Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3687 insertions, 0 deletions

diff --git a/gfx/harfbuzz/src/hb-ot-layout-common.hh b/gfx/harfbuzz/src/hb-ot-layout-common.hh
new file mode 100644
index 0000000000..0f424f5aa6
--- /dev/null
+++ b/gfx/harfbuzz/src/hb-ot-layout-common.hh
@@ -0,0 +1,3687 @@
+/*
+ * Copyright © 2007,2008,2009  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
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Red Hat Author(s): Behdad Esfahbod
+ * Google Author(s): Behdad Esfahbod
+ */
+
+#ifndef HB_OT_LAYOUT_COMMON_HH
+#define HB_OT_LAYOUT_COMMON_HH
+
+#include "hb.hh"
+#include "hb-ot-layout.hh"
+#include "hb-open-type.hh"
+#include "hb-set.hh"
+#include "hb-bimap.hh"
+
+#include "OT/Layout/Common/Coverage.hh"
+#include "OT/Layout/types.hh"
+
+// TODO(garretrieger): cleanup these after migration.
+using OT::Layout::Common::Coverage;
+using OT::Layout::Common::RangeRecord;
+using OT::Layout::SmallTypes;
+using OT::Layout::MediumTypes;
+
+#ifndef HB_MAX_NESTING_LEVEL
+#define HB_MAX_NESTING_LEVEL	64
+#endif
+#ifndef HB_MAX_CONTEXT_LENGTH
+#define HB_MAX_CONTEXT_LENGTH	64
+#endif
+#ifndef HB_CLOSURE_MAX_STAGES
+/*
+ * The maximum number of times a lookup can be applied during shaping.
+ * Used to limit the number of iterations of the closure algorithm.
+ * This must be larger than the number of times add_gsub_pause() is
+ * called in a collect_features call of any shaper.
+ */
+#define HB_CLOSURE_MAX_STAGES	12
+#endif
+
+#ifndef HB_MAX_SCRIPTS
+#define HB_MAX_SCRIPTS	500
+#endif
+
+#ifndef HB_MAX_LANGSYS
+#define HB_MAX_LANGSYS	2000
+#endif
+
+#ifndef HB_MAX_LANGSYS_FEATURE_COUNT
+#define HB_MAX_LANGSYS_FEATURE_COUNT 50000
+#endif
+
+#ifndef HB_MAX_FEATURE_INDICES
+#define HB_MAX_FEATURE_INDICES	1500
+#endif
+
+#ifndef HB_MAX_LOOKUP_VISIT_COUNT
+#define HB_MAX_LOOKUP_VISIT_COUNT	35000
+#endif
+
+
+namespace OT {
+
+template<typename Iterator>
+static inline bool ClassDef_serialize (hb_serialize_context_t *c,
+				       Iterator it);
+
+static bool ClassDef_remap_and_serialize (
+    hb_serialize_context_t *c,
+    const hb_set_t &klasses,
+    bool use_class_zero,
+    hb_sorted_vector_t<hb_pair_t<hb_codepoint_t, hb_codepoint_t>> &glyph_and_klass, /* IN/OUT */
+    hb_map_t *klass_map /*IN/OUT*/);
+
+struct hb_collect_feature_substitutes_with_var_context_t
+{
+  const hb_map_t *axes_index_tag_map;
+  const hb_hashmap_t<hb_tag_t, int> *axes_location;
+  hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> *record_cond_idx_map;
+  hb_hashmap_t<unsigned, const Feature*> *feature_substitutes_map;
+
+  // not stored in subset_plan
+  hb_set_t *feature_indices;
+  bool apply;
+  unsigned cur_record_idx;
+  hb_hashmap_t<hb::shared_ptr<hb_map_t>, unsigned> *conditionset_map;
+};
+
+struct hb_prune_langsys_context_t
+{
+  hb_prune_langsys_context_t (const void         *table_,
+                              hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *script_langsys_map_,
+                              const hb_map_t     *duplicate_feature_map_,
+                              hb_set_t           *new_collected_feature_indexes_)
+      :table (table_),
+      script_langsys_map (script_langsys_map_),
+      duplicate_feature_map (duplicate_feature_map_),
+      new_feature_indexes (new_collected_feature_indexes_),
+      script_count (0),langsys_feature_count (0) {}
+
+  bool visitScript ()
+  { return script_count++ < HB_MAX_SCRIPTS; }
+
+  bool visitLangsys (unsigned feature_count)
+  {
+    langsys_feature_count += feature_count;
+    return langsys_feature_count < HB_MAX_LANGSYS_FEATURE_COUNT;
+  }
+
+  public:
+  const void *table;
+  hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *script_langsys_map;
+  const hb_map_t     *duplicate_feature_map;
+  hb_set_t           *new_feature_indexes;
+
+  private:
+  unsigned script_count;
+  unsigned langsys_feature_count;
+};
+
+struct hb_subset_layout_context_t :
+  hb_dispatch_context_t<hb_subset_layout_context_t, hb_empty_t, HB_DEBUG_SUBSET>
+{
+  const char *get_name () { return "SUBSET_LAYOUT"; }
+  static return_t default_return_value () { return hb_empty_t (); }
+
+  bool visitScript ()
+  {
+    return script_count++ < HB_MAX_SCRIPTS;
+  }
+
+  bool visitLangSys ()
+  {
+    return langsys_count++ < HB_MAX_LANGSYS;
+  }
+
+  bool visitFeatureIndex (int count)
+  {
+    feature_index_count += count;
+    return feature_index_count < HB_MAX_FEATURE_INDICES;
+  }
+
+  bool visitLookupIndex()
+  {
+    lookup_index_count++;
+    return lookup_index_count < HB_MAX_LOOKUP_VISIT_COUNT;
+  }
+
+  hb_subset_context_t *subset_context;
+  const hb_tag_t table_tag;
+  const hb_map_t *lookup_index_map;
+  const hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *script_langsys_map;
+  const hb_map_t *feature_index_map;
+  const hb_hashmap_t<unsigned, const Feature*> *feature_substitutes_map;
+  hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> *feature_record_cond_idx_map;
+
+  unsigned cur_script_index;
+  unsigned cur_feature_var_record_idx;
+
+  hb_subset_layout_context_t (hb_subset_context_t *c_,
+			      hb_tag_t tag_) :
+				subset_context (c_),
+				table_tag (tag_),
+				cur_script_index (0xFFFFu),
+				cur_feature_var_record_idx (0u),
+				script_count (0),
+				langsys_count (0),
+				feature_index_count (0),
+				lookup_index_count (0)
+  {
+    if (tag_ == HB_OT_TAG_GSUB)
+    {
+      lookup_index_map = c_->plan->gsub_lookups;
+      script_langsys_map = c_->plan->gsub_langsys;
+      feature_index_map = c_->plan->gsub_features;
+      feature_substitutes_map = c_->plan->gsub_feature_substitutes_map;
+      feature_record_cond_idx_map = c_->plan->user_axes_location->is_empty () ? nullptr : c_->plan->gsub_feature_record_cond_idx_map;
+    }
+    else
+    {
+      lookup_index_map = c_->plan->gpos_lookups;
+      script_langsys_map = c_->plan->gpos_langsys;
+      feature_index_map = c_->plan->gpos_features;
+      feature_substitutes_map = c_->plan->gpos_feature_substitutes_map;
+      feature_record_cond_idx_map = c_->plan->user_axes_location->is_empty () ? nullptr : c_->plan->gpos_feature_record_cond_idx_map;
+    }
+  }
+
+  private:
+  unsigned script_count;
+  unsigned langsys_count;
+  unsigned feature_index_count;
+  unsigned lookup_index_count;
+};
+
+struct VariationStore;
+struct hb_collect_variation_indices_context_t :
+       hb_dispatch_context_t<hb_collect_variation_indices_context_t>
+{
+  template <typename T>
+  return_t dispatch (const T &obj) { obj.collect_variation_indices (this); return hb_empty_t (); }
+  static return_t default_return_value () { return hb_empty_t (); }
+
+  hb_set_t *layout_variation_indices;
+  hb_hashmap_t<unsigned, hb_pair_t<unsigned, int>> *varidx_delta_map;
+  hb_font_t *font;
+  const VariationStore *var_store;
+  const hb_set_t *glyph_set;
+  const hb_map_t *gpos_lookups;
+  float *store_cache;
+
+  hb_collect_variation_indices_context_t (hb_set_t *layout_variation_indices_,
+					  hb_hashmap_t<unsigned, hb_pair_t<unsigned, int>> *varidx_delta_map_,
+					  hb_font_t *font_,
+					  const VariationStore *var_store_,
+					  const hb_set_t *glyph_set_,
+					  const hb_map_t *gpos_lookups_,
+					  float *store_cache_) :
+					layout_variation_indices (layout_variation_indices_),
+					varidx_delta_map (varidx_delta_map_),
+					font (font_),
+					var_store (var_store_),
+					glyph_set (glyph_set_),
+					gpos_lookups (gpos_lookups_),
+					store_cache (store_cache_) {}
+};
+
+template<typename OutputArray>
+struct subset_offset_array_t
+{
+  subset_offset_array_t (hb_subset_context_t *subset_context_,
+			 OutputArray& out_,
+			 const void *base_) : subset_context (subset_context_),
+					      out (out_), base (base_) {}
+
+  template <typename T>
+  bool operator () (T&& offset)
+  {
+    auto snap = subset_context->serializer->snapshot ();
+    auto *o = out.serialize_append (subset_context->serializer);
+    if (unlikely (!o)) return false;
+    bool ret = o->serialize_subset (subset_context, offset, base);
+    if (!ret)
+    {
+      out.pop ();
+      subset_context->serializer->revert (snap);
+    }
+    return ret;
+  }
+
+  private:
+  hb_subset_context_t *subset_context;
+  OutputArray &out;
+  const void *base;
+};
+
+
+template<typename OutputArray, typename Arg>
+struct subset_offset_array_arg_t
+{
+  subset_offset_array_arg_t (hb_subset_context_t *subset_context_,
+			     OutputArray& out_,
+			     const void *base_,
+			     Arg &&arg_) : subset_context (subset_context_), out (out_),
+					  base (base_), arg (arg_) {}
+
+  template <typename T>
+  bool operator () (T&& offset)
+  {
+    auto snap = subset_context->serializer->snapshot ();
+    auto *o = out.serialize_append (subset_context->serializer);
+    if (unlikely (!o)) return false;
+    bool ret = o->serialize_subset (subset_context, offset, base, arg);
+    if (!ret)
+    {
+      out.pop ();
+      subset_context->serializer->revert (snap);
+    }
+    return ret;
+  }
+
+  private:
+  hb_subset_context_t *subset_context;
+  OutputArray &out;
+  const void *base;
+  Arg &&arg;
+};
+
+/*
+ * Helper to subset an array of offsets. Subsets the thing pointed to by each offset
+ * and discards the offset in the array if the subset operation results in an empty
+ * thing.
+ */
+struct
+{
+  template<typename OutputArray>
+  subset_offset_array_t<OutputArray>
+  operator () (hb_subset_context_t *subset_context, OutputArray& out,
+	       const void *base) const
+  { return subset_offset_array_t<OutputArray> (subset_context, out, base); }
+
+  /* Variant with one extra argument passed to serialize_subset */
+  template<typename OutputArray, typename Arg>
+  subset_offset_array_arg_t<OutputArray, Arg>
+  operator () (hb_subset_context_t *subset_context, OutputArray& out,
+	       const void *base, Arg &&arg) const
+  { return subset_offset_array_arg_t<OutputArray, Arg> (subset_context, out, base, arg); }
+}
+HB_FUNCOBJ (subset_offset_array);
+
+template<typename OutputArray>
+struct subset_record_array_t
+{
+  subset_record_array_t (hb_subset_layout_context_t *c_, OutputArray* out_,
+			 const void *base_) : subset_layout_context (c_),
+					      out (out_), base (base_) {}
+
+  template <typename T>
+  void
+  operator () (T&& record)
+  {
+    auto snap = subset_layout_context->subset_context->serializer->snapshot ();
+    bool ret = record.subset (subset_layout_context, base);
+    if (!ret) subset_layout_context->subset_context->serializer->revert (snap);
+    else out->len++;
+  }
+
+  private:
+  hb_subset_layout_context_t *subset_layout_context;
+  OutputArray *out;
+  const void *base;
+};
+
+template<typename OutputArray, typename Arg>
+struct subset_record_array_arg_t
+{
+  subset_record_array_arg_t (hb_subset_layout_context_t *c_, OutputArray* out_,
+			     const void *base_,
+			     Arg &&arg_) : subset_layout_context (c_),
+					   out (out_), base (base_), arg (arg_) {}
+
+  template <typename T>
+  void
+  operator () (T&& record)
+  {
+    auto snap = subset_layout_context->subset_context->serializer->snapshot ();
+    bool ret = record.subset (subset_layout_context, base, arg);
+    if (!ret) subset_layout_context->subset_context->serializer->revert (snap);
+    else out->len++;
+  }
+
+  private:
+  hb_subset_layout_context_t *subset_layout_context;
+  OutputArray *out;
+  const void *base;
+  Arg &&arg;
+};
+
+/*
+ * Helper to subset a RecordList/record array. Subsets each Record in the array and
+ * discards the record if the subset operation returns false.
+ */
+struct
+{
+  template<typename OutputArray>
+  subset_record_array_t<OutputArray>
+  operator () (hb_subset_layout_context_t *c, OutputArray* out,
+	       const void *base) const
+  { return subset_record_array_t<OutputArray> (c, out, base); }
+
+  /* Variant with one extra argument passed to subset */
+  template<typename OutputArray, typename Arg>
+  subset_record_array_arg_t<OutputArray, Arg>
+  operator () (hb_subset_layout_context_t *c, OutputArray* out,
+               const void *base, Arg &&arg) const
+  { return subset_record_array_arg_t<OutputArray, Arg> (c, out, base, arg); }
+}
+HB_FUNCOBJ (subset_record_array);
+
+
+template<typename OutputArray>
+struct serialize_math_record_array_t
+{
+  serialize_math_record_array_t (hb_serialize_context_t *serialize_context_,
+                         OutputArray& out_,
+                         const void *base_) : serialize_context (serialize_context_),
+                                              out (out_), base (base_) {}
+
+  template <typename T>
+  bool operator () (T&& record)
+  {
+    if (!serialize_context->copy (record, base)) return false;
+    out.len++;
+    return true;
+  }
+
+  private:
+  hb_serialize_context_t *serialize_context;
+  OutputArray &out;
+  const void *base;
+};
+
+/*
+ * Helper to serialize an array of MATH records.
