
-        hb_auto_trace_t<HB_DEBUG_APPLY> trace (&c->debug_depth, "APPLY", this, HB_FUNC, "idx %d codepoint %u", c->buffer->cur().codepoint);
-
+        hb_auto_trace_t<HB_DEBUG_APPLY> trace (&c->debug_depth, "APPLY", this, HB_FUNC, "idx %d codepoint %u", c->buffer->idx, c->buffer->cur().codepoint);
 
 
 struct hb_apply_context_t
 {
   hb_font_t *font;
   hb_face_t *face;
   hb_buffer_t *buffer;
   hb_direction_t direction;
   hb_mask_t lookup_mask;
   unsigned int nesting_level_left;
   unsigned int lookup_props;
   unsigned int property; /* propety of first glyph */
   unsigned int debug_depth;
+  const GDEF &gdef;
+  bool has_glyph_classes;
 
 
   hb_apply_context_t (hb_font_t *font_,
-                      hb_face_t *face_,
                       hb_buffer_t *buffer_,
                       hb_mask_t lookup_mask_) :
-                        font (font_), face (face_), buffer (buffer_),
+                        font (font_), face (font->face), buffer (buffer_),
                         direction (buffer_->props.direction),
                         lookup_mask (lookup_mask_),
                         nesting_level_left (MAX_NESTING_LEVEL),
-                        lookup_props (0), property (0), debug_depth (0) {}
+                        lookup_props (0), property (0), debug_depth (0),
+                        gdef (*hb_ot_layout_from_face (face)->gdef),
+                        has_glyph_classes (gdef.has_glyph_classes ()) {}
+
+  void set_lookup_props (unsigned int lookup_props_) {
+    lookup_props = lookup_props_;
+  }
 
   void set_lookup (const Lookup &l) {
     lookup_props = l.get_props ();
   }
 
   struct mark_skipping_forward_iterator_t
   {
     inline mark_skipping_forward_iterator_t (hb_apply_context_t *c_,
                                              unsigned int start_index_,
                                              unsigned int num_items_,
                                              bool context_match = false)
     {
       c = c_;
       idx = start_index_;
       num_items = num_items_;
       mask = context_match ? -1 : c->lookup_mask;
       syllable = context_match ? 0 : c->buffer->cur().syllable ();
       end = c->buffer->len;
     }
     inline bool has_no_chance (void) const
     {
       return unlikely (num_items && idx + num_items >= end);
     }
+    inline void reject (void)
+    {
+      num_items++;
+    }
     inline bool next (unsigned int *property_out,
-                      unsigned int lookup_props)
+                      unsigned int  lookup_props)
     {
       assert (num_items > 0);
       do
       {
         if (has_no_chance ())
           return false;
         idx++;
-      } while (_hb_ot_layout_skip_mark (c->face, &c->buffer->info[idx], lookup_props, property_out));
+      } while (c->should_skip_mark (&c->buffer->info[idx], lookup_props, property_out));
       num_items--;
       return (c->buffer->info[idx].mask & mask) && (!syllable || syllable == c->buffer->info[idx].syllable ());
     }
     inline bool next (unsigned int *property_out = NULL)
     {
       return next (property_out, c->lookup_props);
     }
 
     unsigned int idx;
-    private:
+    protected:
     hb_apply_context_t *c;
     unsigned int num_items;
     hb_mask_t mask;
     uint8_t syllable;
     unsigned int end;
   };
 
   struct mark_skipping_backward_iterator_t
   {
     inline mark_skipping_backward_iterator_t (hb_apply_context_t *c_,
                                               unsigned int start_index_,
                                               unsigned int num_items_,
                                               hb_mask_t mask_ = 0,
                                               bool match_syllable_ = true)
     {
       c = c_;
       idx = start_index_;
       num_items = num_items_;
       mask = mask_ ? mask_ : c->lookup_mask;
       syllable = match_syllable_ ? c->buffer->cur().syllable () : 0;
     }
     inline bool has_no_chance (void) const
     {
       return unlikely (idx < num_items);
     }
+    inline void reject (void)
+    {
+      num_items++;
+    }
     inline bool prev (unsigned int *property_out,
-                      unsigned int lookup_props)
+                      unsigned int  lookup_props)
     {
       assert (num_items > 0);
       do
       {
         if (has_no_chance ())
           return false;
         idx--;
-      } while (_hb_ot_layout_skip_mark (c->face, &c->buffer->out_info[idx], lookup_props, property_out));
+      } while (c->should_skip_mark (&c->buffer->out_info[idx], lookup_props, property_out));
       num_items--;
       return (c->buffer->out_info[idx].mask & mask) && (!syllable || syllable == c->buffer->out_info[idx].syllable ());
     }
     inline bool prev (unsigned int *property_out = NULL)
     {
       return prev (property_out, c->lookup_props);
     }
 
     unsigned int idx;
-    private:
+    protected:
     hb_apply_context_t *c;
     unsigned int num_items;
     hb_mask_t mask;
     uint8_t syllable;
   };
 
-  inline bool should_mark_skip_current_glyph (void) const
+  inline bool
+  match_properties_mark (hb_codepoint_t  glyph,
+                         unsigned int    glyph_props,
+                         unsigned int    lookup_props) const
   {
-    return _hb_ot_layout_skip_mark (face, &buffer->cur(), lookup_props, NULL);
+    /* If using mark filtering sets, the high short of
+     * lookup_props has the set index.
+     */
+    if (lookup_props & LookupFlag::UseMarkFilteringSet)
+      return gdef.mark_set_covers (lookup_props >> 16, glyph);
+
+    /* The second byte of lookup_props has the meaning
+     * "ignore marks of attachment type different than
+     * the attachment type specified."
+     */
+    if (lookup_props & LookupFlag::MarkAttachmentType)
+      return (lookup_props & LookupFlag::MarkAttachmentType) == (glyph_props & LookupFlag::MarkAttachmentType);
+
+    return true;
+  }
+
+  inline bool
+  match_properties (hb_codepoint_t  glyph,
+                    unsigned int    glyph_props,
+                    unsigned int    lookup_props) const
+  {
+    /* Not covered, if, for example, glyph class is ligature and
+     * lookup_props includes LookupFlags::IgnoreLigatures
+     */
+    if (glyph_props & lookup_props & LookupFlag::IgnoreFlags)
+      return false;
+
+    if (unlikely (glyph_props & HB_OT_LAYOUT_GLYPH_CLASS_MARK))
+      return match_properties_mark (glyph, glyph_props, lookup_props);
+
+    return true;
+  }
+
+  inline bool
+  check_glyph_property (hb_glyph_info_t *info,
+                        unsigned int  lookup_props,
+                        unsigned int *property_out) const
+  {
+    unsigned int property;
+
+    property = info->glyph_props();
+    *property_out = property;
+
+    return match_properties (info->codepoint, property, lookup_props);
+  }
+
+  inline bool
+  should_skip_mark (hb_glyph_info_t *info,
+                   unsigned int  lookup_props,
+                   unsigned int *property_out) const
+  {
+    unsigned int property;
+
+    property = info->glyph_props();
+    if (property_out)
+      *property_out = property;
+
+    /* If it's a mark, skip it if we don't accept it. */
+    if (unlikely (property & HB_OT_LAYOUT_GLYPH_CLASS_MARK))
+      return !match_properties (info->codepoint, property, lookup_props);
+
+    /* If not a mark, don't skip. */
+    return false;
   }
 
