[instancer] add serialize() for VariationStore

Input region_list and encoding_rows are from item_variations_t

src/hb-ot-layout-common.hh

@@ -2735,6 +2735,81 @@ struct VarData
 				  get_row_size ()));
   }
 
+  bool serialize (hb_serialize_context_t *c,
+                  bool has_long,
+                  const hb_vector_t<const hb_vector_t<int>*>& rows)
+  {
+    TRACE_SERIALIZE (this);
+    if (unlikely (!c->extend_min (this))) return_trace (false);
+    unsigned row_count = rows.length;
+    itemCount = row_count;
+
+    int min_threshold = has_long ? -65536 : -128;
+    int max_threshold = has_long ? +65535 : +127;
+    enum delta_size_t { kZero=0, kNonWord, kWord };
+    hb_vector_t<delta_size_t> delta_sz;
+    unsigned num_regions = rows[0]->length;
+    if (!delta_sz.resize (num_regions))
+      return_trace (false);
+
+    unsigned word_count = 0;
+    for (unsigned r = 0; r < num_regions; r++)
+    {
+      for (unsigned i = 0; i < row_count; i++)
+      {
+        int delta = rows[i]->arrayZ[r];
+        if (delta < min_threshold || delta > max_threshold)
+        {
+          delta_sz[r] = kWord;
+          word_count++;
+          break;
+        }
+        else if (delta != 0)
+        {
+          delta_sz[r] = kNonWord;
+        }
+      }
+    }
+
+    /* reorder regions: words and then non-words*/
+    unsigned word_index = 0;
+    unsigned non_word_index = word_count;
+    hb_map_t ri_map;
+    for (unsigned r = 0; r < num_regions; r++)
+    {
+      if (!delta_sz[r]) continue;
+      unsigned new_r = (delta_sz[r] == kWord)? word_index++ : non_word_index++;
+      if (!ri_map.set (new_r, r))
+        return_trace (false);
+    }
+
+    wordSizeCount = word_count | (has_long ? 0x8000u /* LONG_WORDS */ : 0);
+
+    unsigned ri_count = ri_map.get_population ();
+    regionIndices.len = ri_count;
+    if (unlikely (!c->extend (this))) return_trace (false);
+
+    for (unsigned r = 0; r < ri_count; r++)
+    {
+      hb_codepoint_t *idx;
+      if (!ri_map.has (r, &idx))
+        return_trace (false);
+      regionIndices[r] = *idx;
+    }
+
+    HBUINT8 *delta_bytes = get_delta_bytes ();
+    unsigned row_size = get_row_size ();
+    for (unsigned int i = 0; i < row_count; i++)
+    {
+      for (unsigned int r = 0; r < ri_count; r++)
+      {
+        int delta = rows[i]->arrayZ[ri_map[r]];
+        set_item_delta_fast (i, r, delta, delta_bytes, row_size);
+      }
+    }
+    return_trace (true);
+  }
+
   bool serialize (hb_serialize_context_t *c,
 		  const VarData *src,
 		  const hb_inc_bimap_t &inner_map,
@@ -2894,6 +2969,7 @@ struct VarData
 				 get_row_size ());
   }
 
+  protected:
   void set_item_delta_fast (unsigned int item, unsigned int region, int32_t delta,
 			    HBUINT8 *delta_bytes, unsigned row_size)
   {
@@ -3007,6 +3083,36 @@ struct VariationStore
 		  dataSets.sanitize (c, this));
   }
 
+  bool serialize (hb_serialize_context_t *c,
+                  bool has_long,
+                  const hb_vector_t<hb_tag_t>& axis_tags,
+                  const hb_vector_t<const hb_hashmap_t<hb_tag_t, Triple>*>& region_list,
+                  const hb_vector_t<delta_row_encoding_t>& vardata_encodings)
+  {
+    TRACE_SERIALIZE (this);
+#ifdef HB_NO_VAR
+    return_trace (false);
+#endif
+    if (unlikely (!c->extend_min (this))) return_trace (false);
+    
+    format = 1;
+    if (!regions.serialize_serialize (c, axis_tags, region_list))
+      return_trace (false);
+
+    unsigned num_var_data = vardata_encodings.length;
+    if (!num_var_data) return_trace (false);
+    if (unlikely (!c->check_assign (dataSets.len, num_var_data,
+                                    HB_SERIALIZE_ERROR_INT_OVERFLOW)))
+      return_trace (false);
+
+    if (unlikely (!c->extend (dataSets))) return_trace (false);
+    for (unsigned i = 0; i < num_var_data; i++)
+      if (!dataSets[i].serialize_serialize (c, has_long, vardata_encodings[i].items))
+        return_trace (false);
+    
+    return_trace (true);
+  }
+
   bool serialize (hb_serialize_context_t *c,
 		  const VariationStore *src,
 		  const hb_array_t <const hb_inc_bimap_t> &inner_maps)