+ */
+struct
+{
+  template<typename OutputArray>
+  serialize_math_record_array_t<OutputArray>
+  operator () (hb_serialize_context_t *serialize_context, OutputArray& out,
+               const void *base) const
+  { return serialize_math_record_array_t<OutputArray> (serialize_context, out, base); }
+
+}
+HB_FUNCOBJ (serialize_math_record_array);
+
+/*
+ *
+ * OpenType Layout Common Table Formats
+ *
+ */
+
+
+/*
+ * Script, ScriptList, LangSys, Feature, FeatureList, Lookup, LookupList
+ */
+
+struct IndexArray : Array16Of<Index>
+{
+  bool intersects (const hb_map_t *indexes) const
+  { return hb_any (*this, indexes); }
+
+  template <typename Iterator,
+	    hb_requires (hb_is_iterator (Iterator))>
+  void serialize (hb_serialize_context_t *c,
+		  hb_subset_layout_context_t *l,
+		  Iterator it)
+  {
+    if (!it) return;
+    if (unlikely (!c->extend_min ((*this)))) return;
+
+    for (const auto _ : it)
+    {
+      if (!l->visitLookupIndex()) break;
+
+      Index i;
+      i = _;
+      c->copy (i);
+      this->len++;
+    }
+  }
+
+  unsigned int get_indexes (unsigned int start_offset,
+			    unsigned int *_count /* IN/OUT */,
+			    unsigned int *_indexes /* OUT */) const
+  {
+    if (_count)
+    {
+      + this->as_array ().sub_array (start_offset, _count)
+      | hb_sink (hb_array (_indexes, *_count))
+      ;
+    }
+    return this->len;
+  }
+
+  void add_indexes_to (hb_set_t* output /* OUT */) const
+  {
+    output->add_array (as_array ());
+  }
+};
+
+
+/* https://docs.microsoft.com/en-us/typography/opentype/spec/features_pt#size */
+struct FeatureParamsSize
+{
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    if (unlikely (!c->check_struct (this))) return_trace (false);
+
+    /* This subtable has some "history", if you will.  Some earlier versions of
+     * Adobe tools calculated the offset of the FeatureParams subtable from the
+     * beginning of the FeatureList table!  Now, that is dealt with in the
+     * Feature implementation.  But we still need to be able to tell junk from
+     * real data.  Note: We don't check that the nameID actually exists.
+     *
+     * Read Roberts wrote on 9/15/06 on opentype-list@indx.co.uk :
+     *
+     * Yes, it is correct that a new version of the AFDKO (version 2.0) will be
+     * coming out soon, and that the makeotf program will build a font with a
+     * 'size' feature that is correct by the specification.
+     *
+     * The specification for this feature tag is in the "OpenType Layout Tag
+     * Registry". You can see a copy of this at:
+     * https://docs.microsoft.com/en-us/typography/opentype/spec/features_pt#tag-size
+     *
+     * Here is one set of rules to determine if the 'size' feature is built
+     * correctly, or as by the older versions of MakeOTF. You may be able to do
+     * better.
+     *
+     * Assume that the offset to the size feature is according to specification,
+     * and make the following value checks. If it fails, assume the size
+     * feature is calculated as versions of MakeOTF before the AFDKO 2.0 built it.
+     * If this fails, reject the 'size' feature. The older makeOTF's calculated the
+     * offset from the beginning of the FeatureList table, rather than from the
+     * beginning of the 'size' Feature table.
+     *
+     * If "design size" == 0:
+     *     fails check
+     *
+     * Else if ("subfamily identifier" == 0 and
+     *     "range start" == 0 and
+     *     "range end" == 0 and
+     *     "range start" == 0 and
+     *     "menu name ID" == 0)
+     *     passes check: this is the format used when there is a design size
+     * specified, but there is no recommended size range.
+     *
+     * Else if ("design size" <  "range start" or
+     *     "design size" >   "range end" or
+     *     "range end" <= "range start" or
+     *     "menu name ID"  < 256 or
+     *     "menu name ID"  > 32767 or
+     *     menu name ID is not a name ID which is actually in the name table)
+     *     fails test
+     * Else
+     *     passes test.
+     */
+
+    if (!designSize)
+      return_trace (false);
+    else if (subfamilyID == 0 &&
+	     subfamilyNameID == 0 &&
+	     rangeStart == 0 &&
+	     rangeEnd == 0)
+      return_trace (true);
+    else if (designSize < rangeStart ||
+	     designSize > rangeEnd ||
+	     subfamilyNameID < 256 ||
+	     subfamilyNameID > 32767)
+      return_trace (false);
+    else
+      return_trace (true);
+  }
+
+  bool subset (hb_subset_context_t *c) const
+  {
+    TRACE_SUBSET (this);
+    return_trace ((bool) c->serializer->embed (*this));
+  }
+
+  HBUINT16	designSize;	/* Represents the design size in 720/inch
+				 * units (decipoints).  The design size entry
+				 * must be non-zero.  When there is a design
+				 * size but no recommended size range, the
+				 * rest of the array will consist of zeros. */
+  HBUINT16	subfamilyID;	/* Has no independent meaning, but serves
+				 * as an identifier that associates fonts
+				 * in a subfamily. All fonts which share a
+				 * Preferred or Font Family name and which
+				 * differ only by size range shall have the
+				 * same subfamily value, and no fonts which
+				 * differ in weight or style shall have the
+				 * same subfamily value. If this value is
+				 * zero, the remaining fields in the array
+				 * will be ignored. */
+  NameID	subfamilyNameID;/* If the preceding value is non-zero, this
+				 * value must be set in the range 256 - 32767
+				 * (inclusive). It records the value of a
+				 * field in the name table, which must
+				 * contain English-language strings encoded
+				 * in Windows Unicode and Macintosh Roman,
+				 * and may contain additional strings
+				 * localized to other scripts and languages.
+				 * Each of these strings is the name an
+				 * application should use, in combination
+				 * with the family name, to represent the
+				 * subfamily in a menu.  Applications will
+				 * choose the appropriate version based on
+				 * their selection criteria. */
+  HBUINT16	rangeStart;	/* Large end of the recommended usage range
+				 * (inclusive), stored in 720/inch units
+				 * (decipoints). */
+  HBUINT16	rangeEnd;	/* Small end of the recommended usage range
+				   (exclusive), stored in 720/inch units
+				 * (decipoints). */
+  public:
+  DEFINE_SIZE_STATIC (10);
+};
+
+/* https://docs.microsoft.com/en-us/typography/opentype/spec/features_pt#ssxx */
+struct FeatureParamsStylisticSet
+{
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    /* Right now minorVersion is at zero.  Which means, any table supports
+     * the uiNameID field. */
+    return_trace (c->check_struct (this));
+  }
+
+  bool subset (hb_subset_context_t *c) const
+  {
+    TRACE_SUBSET (this);
+    return_trace ((bool) c->serializer->embed (*this));
+  }
+
+  HBUINT16	version;	/* (set to 0): This corresponds to a “minor”
+				 * version number. Additional data may be
+				 * added to the end of this Feature Parameters
+				 * table in the future. */
+
+  NameID	uiNameID;	/* The 'name' table name ID that specifies a
+				 * string (or strings, for multiple languages)
+				 * for a user-interface label for this
+				 * feature.  The values of uiLabelNameId and
+				 * sampleTextNameId are expected to be in the
+				 * font-specific name ID range (256-32767),
+				 * though that is not a requirement in this
+				 * Feature Parameters specification. The
+				 * user-interface label for the feature can
+				 * be provided in multiple languages. An
+				 * English string should be included as a
+				 * fallback. The string should be kept to a
+				 * minimal length to fit comfortably with
+				 * different application interfaces. */
+  public:
+  DEFINE_SIZE_STATIC (4);
+};
+
+/* https://docs.microsoft.com/en-us/typography/opentype/spec/features_ae#cv01-cv99 */
+struct FeatureParamsCharacterVariants
+{
+  unsigned
+  get_characters (unsigned start_offset, unsigned *char_count, hb_codepoint_t *chars) const
+  {
+    if (char_count)
+    {
+      + characters.as_array ().sub_array (start_offset, char_count)
+      | hb_sink (hb_array (chars, *char_count))
+      ;
+    }
+    return characters.len;
+  }
+
+  unsigned get_size () const
+  { return min_size + characters.len * HBUINT24::static_size; }
+
+  bool subset (hb_subset_context_t *c) const
+  {
+    TRACE_SUBSET (this);
+    return_trace ((bool) c->serializer->embed (*this));
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this) &&
+		  characters.sanitize (c));
+  }
+
+  HBUINT16	format;			/* Format number is set to 0. */
+  NameID	featUILableNameID;	/* The ‘name’ table name ID that
+					 * specifies a string (or strings,
+					 * for multiple languages) for a
+					 * user-interface label for this
+					 * feature. (May be NULL.) */
+  NameID	featUITooltipTextNameID;/* The ‘name’ table name ID that
+					 * specifies a string (or strings,
+					 * for multiple languages) that an
+					 * application can use for tooltip
+					 * text for this feature. (May be
+					 * nullptr.) */
+  NameID	sampleTextNameID;	/* The ‘name’ table name ID that
+					 * specifies sample text that
+					 * illustrates the effect of this
+					 * feature. (May be NULL.) */
+  HBUINT16	numNamedParameters;	/* Number of named parameters. (May
+					 * be zero.) */
+  NameID	firstParamUILabelNameID;/* The first ‘name’ table name ID
+					 * used to specify strings for
+					 * user-interface labels for the
+					 * feature parameters. (Must be zero
+					 * if numParameters is zero.) */
+  Array16Of<HBUINT24>
+		characters;		/* Array of the Unicode Scalar Value
+					 * of the characters for which this
+					 * feature provides glyph variants.
+					 * (May be zero.) */
+  public:
+  DEFINE_SIZE_ARRAY (14, characters);
+};
+
+struct FeatureParams
+{
+  bool sanitize (hb_sanitize_context_t *c, hb_tag_t tag) const
+  {
+#ifdef HB_NO_LAYOUT_FEATURE_PARAMS
+    return true;
+#endif
+    TRACE_SANITIZE (this);
+    if (tag == HB_TAG ('s','i','z','e'))
+      return_trace (u.size.sanitize (c));
+    if ((tag & 0xFFFF0000u) == HB_TAG ('s','s','\0','\0')) /* ssXX */
+      return_trace (u.stylisticSet.sanitize (c));
+    if ((tag & 0xFFFF0000u) == HB_TAG ('c','v','\0','\0')) /* cvXX */
+      return_trace (u.characterVariants.sanitize (c));
+    return_trace (true);
+  }
+
+  bool subset (hb_subset_context_t *c, const Tag* tag) const
+  {
+    TRACE_SUBSET (this);
+    if (!tag) return_trace (false);
+    if (*tag == HB_TAG ('s','i','z','e'))
+      return_trace (u.size.subset (c));
+    if ((*tag & 0xFFFF0000u) == HB_TAG ('s','s','\0','\0')) /* ssXX */
+      return_trace (u.stylisticSet.subset (c));
+    if ((*tag & 0xFFFF0000u) == HB_TAG ('c','v','\0','\0')) /* cvXX */
+      return_trace (u.characterVariants.subset (c));
+    return_trace (false);
+  }
+
+#ifndef HB_NO_LAYOUT_FEATURE_PARAMS
+  const FeatureParamsSize& get_size_params (hb_tag_t tag) const
+  {
+    if (tag == HB_TAG ('s','i','z','e'))
+      return u.size;
+    return Null (FeatureParamsSize);
+  }
+  const FeatureParamsStylisticSet& get_stylistic_set_params (hb_tag_t tag) const
+  {
+    if ((tag & 0xFFFF0000u) == HB_TAG ('s','s','\0','\0')) /* ssXX */
+      return u.stylisticSet;
+    return Null (FeatureParamsStylisticSet);
+  }
+  const FeatureParamsCharacterVariants& get_character_variants_params (hb_tag_t tag) const
+  {
+    if ((tag & 0xFFFF0000u) == HB_TAG ('c','v','\0','\0')) /* cvXX */
+      return u.characterVariants;
+    return Null (FeatureParamsCharacterVariants);
+  }
+#endif
+
+  private:
+  union {
+  FeatureParamsSize			size;
+  FeatureParamsStylisticSet		stylisticSet;
+  FeatureParamsCharacterVariants	characterVariants;
+  } u;
+  public:
+  DEFINE_SIZE_MIN (0);
+};
+
+struct Record_sanitize_closure_t {
+  hb_tag_t tag;
+  const void *list_base;
+};
+
+struct Feature
+{
+  unsigned int get_lookup_count () const
+  { return lookupIndex.len; }
+  hb_tag_t get_lookup_index (unsigned int i) const
+  { return lookupIndex[i]; }
+  unsigned int get_lookup_indexes (unsigned int start_index,
+				   unsigned int *lookup_count /* IN/OUT */,
+				   unsigned int *lookup_tags /* OUT */) const
+  { return lookupIndex.get_indexes (start_index, lookup_count, lookup_tags); }
+  void add_lookup_indexes_to (hb_set_t *lookup_indexes) const
+  { lookupIndex.add_indexes_to (lookup_indexes); }
+
+  const FeatureParams &get_feature_params () const
+  { return this+featureParams; }
+
+  bool intersects_lookup_indexes (const hb_map_t *lookup_indexes) const
+  { return lookupIndex.intersects (lookup_indexes); }
+
+  bool subset (hb_subset_context_t         *c,
+	       hb_subset_layout_context_t  *l,
+	       const Tag                   *tag = nullptr) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->serializer->start_embed (*this);
+    if (unlikely (!out || !c->serializer->extend_min (out))) return_trace (false);
+
+    out->featureParams.serialize_subset (c, featureParams, this, tag);
+
+    auto it =
+    + hb_iter (lookupIndex)
+    | hb_filter (l->lookup_index_map)
+    | hb_map (l->lookup_index_map)
+    ;
+
+    out->lookupIndex.serialize (c->serializer, l, it);
+    // The decision to keep or drop this feature is already made before we get here
+    // so always retain it.
+    return_trace (true);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c,
+		 const Record_sanitize_closure_t *closure = nullptr) const
+  {
+    TRACE_SANITIZE (this);
+    if (unlikely (!(c->check_struct (this) && lookupIndex.sanitize (c))))
+      return_trace (false);
+
+    /* Some earlier versions of Adobe tools calculated the offset of the
+     * FeatureParams subtable from the beginning of the FeatureList table!
+     *
+     * If sanitizing "failed" for the FeatureParams subtable, try it with the
+     * alternative location.  We would know sanitize "failed" if old value
+     * of the offset was non-zero, but it's zeroed now.
+     *
+     * Only do this for the 'size' feature, since at the time of the faulty
+     * Adobe tools, only the 'size' feature had FeatureParams defined.