 
+  inline bool should_mark_skip_current_glyph (void) const
+  {
+    return should_skip_mark (&buffer->cur(), lookup_props, NULL);
+  }
 
+  inline void set_class (hb_codepoint_t glyph_index, unsigned int class_guess) const
+  {
+    if (likely (has_glyph_classes))
+      buffer->cur().glyph_props() = gdef.get_glyph_props (glyph_index);
+    else if (class_guess)
+      buffer->cur().glyph_props() = class_guess;
+  }
+
+  inline void output_glyph (hb_codepoint_t glyph_index,
+                            unsigned int class_guess = 0) const
+  {
+    set_class (glyph_index, class_guess);
+    buffer->output_glyph (glyph_index);
+  }
   inline void replace_glyph (hb_codepoint_t glyph_index,
-                             unsigned int klass = 0) const
+                             unsigned int class_guess = 0) const
   {
-    buffer->cur().props_cache() = klass; /*XXX if has gdef? */
+    set_class (glyph_index, class_guess);
     buffer->replace_glyph (glyph_index);
   }
-  inline void replace_glyphs_be16 (unsigned int num_in,
-                                   unsigned int num_out,
-                                   const char *glyph_data_be,
-                                   unsigned int klass = 0) const
+  inline void replace_glyph_inplace (hb_codepoint_t glyph_index,
+                                     unsigned int class_guess = 0) const
   {
-    buffer->cur().props_cache() = klass; /* XXX if has gdef? */
-    buffer->replace_glyphs_be16 (num_in, num_out, glyph_data_be);
+    set_class (glyph_index, class_guess);
+    buffer->cur().codepoint = glyph_index;
   }
 };
 
 
 
 typedef bool (*intersects_func_t) (hb_set_t *glyphs, const USHORT &value, const void *data);
 typedef bool (*match_func_t) (hb_codepoint_t glyph_id, const USHORT &value, const void *data);
 typedef void (*closure_lookup_func_t) (hb_closure_context_t *c, unsigned int lookup_index);
 typedef bool (*apply_lookup_func_t) (hb_apply_context_t *c, unsigned int lookup_index);
 
@@ skipping 45 matching lines @@
   const ClassDef &class_def = *reinterpret_cast<const ClassDef *>(data);
   return class_def.get_class (glyph_id) == value;
 }
 static inline bool match_coverage (hb_codepoint_t glyph_id, const USHORT &value, const void *data)
 {
   const OffsetTo<Coverage> &coverage = (const OffsetTo<Coverage>&)value;
   return (data+coverage).get_coverage (glyph_id) != NOT_COVERED;
 }
 
 
+static inline bool would_match_input (hb_would_apply_context_t *c,
+                                      unsigned int count, /* Including the first glyph (not matched) */
+                                      const USHORT input[], /* Array of input values--start with second glyph */
+                                      match_func_t match_func,
+                                      const void *match_data)
+{
+  if (count != c->len)
+    return false;
+
+  for (unsigned int i = 1; i < count; i++)
+    if (likely (!match_func (c->glyphs[i], input[i - 1], match_data)))
+      return false;
+
+  return true;
+}
 static inline bool match_input (hb_apply_context_t *c,
                                 unsigned int count, /* Including the first glyph (not matched) */
                                 const USHORT input[], /* Array of input values--start with second glyph */
                                 match_func_t match_func,
                                 const void *match_data,
-                                unsigned int *end_offset = NULL)
+                                unsigned int *end_offset = NULL,
+                                bool *p_is_mark_ligature = NULL,
+                                unsigned int *p_total_component_count = NULL)
 {
+  hb_auto_trace_t<HB_DEBUG_APPLY> trace (&c->debug_depth, "APPLY", NULL, HB_FUNC, "idx %d codepoint %u", c->buffer->idx, c->buffer->cur().codepoint);
+
   hb_apply_context_t::mark_skipping_forward_iterator_t skippy_iter (c, c->buffer->idx, count - 1);
-  if (skippy_iter.has_no_chance ())
-    return false;
+  if (skippy_iter.has_no_chance ()) return TRACE_RETURN (false);
+
+  /*
+   * This is perhaps the trickiest part of OpenType...  Remarks:
+   *
+   * - If all components of the ligature were marks, we call this a mark ligature.
+   *
+   * - If there is no GDEF, and the ligature is NOT a mark ligature, we categorize
+   *   it as a ligature glyph.
+   *
+   * - Ligatures cannot be formed across glyphs attached to different components
+   *   of previous ligatures.  Eg. the sequence is LAM,SHADDA,LAM,FATHA,HEH, and
+   *   LAM,LAM,HEH form a ligature, leaving SHADDA,FATHA next to eachother.
+   *   However, it would be wrong to ligate that SHADDA,FATHA sequence.o
+   *   There is an exception to this: If a ligature tries ligating with marks that
+   *   belong to it itself, go ahead, assuming that the font designer knows what
+   *   they are doing (otherwise it can break Indic stuff when a matra wants to
+   *   ligate with a conjunct...)
+   */
+
+  bool is_mark_ligature = !!(c->property & HB_OT_LAYOUT_GLYPH_CLASS_MARK);
+
+  unsigned int total_component_count = 0;
+  total_component_count += get_lig_num_comps (c->buffer->cur());
+
+  unsigned int first_lig_id = get_lig_id (c->buffer->cur());
+  unsigned int first_lig_comp = get_lig_comp (c->buffer->cur());
 
   for (unsigned int i = 1; i < count; i++)
   {
-    if (!skippy_iter.next ())
-      return false;
+    unsigned int property;
 
