[instancer] add serialize() for VarRegionList

The region list argument comes from item_variations_t.get_region_list()

src/hb-ot-layout-common.hh

@@ -2475,6 +2475,12 @@ struct VarRegionAxis
      * have to do that at runtime. */
   }
 
+  bool serialize (hb_serialize_context_t *c) const
+  {
+    TRACE_SERIALIZE (this);
+    return_trace (c->embed (this));
+  }
+
   public:
   F2DOT14	startCoord;
   F2DOT14	peakCoord;
@@ -2532,6 +2538,47 @@ struct VarRegionList
     return_trace (c->check_struct (this) && axesZ.sanitize (c, axisCount * regionCount));
   }
 
+  bool serialize (hb_serialize_context_t *c,
+                  const hb_vector_t<hb_tag_t>& axis_tags,
+                  const hb_vector_t<const hb_hashmap_t<hb_tag_t, Triple>*>& regions)
+  {
+    TRACE_SERIALIZE (this);
+    unsigned axis_count = axis_tags.length;
+    unsigned region_count = regions.length;
+    if (!axis_count || !region_count) return_trace (false);
+    if (unlikely (hb_unsigned_mul_overflows (axis_count * region_count,
+                                             VarRegionAxis::static_size))) return_trace (false);
+    if (unlikely (!c->extend_min (this))) return_trace (false);
+    axisCount = axis_count;
+    regionCount = region_count;
+
+    for (unsigned r = 0; r < region_count; r++)
+    {
+      const auto& region = regions[r];
+      for (unsigned i = 0; i < axis_count; i++)
+      {
+        hb_tag_t tag = axis_tags.arrayZ[i];
+        VarRegionAxis var_region_rec;
+        Triple *coords;
+        if (region->has (tag, &coords))
+        {
+          var_region_rec.startCoord.set_float (coords->minimum);
+          var_region_rec.peakCoord.set_float (coords->middle);
+          var_region_rec.endCoord.set_float (coords->maximum);
+        }
+        else
+        {
+          var_region_rec.startCoord.set_int (0);
+          var_region_rec.peakCoord.set_int (0);
+          var_region_rec.endCoord.set_int (0);
+        }
+        if (!var_region_rec.serialize (c))
+          return_trace (false);
+      }
+    }
+    return_trace (true);
+  }
+
   bool serialize (hb_serialize_context_t *c, const VarRegionList *src, const hb_inc_bimap_t &region_map)
   {
     TRACE_SERIALIZE (this);

src/hb-subset-plan-member-list.hh

@@ -113,6 +113,8 @@ HB_SUBSET_PLAN_MEMBER (hb_map_t, axes_index_map)
 
 //axis_index->axis_tag mapping in fvar axis array
 HB_SUBSET_PLAN_MEMBER (hb_map_t, axes_old_index_tag_map)
+//vector of retained axis tags in the order of axes given in the 'fvar' table
+HB_SUBSET_PLAN_MEMBER (hb_vector_t<hb_tag_t>, axis_tags)
 
 //hmtx metrics map: new gid->(advance, lsb)
 HB_SUBSET_PLAN_MEMBER (mutable hb_hashmap_t E(<hb_codepoint_t, hb_pair_t E(<unsigned, int>)>), hmtx_map)

src/hb-subset-plan.cc

@@ -927,6 +927,7 @@ _normalize_axes_location (hb_face_t *face, hb_subset_plan_t *plan)
     {
       axis_not_pinned = true;
       plan->axes_index_map.set (old_axis_idx, new_axis_idx);
+      plan->axis_tags.push (axis_tag);
       new_axis_idx++;
     }