+     */
+
+    if (likely (featureParams.is_null ()))
+      return_trace (true);
+
+    unsigned int orig_offset = featureParams;
+    if (unlikely (!featureParams.sanitize (c, this, closure ? closure->tag : HB_TAG_NONE)))
+      return_trace (false);
+
+    if (featureParams == 0 && closure &&
+	closure->tag == HB_TAG ('s','i','z','e') &&
+	closure->list_base && closure->list_base < this)
+    {
+      unsigned int new_offset_int = orig_offset -
+				    (((char *) this) - ((char *) closure->list_base));
+
+      Offset16To<FeatureParams> new_offset;
+      /* Check that it would not overflow. */
+      new_offset = new_offset_int;
+      if (new_offset == new_offset_int &&
+	  c->try_set (&featureParams, new_offset_int) &&
+	  !featureParams.sanitize (c, this, closure ? closure->tag : HB_TAG_NONE))
+	return_trace (false);
+    }
+
+    return_trace (true);
+  }
+
+  Offset16To<FeatureParams>
+		 featureParams;	/* Offset to Feature Parameters table (if one
+				 * has been defined for the feature), relative
+				 * to the beginning of the Feature Table; = Null
+				 * if not required */
+  IndexArray	 lookupIndex;	/* Array of LookupList indices */
+  public:
+  DEFINE_SIZE_ARRAY_SIZED (4, lookupIndex);
+};
+
+template <typename Type>
+struct Record
+{
+  int cmp (hb_tag_t a) const { return tag.cmp (a); }
+
+  bool subset (hb_subset_layout_context_t *c, const void *base, const void *f_sub = nullptr) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->subset_context->serializer->embed (this);
+    if (unlikely (!out)) return_trace (false);
+
+    if (!f_sub)
+      return_trace (out->offset.serialize_subset (c->subset_context, offset, base, c, &tag));
+
+    const Feature& f = *reinterpret_cast<const Feature *> (f_sub);
+    auto *s = c->subset_context->serializer;
+    s->push ();
+
+    out->offset = 0;
+    bool ret = f.subset (c->subset_context, c, &tag);
+    if (ret)
+      s->add_link (out->offset, s->pop_pack ());
+    else
+      s->pop_discard ();
+
+    return_trace (ret);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c, const void *base) const
+  {
+    TRACE_SANITIZE (this);
+    const Record_sanitize_closure_t closure = {tag, base};
+    return_trace (c->check_struct (this) && offset.sanitize (c, base, &closure));
+  }
+
+  Tag           tag;            /* 4-byte Tag identifier */
+  Offset16To<Type>
+                offset;         /* Offset from beginning of object holding
+                                 * the Record */
+  public:
+  DEFINE_SIZE_STATIC (6);
+};
+
+template <typename Type>
+struct RecordArrayOf : SortedArray16Of<Record<Type>>
+{
+  const Offset16To<Type>& get_offset (unsigned int i) const
+  { return (*this)[i].offset; }
+  Offset16To<Type>& get_offset (unsigned int i)
+  { return (*this)[i].offset; }
+  const Tag& get_tag (unsigned int i) const
+  { return (*this)[i].tag; }
+  unsigned int get_tags (unsigned int start_offset,
+                         unsigned int *record_count /* IN/OUT */,
+                         hb_tag_t     *record_tags /* OUT */) const
+  {
+    if (record_count)
+    {
+      + this->as_array ().sub_array (start_offset, record_count)
+      | hb_map (&Record<Type>::tag)
+      | hb_sink (hb_array (record_tags, *record_count))
+      ;
+    }
+    return this->len;
+  }
+  bool find_index (hb_tag_t tag, unsigned int *index) const
+  {
+    return this->bfind (tag, index, HB_NOT_FOUND_STORE, Index::NOT_FOUND_INDEX);
+  }
+};
+
+template <typename Type>
+struct RecordListOf : RecordArrayOf<Type>
+{
+  const Type& operator [] (unsigned int i) const
+  { return this+this->get_offset (i); }
+
+  bool subset (hb_subset_context_t *c,
+               hb_subset_layout_context_t *l) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->serializer->start_embed (*this);
+    if (unlikely (!c->serializer->extend_min (out))) return_trace (false);
+
+    + this->iter ()
+    | hb_apply (subset_record_array (l, out, this))
+    ;
+    return_trace (true);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (RecordArrayOf<Type>::sanitize (c, this));
+  }
+};
+
+struct RecordListOfFeature : RecordListOf<Feature>
+{
+  bool subset (hb_subset_context_t *c,
+	       hb_subset_layout_context_t *l) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->serializer->start_embed (*this);
+    if (unlikely (!out || !c->serializer->extend_min (out))) return_trace (false);
+
+    + hb_enumerate (*this)
+    | hb_filter (l->feature_index_map, hb_first)
+    | hb_apply ([l, out, this] (const hb_pair_t<unsigned, const Record<Feature>&>& _)
+                {
+                  const Feature *f_sub = nullptr;
+                  const Feature **f = nullptr;
+                  if (l->feature_substitutes_map->has (_.first, &f))
+                    f_sub = *f;
+
+                  subset_record_array (l, out, this, f_sub) (_.second);
+                })
+    ;
+
+    return_trace (true);
+  }
+};
+
+typedef RecordListOf<Feature> FeatureList;
+
+
+struct LangSys
+{
+  unsigned int get_feature_count () const
+  { return featureIndex.len; }
+  hb_tag_t get_feature_index (unsigned int i) const
+  { return featureIndex[i]; }
+  unsigned int get_feature_indexes (unsigned int start_offset,
+				    unsigned int *feature_count /* IN/OUT */,
+				    unsigned int *feature_indexes /* OUT */) const
+  { return featureIndex.get_indexes (start_offset, feature_count, feature_indexes); }
+  void add_feature_indexes_to (hb_set_t *feature_indexes) const
+  { featureIndex.add_indexes_to (feature_indexes); }
+
+  bool has_required_feature () const { return reqFeatureIndex != 0xFFFFu; }
+  unsigned int get_required_feature_index () const
+  {
+    if (reqFeatureIndex == 0xFFFFu)
+      return Index::NOT_FOUND_INDEX;
+   return reqFeatureIndex;
+  }
+
+  LangSys* copy (hb_serialize_context_t *c) const
+  {
+    TRACE_SERIALIZE (this);
+    return_trace (c->embed (*this));
+  }
+
+  bool compare (const LangSys& o, const hb_map_t *feature_index_map) const
+  {
+    if (reqFeatureIndex != o.reqFeatureIndex)
+      return false;
+
+    auto iter =
+    + hb_iter (featureIndex)
+    | hb_filter (feature_index_map)
+    | hb_map (feature_index_map)
+    ;
+
+    auto o_iter =
+    + hb_iter (o.featureIndex)
+    | hb_filter (feature_index_map)
+    | hb_map (feature_index_map)
+    ;
+
+    for (; iter && o_iter; iter++, o_iter++)
+    {
+      unsigned a = *iter;
+      unsigned b = *o_iter;
+      if (a != b) return false;
+    }
+
+    if (iter || o_iter) return false;
+
+    return true;
+  }
+
+  void collect_features (hb_prune_langsys_context_t *c) const
+  {
+    if (!has_required_feature () && !get_feature_count ()) return;
+    if (has_required_feature () &&
+        c->duplicate_feature_map->has (reqFeatureIndex))
+      c->new_feature_indexes->add (get_required_feature_index ());
+
+    + hb_iter (featureIndex)
+    | hb_filter (c->duplicate_feature_map)
+    | hb_sink (c->new_feature_indexes)
+    ;
+  }
+
+  bool subset (hb_subset_context_t        *c,
+	       hb_subset_layout_context_t *l,
+	       const Tag                  *tag = nullptr) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->serializer->start_embed (*this);
+    if (unlikely (!out || !c->serializer->extend_min (out))) return_trace (false);
+
+    const uint32_t *v;
+    out->reqFeatureIndex = l->feature_index_map->has (reqFeatureIndex, &v) ? *v : 0xFFFFu;
+
+    if (!l->visitFeatureIndex (featureIndex.len))
+      return_trace (false);
+
+    auto it =
+    + hb_iter (featureIndex)
+    | hb_filter (l->feature_index_map)
+    | hb_map (l->feature_index_map)
+    ;
+
+    bool ret = bool (it);
+    out->featureIndex.serialize (c->serializer, l, it);
+    return_trace (ret);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c,
+		 const Record_sanitize_closure_t * = nullptr) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this) && featureIndex.sanitize (c));
+  }
+
+  Offset16	lookupOrderZ;	/* = Null (reserved for an offset to a
+				 * reordering table) */
+  HBUINT16	reqFeatureIndex;/* Index of a feature required for this
+				 * language system--if no required features
+				 * = 0xFFFFu */
+  IndexArray	featureIndex;	/* Array of indices into the FeatureList */
+  public:
+  DEFINE_SIZE_ARRAY_SIZED (6, featureIndex);
+};
+DECLARE_NULL_NAMESPACE_BYTES (OT, LangSys);
+
+struct Script
+{
+  unsigned int get_lang_sys_count () const
+  { return langSys.len; }
+  const Tag& get_lang_sys_tag (unsigned int i) const
+  { return langSys.get_tag (i); }
+  unsigned int get_lang_sys_tags (unsigned int start_offset,
+				  unsigned int *lang_sys_count /* IN/OUT */,
+				  hb_tag_t     *lang_sys_tags /* OUT */) const
+  { return langSys.get_tags (start_offset, lang_sys_count, lang_sys_tags); }
+  const LangSys& get_lang_sys (unsigned int i) const
+  {
+    if (i == Index::NOT_FOUND_INDEX) return get_default_lang_sys ();
+    return this+langSys[i].offset;
+  }
+  bool find_lang_sys_index (hb_tag_t tag, unsigned int *index) const
+  { return langSys.find_index (tag, index); }
+
+  bool has_default_lang_sys () const           { return defaultLangSys != 0; }
+  const LangSys& get_default_lang_sys () const { return this+defaultLangSys; }
+
+  void prune_langsys (hb_prune_langsys_context_t *c,
+                      unsigned script_index) const
+  {
+    if (!has_default_lang_sys () && !get_lang_sys_count ()) return;
+    if (!c->visitScript ()) return;
+
+    if (!c->script_langsys_map->has (script_index))
+    {
+      if (unlikely (!c->script_langsys_map->set (script_index, hb::unique_ptr<hb_set_t> {hb_set_create ()})))
+	return;
+    }
+
+    if (has_default_lang_sys ())
+    {
+      //only collect features from non-redundant langsys
+      const LangSys& d = get_default_lang_sys ();
+      if (c->visitLangsys (d.get_feature_count ())) {
+        d.collect_features (c);
+      }
+
+      for (auto _ : + hb_enumerate (langSys))
+      {
+        const LangSys& l = this+_.second.offset;
+        if (!c->visitLangsys (l.get_feature_count ())) continue;
+        if (l.compare (d, c->duplicate_feature_map)) continue;
+
+        l.collect_features (c);
+        c->script_langsys_map->get (script_index)->add (_.first);
+      }
+    }
+    else
+    {
+      for (auto _ : + hb_enumerate (langSys))
+      {
+        const LangSys& l = this+_.second.offset;
+        if (!c->visitLangsys (l.get_feature_count ())) continue;
+        l.collect_features (c);
+        c->script_langsys_map->get (script_index)->add (_.first);
+      }
+    }
+  }
+
+  bool subset (hb_subset_context_t         *c,
+	       hb_subset_layout_context_t  *l,
+	       const Tag                   *tag) const
+  {
+    TRACE_SUBSET (this);
+    if (!l->visitScript ()) return_trace (false);
+    if (tag && !c->plan->layout_scripts->has (*tag))
+      return false;
+
+    auto *out = c->serializer->start_embed (*this);
+    if (unlikely (!out || !c->serializer->extend_min (out))) return_trace (false);
+
+    bool defaultLang = false;
+    if (has_default_lang_sys ())
+    {
+      c->serializer->push ();
+      const LangSys& ls = this+defaultLangSys;
+      bool ret = ls.subset (c, l);
+      if (!ret && tag && *tag != HB_TAG ('D', 'F', 'L', 'T'))
+      {
+	c->serializer->pop_discard ();
+	out->defaultLangSys = 0;
+      }
+      else
+      {
+	c->serializer->add_link (out->defaultLangSys, c->serializer->pop_pack ());
+	defaultLang = true;
+      }
+    }
+
+    const hb_set_t *active_langsys = l->script_langsys_map->get (l->cur_script_index);
+    if (active_langsys)
+    {
+      + hb_enumerate (langSys)
+      | hb_filter (active_langsys, hb_first)
+      | hb_map (hb_second)
+      | hb_filter ([=] (const Record<LangSys>& record) {return l->visitLangSys (); })
+      | hb_apply (subset_record_array (l, &(out->langSys), this))
+      ;
+    }
+
+    return_trace (bool (out->langSys.len) || defaultLang || l->table_tag == HB_OT_TAG_GSUB);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c,
+		 const Record_sanitize_closure_t * = nullptr) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (defaultLangSys.sanitize (c, this) && langSys.sanitize (c, this));
+  }
+
+  protected:
+  Offset16To<LangSys>
+		defaultLangSys;	/* Offset to DefaultLangSys table--from
+				 * beginning of Script table--may be Null */
+  RecordArrayOf<LangSys>
+		langSys;	/* Array of LangSysRecords--listed
+				 * alphabetically by LangSysTag */
+  public:
+  DEFINE_SIZE_ARRAY_SIZED (4, langSys);
+};
+
+struct RecordListOfScript : RecordListOf<Script>
+{
+  bool subset (hb_subset_context_t *c,
+               hb_subset_layout_context_t *l) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->serializer->start_embed (*this);
+    if (unlikely (!out || !c->serializer->extend_min (out))) return_trace (false);
+
+    for (auto _ : + hb_enumerate (*this))
+    {
+      auto snap = c->serializer->snapshot ();
+      l->cur_script_index = _.first;
+      bool ret = _.second.subset (l, this);
+      if (!ret) c->serializer->revert (snap);
+      else out->len++;
+    }
+
+    return_trace (true);
+  }
+};
+
+typedef RecordListOfScript ScriptList;
+
+
+
+struct LookupFlag : HBUINT16
+{
+  enum Flags {
+    RightToLeft		= 0x0001u,
+    IgnoreBaseGlyphs	= 0x0002u,
+    IgnoreLigatures	= 0x0004u,
+    IgnoreMarks		= 0x0008u,
+    IgnoreFlags		= 0x000Eu,
+    UseMarkFilteringSet	= 0x0010u,
+    Reserved		= 0x00E0u,
+    MarkAttachmentType	= 0xFF00u
+  };
+  public:
+  DEFINE_SIZE_STATIC (2);
+};
+
+} /* namespace OT */
+/* This has to be outside the namespace. */
+HB_MARK_AS_FLAG_T (OT::LookupFlag::Flags);
+namespace OT {
+
+struct Lookup
+{
+  unsigned int get_subtable_count () const { return subTable.len; }
+
+  template <typename TSubTable>
+  const Array16OfOffset16To<TSubTable>& get_subtables () const
+  { return reinterpret_cast<const Array16OfOffset16To<TSubTable> &> (subTable); }
+  template <typename TSubTable>
+  Array16OfOffset16To<TSubTable>& get_subtables ()
+  { return reinterpret_cast<Array16OfOffset16To<TSubTable> &> (subTable); }
+
+  template <typename TSubTable>
+  const TSubTable& get_subtable (unsigned int i) const
+  { return this+get_subtables<TSubTable> ()[i]; }
+  template <typename TSubTable>
+  TSubTable& get_subtable (unsigned int i)
+  { return this+get_subtables<TSubTable> ()[i]; }
+
+  unsigned int get_size () const
+  {
+    const HBUINT16 &markFilteringSet = StructAfter<const HBUINT16> (subTable);
+    if (lookupFlag & LookupFlag::UseMarkFilteringSet)
+      return (const char *) &StructAfter<const char> (markFilteringSet) - (const char *) this;
+    return (const char *) &markFilteringSet - (const char *) this;
+  }
+
+  unsigned int get_type () const { return lookupType; }
+
+  /* lookup_props is a 32-bit integer where the lower 16-bit is LookupFlag and
+   * higher 16-bit is mark-filtering-set if the lookup uses one.