-    if (likely (!match_func (c->buffer->info[skippy_iter.idx].codepoint, input[i - 1], match_data)))
-      return false;
+    if (!skippy_iter.next (&property)) return TRACE_RETURN (false);
+
+    if (likely (!match_func (c->buffer->info[skippy_iter.idx].codepoint, input[i - 1], match_data))) return false;
+
+    unsigned int this_lig_id = get_lig_id (c->buffer->info[skippy_iter.idx]);
+    unsigned int this_lig_comp = get_lig_comp (c->buffer->info[skippy_iter.idx]);
+
+    if (first_lig_id && first_lig_comp) {
+      /* If first component was attached to a previous ligature component,
+       * all subsequent components should be attached to the same ligature
+       * component, otherwise we shouldn't ligate them. */
+      if (first_lig_id != this_lig_id || first_lig_comp != this_lig_comp)
+        return TRACE_RETURN (false);
+    } else {
+      /* If first component was NOT attached to a previous ligature component,
+       * all subsequent components should also NOT be attached to any ligature
+       * component, unless they are attached to the first component itself! */
+      if (this_lig_id && this_lig_comp && (this_lig_id != first_lig_id))
+        return TRACE_RETURN (false);
+    }
+
+    is_mark_ligature = is_mark_ligature && (property & HB_OT_LAYOUT_GLYPH_CLASS_MARK);
+    total_component_count += get_lig_num_comps (c->buffer->info[skippy_iter.idx]);
   }
 
   if (end_offset)
     *end_offset = skippy_iter.idx - c->buffer->idx + 1;
 
+  if (p_is_mark_ligature)
+    *p_is_mark_ligature = is_mark_ligature;
+
+  if (p_total_component_count)
+    *p_total_component_count = total_component_count;
+
   return true;
 }
+static inline void ligate_input (hb_apply_context_t *c,
+                                 unsigned int count, /* Including the first glyph (not matched) */
+                                 const USHORT input[], /* Array of input values--start with second glyph */
+                                 hb_codepoint_t lig_glyph,
+                                 match_func_t match_func,
+                                 const void *match_data,
+                                 bool is_mark_ligature,
+                                 unsigned int total_component_count)
+{
+  /*
+   * - If it *is* a mark ligature, we don't allocate a new ligature id, and leave
+   *   the ligature to keep its old ligature id.  This will allow it to attach to
+   *   a base ligature in GPOS.  Eg. if the sequence is: LAM,LAM,SHADDA,FATHA,HEH,
+   *   and LAM,LAM,HEH for a ligature, they will leave SHADDA and FATHA wit a
+   *   ligature id and component value of 2.  Then if SHADDA,FATHA form a ligature
+   *   later, we don't want them to lose their ligature id/component, otherwise
+   *   GPOS will fail to correctly position the mark ligature on top of the
+   *   LAM,LAM,HEH ligature.  See:
+   *     https://bugzilla.gnome.org/show_bug.cgi?id=676343
+   *
+   * - If a ligature is formed of components that some of which are also ligatures
+   *   themselves, and those ligature components had marks attached to *their*
+   *   components, we have to attach the marks to the new ligature component
+   *   positions!  Now *that*'s tricky!  And these marks may be following the
+   *   last component of the whole sequence, so we should loop forward looking
+   *   for them and update them.
+   *
+   *   Eg. the sequence is LAM,LAM,SHADDA,FATHA,HEH, and the font first forms a
+   *   'calt' ligature of LAM,HEH, leaving the SHADDA and FATHA with a ligature
+   *   id and component == 1.  Now, during 'liga', the LAM and the LAM-HEH ligature
+   *   form a LAM-LAM-HEH ligature.  We need to reassign the SHADDA and FATHA to
+   *   the new ligature with a component value of 2.
+   *
+   *   This in fact happened to a font...  See:
+   *   https://bugzilla.gnome.org/show_bug.cgi?id=437633
+   */
+
+  unsigned int klass = is_mark_ligature ? 0 : HB_OT_LAYOUT_GLYPH_CLASS_LIGATURE;
+  unsigned int lig_id = is_mark_ligature ? 0 : allocate_lig_id (c->buffer);
+  unsigned int last_lig_id = get_lig_id (c->buffer->cur());
+  unsigned int last_num_components = get_lig_num_comps (c->buffer->cur());
+  unsigned int components_so_far = last_num_components;
+
+  if (!is_mark_ligature)
+    set_lig_props_for_ligature (c->buffer->cur(), lig_id, total_component_count);
+  c->replace_glyph (lig_glyph, klass);
+
+  for (unsigned int i = 1; i < count; i++)
+  {
+    while (c->should_mark_skip_current_glyph ())
+    {
+      if (!is_mark_ligature) {
+        unsigned int new_lig_comp = components_so_far - last_num_components +
+                                    MIN (MAX (get_lig_comp (c->buffer->cur()), 1u), last_num_components);
+        set_lig_props_for_mark (c->buffer->cur(), lig_id, new_lig_comp);
+      }
+      c->buffer->next_glyph ();
+    }
+
+    last_lig_id = get_lig_id (c->buffer->cur());
+    last_num_components = get_lig_num_comps (c->buffer->cur());
+    components_so_far += last_num_components;
+
+    /* Skip the base glyph */
+    c->buffer->idx++;
+  }
+
+  if (!is_mark_ligature && last_lig_id) {
+    /* Re-adjust components for any marks following. */
+    for (unsigned int i = c->buffer->idx; i < c->buffer->len; i++) {
+      if (last_lig_id == get_lig_id (c->buffer->info[i])) {
+        unsigned int new_lig_comp = components_so_far - last_num_components +
+                                    MIN (MAX (get_lig_comp (c->buffer->info[i]), 1u), last_num_components);
+        set_lig_props_for_mark (c->buffer->info[i], lig_id, new_lig_comp);
+      } else
+        break;
+    }
+  }
+}
 
 static inline bool match_backtrack (hb_apply_context_t *c,
                                     unsigned int count,
                                     const USHORT backtrack[],
                                     match_func_t match_func,
                                     const void *match_data)
 {
+  hb_auto_trace_t<HB_DEBUG_APPLY> trace (&c->debug_depth, "APPLY", NULL, HB_FUNC, "idx %d codepoint %u", c->buffer->idx, c->buffer->cur().codepoint);
+
   hb_apply_context_t::mark_skipping_backward_iterator_t skippy_iter (c, c->buffer->backtrack_len (), count, true);
   if (skippy_iter.has_no_chance ())
-    return false;
+    return TRACE_RETURN (false);
 
   for (unsigned int i = 0; i < count; i++)
   {
     if (!skippy_iter.prev ())
-      return false;
+      return TRACE_RETURN (false);
 
     if (likely (!match_func (c->buffer->out_info[skippy_iter.idx].codepoint, backtrack[i], match_data)))
-      return false;
+      return TRACE_RETURN (false);
   }
 