+   * Not to be confused with glyph_props which is very similar. */
+  uint32_t get_props () const
+  {
+    unsigned int flag = lookupFlag;
+    if (unlikely (flag & LookupFlag::UseMarkFilteringSet))
+    {
+      const HBUINT16 &markFilteringSet = StructAfter<HBUINT16> (subTable);
+      flag += (markFilteringSet << 16);
+    }
+    return flag;
+  }
+
+  template <typename TSubTable, typename context_t, typename ...Ts>
+  typename context_t::return_t dispatch (context_t *c, Ts&&... ds) const
+  {
+    unsigned int lookup_type = get_type ();
+    TRACE_DISPATCH (this, lookup_type);
+    unsigned int count = get_subtable_count ();
+    for (unsigned int i = 0; i < count; i++) {
+      typename context_t::return_t r = get_subtable<TSubTable> (i).dispatch (c, lookup_type, std::forward<Ts> (ds)...);
+      if (c->stop_sublookup_iteration (r))
+	return_trace (r);
+    }
+    return_trace (c->default_return_value ());
+  }
+
+  bool serialize (hb_serialize_context_t *c,
+		  unsigned int lookup_type,
+		  uint32_t lookup_props,
+		  unsigned int num_subtables)
+  {
+    TRACE_SERIALIZE (this);
+    if (unlikely (!c->extend_min (this))) return_trace (false);
+    lookupType = lookup_type;
+    lookupFlag = lookup_props & 0xFFFFu;
+    if (unlikely (!subTable.serialize (c, num_subtables))) return_trace (false);
+    if (lookupFlag & LookupFlag::UseMarkFilteringSet)
+    {
+      if (unlikely (!c->extend (this))) return_trace (false);
+      HBUINT16 &markFilteringSet = StructAfter<HBUINT16> (subTable);
+      markFilteringSet = lookup_props >> 16;
+    }
+    return_trace (true);
+  }
+
+  template <typename TSubTable>
+  bool subset (hb_subset_context_t *c) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->serializer->start_embed (*this);
+    if (unlikely (!out || !c->serializer->extend_min (out))) return_trace (false);
+    out->lookupType = lookupType;
+    out->lookupFlag = lookupFlag;
+
+    const hb_set_t *glyphset = c->plan->glyphset_gsub ();
+    unsigned int lookup_type = get_type ();
+    + hb_iter (get_subtables <TSubTable> ())
+    | hb_filter ([this, glyphset, lookup_type] (const Offset16To<TSubTable> &_) { return (this+_).intersects (glyphset, lookup_type); })
+    | hb_apply (subset_offset_array (c, out->get_subtables<TSubTable> (), this, lookup_type))
+    ;
+
+    if (lookupFlag & LookupFlag::UseMarkFilteringSet)
+    {
+      if (unlikely (!c->serializer->extend (out))) return_trace (false);
+      const HBUINT16 &markFilteringSet = StructAfter<HBUINT16> (subTable);
+      HBUINT16 &outMarkFilteringSet = StructAfter<HBUINT16> (out->subTable);
+      outMarkFilteringSet = markFilteringSet;
+    }
+
+    // Always keep the lookup even if it's empty. The rest of layout subsetting depends on lookup
+    // indices being consistent with those computed during planning. So if an empty lookup is
+    // discarded during the subset phase it will invalidate all subsequent lookup indices.
+    // Generally we shouldn't end up with an empty lookup as we pre-prune them during the planning
+    // phase, but it can happen in rare cases such as when during closure subtable is considered
+    // degenerate (see: https://github.com/harfbuzz/harfbuzz/issues/3853)
+    return true;
+  }
+
+  template <typename TSubTable>
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    if (!(c->check_struct (this) && subTable.sanitize (c))) return_trace (false);
+
+    unsigned subtables = get_subtable_count ();
+    if (unlikely (!c->visit_subtables (subtables))) return_trace (false);
+
+    if (lookupFlag & LookupFlag::UseMarkFilteringSet)
+    {
+      const HBUINT16 &markFilteringSet = StructAfter<HBUINT16> (subTable);
+      if (!markFilteringSet.sanitize (c)) return_trace (false);
+    }
+
+    if (unlikely (!get_subtables<TSubTable> ().sanitize (c, this, get_type ())))
+      return_trace (false);
+
+    if (unlikely (get_type () == TSubTable::Extension && !c->get_edit_count ()))
+    {
+      /* The spec says all subtables of an Extension lookup should
+       * have the same type, which shall not be the Extension type
+       * itself (but we already checked for that).
+       * This is specially important if one has a reverse type!
+       *
+       * We only do this if sanitizer edit_count is zero.  Otherwise,
+       * some of the subtables might have become insane after they
+       * were sanity-checked by the edits of subsequent subtables.
+       * https://bugs.chromium.org/p/chromium/issues/detail?id=960331
+       */
+      unsigned int type = get_subtable<TSubTable> (0).u.extension.get_type ();
+      for (unsigned int i = 1; i < subtables; i++)
+	if (get_subtable<TSubTable> (i).u.extension.get_type () != type)
+	  return_trace (false);
+    }
+    return_trace (true);
+  }
+
+  protected:
+  HBUINT16	lookupType;		/* Different enumerations for GSUB and GPOS */
+  HBUINT16	lookupFlag;		/* Lookup qualifiers */
+  Array16Of<Offset16>
+		subTable;		/* Array of SubTables */
+/*HBUINT16	markFilteringSetX[HB_VAR_ARRAY];*//* Index (base 0) into GDEF mark glyph sets
+					 * structure. This field is only present if bit
+					 * UseMarkFilteringSet of lookup flags is set. */
+  public:
+  DEFINE_SIZE_ARRAY (6, subTable);
+};
+
+template <typename Types>
+using LookupList = List16OfOffsetTo<Lookup, typename Types::HBUINT>;
+
+template <typename TLookup, typename OffsetType>
+struct LookupOffsetList : List16OfOffsetTo<TLookup, OffsetType>
+{
+  bool subset (hb_subset_context_t        *c,
+	       hb_subset_layout_context_t *l) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->serializer->start_embed (this);
+    if (unlikely (!out || !c->serializer->extend_min (out))) return_trace (false);
+
+    + hb_enumerate (*this)
+    | hb_filter (l->lookup_index_map, hb_first)
+    | hb_map (hb_second)
+    | hb_apply (subset_offset_array (c, *out, this))
+    ;
+    return_trace (true);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (List16OfOffset16To<TLookup>::sanitize (c, this));
+  }
+};
+
+
+/*
+ * Coverage Table
+ */
+
+
+static bool ClassDef_remap_and_serialize (hb_serialize_context_t *c,
+					  const hb_set_t &klasses,
+                                          bool use_class_zero,
+                                          hb_sorted_vector_t<hb_pair_t<hb_codepoint_t, hb_codepoint_t>> &glyph_and_klass, /* IN/OUT */
+					  hb_map_t *klass_map /*IN/OUT*/)
+{
+  if (!klass_map)
+    return ClassDef_serialize (c, glyph_and_klass.iter ());
+
+  /* any glyph not assigned a class value falls into Class zero (0),
+   * if any glyph assigned to class 0, remapping must start with 0->0*/
+  if (!use_class_zero)
+    klass_map->set (0, 0);
+
+  unsigned idx = klass_map->has (0) ? 1 : 0;
+  for (const unsigned k: klasses)
+  {
+    if (klass_map->has (k)) continue;
+    klass_map->set (k, idx);
+    idx++;
+  }
+
+
+  for (unsigned i = 0; i < glyph_and_klass.length; i++)
+  {
+    hb_codepoint_t klass = glyph_and_klass[i].second;
+    glyph_and_klass[i].second = klass_map->get (klass);
+  }
+
+  c->propagate_error (glyph_and_klass, klasses);
+  return ClassDef_serialize (c, glyph_and_klass.iter ());
+}
+
+/*
+ * Class Definition Table
+ */
+
+template <typename Types>
+struct ClassDefFormat1_3
+{
+  friend struct ClassDef;
+
+  private:
+  unsigned int get_class (hb_codepoint_t glyph_id) const
+  {
+    return classValue[(unsigned int) (glyph_id - startGlyph)];
+  }
+
+  unsigned get_population () const
+  {
+    return classValue.len;
+  }
+
+  template<typename Iterator,
+	   hb_requires (hb_is_sorted_source_of (Iterator, hb_codepoint_t))>
+  bool serialize (hb_serialize_context_t *c,
+		  Iterator it)
+  {
+    TRACE_SERIALIZE (this);
+    if (unlikely (!c->extend_min (this))) return_trace (false);
+
+    if (unlikely (!it))
+    {
+      classFormat = 1;
+      startGlyph = 0;
+      classValue.len = 0;
+      return_trace (true);
+    }
+
+    hb_codepoint_t glyph_min = (*it).first;
+    hb_codepoint_t glyph_max = + it
+			       | hb_map (hb_first)
+			       | hb_reduce (hb_max, 0u);
+    unsigned glyph_count = glyph_max - glyph_min + 1;
+
+    startGlyph = glyph_min;
+    if (unlikely (!classValue.serialize (c, glyph_count))) return_trace (false);
+    for (const hb_pair_t<hb_codepoint_t, uint32_t> gid_klass_pair : + it)
+    {
+      unsigned idx = gid_klass_pair.first - glyph_min;
+      classValue[idx] = gid_klass_pair.second;
+    }
+    return_trace (true);
+  }
+
+  bool subset (hb_subset_context_t *c,
+	       hb_map_t *klass_map = nullptr /*OUT*/,
+               bool keep_empty_table = true,
+               bool use_class_zero = true,
+               const Coverage* glyph_filter = nullptr) const
+  {
+    TRACE_SUBSET (this);
+    const hb_map_t &glyph_map = *c->plan->glyph_map_gsub;
+
+    hb_sorted_vector_t<hb_pair_t<hb_codepoint_t, hb_codepoint_t>> glyph_and_klass;
+    hb_set_t orig_klasses;
+
+    hb_codepoint_t start = startGlyph;
+    hb_codepoint_t end   = start + classValue.len;
+
+    for (const hb_codepoint_t gid : + hb_range (start, end))
+    {
+      hb_codepoint_t new_gid = glyph_map[gid];
+      if (new_gid == HB_MAP_VALUE_INVALID) continue;
+      if (glyph_filter && !glyph_filter->has(gid)) continue;
+
+      unsigned klass = classValue[gid - start];
+      if (!klass) continue;
+
+      glyph_and_klass.push (hb_pair (new_gid, klass));
+      orig_klasses.add (klass);
+    }
+
+    unsigned glyph_count = glyph_filter
+                           ? hb_len (hb_iter (glyph_map.keys()) | hb_filter (glyph_filter))
+                           : glyph_map.get_population ();
+    use_class_zero = use_class_zero && glyph_count <= glyph_and_klass.length;
+    if (!ClassDef_remap_and_serialize (c->serializer,
+                                       orig_klasses,
+                                       use_class_zero,
+                                       glyph_and_klass,
+                                       klass_map))
+      return_trace (false);
+    return_trace (keep_empty_table || (bool) glyph_and_klass);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this) && classValue.sanitize (c));
+  }
+
+  unsigned cost () const { return 1; }
+
+  template <typename set_t>
+  bool collect_coverage (set_t *glyphs) const
+  {
+    unsigned int start = 0;
+    unsigned int count = classValue.len;
+    for (unsigned int i = 0; i < count; i++)
+    {
+      if (classValue[i])
+	continue;
+
+      if (start != i)
+	if (unlikely (!glyphs->add_range (startGlyph + start, startGlyph + i)))
+	  return false;
+
+      start = i + 1;
+    }
+    if (start != count)
+      if (unlikely (!glyphs->add_range (startGlyph + start, startGlyph + count)))
+	return false;
+
+    return true;
+  }
+
+  template <typename set_t>
+  bool collect_class (set_t *glyphs, unsigned klass) const
+  {
+    unsigned int count = classValue.len;
+    for (unsigned int i = 0; i < count; i++)
+      if (classValue[i] == klass) glyphs->add (startGlyph + i);
+    return true;
+  }
+
+  bool intersects (const hb_set_t *glyphs) const
+  {
+    hb_codepoint_t start = startGlyph;
+    hb_codepoint_t end = startGlyph + classValue.len;
+    for (hb_codepoint_t iter = startGlyph - 1;
+	 glyphs->next (&iter) && iter < end;)
+      if (classValue[iter - start]) return true;
+    return false;
+  }
+  bool intersects_class (const hb_set_t *glyphs, uint16_t klass) const
+  {
+    unsigned int count = classValue.len;
+    if (klass == 0)
+    {
+      /* Match if there's any glyph that is not listed! */
+      hb_codepoint_t g = HB_SET_VALUE_INVALID;
+      if (!glyphs->next (&g)) return false;
+      if (g < startGlyph) return true;
+      g = startGlyph + count - 1;
+      if (glyphs->next (&g)) return true;
+      /* Fall through. */
+    }
+    /* TODO Speed up, using set overlap first? */
+    /* TODO(iter) Rewrite as dagger. */
+    const HBUINT16 *arr = classValue.arrayZ;
+    for (unsigned int i = 0; i < count; i++)
+      if (arr[i] == klass && glyphs->has (startGlyph + i))
+	return true;
+    return false;
+  }
+
+  void intersected_class_glyphs (const hb_set_t *glyphs, unsigned klass, hb_set_t *intersect_glyphs) const
+  {
+    unsigned count = classValue.len;
+    if (klass == 0)
+    {
+      unsigned start_glyph = startGlyph;
+      for (uint32_t g = HB_SET_VALUE_INVALID;
+	   glyphs->next (&g) && g < start_glyph;)
+	intersect_glyphs->add (g);
+
+      for (uint32_t g = startGlyph + count - 1;
+	   glyphs-> next (&g);)
+	intersect_glyphs->add (g);
+
+      return;
+    }
+
+    for (unsigned i = 0; i < count; i++)
+      if (classValue[i] == klass && glyphs->has (startGlyph + i))
+	intersect_glyphs->add (startGlyph + i);
+
+#if 0
+    /* The following implementation is faster asymptotically, but slower
+     * in practice. */
+    unsigned start_glyph = startGlyph;
+    unsigned end_glyph = start_glyph + count;
+    for (unsigned g = startGlyph - 1;
+	 glyphs->next (&g) && g < end_glyph;)
+      if (classValue.arrayZ[g - start_glyph] == klass)
+        intersect_glyphs->add (g);
+#endif
+  }
+
+  void intersected_classes (const hb_set_t *glyphs, hb_set_t *intersect_classes) const
+  {
+    if (glyphs->is_empty ()) return;
+    hb_codepoint_t end_glyph = startGlyph + classValue.len - 1;
+    if (glyphs->get_min () < startGlyph ||
+        glyphs->get_max () > end_glyph)
+      intersect_classes->add (0);
+
+    for (const auto& _ : + hb_enumerate (classValue))
+    {
+      hb_codepoint_t g = startGlyph + _.first;
+      if (glyphs->has (g))
+        intersect_classes->add (_.second);
+    }
+  }
+
+  protected:
+  HBUINT16	classFormat;	/* Format identifier--format = 1 */
+  typename Types::HBGlyphID
+		 startGlyph;	/* First GlyphID of the classValueArray */
+  typename Types::template ArrayOf<HBUINT16>
+		classValue;	/* Array of Class Values--one per GlyphID */
+  public:
+  DEFINE_SIZE_ARRAY (2 + 2 * Types::size, classValue);
+};
+
+template <typename Types>
+struct ClassDefFormat2_4
+{
+  friend struct ClassDef;
+
+  private:
+  unsigned int get_class (hb_codepoint_t glyph_id) const
+  {
+    return rangeRecord.bsearch (glyph_id).value;
+  }
+
+  unsigned get_population () const
+  {
+    typename Types::large_int ret = 0;
+    for (const auto &r : rangeRecord)
+      ret += r.get_population ();
+    return ret > UINT_MAX ? UINT_MAX : (unsigned) ret;
+  }
+
+  template<typename Iterator,
+	   hb_requires (hb_is_sorted_source_of (Iterator, hb_codepoint_t))>
+  bool serialize (hb_serialize_context_t *c,
+		  Iterator it)
+  {
+    TRACE_SERIALIZE (this);
+    if (unlikely (!c->extend_min (this))) return_trace (false);
+
+    if (unlikely (!it))
+    {
+      classFormat = 2;
+      rangeRecord.len = 0;
+      return_trace (true);
+    }
+
+    unsigned num_ranges = 1;
+    hb_codepoint_t prev_gid = (*it).first;
+    unsigned prev_klass = (*it).second;
+
+    RangeRecord<Types> range_rec;
+    range_rec.first = prev_gid;
+    range_rec.last = prev_gid;
+    range_rec.value = prev_klass;
+
+    auto *record = c->copy (range_rec);
+    if (unlikely (!record)) return_trace (false);
+
+    for (const auto gid_klass_pair : + (++it))
+    {
+      hb_codepoint_t cur_gid = gid_klass_pair.first;
+      unsigned cur_klass = gid_klass_pair.second;
+
+      if (cur_gid != prev_gid + 1 ||
+	  cur_klass != prev_klass)
+      {
+	if (unlikely (!record)) break;
+	record->last = prev_gid;
+	num_ranges++;
+
+	range_rec.first = cur_gid;
+	range_rec.last = cur_gid;
+	range_rec.value = cur_klass;
+
+	record = c->copy (range_rec);
+      }
+
+      prev_klass = cur_klass;
+      prev_gid = cur_gid;
+    }
+
+    if (likely (record)) record->last = prev_gid;
+    rangeRecord.len = num_ranges;
+    return_trace (true);
+  }
+
+  bool subset (hb_subset_context_t *c,
+	       hb_map_t *klass_map = nullptr /*OUT*/,
+               bool keep_empty_table = true,
+               bool use_class_zero = true,
+               const Coverage* glyph_filter = nullptr) const
+  {
+    TRACE_SUBSET (this);
+    const hb_map_t &glyph_map = *c->plan->glyph_map_gsub;
+    const hb_set_t &glyph_set = *c->plan->glyphset_gsub ();
+
+    hb_sorted_vector_t<hb_pair_t<hb_codepoint_t, hb_codepoint_t>> glyph_and_klass;
+    hb_set_t orig_klasses;
+
+    if (glyph_set.get_population () * hb_bit_storage ((unsigned) rangeRecord.len) / 2
+	< get_population ())
+    {
+      for (hb_codepoint_t g : glyph_set)
+      {
+	unsigned klass = get_class (g);
+	if (!klass) continue;
+	hb_codepoint_t new_gid = glyph_map[g];
+	if (new_gid == HB_MAP_VALUE_INVALID) continue;
+	if (glyph_filter && !glyph_filter->has (g)) continue;
+	glyph_and_klass.push (hb_pair (new_gid, klass));
+	orig_klasses.add (klass);
+      }
+    }
+    else
+    {
+      unsigned num_source_glyphs = c->plan->source->get_num_glyphs ();
+      for (auto &range : rangeRecord)
+      {
+	unsigned klass = range.value;
+	if (!klass) continue;
+	hb_codepoint_t start = range.first;
+	hb_codepoint_t end   = hb_min (range.last + 1, num_source_glyphs);
+	for (hb_codepoint_t g = start; g < end; g++)
+	{
+	  hb_codepoint_t new_gid = glyph_map[g];
+	  if (new_gid == HB_MAP_VALUE_INVALID) continue;
+	  if (glyph_filter && !glyph_filter->has (g)) continue;
+
+	  glyph_and_klass.push (hb_pair (new_gid, klass));
+	  orig_klasses.add (klass);
+	}
+      }
+    }
+
+    const hb_set_t& glyphset = *c->plan->glyphset_gsub ();
+    unsigned glyph_count = glyph_filter
+                           ? hb_len (hb_iter (glyphset) | hb_filter (glyph_filter))
+                           : glyph_map.get_population ();
+    use_class_zero = use_class_zero && glyph_count <= glyph_and_klass.length;
+    if (!ClassDef_remap_and_serialize (c->serializer,
+                                       orig_klasses,
+                                       use_class_zero,
+                                       glyph_and_klass,
+                                       klass_map))
+      return_trace (false);
+    return_trace (keep_empty_table || (bool) glyph_and_klass);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (rangeRecord.sanitize (c));
+  }
+
+  unsigned cost () const { return hb_bit_storage ((unsigned) rangeRecord.len); /* bsearch cost */ }
+
+  template <typename set_t>
+  bool collect_coverage (set_t *glyphs) const
+  {
+    for (auto &range : rangeRecord)
+      if (range.value)
+	if (unlikely (!range.collect_coverage (glyphs)))
+	  return false;
+    return true;
+  }
+
+  template <typename set_t>
+  bool collect_class (set_t *glyphs, unsigned int klass) const
+  {
+    for (auto &range : rangeRecord)
+    {
+      if (range.value == klass)
+	if (unlikely (!range.collect_coverage (glyphs)))
+	  return false;
+    }
+    return true;
+  }
+
+  bool intersects (const hb_set_t *glyphs) const
+  {
+    if (rangeRecord.len > glyphs->get_population () * hb_bit_storage ((unsigned) rangeRecord.len) / 2)
+    {
+      for (hb_codepoint_t g = HB_SET_VALUE_INVALID; glyphs->next (&g);)
+        if (get_class (g))
+	  return true;
+      return false;
+    }
+
+    return hb_any (+ hb_iter (rangeRecord)
+                   | hb_map ([glyphs] (const RangeRecord<Types> &range) { return range.intersects (*glyphs) && range.value; }));
+  }
+  bool intersects_class (const hb_set_t *glyphs, uint16_t klass) const
+  {
+    if (klass == 0)
+    {
+      /* Match if there's any glyph that is not listed! */
+      hb_codepoint_t g = HB_SET_VALUE_INVALID;
+      for (auto &range : rangeRecord)
+      {
+	if (!glyphs->next (&g))
+	  break;
+	if (g < range.first)
+	  return true;
+	g = range.last;
+      }
+      if (g != HB_SET_VALUE_INVALID && glyphs->next (&g))
+	return true;
+      /* Fall through. */
+    }
+    for (const auto &range : rangeRecord)
+      if (range.value == klass && range.intersects (*glyphs))
+	return true;
+    return false;
+  }
+
+  void intersected_class_glyphs (const hb_set_t *glyphs, unsigned klass, hb_set_t *intersect_glyphs) const
+  {
+    if (klass == 0)
+    {
+      hb_codepoint_t g = HB_SET_VALUE_INVALID;
+      for (auto &range : rangeRecord)
+      {
+	if (!glyphs->next (&g))
+	  goto done;
+	while (g < range.first)
+	{
+	  intersect_glyphs->add (g);
+	  if (!glyphs->next (&g))
+	    goto done;
+        }
+        g = range.last;
+      }
+      while (glyphs->next (&g))
+	intersect_glyphs->add (g);
+      done:
+
+      return;
+    }
+
+    unsigned count = rangeRecord.len;
+    if (count > glyphs->get_population () * hb_bit_storage (count) * 8)
+    {
+      for (hb_codepoint_t g = HB_SET_VALUE_INVALID;
+	   glyphs->next (&g);)
+      {
+        unsigned i;
+        if (rangeRecord.as_array ().bfind (g, &i) &&
+	    rangeRecord.arrayZ[i].value == klass)
+	  intersect_glyphs->add (g);
+      }
+      return;
+    }
+
+    for (auto &range : rangeRecord)
+    {
+      if (range.value != klass) continue;
+
+      unsigned end = range.last + 1;
+      for (hb_codepoint_t g = range.first - 1;
+	   glyphs->next (&g) && g < end;)
+	intersect_glyphs->add (g);
+    }
+  }
+
+  void intersected_classes (const hb_set_t *glyphs, hb_set_t *intersect_classes) const
+  {
+    if (glyphs->is_empty ()) return;
+
+    hb_codepoint_t g = HB_SET_VALUE_INVALID;
+    for (auto &range : rangeRecord)
+    {
+      if (!glyphs->next (&g))
+        break;
+      if (g < range.first)
+      {
+        intersect_classes->add (0);
+        break;
+      }
+      g = range.last;
+    }
+    if (g != HB_SET_VALUE_INVALID && glyphs->next (&g))
+      intersect_classes->add (0);
+
+    for (const auto& range : rangeRecord)
+      if (range.intersects (*glyphs))
+        intersect_classes->add (range.value);
+  }
+
+  protected:
+  HBUINT16	classFormat;	/* Format identifier--format = 2 */
+  typename Types::template SortedArrayOf<RangeRecord<Types>>
+		rangeRecord;	/* Array of glyph ranges--ordered by
+				 * Start GlyphID */
+  public:
+  DEFINE_SIZE_ARRAY (2 + Types::size, rangeRecord);
+};
+
+struct ClassDef
+{
+  /* Has interface. */
+  unsigned operator [] (hb_codepoint_t k) const { return get (k); }
+  bool has (hb_codepoint_t k) const { return (*this)[k]; }
+  /* Projection. */
+  hb_codepoint_t operator () (hb_codepoint_t k) const { return get (k); }
+
+  unsigned int get (hb_codepoint_t k) const { return get_class (k); }
+  unsigned int get_class (hb_codepoint_t glyph_id) const
+  {
+    switch (u.format) {
+    case 1: return u.format1.get_class (glyph_id);
+    case 2: return u.format2.get_class (glyph_id);
+#ifndef HB_NO_BEYOND_64K
+    case 3: return u.format3.get_class (glyph_id);
+    case 4: return u.format4.get_class (glyph_id);
+#endif
+    default:return 0;
+    }
+  }
+
+  unsigned get_population () const
+  {
+    switch (u.format) {
+    case 1: return u.format1.get_population ();
+    case 2: return u.format2.get_population ();
+#ifndef HB_NO_BEYOND_64K
+    case 3: return u.format3.get_population ();
+    case 4: return u.format4.get_population ();
+#endif
+    default:return NOT_COVERED;
+    }
+  }
+
+  template<typename Iterator,
+	   hb_requires (hb_is_sorted_source_of (Iterator, hb_codepoint_t))>
+  bool serialize (hb_serialize_context_t *c, Iterator it_with_class_zero)
+  {
+    TRACE_SERIALIZE (this);
+    if (unlikely (!c->extend_min (this))) return_trace (false);
+
+    auto it = + it_with_class_zero | hb_filter (hb_second);
+
+    unsigned format = 2;
+    hb_codepoint_t glyph_max = 0;
+    if (likely (it))
+    {
+      hb_codepoint_t glyph_min = (*it).first;
+      glyph_max = glyph_min;
+
+      unsigned num_glyphs = 0;
+      unsigned num_ranges = 1;
+      hb_codepoint_t prev_gid = glyph_min;
+      unsigned prev_klass = (*it).second;
+
+      for (const auto gid_klass_pair : it)
+      {
+	hb_codepoint_t cur_gid = gid_klass_pair.first;
+	unsigned cur_klass = gid_klass_pair.second;
+        num_glyphs++;
+	if (cur_gid == glyph_min) continue;
+        if (cur_gid > glyph_max) glyph_max = cur_gid;
+	if (cur_gid != prev_gid + 1 ||
+	    cur_klass != prev_klass)
+	  num_ranges++;
+
+	prev_gid = cur_gid;
+	prev_klass = cur_klass;
+      }
+
+      if (num_glyphs && 1 + (glyph_max - glyph_min + 1) <= num_ranges * 3)
+	format = 1;
+    }
+
+#ifndef HB_NO_BEYOND_64K
+    if (glyph_max > 0xFFFFu)
+      format += 2;
+#endif
+
+    u.format = format;
+
+    switch (u.format)
+    {
+    case 1: return_trace (u.format1.serialize (c, it));
+    case 2: return_trace (u.format2.serialize (c, it));
+#ifndef HB_NO_BEYOND_64K
+    case 3: return_trace (u.format3.serialize (c, it));
+    case 4: return_trace (u.format4.serialize (c, it));
+#endif
+    default:return_trace (false);
+    }
+  }
+
+  bool subset (hb_subset_context_t *c,
+	       hb_map_t *klass_map = nullptr /*OUT*/,
+               bool keep_empty_table = true,
+               bool use_class_zero = true,
+               const Coverage* glyph_filter = nullptr) const
+  {
+    TRACE_SUBSET (this);
+    switch (u.format) {
+    case 1: return_trace (u.format1.subset (c, klass_map, keep_empty_table, use_class_zero, glyph_filter));
+    case 2: return_trace (u.format2.subset (c, klass_map, keep_empty_table, use_class_zero, glyph_filter));
+#ifndef HB_NO_BEYOND_64K
+    case 3: return_trace (u.format3.subset (c, klass_map, keep_empty_table, use_class_zero, glyph_filter));
+    case 4: return_trace (u.format4.subset (c, klass_map, keep_empty_table, use_class_zero, glyph_filter));
+#endif
+    default:return_trace (false);
+    }
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    if (!u.format.sanitize (c)) return_trace (false);
+    switch (u.format) {
+    case 1: return_trace (u.format1.sanitize (c));
+    case 2: return_trace (u.format2.sanitize (c));
+#ifndef HB_NO_BEYOND_64K
+    case 3: return_trace (u.format3.sanitize (c));
+    case 4: return_trace (u.format4.sanitize (c));
+#endif
+    default:return_trace (true);
+    }
+  }
+
+  unsigned cost () const
+  {
+    switch (u.format) {
+    case 1: return u.format1.cost ();
+    case 2: return u.format2.cost ();
+#ifndef HB_NO_BEYOND_64K
+    case 3: return u.format3.cost ();
+    case 4: return u.format4.cost ();
+#endif
+    default:return 0u;
+    }
+  }
+
+  /* Might return false if array looks unsorted.
+   * Used for faster rejection of corrupt data. */
+  template <typename set_t>
+  bool collect_coverage (set_t *glyphs) const
+  {
+    switch (u.format) {
+    case 1: return u.format1.collect_coverage (glyphs);
+    case 2: return u.format2.collect_coverage (glyphs);
+#ifndef HB_NO_BEYOND_64K
+    case 3: return u.format3.collect_coverage (glyphs);
+    case 4: return u.format4.collect_coverage (glyphs);
+#endif
+    default:return false;
+    }
+  }
+
+  /* Might return false if array looks unsorted.