-  return true;
+  return TRACE_RETURN (true);
 }
 
 static inline bool match_lookahead (hb_apply_context_t *c,
                                     unsigned int count,
                                     const USHORT lookahead[],
                                     match_func_t match_func,
                                     const void *match_data,
                                     unsigned int offset)
 {
+  hb_auto_trace_t<HB_DEBUG_APPLY> trace (&c->debug_depth, "APPLY", NULL, HB_FUNC, "idx %d codepoint %u", c->buffer->idx, c->buffer->cur().codepoint);
+
   hb_apply_context_t::mark_skipping_forward_iterator_t skippy_iter (c, c->buffer->idx + offset - 1, count, true);
   if (skippy_iter.has_no_chance ())
-    return false;
+    return TRACE_RETURN (false);
 
   for (unsigned int i = 0; i < count; i++)
   {
     if (!skippy_iter.next ())
-      return false;
+      return TRACE_RETURN (false);
 
     if (likely (!match_func (c->buffer->info[skippy_iter.idx].codepoint, lookahead[i], match_data)))
-      return false;
+      return TRACE_RETURN (false);
   }
 
-  return true;
+  return TRACE_RETURN (true);
 }
 
 
 
 struct LookupRecord
 {
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     return TRACE_RETURN (c->check_struct (this));
   }
@@ skipping 99 matching lines @@
 {
   if (intersects_array (c,
                         inputCount ? inputCount - 1 : 0, input,
                         lookup_context.funcs.intersects, lookup_context.intersects_data))
     closure_lookup (c,
                     lookupCount, lookupRecord,
                     lookup_context.funcs.closure);
 }
 
 
+static inline bool context_would_apply_lookup (hb_would_apply_context_t *c,
+                                               unsigned int inputCount, /* Including the first glyph (not matched) */
+                                               const USHORT input[], /* Array of input values--start with second glyph */
+                                               unsigned int lookupCount,
+                                               const LookupRecord lookupRecord[],
+                                               ContextApplyLookupContext &lookup_context)
+{
+  return would_match_input (c,
+                            inputCount, input,
+                            lookup_context.funcs.match, lookup_context.match_data);
+}
 static inline bool context_apply_lookup (hb_apply_context_t *c,
                                          unsigned int inputCount, /* Including the first glyph (not matched) */
                                          const USHORT input[], /* Array of input values--start with second glyph */
                                          unsigned int lookupCount,
                                          const LookupRecord lookupRecord[],
                                          ContextApplyLookupContext &lookup_context)
 {
   return match_input (c,
                       inputCount, input,
                       lookup_context.funcs.match, lookup_context.match_data)
@@ skipping 12 matching lines @@
   inline void closure (hb_closure_context_t *c, ContextClosureLookupContext &lookup_context) const
   {
     TRACE_CLOSURE ();
     const LookupRecord *lookupRecord = &StructAtOffset<LookupRecord> (input, input[0].static_size * (inputCount ? inputCount - 1 : 0));
     context_closure_lookup (c,
                             inputCount, input,
                             lookupCount, lookupRecord,
                             lookup_context);
   }
 
+  inline bool would_apply (hb_would_apply_context_t *c, ContextApplyLookupContext &lookup_context) const
+  {
+    TRACE_WOULD_APPLY ();
+    const LookupRecord *lookupRecord = &StructAtOffset<LookupRecord> (input, input[0].static_size * (inputCount ? inputCount - 1 : 0));
+    return TRACE_RETURN (context_would_apply_lookup (c, inputCount, input, lookupCount, lookupRecord, lookup_context));
+  }
+
   inline bool apply (hb_apply_context_t *c, ContextApplyLookupContext &lookup_context) const
   {
     TRACE_APPLY ();
     const LookupRecord *lookupRecord = &StructAtOffset<LookupRecord> (input, input[0].static_size * (inputCount ? inputCount - 1 : 0));
     return TRACE_RETURN (context_apply_lookup (c, inputCount, input, lookupCount, lookupRecord, lookup_context));
   }
 
   public:
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     return inputCount.sanitize (c)
         && lookupCount.sanitize (c)
         && c->check_range (input,
                            input[0].static_size * inputCount
                            + lookupRecordX[0].static_size * lookupCount);
   }
 
-  private:
+  protected:
   USHORT        inputCount;             /* Total number of glyphs in input
                                          * glyph sequence--includes the first
                                          * glyph */
   USHORT        lookupCount;            /* Number of LookupRecords */
   USHORT        input[VAR];             /* Array of match inputs--start with
                                          * second glyph */
   LookupRecord  lookupRecordX[VAR];     /* Array of LookupRecords--in
                                          * design order */
   public:
   DEFINE_SIZE_ARRAY2 (4, input, lookupRecordX);
 };
 
 struct RuleSet
 {
   inline void closure (hb_closure_context_t *c, ContextClosureLookupContext &lookup_context) const
   {
     TRACE_CLOSURE ();
     unsigned int num_rules = rule.len;
     for (unsigned int i = 0; i < num_rules; i++)
       (this+rule[i]).closure (c, lookup_context);
   }
 
+  inline bool would_apply (hb_would_apply_context_t *c, ContextApplyLookupContext &lookup_context) const
+  {
+    TRACE_WOULD_APPLY ();
+    unsigned int num_rules = rule.len;
+    for (unsigned int i = 0; i < num_rules; i++)
+    {
+      if ((this+rule[i]).would_apply (c, lookup_context))
+        return TRACE_RETURN (true);
+    }
+    return TRACE_RETURN (false);
+  }
+
   inline bool apply (hb_apply_context_t *c, ContextApplyLookupContext &lookup_context) const
   {
     TRACE_APPLY ();
     unsigned int num_rules = rule.len;
     for (unsigned int i = 0; i < num_rules; i++)
     {
       if ((this+rule[i]).apply (c, lookup_context))
         return TRACE_RETURN (true);
     }
     return TRACE_RETURN (false);
   }
 
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     return TRACE_RETURN (rule.sanitize (c, this));
   }
 
-  private:
+  protected:
   OffsetArrayOf<Rule>
                 rule;                   /* Array of Rule tables
                                          * ordered by preference */
   public:
   DEFINE_SIZE_ARRAY (2, rule);
 };
 
 
 struct ContextFormat1
 {
@@ skipping 13 matching lines @@
     };
 
     unsigned int count = ruleSet.len;
     for (unsigned int i = 0; i < count; i++)
       if (cov.intersects_coverage (c->glyphs, i)) {
         const RuleSet &rule_set = this+ruleSet[i];
         rule_set.closure (c, lookup_context);
       }
   }
 