+   * Used for faster rejection of corrupt data. */
+  template <typename set_t>
+  bool collect_class (set_t *glyphs, unsigned int klass) const
+  {
+    switch (u.format) {
+    case 1: return u.format1.collect_class (glyphs, klass);
+    case 2: return u.format2.collect_class (glyphs, klass);
+#ifndef HB_NO_BEYOND_64K
+    case 3: return u.format3.collect_class (glyphs, klass);
+    case 4: return u.format4.collect_class (glyphs, klass);
+#endif
+    default:return false;
+    }
+  }
+
+  bool intersects (const hb_set_t *glyphs) const
+  {
+    switch (u.format) {
+    case 1: return u.format1.intersects (glyphs);
+    case 2: return u.format2.intersects (glyphs);
+#ifndef HB_NO_BEYOND_64K
+    case 3: return u.format3.intersects (glyphs);
+    case 4: return u.format4.intersects (glyphs);
+#endif
+    default:return false;
+    }
+  }
+  bool intersects_class (const hb_set_t *glyphs, unsigned int klass) const
+  {
+    switch (u.format) {
+    case 1: return u.format1.intersects_class (glyphs, klass);
+    case 2: return u.format2.intersects_class (glyphs, klass);
+#ifndef HB_NO_BEYOND_64K
+    case 3: return u.format3.intersects_class (glyphs, klass);
+    case 4: return u.format4.intersects_class (glyphs, klass);
+#endif
+    default:return false;
+    }
+  }
+
+  void intersected_class_glyphs (const hb_set_t *glyphs, unsigned klass, hb_set_t *intersect_glyphs) const
+  {
+    switch (u.format) {
+    case 1: return u.format1.intersected_class_glyphs (glyphs, klass, intersect_glyphs);
+    case 2: return u.format2.intersected_class_glyphs (glyphs, klass, intersect_glyphs);
+#ifndef HB_NO_BEYOND_64K
+    case 3: return u.format3.intersected_class_glyphs (glyphs, klass, intersect_glyphs);
+    case 4: return u.format4.intersected_class_glyphs (glyphs, klass, intersect_glyphs);
+#endif
+    default:return;
+    }
+  }
+
+  void intersected_classes (const hb_set_t *glyphs, hb_set_t *intersect_classes) const
+  {
+    switch (u.format) {
+    case 1: return u.format1.intersected_classes (glyphs, intersect_classes);
+    case 2: return u.format2.intersected_classes (glyphs, intersect_classes);
+#ifndef HB_NO_BEYOND_64K
+    case 3: return u.format3.intersected_classes (glyphs, intersect_classes);
+    case 4: return u.format4.intersected_classes (glyphs, intersect_classes);
+#endif
+    default:return;
+    }
+  }
+
+
+  protected:
+  union {
+  HBUINT16			format;		/* Format identifier */
+  ClassDefFormat1_3<SmallTypes>	format1;
+  ClassDefFormat2_4<SmallTypes>	format2;
+#ifndef HB_NO_BEYOND_64K
+  ClassDefFormat1_3<MediumTypes>format3;
+  ClassDefFormat2_4<MediumTypes>format4;
+#endif
+  } u;
+  public:
+  DEFINE_SIZE_UNION (2, format);
+};
+
+template<typename Iterator>
+static inline bool ClassDef_serialize (hb_serialize_context_t *c,
+				       Iterator it)
+{ return (c->start_embed<ClassDef> ()->serialize (c, it)); }
+
+
+/*
+ * Item Variation Store
+ */
+
+struct VarRegionAxis
+{
+  float evaluate (int coord) const
+  {
+    int start = startCoord, peak = peakCoord, end = endCoord;
+
+    /* TODO Move these to sanitize(). */
+    if (unlikely (start > peak || peak > end))
+      return 1.;
+    if (unlikely (start < 0 && end > 0 && peak != 0))
+      return 1.;
+
+    if (peak == 0 || coord == peak)
+      return 1.;
+
+    if (coord <= start || end <= coord)
+      return 0.;
+
+    /* Interpolate */
+    if (coord < peak)
+      return float (coord - start) / (peak - start);
+    else
+      return float (end - coord) / (end - peak);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this));
+    /* TODO Handle invalid start/peak/end configs, so we don't
+     * have to do that at runtime. */
+  }
+
+  public:
+  F2DOT14	startCoord;
+  F2DOT14	peakCoord;
+  F2DOT14	endCoord;
+  public:
+  DEFINE_SIZE_STATIC (6);
+};
+
+#define REGION_CACHE_ITEM_CACHE_INVALID 2.f
+
+struct VarRegionList
+{
+  using cache_t = float;
+
+  float evaluate (unsigned int region_index,
+		  const int *coords, unsigned int coord_len,
+		  cache_t *cache = nullptr) const
+  {
+    if (unlikely (region_index >= regionCount))
+      return 0.;
+
+    float *cached_value = nullptr;
+    if (cache)
+    {
+      cached_value = &(cache[region_index]);
+      if (likely (*cached_value != REGION_CACHE_ITEM_CACHE_INVALID))
+	return *cached_value;
+    }
+
+    const VarRegionAxis *axes = axesZ.arrayZ + (region_index * axisCount);
+
+    float v = 1.;
+    unsigned int count = axisCount;
+    for (unsigned int i = 0; i < count; i++)
+    {
+      int coord = i < coord_len ? coords[i] : 0;
+      float factor = axes[i].evaluate (coord);
+      if (factor == 0.f)
+      {
+        if (cache)
+	  *cached_value = 0.;
+	return 0.;
+      }
+      v *= factor;
+    }
+
+    if (cache)
+      *cached_value = v;
+    return v;
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this) && axesZ.sanitize (c, axisCount * regionCount));
+  }
+
+  bool serialize (hb_serialize_context_t *c, const VarRegionList *src, const hb_bimap_t &region_map)
+  {
+    TRACE_SERIALIZE (this);
+    if (unlikely (!c->extend_min (this))) return_trace (false);
+    axisCount = src->axisCount;
+    regionCount = region_map.get_population ();
+    if (unlikely (hb_unsigned_mul_overflows (axisCount * regionCount,
+					     VarRegionAxis::static_size))) return_trace (false);
+    if (unlikely (!c->extend (this))) return_trace (false);
+    unsigned int region_count = src->regionCount;
+    for (unsigned int r = 0; r < regionCount; r++)
+    {
+      unsigned int backward = region_map.backward (r);
+      if (backward >= region_count) return_trace (false);
+      hb_memcpy (&axesZ[axisCount * r], &src->axesZ[axisCount * backward], VarRegionAxis::static_size * axisCount);
+    }
+
+    return_trace (true);
+  }
+
+  unsigned int get_size () const { return min_size + VarRegionAxis::static_size * axisCount * regionCount; }
+
+  public:
+  HBUINT16	axisCount;
+  HBUINT15	regionCount;
+  protected:
+  UnsizedArrayOf<VarRegionAxis>
+		axesZ;
+  public:
+  DEFINE_SIZE_ARRAY (4, axesZ);
+};
+
+struct VarData
+{
+  unsigned int get_region_index_count () const
+  { return regionIndices.len; }
+
+  unsigned int get_row_size () const
+  { return (wordCount () + regionIndices.len) * (longWords () ? 2 : 1); }
+
+  unsigned int get_size () const
+  { return min_size
+	 - regionIndices.min_size + regionIndices.get_size ()
+	 + itemCount * get_row_size ();
+  }
+
+  float get_delta (unsigned int inner,
+		   const int *coords, unsigned int coord_count,
+		   const VarRegionList &regions,
+		   VarRegionList::cache_t *cache = nullptr) const
+  {
+    if (unlikely (inner >= itemCount))
+      return 0.;
+
+   unsigned int count = regionIndices.len;
+   bool is_long = longWords ();
+   unsigned word_count = wordCount ();
+   unsigned int scount = is_long ? count : word_count;
+   unsigned int lcount = is_long ? word_count : 0;
+
+   const HBUINT8 *bytes = get_delta_bytes ();
+   const HBUINT8 *row = bytes + inner * get_row_size ();
+
+   float delta = 0.;
+   unsigned int i = 0;
+
+   const HBINT32 *lcursor = reinterpret_cast<const HBINT32 *> (row);
+   for (; i < lcount; i++)
+   {
+     float scalar = regions.evaluate (regionIndices.arrayZ[i], coords, coord_count, cache);
+     delta += scalar * *lcursor++;
+   }
+   const HBINT16 *scursor = reinterpret_cast<const HBINT16 *> (lcursor);
+   for (; i < scount; i++)
+   {
+     float scalar = regions.evaluate (regionIndices.arrayZ[i], coords, coord_count, cache);
+     delta += scalar * *scursor++;
+   }
+   const HBINT8 *bcursor = reinterpret_cast<const HBINT8 *> (scursor);
+   for (; i < count; i++)
+   {
+     float scalar = regions.evaluate (regionIndices.arrayZ[i], coords, coord_count, cache);
+     delta += scalar * *bcursor++;
+   }
+
+   return delta;
+  }
+
+  void get_region_scalars (const int *coords, unsigned int coord_count,
+			   const VarRegionList &regions,
+			   float *scalars /*OUT */,
+			   unsigned int num_scalars) const
+  {
+    unsigned count = hb_min (num_scalars, regionIndices.len);
+    for (unsigned int i = 0; i < count; i++)
+      scalars[i] = regions.evaluate (regionIndices.arrayZ[i], coords, coord_count);
+    for (unsigned int i = count; i < num_scalars; i++)
+      scalars[i] = 0.f;
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this) &&
+		  regionIndices.sanitize (c) &&
+		  wordCount () <= regionIndices.len &&
+		  c->check_range (get_delta_bytes (),
+				  itemCount,
+				  get_row_size ()));
+  }
+
+  bool serialize (hb_serialize_context_t *c,
+		  const VarData *src,
+		  const hb_inc_bimap_t &inner_map,
+		  const hb_bimap_t &region_map)
+  {
+    TRACE_SERIALIZE (this);
+    if (unlikely (!c->extend_min (this))) return_trace (false);
+    itemCount = inner_map.get_next_value ();
+
+    /* Optimize word count */
+    unsigned ri_count = src->regionIndices.len;
+    enum delta_size_t { kZero=0, kNonWord, kWord };
+    hb_vector_t<delta_size_t> delta_sz;
+    hb_vector_t<unsigned int> ri_map;	/* maps new index to old index */
+    delta_sz.resize (ri_count);
+    ri_map.resize (ri_count);
+    unsigned int new_word_count = 0;
+    unsigned int r;
+
+    const HBUINT8 *src_delta_bytes = src->get_delta_bytes ();
+    unsigned src_row_size = src->get_row_size ();
+    unsigned src_word_count = src->wordCount ();
+    bool     src_long_words = src->longWords ();
+
+    bool has_long = false;
+    if (src_long_words)
+    {
+      for (r = 0; r < src_word_count; r++)
+      {
+	for (unsigned int i = 0; i < inner_map.get_next_value (); i++)
+	{
+	  unsigned int old = inner_map.backward (i);
+	  int32_t delta = src->get_item_delta_fast (old, r, src_delta_bytes, src_row_size);
+	  if (delta < -65536 || 65535 < delta)
+	  {
+	    has_long = true;
+	    break;
+	  }
+        }
+      }
+    }
+
+    signed min_threshold = has_long ? -65536 : -128;
+    signed max_threshold = has_long ? +65535 : +127;
+    for (r = 0; r < ri_count; r++)
+    {
+      bool short_circuit = src_long_words == has_long && src_word_count <= r;
+
+      delta_sz[r] = kZero;
+      for (unsigned int i = 0; i < inner_map.get_next_value (); i++)
+      {
+	unsigned int old = inner_map.backward (i);
+	int32_t delta = src->get_item_delta_fast (old, r, src_delta_bytes, src_row_size);
+	if (delta < min_threshold || max_threshold < delta)
+	{
+	  delta_sz[r] = kWord;
+	  new_word_count++;
+	  break;
+	}
+	else if (delta != 0)
+	{
+	  delta_sz[r] = kNonWord;
+	  if (short_circuit)
+	    break;
+	}
+      }
+    }
+
+    unsigned int word_index = 0;
+    unsigned int non_word_index = new_word_count;
+    unsigned int new_ri_count = 0;
+    for (r = 0; r < ri_count; r++)
+      if (delta_sz[r])
+      {
+	unsigned new_r = (delta_sz[r] == kWord)? word_index++ : non_word_index++;
+	ri_map[new_r] = r;
+	new_ri_count++;
+      }
+
+    wordSizeCount = new_word_count | (has_long ? 0x8000u /* LONG_WORDS */ : 0);
+
+    regionIndices.len = new_ri_count;
+
+    if (unlikely (!c->extend (this))) return_trace (false);
+
+    for (r = 0; r < new_ri_count; r++)
+      regionIndices[r] = region_map[src->regionIndices[ri_map[r]]];
+
+    HBUINT8 *delta_bytes = get_delta_bytes ();
+    unsigned row_size = get_row_size ();
+    unsigned count = itemCount;
+    for (unsigned int i = 0; i < count; i++)
+    {
+      unsigned int old = inner_map.backward (i);
+      for (unsigned int r = 0; r < new_ri_count; r++)
+	set_item_delta_fast (i, r,
+			     src->get_item_delta_fast (old, ri_map[r],
+						       src_delta_bytes, src_row_size),
+			     delta_bytes, row_size);
+    }
+
+    return_trace (true);
+  }
+
+  void collect_region_refs (hb_set_t &region_indices, const hb_inc_bimap_t &inner_map) const
+  {
+    const HBUINT8 *delta_bytes = get_delta_bytes ();
+    unsigned row_size = get_row_size ();
+
+    for (unsigned int r = 0; r < regionIndices.len; r++)
+    {
+      unsigned int region = regionIndices.arrayZ[r];
+      if (region_indices.has (region)) continue;
+      for (unsigned int i = 0; i < inner_map.get_next_value (); i++)
+	if (get_item_delta_fast (inner_map.backward (i), r, delta_bytes, row_size) != 0)
+	{
+	  region_indices.add (region);
+	  break;
+	}
+    }
+  }
+
+  protected:
+  const HBUINT8 *get_delta_bytes () const
+  { return &StructAfter<HBUINT8> (regionIndices); }
+
+  HBUINT8 *get_delta_bytes ()
+  { return &StructAfter<HBUINT8> (regionIndices); }
+
+  int32_t get_item_delta_fast (unsigned int item, unsigned int region,
+			       const HBUINT8 *delta_bytes, unsigned row_size) const
+  {
+    if (unlikely (item >= itemCount || region >= regionIndices.len)) return 0;
+
+    const HBINT8 *p = (const HBINT8 *) delta_bytes + item * row_size;
+    unsigned word_count = wordCount ();
+    bool is_long = longWords ();
+    if (is_long)
+    {
+      if (region < word_count)
+	return ((const HBINT32 *) p)[region];
+      else
+	return ((const HBINT16 *)(p + HBINT32::static_size * word_count))[region - word_count];
+    }
+    else
+    {
+      if (region < word_count)
+	return ((const HBINT16 *) p)[region];
+      else
+	return (p + HBINT16::static_size * word_count)[region - word_count];
+    }
+  }
+  int32_t get_item_delta (unsigned int item, unsigned int region) const
+  {
+     return get_item_delta_fast (item, region,
+				 get_delta_bytes (),
+				 get_row_size ());
+  }
+
+  void set_item_delta_fast (unsigned int item, unsigned int region, int32_t delta,
+			    HBUINT8 *delta_bytes, unsigned row_size)
+  {
+    HBINT8 *p = (HBINT8 *) delta_bytes + item * row_size;
+    unsigned word_count = wordCount ();
+    bool is_long = longWords ();
+    if (is_long)
+    {
+      if (region < word_count)