+  inline bool would_apply (hb_would_apply_context_t *c) const
+  {
+    TRACE_WOULD_APPLY ();
+
+    const RuleSet &rule_set = this+ruleSet[(this+coverage) (c->glyphs[0])];
+    struct ContextApplyLookupContext lookup_context = {
+      {match_glyph, NULL},
+      NULL
+    };
+    return TRACE_RETURN (rule_set.would_apply (c, lookup_context));
+  }
+
   inline bool apply (hb_apply_context_t *c, apply_lookup_func_t apply_func) const
   {
     TRACE_APPLY ();
     unsigned int index = (this+coverage) (c->buffer->cur().codepoint);
     if (likely (index == NOT_COVERED))
       return TRACE_RETURN (false);
 
     const RuleSet &rule_set = this+ruleSet[index];
     struct ContextApplyLookupContext lookup_context = {
       {match_glyph, apply_func},
       NULL
     };
     return TRACE_RETURN (rule_set.apply (c, lookup_context));
   }
 
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     return TRACE_RETURN (coverage.sanitize (c, this) && ruleSet.sanitize (c, this));
   }
 
-  private:
+  protected:
   USHORT        format;                 /* Format identifier--format = 1 */
   OffsetTo<Coverage>
                 coverage;               /* Offset to Coverage table--from
                                          * beginning of table */
   OffsetArrayOf<RuleSet>
                 ruleSet;                /* Array of RuleSet tables
                                          * ordered by Coverage Index */
   public:
   DEFINE_SIZE_ARRAY (6, ruleSet);
 };
@@ skipping 19 matching lines @@
     };
 
     unsigned int count = ruleSet.len;
     for (unsigned int i = 0; i < count; i++)
       if (class_def.intersects_class (c->glyphs, i)) {
         const RuleSet &rule_set = this+ruleSet[i];
         rule_set.closure (c, lookup_context);
       }
   }
 
+  inline bool would_apply (hb_would_apply_context_t *c) const
+  {
+    TRACE_WOULD_APPLY ();
+
+    const ClassDef &class_def = this+classDef;
+    unsigned int index = class_def (c->glyphs[0]);
+    const RuleSet &rule_set = this+ruleSet[index];
+    struct ContextApplyLookupContext lookup_context = {
+      {match_class, NULL},
+      &class_def
+    };
+    return TRACE_RETURN (rule_set.would_apply (c, lookup_context));
+  }
+
   inline bool apply (hb_apply_context_t *c, apply_lookup_func_t apply_func) const
   {
     TRACE_APPLY ();
     unsigned int index = (this+coverage) (c->buffer->cur().codepoint);
     if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);
 
     const ClassDef &class_def = this+classDef;
     index = class_def (c->buffer->cur().codepoint);
     const RuleSet &rule_set = this+ruleSet[index];
     struct ContextApplyLookupContext lookup_context = {
       {match_class, apply_func},
       &class_def
     };
     return TRACE_RETURN (rule_set.apply (c, lookup_context));
   }
 
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     return TRACE_RETURN (coverage.sanitize (c, this) && classDef.sanitize (c, this) && ruleSet.sanitize (c, this));
   }
 
-  private:
+  protected:
   USHORT        format;                 /* Format identifier--format = 2 */
   OffsetTo<Coverage>
                 coverage;               /* Offset to Coverage table--from
                                          * beginning of table */
   OffsetTo<ClassDef>
                 classDef;               /* Offset to glyph ClassDef table--from
                                          * beginning of table */
   OffsetArrayOf<RuleSet>
                 ruleSet;                /* Array of RuleSet tables
                                          * ordered by class */
@@ skipping 18 matching lines @@
     struct ContextClosureLookupContext lookup_context = {
       {intersects_coverage, closure_func},
       this
     };
     context_closure_lookup (c,
                             glyphCount, (const USHORT *) (coverage + 1),
                             lookupCount, lookupRecord,
                             lookup_context);
   }
 
+  inline bool would_apply (hb_would_apply_context_t *c) const
+  {
+    TRACE_WOULD_APPLY ();
+
+    const LookupRecord *lookupRecord = &StructAtOffset<LookupRecord> (coverage, coverage[0].static_size * glyphCount);
+    struct ContextApplyLookupContext lookup_context = {
+      {match_coverage, NULL},
+      this
+    };
+    return TRACE_RETURN (context_would_apply_lookup (c, glyphCount, (const USHORT *) (coverage + 1), lookupCount, lookupRecord, lookup_context));
+  }
+
   inline bool apply (hb_apply_context_t *c, apply_lookup_func_t apply_func) const
   {
     TRACE_APPLY ();
     unsigned int index = (this+coverage[0]) (c->buffer->cur().codepoint);
     if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);
 
     const LookupRecord *lookupRecord = &StructAtOffset<LookupRecord> (coverage, coverage[0].static_size * glyphCount);
     struct ContextApplyLookupContext lookup_context = {
       {match_coverage, apply_func},
       this
     };
     return TRACE_RETURN (context_apply_lookup (c, glyphCount, (const USHORT *) (coverage + 1), lookupCount, lookupRecord, lookup_context));
   }
 
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     if (!c->check_struct (this)) return TRACE_RETURN (false);
     unsigned int count = glyphCount;
     if (!c->check_array (coverage, coverage[0].static_size, count)) return TRACE_RETURN (false);
     for (unsigned int i = 0; i < count; i++)
       if (!coverage[i].sanitize (c, this)) return TRACE_RETURN (false);
     LookupRecord *lookupRecord = &StructAtOffset<LookupRecord> (coverage, coverage[0].static_size * count);
     return TRACE_RETURN (c->check_array (lookupRecord, lookupRecord[0].static_size, lookupCount));
   }
 
-  private:
+  protected:
   USHORT        format;                 /* Format identifier--format = 3 */
   USHORT        glyphCount;             /* Number of glyphs in the input glyph
                                          * sequence */
   USHORT        lookupCount;            /* Number of LookupRecords */
   OffsetTo<Coverage>
                 coverage[VAR];          /* Array of offsets to Coverage
                                          * table in glyph sequence order */
   LookupRecord  lookupRecordX[VAR];     /* Array of LookupRecords--in
                                          * design order */
   public:
   DEFINE_SIZE_ARRAY2 (6, coverage, lookupRecordX);
 };
 
 struct Context
 {
   protected:
 
   inline void closure (hb_closure_context_t *c, closure_lookup_func_t closure_func) const
   {
     TRACE_CLOSURE ();
     switch (u.format) {
     case 1: u.format1.closure (c, closure_func); break;
     case 2: u.format2.closure (c, closure_func); break;
     case 3: u.format3.closure (c, closure_func); break;
     default:                                     break;
     }
   }
 