+	((HBINT32 *) p)[region] = delta;
+      else
+	((HBINT16 *)(p + HBINT32::static_size * word_count))[region - word_count] = delta;
+    }
+    else
+    {
+      if (region < word_count)
+	((HBINT16 *) p)[region] = delta;
+      else
+	(p + HBINT16::static_size * word_count)[region - word_count] = delta;
+    }
+  }
+  void set_item_delta (unsigned int item, unsigned int region, int32_t delta)
+  {
+    set_item_delta_fast (item, region, delta,
+			 get_delta_bytes (),
+			 get_row_size ());
+  }
+
+  bool longWords () const { return wordSizeCount & 0x8000u /* LONG_WORDS */; }
+  unsigned wordCount () const { return wordSizeCount & 0x7FFFu /* WORD_DELTA_COUNT_MASK */; }
+
+  protected:
+  HBUINT16		itemCount;
+  HBUINT16		wordSizeCount;
+  Array16Of<HBUINT16>	regionIndices;
+/*UnsizedArrayOf<HBUINT8>bytesX;*/
+  public:
+  DEFINE_SIZE_ARRAY (6, regionIndices);
+};
+
+struct VariationStore
+{
+  using cache_t = VarRegionList::cache_t;
+
+  cache_t *create_cache () const
+  {
+#ifdef HB_NO_VAR
+    return nullptr;
+#endif
+    auto &r = this+regions;
+    unsigned count = r.regionCount;
+
+    float *cache = (float *) hb_malloc (sizeof (float) * count);
+    if (unlikely (!cache)) return nullptr;
+
+    for (unsigned i = 0; i < count; i++)
+      cache[i] = REGION_CACHE_ITEM_CACHE_INVALID;
+
+    return cache;
+  }
+
+  static void destroy_cache (cache_t *cache) { hb_free (cache); }
+
+  private:
+  float get_delta (unsigned int outer, unsigned int inner,
+		   const int *coords, unsigned int coord_count,
+		   VarRegionList::cache_t *cache = nullptr) const
+  {
+#ifdef HB_NO_VAR
+    return 0.f;
+#endif
+
+    if (unlikely (outer >= dataSets.len))
+      return 0.f;
+
+    return (this+dataSets[outer]).get_delta (inner,
+					     coords, coord_count,
+					     this+regions,
+					     cache);
+  }
+
+  public:
+  float get_delta (unsigned int index,
+		   const int *coords, unsigned int coord_count,
+		   VarRegionList::cache_t *cache = nullptr) const
+  {
+    unsigned int outer = index >> 16;
+    unsigned int inner = index & 0xFFFF;
+    return get_delta (outer, inner, coords, coord_count, cache);
+  }
+  float get_delta (unsigned int index,
+		   hb_array_t<int> coords,
+		   VarRegionList::cache_t *cache = nullptr) const
+  {
+    return get_delta (index,
+		      coords.arrayZ, coords.length,
+		      cache);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+#ifdef HB_NO_VAR
+    return true;
+#endif
+
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this) &&
+		  format == 1 &&
+		  regions.sanitize (c, this) &&
+		  dataSets.sanitize (c, this));
+  }
+
+  bool serialize (hb_serialize_context_t *c,
+		  const VariationStore *src,
+		  const hb_array_t <const hb_inc_bimap_t> &inner_maps)
+  {
+    TRACE_SERIALIZE (this);
+#ifdef HB_NO_VAR
+    return_trace (false);
+#endif
+
+    if (unlikely (!c->extend_min (this))) return_trace (false);
+
+    unsigned int set_count = 0;
+    for (unsigned int i = 0; i < inner_maps.length; i++)
+      if (inner_maps[i].get_population ())
+	set_count++;
+
+    format = 1;
+
+    const auto &src_regions = src+src->regions;
+
+    hb_set_t region_indices;
+    for (unsigned int i = 0; i < inner_maps.length; i++)
+      (src+src->dataSets[i]).collect_region_refs (region_indices, inner_maps[i]);
+
+    if (region_indices.in_error ())
+      return_trace (false);
+
+    region_indices.del_range ((src_regions).regionCount, hb_set_t::INVALID);
+
+    /* TODO use constructor when our data-structures support that. */
+    hb_inc_bimap_t region_map;
+    + hb_iter (region_indices)
+    | hb_apply ([&region_map] (unsigned _) { region_map.add(_); })
+    ;
+    if (region_map.in_error())
+      return_trace (false);
+
+    if (unlikely (!regions.serialize_serialize (c, &src_regions, region_map)))
+      return_trace (false);
+
+    dataSets.len = set_count;
+    if (unlikely (!c->extend (dataSets))) return_trace (false);
+
+    /* TODO: The following code could be simplified when
+     * List16OfOffset16To::subset () can take a custom param to be passed to VarData::serialize () */
+    unsigned int set_index = 0;
+    for (unsigned int i = 0; i < inner_maps.length; i++)
+    {
+      if (!inner_maps[i].get_population ()) continue;
+      if (unlikely (!dataSets[set_index++]
+		     .serialize_serialize (c, &(src+src->dataSets[i]), inner_maps[i], region_map)))
+	return_trace (false);
+    }
+
+    return_trace (true);
+  }
+
+  bool subset (hb_subset_context_t *c, const hb_array_t<const hb_inc_bimap_t> &inner_maps) const
+  {
+    TRACE_SUBSET (this);
+#ifdef HB_NO_VAR
+    return_trace (false);
+#endif
+
+    VariationStore *varstore_prime = c->serializer->start_embed<VariationStore> ();
+    if (unlikely (!varstore_prime)) return_trace (false);
+
+    varstore_prime->serialize (c->serializer, this, inner_maps);
+
+    return_trace (
+        !c->serializer->in_error()
+        && varstore_prime->dataSets);
+  }
+
+  unsigned int get_region_index_count (unsigned int major) const
+  {
+#ifdef HB_NO_VAR
+    return 0;
+#endif
+    return (this+dataSets[major]).get_region_index_count ();
+  }
+
+  void get_region_scalars (unsigned int major,
+			   const int *coords, unsigned int coord_count,
+			   float *scalars /*OUT*/,
+			   unsigned int num_scalars) const
+  {
+#ifdef HB_NO_VAR
+    for (unsigned i = 0; i < num_scalars; i++)
+      scalars[i] = 0.f;
+    return;
+#endif
+
+    (this+dataSets[major]).get_region_scalars (coords, coord_count,
+					       this+regions,
+					       &scalars[0], num_scalars);
+  }
+
+  unsigned int get_sub_table_count () const
+   {
+#ifdef HB_NO_VAR
+     return 0;
+#endif
+     return dataSets.len;
+   }
+
+  protected:
+  HBUINT16				format;
+  Offset32To<VarRegionList>		regions;
+  Array16OfOffset32To<VarData>		dataSets;
+  public:
+  DEFINE_SIZE_ARRAY_SIZED (8, dataSets);
+};
+
+#undef REGION_CACHE_ITEM_CACHE_INVALID
+
+/*
+ * Feature Variations
+ */
+enum Cond_with_Var_flag_t
+{
+  KEEP_COND_WITH_VAR = 0,
+  DROP_COND_WITH_VAR = 1,
+  DROP_RECORD_WITH_VAR = 2,
+  MEM_ERR_WITH_VAR = 3,
+};
+
+struct ConditionFormat1
+{
+  friend struct Condition;
+
+  bool subset (hb_subset_context_t *c) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->serializer->embed (this);
+    if (unlikely (!out)) return_trace (false);
+
+    const hb_map_t *index_map = c->plan->axes_index_map;
+    if (index_map->is_empty ()) return_trace (true);
+
+    if (!index_map->has (axisIndex))
+      return_trace (false);
+
+    return_trace (c->serializer->check_assign (out->axisIndex, index_map->get (axisIndex),
+                                               HB_SERIALIZE_ERROR_INT_OVERFLOW));
+  }
+
+  private:
+  Cond_with_Var_flag_t keep_with_variations (hb_collect_feature_substitutes_with_var_context_t *c,
+                                             hb_map_t *condition_map /* OUT */) const
+  {
+    //invalid axis index, drop the entire record
+    if (!c->axes_index_tag_map->has (axisIndex))
+      return DROP_RECORD_WITH_VAR;
+
+    hb_tag_t axis_tag = c->axes_index_tag_map->get (axisIndex);
+
+    //axis not pinned, keep the condition
+    if (!c->axes_location->has (axis_tag))
+    {
+      // add axisIndex->value into the hashmap so we can check if the record is
+      // unique with variations
+      int16_t min_val = filterRangeMinValue;
+      int16_t max_val = filterRangeMaxValue;
+      hb_codepoint_t val = (max_val << 16) + min_val;
+
+      condition_map->set (axisIndex, val);
+      return KEEP_COND_WITH_VAR;
+    }
+
+    //axis pinned, check if condition is met
+    //TODO: add check for axis Ranges
+    int v = c->axes_location->get (axis_tag);
+
+    //condition not met, drop the entire record
+    if (v < filterRangeMinValue || v > filterRangeMaxValue)
+      return DROP_RECORD_WITH_VAR;
+
+    //axis pinned and condition met, drop the condition
+    return DROP_COND_WITH_VAR;
+  }
+
+  bool evaluate (const int *coords, unsigned int coord_len) const
+  {
+    int coord = axisIndex < coord_len ? coords[axisIndex] : 0;
+    return filterRangeMinValue <= coord && coord <= filterRangeMaxValue;
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this));
+  }
+
+  protected:
+  HBUINT16	format;		/* Format identifier--format = 1 */
+  HBUINT16	axisIndex;
+  F2DOT14	filterRangeMinValue;
+  F2DOT14	filterRangeMaxValue;
+  public:
+  DEFINE_SIZE_STATIC (8);
+};
+
+struct Condition
+{
+  bool evaluate (const int *coords, unsigned int coord_len) const
+  {
+    switch (u.format) {
+    case 1: return u.format1.evaluate (coords, coord_len);
+    default:return false;
+    }
+  }
+
+  Cond_with_Var_flag_t keep_with_variations (hb_collect_feature_substitutes_with_var_context_t *c,
+                                             hb_map_t *condition_map /* OUT */) const
+  {
+    switch (u.format) {
+    case 1: return u.format1.keep_with_variations (c, condition_map);
+    default:return KEEP_COND_WITH_VAR;
+    }
+  }
+
+  template <typename context_t, typename ...Ts>
+  typename context_t::return_t dispatch (context_t *c, Ts&&... ds) const
+  {
+    TRACE_DISPATCH (this, u.format);
+    if (unlikely (!c->may_dispatch (this, &u.format))) return_trace (c->no_dispatch_return_value ());
+    switch (u.format) {
+    case 1: return_trace (c->dispatch (u.format1, std::forward<Ts> (ds)...));
+    default:return_trace (c->default_return_value ());
+    }
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    if (!u.format.sanitize (c)) return_trace (false);
+    switch (u.format) {
+    case 1: return_trace (u.format1.sanitize (c));
+    default:return_trace (true);
+    }
+  }
+
+  protected:
+  union {
+  HBUINT16		format;		/* Format identifier */
+  ConditionFormat1	format1;
+  } u;
+  public:
+  DEFINE_SIZE_UNION (2, format);
+};
+
+struct ConditionSet
+{
+  bool evaluate (const int *coords, unsigned int coord_len) const
+  {
+    unsigned int count = conditions.len;
+    for (unsigned int i = 0; i < count; i++)
+      if (!(this+conditions.arrayZ[i]).evaluate (coords, coord_len))
+	return false;
+    return true;
+  }
+
+  Cond_with_Var_flag_t keep_with_variations (hb_collect_feature_substitutes_with_var_context_t *c) const
+  {
+    hb_map_t *condition_map = hb_map_create ();
+    if (unlikely (!condition_map)) return MEM_ERR_WITH_VAR;
+    hb::shared_ptr<hb_map_t> p {condition_map};
+
+    hb_set_t *cond_set = hb_set_create ();
+    if (unlikely (!cond_set)) return MEM_ERR_WITH_VAR;
+    hb::shared_ptr<hb_set_t> s {cond_set};
+
+    unsigned num_kept_cond = 0, cond_idx = 0;
+    for (const auto& offset : conditions)
+    {
+      Cond_with_Var_flag_t ret = (this+offset).keep_with_variations (c, condition_map);
+      // one condition is not met, drop the entire record
+      if (ret == DROP_RECORD_WITH_VAR)
+        return DROP_RECORD_WITH_VAR;
+
+      // axis not pinned, keep this condition
+      if (ret == KEEP_COND_WITH_VAR)
+      {
+        cond_set->add (cond_idx);
+        num_kept_cond++;
+      }
+      cond_idx++;
+    }
+
+    // all conditions met
+    if (num_kept_cond == 0) return DROP_COND_WITH_VAR;
+
+    //check if condition_set is unique with variations
+    if (c->conditionset_map->has (p))
+      //duplicate found, drop the entire record
+      return DROP_RECORD_WITH_VAR;
+
+    c->conditionset_map->set (p, 1);
+    c->record_cond_idx_map->set (c->cur_record_idx, s);
+
+    return KEEP_COND_WITH_VAR;
+  }
+
+  bool subset (hb_subset_context_t *c,
+               hb_subset_layout_context_t *l) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->serializer->start_embed (this);
+    if (unlikely (!out || !c->serializer->extend_min (out))) return_trace (false);
+
+    hb_set_t *retained_cond_set = nullptr;
+    if (l->feature_record_cond_idx_map != nullptr)
+      retained_cond_set = l->feature_record_cond_idx_map->get (l->cur_feature_var_record_idx);
+
+    unsigned int count = conditions.len;
+    for (unsigned int i = 0; i < count; i++)
+    {
+      if (retained_cond_set != nullptr && !retained_cond_set->has (i))
+        continue;
+      subset_offset_array (c, out->conditions, this) (conditions[i]);
+    }
+
+    return_trace (bool (out->conditions));
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (conditions.sanitize (c, this));
+  }
+
+  protected:
+  Array16OfOffset32To<Condition>	conditions;
+  public:
+  DEFINE_SIZE_ARRAY (2, conditions);
+};
+
+struct FeatureTableSubstitutionRecord
+{
+  friend struct FeatureTableSubstitution;
+
+  void collect_lookups (const void *base, hb_set_t *lookup_indexes /* OUT */) const
+  {
+    return (base+feature).add_lookup_indexes_to (lookup_indexes);
+  }
+
+  void closure_features (const void *base,
+			 const hb_map_t *lookup_indexes,
+			 hb_set_t       *feature_indexes /* OUT */) const
+  {
+    if ((base+feature).intersects_lookup_indexes (lookup_indexes))
+      feature_indexes->add (featureIndex);
+  }
+
+  void collect_feature_substitutes_with_variations (hb_hashmap_t<unsigned, const Feature*> *feature_substitutes_map,
+                                                    const hb_set_t *feature_indices,
+                                                    const void *base) const
+  {
+    if (feature_indices->has (featureIndex))
+      feature_substitutes_map->set (featureIndex, &(base+feature));
+  }
+
+  bool subset (hb_subset_layout_context_t *c, const void *base) const
+  {
+    TRACE_SUBSET (this);
+    if (!c->feature_index_map->has (featureIndex) ||
+        c->feature_substitutes_map->has (featureIndex)) {
+      // Feature that is being substituted is not being retained, so we don't
+      // need this.