+  inline const Coverage &get_coverage (void) const
+  {
+    switch (u.format) {
+    case 1: return this + u.format1.coverage;
+    case 2: return this + u.format2.coverage;
+    case 3: return this + u.format3.coverage[0];
+    default:return Null(Coverage);
+    }
+  }
+
+  inline bool would_apply (hb_would_apply_context_t *c) const
+  {
+    switch (u.format) {
+    case 1: return u.format1.would_apply (c);
+    case 2: return u.format2.would_apply (c);
+    case 3: return u.format3.would_apply (c);
+    default:return false;
+    }
+  }
+
   inline bool apply (hb_apply_context_t *c, apply_lookup_func_t apply_func) const
   {
     TRACE_APPLY ();
     switch (u.format) {
     case 1: return TRACE_RETURN (u.format1.apply (c, apply_func));
     case 2: return TRACE_RETURN (u.format2.apply (c, apply_func));
     case 3: return TRACE_RETURN (u.format3.apply (c, apply_func));
     default:return TRACE_RETURN (false);
     }
   }
 
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     if (!u.format.sanitize (c)) return TRACE_RETURN (false);
     switch (u.format) {
     case 1: return TRACE_RETURN (u.format1.sanitize (c));
     case 2: return TRACE_RETURN (u.format2.sanitize (c));
     case 3: return TRACE_RETURN (u.format3.sanitize (c));
     default:return TRACE_RETURN (true);
     }
   }
 
-  private:
+  protected:
   union {
   USHORT                format;         /* Format identifier */
   ContextFormat1        format1;
   ContextFormat2        format2;
   ContextFormat3        format3;
   } u;
 };
 
 
 /* Chaining Contextual lookups */
@@ skipping 28 matching lines @@
                         inputCount ? inputCount - 1 : 0, input,
                         lookup_context.funcs.intersects, lookup_context.intersects_data[1])
   && intersects_array (c,
                        lookaheadCount, lookahead,
                        lookup_context.funcs.intersects, lookup_context.intersects_data[2]))
     closure_lookup (c,
                     lookupCount, lookupRecord,
                     lookup_context.funcs.closure);
 }
 
+static inline bool chain_context_would_apply_lookup (hb_would_apply_context_t *c,
+                                                     unsigned int backtrackCount,
+                                                     const USHORT backtrack[],
+                                                     unsigned int inputCount, /* Including the first glyph (not matched) */
+                                                     const USHORT input[], /* Array of input values--start with second glyph */
+                                                     unsigned int lookaheadCount,
+                                                     const USHORT lookahead[],
+                                                     unsigned int lookupCount,
+                                                     const LookupRecord lookupRecord[],
+                                                     ChainContextApplyLookupContext &lookup_context)
+{
+  return (c->zero_context ? !backtrackCount && !lookaheadCount : true)
+      && would_match_input (c,
+                            inputCount, input,
+                            lookup_context.funcs.match, lookup_context.match_data[1]);
+}
+
 static inline bool chain_context_apply_lookup (hb_apply_context_t *c,
                                                unsigned int backtrackCount,
                                                const USHORT backtrack[],
                                                unsigned int inputCount, /* Including the first glyph (not matched) */
                                                const USHORT input[], /* Array of input values--start with second glyph */
                                                unsigned int lookaheadCount,
                                                const USHORT lookahead[],
                                                unsigned int lookupCount,
                                                const LookupRecord lookupRecord[],
                                                ChainContextApplyLookupContext &lookup_context)
 {
   unsigned int lookahead_offset;
-  return match_backtrack (c,
-                          backtrackCount, backtrack,
-                          lookup_context.funcs.match, lookup_context.match_data[0])
-      && match_input (c,
+  return match_input (c,
                       inputCount, input,
                       lookup_context.funcs.match, lookup_context.match_data[1],
                       &lookahead_offset)
+      && match_backtrack (c,
+                          backtrackCount, backtrack,
+                          lookup_context.funcs.match, lookup_context.match_data[0])
       && match_lookahead (c,
                           lookaheadCount, lookahead,
                           lookup_context.funcs.match, lookup_context.match_data[2],
                           lookahead_offset)
       && apply_lookup (c,
                        inputCount,
                        lookupCount, lookupRecord,
                        lookup_context.funcs.apply);
 }
 
@@ skipping 10 matching lines @@
     const ArrayOf<USHORT> &lookahead = StructAfter<ArrayOf<USHORT> > (input);
     const ArrayOf<LookupRecord> &lookup = StructAfter<ArrayOf<LookupRecord> > (lookahead);
     chain_context_closure_lookup (c,
                                   backtrack.len, backtrack.array,
                                   input.len, input.array,
                                   lookahead.len, lookahead.array,
                                   lookup.len, lookup.array,
                                   lookup_context);
   }
 
+  inline bool would_apply (hb_would_apply_context_t *c, ChainContextApplyLookupContext &lookup_context) const
+  {
+    TRACE_WOULD_APPLY ();
+    const HeadlessArrayOf<USHORT> &input = StructAfter<HeadlessArrayOf<USHORT> > (backtrack);
+    const ArrayOf<USHORT> &lookahead = StructAfter<ArrayOf<USHORT> > (input);
+    const ArrayOf<LookupRecord> &lookup = StructAfter<ArrayOf<LookupRecord> > (lookahead);
+    return TRACE_RETURN (chain_context_would_apply_lookup (c,
+                                                           backtrack.len, backtrack.array,
+                                                           input.len, input.array,
+                                                           lookahead.len, lookahead.array, lookup.len,
+                                                           lookup.array, lookup_context));
+  }
+
   inline bool apply (hb_apply_context_t *c, ChainContextApplyLookupContext &lookup_context) const
   {
     TRACE_APPLY ();
     const HeadlessArrayOf<USHORT> &input = StructAfter<HeadlessArrayOf<USHORT> > (backtrack);
     const ArrayOf<USHORT> &lookahead = StructAfter<ArrayOf<USHORT> > (input);
     const ArrayOf<LookupRecord> &lookup = StructAfter<ArrayOf<LookupRecord> > (lookahead);
     return TRACE_RETURN (chain_context_apply_lookup (c,
                                                      backtrack.len, backtrack.array,
                                                      input.len, input.array,
                                                      lookahead.len, lookahead.array, lookup.len,
                                                      lookup.array, lookup_context));
   }
 
   public:
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     if (!backtrack.sanitize (c)) return TRACE_RETURN (false);
     HeadlessArrayOf<USHORT> &input = StructAfter<HeadlessArrayOf<USHORT> > (backtrack);
     if (!input.sanitize (c)) return TRACE_RETURN (false);
     ArrayOf<USHORT> &lookahead = StructAfter<ArrayOf<USHORT> > (input);
     if (!lookahead.sanitize (c)) return TRACE_RETURN (false);
     ArrayOf<LookupRecord> &lookup = StructAfter<ArrayOf<LookupRecord> > (lookahead);
     return TRACE_RETURN (lookup.sanitize (c));
   }
 