+      return_trace (false);
+    }
+
+    auto *out = c->subset_context->serializer->embed (this);
+    if (unlikely (!out)) return_trace (false);
+
+    out->featureIndex = c->feature_index_map->get (featureIndex);
+    bool ret = out->feature.serialize_subset (c->subset_context, feature, base, c);
+    return_trace (ret);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c, const void *base) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this) && feature.sanitize (c, base));
+  }
+
+  protected:
+  HBUINT16		featureIndex;
+  Offset32To<Feature>	feature;
+  public:
+  DEFINE_SIZE_STATIC (6);
+};
+
+struct FeatureTableSubstitution
+{
+  const Feature *find_substitute (unsigned int feature_index) const
+  {
+    unsigned int count = substitutions.len;
+    for (unsigned int i = 0; i < count; i++)
+    {
+      const FeatureTableSubstitutionRecord &record = substitutions.arrayZ[i];
+      if (record.featureIndex == feature_index)
+	return &(this+record.feature);
+    }
+    return nullptr;
+  }
+
+  void collect_lookups (const hb_set_t *feature_indexes,
+			const hb_hashmap_t<unsigned, const Feature*> *feature_substitutes_map,
+			hb_set_t       *lookup_indexes /* OUT */) const
+  {
+    + hb_iter (substitutions)
+    | hb_filter (feature_indexes, &FeatureTableSubstitutionRecord::featureIndex)
+    | hb_filter ([feature_substitutes_map] (const FeatureTableSubstitutionRecord& record)
+                 {
+                   if (feature_substitutes_map == nullptr) return true;
+                   return !feature_substitutes_map->has (record.featureIndex);
+                 })
+    | hb_apply ([this, lookup_indexes] (const FeatureTableSubstitutionRecord& r)
+		{ r.collect_lookups (this, lookup_indexes); })
+    ;
+  }
+
+  void closure_features (const hb_map_t *lookup_indexes,
+			 hb_set_t       *feature_indexes /* OUT */) const
+  {
+    for (const FeatureTableSubstitutionRecord& record : substitutions)
+      record.closure_features (this, lookup_indexes, feature_indexes);
+  }
+
+  bool intersects_features (const hb_map_t *feature_index_map) const
+  {
+    for (const FeatureTableSubstitutionRecord& record : substitutions)
+    {
+      if (feature_index_map->has (record.featureIndex)) return true;
+    }
+    return false;
+  }
+
+  void collect_feature_substitutes_with_variations (hb_collect_feature_substitutes_with_var_context_t *c) const
+  {
+    for (const FeatureTableSubstitutionRecord& record : substitutions)
+      record.collect_feature_substitutes_with_variations (c->feature_substitutes_map, c->feature_indices, this);
+  }
+
+  bool subset (hb_subset_context_t        *c,
+	       hb_subset_layout_context_t *l) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->serializer->start_embed (*this);
+    if (unlikely (!out || !c->serializer->extend_min (out))) return_trace (false);
+
+    out->version.major = version.major;
+    out->version.minor = version.minor;
+
+    + substitutions.iter ()
+    | hb_apply (subset_record_array (l, &(out->substitutions), this))
+    ;
+
+    return_trace (bool (out->substitutions));
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (version.sanitize (c) &&
+		  likely (version.major == 1) &&
+		  substitutions.sanitize (c, this));
+  }
+
+  protected:
+  FixedVersion<>	version;	/* Version--0x00010000u */
+  Array16Of<FeatureTableSubstitutionRecord>
+			substitutions;
+  public:
+  DEFINE_SIZE_ARRAY (6, substitutions);
+};
+
+struct FeatureVariationRecord
+{
+  friend struct FeatureVariations;
+
+  void collect_lookups (const void     *base,
+			const hb_set_t *feature_indexes,
+			const hb_hashmap_t<unsigned, const Feature*> *feature_substitutes_map,
+			hb_set_t       *lookup_indexes /* OUT */) const
+  {
+    return (base+substitutions).collect_lookups (feature_indexes, feature_substitutes_map, lookup_indexes);
+  }
+
+  void closure_features (const void     *base,
+			 const hb_map_t *lookup_indexes,
+			 hb_set_t       *feature_indexes /* OUT */) const
+  {
+    (base+substitutions).closure_features (lookup_indexes, feature_indexes);
+  }
+
+  bool intersects_features (const void *base, const hb_map_t *feature_index_map) const
+  {
+    return (base+substitutions).intersects_features (feature_index_map);
+  }
+
+  void collect_feature_substitutes_with_variations (hb_collect_feature_substitutes_with_var_context_t *c,
+                                                    const void *base) const
+  {
+    // ret == 1, all conditions met
+    if ((base+conditions).keep_with_variations (c) == DROP_COND_WITH_VAR &&
+        c->apply)
+    {
+      (base+substitutions).collect_feature_substitutes_with_variations (c);
+      c->apply = false; // set variations only once
+    }
+  }
+
+  bool subset (hb_subset_layout_context_t *c, const void *base) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->subset_context->serializer->embed (this);
+    if (unlikely (!out)) return_trace (false);
+
+    out->conditions.serialize_subset (c->subset_context, conditions, base, c);
+    out->substitutions.serialize_subset (c->subset_context, substitutions, base, c);
+
+    return_trace (true);
+  }
+
+  bool sanitize (hb_sanitize_context_t *c, const void *base) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (conditions.sanitize (c, base) &&
+		  substitutions.sanitize (c, base));
+  }
+
+  protected:
+  Offset32To<ConditionSet>
+			conditions;
+  Offset32To<FeatureTableSubstitution>
+			substitutions;
+  public:
+  DEFINE_SIZE_STATIC (8);
+};
+
+struct FeatureVariations
+{
+  static constexpr unsigned NOT_FOUND_INDEX = 0xFFFFFFFFu;
+
+  bool find_index (const int *coords, unsigned int coord_len,
+		   unsigned int *index) const
+  {
+    unsigned int count = varRecords.len;
+    for (unsigned int i = 0; i < count; i++)
+    {
+      const FeatureVariationRecord &record = varRecords.arrayZ[i];
+      if ((this+record.conditions).evaluate (coords, coord_len))
+      {
+	*index = i;
+	return true;
+      }
+    }
+    *index = NOT_FOUND_INDEX;
+    return false;
+  }
+
+  const Feature *find_substitute (unsigned int variations_index,
+				  unsigned int feature_index) const
+  {
+    const FeatureVariationRecord &record = varRecords[variations_index];
+    return (this+record.substitutions).find_substitute (feature_index);
+  }
+
+  void collect_feature_substitutes_with_variations (hb_collect_feature_substitutes_with_var_context_t *c) const
+  {
+    unsigned int count = varRecords.len;
+    for (unsigned int i = 0; i < count; i++)
+    {
+      c->cur_record_idx = i;
+      varRecords[i].collect_feature_substitutes_with_variations (c, this);
+    }
+  }
+
+  FeatureVariations* copy (hb_serialize_context_t *c) const
+  {
+    TRACE_SERIALIZE (this);
+    return_trace (c->embed (*this));
+  }
+
+  void collect_lookups (const hb_set_t *feature_indexes,
+			const hb_hashmap_t<unsigned, const Feature*> *feature_substitutes_map,
+			hb_set_t       *lookup_indexes /* OUT */) const
+  {
+    for (const FeatureVariationRecord& r : varRecords)
+      r.collect_lookups (this, feature_indexes, feature_substitutes_map, lookup_indexes);
+  }
+
+  void closure_features (const hb_map_t *lookup_indexes,
+			 const hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> *feature_record_cond_idx_map,
+			 hb_set_t       *feature_indexes /* OUT */) const
+  {
+    unsigned int count = varRecords.len;
+    for (unsigned int i = 0; i < count; i++)
+    {
+      if (feature_record_cond_idx_map != nullptr &&
+          !feature_record_cond_idx_map->has (i))
+        continue;
+      varRecords[i].closure_features (this, lookup_indexes, feature_indexes);
+    }
+  }
+
+  bool subset (hb_subset_context_t *c,
+	       hb_subset_layout_context_t *l) const
+  {
+    TRACE_SUBSET (this);
+    auto *out = c->serializer->start_embed (*this);
+    if (unlikely (!out || !c->serializer->extend_min (out))) return_trace (false);
+
+    out->version.major = version.major;
+    out->version.minor = version.minor;
+
+    int keep_up_to = -1;
+    for (int i = varRecords.len - 1; i >= 0; i--) {
+      if (varRecords[i].intersects_features (this, l->feature_index_map)) {
+        keep_up_to = i;
+        break;
+      }
+    }
+
+    unsigned count = (unsigned) (keep_up_to + 1);
+    for (unsigned i = 0; i < count; i++)
+    {
+      if (l->feature_record_cond_idx_map != nullptr &&
+          !l->feature_record_cond_idx_map->has (i))
+        continue;
+
+      l->cur_feature_var_record_idx = i;
+      subset_record_array (l, &(out->varRecords), this) (varRecords[i]);
+    }
+    return_trace (bool (out->varRecords));
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (version.sanitize (c) &&
+		  likely (version.major == 1) &&
+		  varRecords.sanitize (c, this));
+  }
+
+  protected:
+  FixedVersion<>	version;	/* Version--0x00010000u */
+  Array32Of<FeatureVariationRecord>
+			varRecords;
+  public:
+  DEFINE_SIZE_ARRAY_SIZED (8, varRecords);
+};
+
+
+/*
+ * Device Tables
+ */
+
+struct HintingDevice
+{
+  friend struct Device;
+
+  private:
+
+  hb_position_t get_x_delta (hb_font_t *font) const
+  { return get_delta (font->x_ppem, font->x_scale); }
+
+  hb_position_t get_y_delta (hb_font_t *font) const
+  { return get_delta (font->y_ppem, font->y_scale); }
+
+  public:
+
+  unsigned int get_size () const
+  {
+    unsigned int f = deltaFormat;
+    if (unlikely (f < 1 || f > 3 || startSize > endSize)) return 3 * HBUINT16::static_size;
+    return HBUINT16::static_size * (4 + ((endSize - startSize) >> (4 - f)));
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this) && c->check_range (this, this->get_size ()));
+  }
+
+  HintingDevice* copy (hb_serialize_context_t *c) const
+  {
+    TRACE_SERIALIZE (this);
+    return_trace (c->embed<HintingDevice> (this));
+  }
+
+  private:
+
+  int get_delta (unsigned int ppem, int scale) const
+  {
+    if (!ppem) return 0;
+
+    int pixels = get_delta_pixels (ppem);
+
+    if (!pixels) return 0;
+
+    return (int) (pixels * (int64_t) scale / ppem);
+  }
+  int get_delta_pixels (unsigned int ppem_size) const
+  {
+    unsigned int f = deltaFormat;
+    if (unlikely (f < 1 || f > 3))
+      return 0;
+
+    if (ppem_size < startSize || ppem_size > endSize)
+      return 0;
+
+    unsigned int s = ppem_size - startSize;
+
+    unsigned int byte = deltaValueZ[s >> (4 - f)];
+    unsigned int bits = (byte >> (16 - (((s & ((1 << (4 - f)) - 1)) + 1) << f)));
+    unsigned int mask = (0xFFFFu >> (16 - (1 << f)));
+
+    int delta = bits & mask;
+
+    if ((unsigned int) delta >= ((mask + 1) >> 1))
+      delta -= mask + 1;
+
+    return delta;
+  }
+
+  protected:
+  HBUINT16	startSize;		/* Smallest size to correct--in ppem */
+  HBUINT16	endSize;		/* Largest size to correct--in ppem */
+  HBUINT16	deltaFormat;		/* Format of DeltaValue array data: 1, 2, or 3
+					 * 1	Signed 2-bit value, 8 values per uint16
+					 * 2	Signed 4-bit value, 4 values per uint16
+					 * 3	Signed 8-bit value, 2 values per uint16
+					 */
+  UnsizedArrayOf<HBUINT16>
+		deltaValueZ;		/* Array of compressed data */
+  public:
+  DEFINE_SIZE_ARRAY (6, deltaValueZ);
+};
+
+struct VariationDevice
+{
+  friend struct Device;
+
+  private:
+
+  hb_position_t get_x_delta (hb_font_t *font,
+			     const VariationStore &store,
+			     VariationStore::cache_t *store_cache = nullptr) const
+  { return font->em_scalef_x (get_delta (font, store, store_cache)); }
+
+  hb_position_t get_y_delta (hb_font_t *font,
+			     const VariationStore &store,
+			     VariationStore::cache_t *store_cache = nullptr) const
+  { return font->em_scalef_y (get_delta (font, store, store_cache)); }
+
+  VariationDevice* copy (hb_serialize_context_t *c,
+                         const hb_hashmap_t<unsigned, hb_pair_t<unsigned, int>> *layout_variation_idx_delta_map) const
+  {
+    TRACE_SERIALIZE (this);
+    if (!layout_variation_idx_delta_map) return_trace (nullptr);
+
+    hb_pair_t<unsigned, int> *v;
+    if (!layout_variation_idx_delta_map->has (varIdx, &v))
+      return_trace (nullptr);
+
+    c->start_zerocopy (this->static_size);
+    auto *out = c->embed (this);
+    if (unlikely (!out)) return_trace (nullptr);
+
+    unsigned new_idx = hb_first (*v);
+    out->varIdx = new_idx;
+    return_trace (out);
+  }
+
+  void collect_variation_index (hb_collect_variation_indices_context_t *c) const
+  {
+    c->layout_variation_indices->add (varIdx);
+    int delta = 0;
+    if (c->font && c->var_store)
+      delta = roundf (get_delta (c->font, *c->var_store, c->store_cache));
+
+    /* set new varidx to HB_OT_LAYOUT_NO_VARIATIONS_INDEX here, will remap
+     * varidx later*/
+    c->varidx_delta_map->set (varIdx, hb_pair_t<unsigned, int> (HB_OT_LAYOUT_NO_VARIATIONS_INDEX, delta));
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this));
+  }
+
+  private:
+
+  float get_delta (hb_font_t *font,
+		   const VariationStore &store,
+		   VariationStore::cache_t *store_cache = nullptr) const
+  {
+    return store.get_delta (varIdx, font->coords, font->num_coords, (VariationStore::cache_t *) store_cache);
+  }
+
+  protected:
+  VarIdx	varIdx;
+  HBUINT16	deltaFormat;	/* Format identifier for this table: 0x0x8000 */
+  public:
+  DEFINE_SIZE_STATIC (6);
+};
+
+struct DeviceHeader
+{
+  protected:
+  HBUINT16		reserved1;
+  HBUINT16		reserved2;
+  public:
+  HBUINT16		format;		/* Format identifier */
+  public:
+  DEFINE_SIZE_STATIC (6);
+};
+
+struct Device
+{
+  hb_position_t get_x_delta (hb_font_t *font,
+			     const VariationStore &store=Null (VariationStore),
+			     VariationStore::cache_t *store_cache = nullptr) const
+  {
+    switch (u.b.format)
+    {
+#ifndef HB_NO_HINTING
+    case 1: case 2: case 3:
+      return u.hinting.get_x_delta (font);
+#endif
+#ifndef HB_NO_VAR
+    case 0x8000:
+      return u.variation.get_x_delta (font, store, store_cache);
+#endif
+    default:
+      return 0;
+    }
+  }
+  hb_position_t get_y_delta (hb_font_t *font,
+			     const VariationStore &store=Null (VariationStore),
+			     VariationStore::cache_t *store_cache = nullptr) const
+  {
+    switch (u.b.format)
+    {
+    case 1: case 2: case 3:
+#ifndef HB_NO_HINTING
+      return u.hinting.get_y_delta (font);
+#endif
+#ifndef HB_NO_VAR
+    case 0x8000:
+      return u.variation.get_y_delta (font, store, store_cache);
+#endif
+    default:
+      return 0;
+    }
+  }
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    if (!u.b.format.sanitize (c)) return_trace (false);
+    switch (u.b.format) {
+#ifndef HB_NO_HINTING
+    case 1: case 2: case 3:
+      return_trace (u.hinting.sanitize (c));
+#endif
+#ifndef HB_NO_VAR
+    case 0x8000:
+      return_trace (u.variation.sanitize (c));
+#endif
+    default:
+      return_trace (true);
+    }
+  }
+
+  Device* copy (hb_serialize_context_t *c,
+                const hb_hashmap_t<unsigned, hb_pair_t<unsigned, int>> *layout_variation_idx_delta_map=nullptr) const
+  {
+    TRACE_SERIALIZE (this);
+    switch (u.b.format) {
+#ifndef HB_NO_HINTING
+    case 1:
+    case 2:
+    case 3:
+      return_trace (reinterpret_cast<Device *> (u.hinting.copy (c)));
+#endif
+#ifndef HB_NO_VAR
+    case 0x8000:
+      return_trace (reinterpret_cast<Device *> (u.variation.copy (c, layout_variation_idx_delta_map)));
+#endif
+    default:
+      return_trace (nullptr);
+    }
+  }
+
+  void collect_variation_indices (hb_collect_variation_indices_context_t *c) const
+  {
+    switch (u.b.format) {
+#ifndef HB_NO_HINTING
+    case 1:
+    case 2:
+    case 3:
+      return;
+#endif
+#ifndef HB_NO_VAR
+    case 0x8000:
+      u.variation.collect_variation_index (c);
+      return;
+#endif
+    default:
+      return;
+    }
+  }
+
+  unsigned get_variation_index () const
+  {
+    switch (u.b.format) {
+#ifndef HB_NO_VAR
+    case 0x8000:
+      return u.variation.varIdx;
+#endif
+    default:
+      return HB_OT_LAYOUT_NO_VARIATIONS_INDEX;
+    }
+  }
+
+  protected:
+  union {
+  DeviceHeader		b;
+  HintingDevice		hinting;
+#ifndef HB_NO_VAR
+  VariationDevice	variation;
+#endif
+  } u;
+  public:
+  DEFINE_SIZE_UNION (6, b);
+};
+
+
+} /* namespace OT */
+
+
+#endif /* HB_OT_LAYOUT_COMMON_HH */