-  private:
+  protected:
   ArrayOf<USHORT>
                 backtrack;              /* Array of backtracking values
                                          * (to be matched before the input
                                          * sequence) */
   HeadlessArrayOf<USHORT>
                 inputX;                 /* Array of input values (start with
                                          * second glyph) */
   ArrayOf<USHORT>
                 lookaheadX;             /* Array of lookahead values's (to be
                                          * matched after the input sequence) */
   ArrayOf<LookupRecord>
                 lookupX;                /* Array of LookupRecords--in
                                          * design order) */
   public:
   DEFINE_SIZE_MIN (8);
 };
 
 struct ChainRuleSet
 {
   inline void closure (hb_closure_context_t *c, ChainContextClosureLookupContext &lookup_context) const
   {
     TRACE_CLOSURE ();
     unsigned int num_rules = rule.len;
     for (unsigned int i = 0; i < num_rules; i++)
       (this+rule[i]).closure (c, lookup_context);
   }
 
+  inline bool would_apply (hb_would_apply_context_t *c, ChainContextApplyLookupContext &lookup_context) const
+  {
+    TRACE_WOULD_APPLY ();
+    unsigned int num_rules = rule.len;
+    for (unsigned int i = 0; i < num_rules; i++)
+      if ((this+rule[i]).would_apply (c, lookup_context))
+        return TRACE_RETURN (true);
+
+    return TRACE_RETURN (false);
+  }
+
   inline bool apply (hb_apply_context_t *c, ChainContextApplyLookupContext &lookup_context) const
   {
     TRACE_APPLY ();
     unsigned int num_rules = rule.len;
     for (unsigned int i = 0; i < num_rules; i++)
       if ((this+rule[i]).apply (c, lookup_context))
         return TRACE_RETURN (true);
 
     return TRACE_RETURN (false);
   }
 
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     return TRACE_RETURN (rule.sanitize (c, this));
   }
 
-  private:
+  protected:
   OffsetArrayOf<ChainRule>
                 rule;                   /* Array of ChainRule tables
                                          * ordered by preference */
   public:
   DEFINE_SIZE_ARRAY (2, rule);
 };
 
 struct ChainContextFormat1
 {
   friend struct ChainContext;
@@ skipping 11 matching lines @@
     };
 
     unsigned int count = ruleSet.len;
     for (unsigned int i = 0; i < count; i++)
       if (cov.intersects_coverage (c->glyphs, i)) {
         const ChainRuleSet &rule_set = this+ruleSet[i];
         rule_set.closure (c, lookup_context);
       }
   }
 
+  inline bool would_apply (hb_would_apply_context_t *c) const
+  {
+    TRACE_WOULD_APPLY ();
+
+    const ChainRuleSet &rule_set = this+ruleSet[(this+coverage) (c->glyphs[0])];
+    struct ChainContextApplyLookupContext lookup_context = {
+      {match_glyph, NULL},
+      {NULL, NULL, NULL}
+    };
+    return TRACE_RETURN (rule_set.would_apply (c, lookup_context));
+  }
+
   inline bool apply (hb_apply_context_t *c, apply_lookup_func_t apply_func) const
   {
     TRACE_APPLY ();
     unsigned int index = (this+coverage) (c->buffer->cur().codepoint);
     if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);
 
     const ChainRuleSet &rule_set = this+ruleSet[index];
     struct ChainContextApplyLookupContext lookup_context = {
       {match_glyph, apply_func},
       {NULL, NULL, NULL}
     };
     return TRACE_RETURN (rule_set.apply (c, lookup_context));
   }
 
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     return TRACE_RETURN (coverage.sanitize (c, this) && ruleSet.sanitize (c, this));
   }
 
-  private:
+  protected:
   USHORT        format;                 /* Format identifier--format = 1 */
   OffsetTo<Coverage>
                 coverage;               /* Offset to Coverage table--from
                                          * beginning of table */
   OffsetArrayOf<ChainRuleSet>
                 ruleSet;                /* Array of ChainRuleSet tables
                                          * ordered by Coverage Index */
   public:
   DEFINE_SIZE_ARRAY (6, ruleSet);
 };
@@ skipping 22 matching lines @@
     };
 
     unsigned int count = ruleSet.len;
     for (unsigned int i = 0; i < count; i++)
       if (input_class_def.intersects_class (c->glyphs, i)) {
         const ChainRuleSet &rule_set = this+ruleSet[i];
         rule_set.closure (c, lookup_context);
       }
   }
 
+  inline bool would_apply (hb_would_apply_context_t *c) const
+  {
+    TRACE_WOULD_APPLY ();
+
+    const ClassDef &input_class_def = this+inputClassDef;
+
+    unsigned int index = input_class_def (c->glyphs[0]);
+    const ChainRuleSet &rule_set = this+ruleSet[index];
+    struct ChainContextApplyLookupContext lookup_context = {
+      {match_class, NULL},
+      {NULL, &input_class_def, NULL}
+    };
+    return TRACE_RETURN (rule_set.would_apply (c, lookup_context));
+  }
+
   inline bool apply (hb_apply_context_t *c, apply_lookup_func_t apply_func) const
   {
     TRACE_APPLY ();
     unsigned int index = (this+coverage) (c->buffer->cur().codepoint);
     if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);
 
     const ClassDef &backtrack_class_def = this+backtrackClassDef;
     const ClassDef &input_class_def = this+inputClassDef;
     const ClassDef &lookahead_class_def = this+lookaheadClassDef;
 
     index = input_class_def (c->buffer->cur().codepoint);
     const ChainRuleSet &rule_set = this+ruleSet[index];
     struct ChainContextApplyLookupContext lookup_context = {
       {match_class, apply_func},
       {&backtrack_class_def,
        &input_class_def,
        &lookahead_class_def}
     };
     return TRACE_RETURN (rule_set.apply (c, lookup_context));
   }
 
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     return TRACE_RETURN (coverage.sanitize (c, this) && backtrackClassDef.sanitize (c, this) &&
                          inputClassDef.sanitize (c, this) && lookaheadClassDef.sanitize (c, this) &&
                          ruleSet.sanitize (c, this));
   }
 
-  private:
+  protected:
   USHORT        format;                 /* Format identifier--format = 2 */
   OffsetTo<Coverage>
                 coverage;               /* Offset to Coverage table--from
                                          * beginning of table */
   OffsetTo<ClassDef>
                 backtrackClassDef;      /* Offset to glyph ClassDef table
                                          * containing backtrack sequence
                                          * data--from beginning of table */
   OffsetTo<ClassDef>
                 inputClassDef;          /* Offset to glyph ClassDef
@@ skipping 31 matching lines @@
       {this, this, this}
     };
     chain_context_closure_lookup (c,
                                   backtrack.len, (const USHORT *) backtrack.array,
                                   input.len, (const USHORT *) input.array + 1,
                                   lookahead.len, (const USHORT *) lookahead.array,
                                   lookup.len, lookup.array,
                                   lookup_context);
   }
 
+  inline const Coverage &get_coverage (void) const
+  {
+    const OffsetArrayOf<Coverage> &input = StructAfter<OffsetArrayOf<Coverage> > (backtrack);
+    return this+input[0];
+  }
+
+  inline bool would_apply (hb_would_apply_context_t *c) const
+  {
+    TRACE_WOULD_APPLY ();
+
+    const OffsetArrayOf<Coverage> &input = StructAfter<OffsetArrayOf<Coverage> > (backtrack);
+    const OffsetArrayOf<Coverage> &lookahead = StructAfter<OffsetArrayOf<Coverage> > (input);
+    const ArrayOf<LookupRecord> &lookup = StructAfter<ArrayOf<LookupRecord> > (lookahead);
+    struct ChainContextApplyLookupContext lookup_context = {
+      {match_coverage, NULL},
+      {this, this, this}
+    };
+    return TRACE_RETURN (chain_context_would_apply_lookup (c,
+                                                           backtrack.len, (const USHORT *) backtrack.array,
+                                                           input.len, (const USHORT *) input.array + 1,
+                                                           lookahead.len, (const USHORT *) lookahead.array,
+                                                           lookup.len, lookup.array, lookup_context));
+  }
+
   inline bool apply (hb_apply_context_t *c, apply_lookup_func_t apply_func) const
   {
     TRACE_APPLY ();
     const OffsetArrayOf<Coverage> &input = StructAfter<OffsetArrayOf<Coverage> > (backtrack);
 
     unsigned int index = (this+input[0]) (c->buffer->cur().codepoint);
     if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);
 
     const OffsetArrayOf<Coverage> &lookahead = StructAfter<OffsetArrayOf<Coverage> > (input);
     const ArrayOf<LookupRecord> &lookup = StructAfter<ArrayOf<LookupRecord> > (lookahead);
@@ skipping 12 matching lines @@
     TRACE_SANITIZE ();
     if (!backtrack.sanitize (c, this)) return TRACE_RETURN (false);
     OffsetArrayOf<Coverage> &input = StructAfter<OffsetArrayOf<Coverage> > (backtrack);
     if (!input.sanitize (c, this)) return TRACE_RETURN (false);
     OffsetArrayOf<Coverage> &lookahead = StructAfter<OffsetArrayOf<Coverage> > (input);
     if (!lookahead.sanitize (c, this)) return TRACE_RETURN (false);
     ArrayOf<LookupRecord> &lookup = StructAfter<ArrayOf<LookupRecord> > (lookahead);
     return TRACE_RETURN (lookup.sanitize (c));
   }
 
-  private:
+  protected:
   USHORT        format;                 /* Format identifier--format = 3 */
   OffsetArrayOf<Coverage>
                 backtrack;              /* Array of coverage tables
                                          * in backtracking sequence, in  glyph
                                          * sequence order */
   OffsetArrayOf<Coverage>
                 inputX          ;       /* Array of coverage
                                          * tables in input sequence, in glyph
                                          * sequence order */
   OffsetArrayOf<Coverage>
@@ skipping 15 matching lines @@
   {
     TRACE_CLOSURE ();
     switch (u.format) {
     case 1: u.format1.closure (c, closure_func); break;
     case 2: u.format2.closure (c, closure_func); break;
     case 3: u.format3.closure (c, closure_func); break;
     default:                                     break;
     }
   }
 
+  inline const Coverage &get_coverage (void) const
+  {
+    switch (u.format) {
+    case 1: return this + u.format1.coverage;
+    case 2: return this + u.format2.coverage;
+    case 3: return u.format3.get_coverage ();
+    default:return Null(Coverage);
+    }
+  }
+
+  inline bool would_apply (hb_would_apply_context_t *c) const
+  {
+    switch (u.format) {
+    case 1: return u.format1.would_apply (c);
+    case 2: return u.format2.would_apply (c);
+    case 3: return u.format3.would_apply (c);
+    default:return false;
+    }
+  }
+
   inline bool apply (hb_apply_context_t *c, apply_lookup_func_t apply_func) const
   {
     TRACE_APPLY ();
     switch (u.format) {
     case 1: return TRACE_RETURN (u.format1.apply (c, apply_func));
     case 2: return TRACE_RETURN (u.format2.apply (c, apply_func));
     case 3: return TRACE_RETURN (u.format3.apply (c, apply_func));
     default:return TRACE_RETURN (false);
     }
   }
 
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     if (!u.format.sanitize (c)) return TRACE_RETURN (false);
     switch (u.format) {
     case 1: return TRACE_RETURN (u.format1.sanitize (c));
     case 2: return TRACE_RETURN (u.format2.sanitize (c));
     case 3: return TRACE_RETURN (u.format3.sanitize (c));
     default:return TRACE_RETURN (true);
     }
   }
 
-  private:
+  protected:
   union {
   USHORT                format; /* Format identifier */
   ChainContextFormat1   format1;
   ChainContextFormat2   format2;
   ChainContextFormat3   format3;
   } u;
 };
 
 
 struct ExtensionFormat1
 {
   friend struct Extension;
 
   protected:
   inline unsigned int get_type (void) const { return extensionLookupType; }
   inline unsigned int get_offset (void) const { return extensionOffset; }
 
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     return TRACE_RETURN (c->check_struct (this));
   }
 
-  private:
+  protected:
   USHORT        format;                 /* Format identifier. Set to 1. */
   USHORT        extensionLookupType;    /* Lookup type of subtable referenced
                                          * by ExtensionOffset (i.e. the
                                          * extension subtable). */
   ULONG         extensionOffset;        /* Offset to the extension subtable,
                                          * of lookup type subtable. */
   public:
   DEFINE_SIZE_STATIC (8);
 };
 
@@ skipping 16 matching lines @@
 
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     if (!u.format.sanitize (c)) return TRACE_RETURN (false);
     switch (u.format) {
     case 1: return TRACE_RETURN (u.format1.sanitize (c));
     default:return TRACE_RETURN (true);
     }
   }
 
-  private:
+  protected:
   union {
   USHORT                format;         /* Format identifier */
   ExtensionFormat1      format1;
   } u;
 };
 
 
 /*
  * GSUB/GPOS Common
  */
@@ skipping 49 matching lines @@
                 scriptList;     /* ScriptList table */
   OffsetTo<FeatureList>
                 featureList;    /* FeatureList table */
   OffsetTo<LookupList>
                 lookupList;     /* LookupList table */
   public:
   DEFINE_SIZE_STATIC (10);
 };
 
 
+} // namespace OT
+
 
 #endif /* HB_OT_LAYOUT_GSUBGPOS_PRIVATE_HH */