[instancer] add struct glyph_variations_t for gvar

-Add compile_peak_coords () in tuple_delta_t
-Add compile_shared_tuples () for glyph_variations_t

src/hb-ot-var-common.hh

@@ -449,6 +449,9 @@ struct tuple_delta_t
   hb_vector_t<char> compiled_tuple_header;
   hb_vector_t<char> compiled_deltas;
 
+  /* compiled peak coords, empty for non-gvar tuples */
+  hb_vector_t<char> compiled_peak_coords;
+
   tuple_delta_t () = default;
   tuple_delta_t (const tuple_delta_t& o) = default;
 
@@ -552,6 +555,36 @@ struct tuple_delta_t
     return out;
   }
 
+  bool compile_peak_coords (const hb_map_t& axes_index_map,
+                            const hb_map_t& axes_old_index_tag_map)
+  {
+    unsigned axis_count = axes_index_map.get_population ();
+    if (unlikely (!compiled_peak_coords.alloc (axis_count * F2DOT14::static_size)))
+      return false;
+
+    unsigned orig_axis_count = axes_old_index_tag_map.get_population ();
+    for (unsigned i = 0; i < orig_axis_count; i++)
+    {
+      if (!axes_index_map.has (i))
+        continue;
+
+      hb_tag_t axis_tag = axes_old_index_tag_map.get (i);
+      Triple *coords;
+      F2DOT14 peak_coord;
+      if (axis_tuples.has (axis_tag, &coords))
+        peak_coord.set_float (coords->middle);
+      else
+        peak_coord.set_int (0);
+
+      /* push F2DOT14 value into char vector */
+      int16_t val = peak_coord.to_int ();
+      compiled_peak_coords.push (static_cast<char> (val >> 8));
+      compiled_peak_coords.push (static_cast<char> (val & 0xFF));
+    }
+
+    return !compiled_peak_coords.in_error ();
+  }
+
   /* deltas should be compiled already before we compile tuple
    * variation header cause we need to fill in the size of the
    * serialized data for this tuple variation */

src/hb-ot-var-gvar-table.hh

@@ -76,6 +76,111 @@ struct contour_point_vector_t : hb_vector_t<contour_point_t>
 struct GlyphVariationData : TupleVariationData
 {};
 
+struct glyph_variations_t
+{
+  using tuple_variations_t = TupleVariationData::tuple_variations_t;
+  hb_vector_t<tuple_variations_t> glyph_variations;
+
+  hb_vector_t<char> compiled_shared_tuples;
+  private:
+  unsigned shared_tuples_count = 0;
+
+  /* shared coords-> index map after instantiation */
+  hb_hashmap_t<const hb_vector_t<char>*, unsigned> shared_tuples_idx_map;
+
+  public:
+  unsigned compiled_shared_tuples_count () const
+  { return shared_tuples_count; }
+
+  bool compile_shared_tuples (const hb_map_t& axes_index_map,
+                              const hb_map_t& axes_old_index_tag_map)
+  {
+    /* key is pointer to compiled_peak_coords inside each tuple, hashing
+     * function will always deref pointers first */
+    hb_hashmap_t<const hb_vector_t<char>*, unsigned> coords_count_map;
+
+    /* count the num of shared coords */
+    for (tuple_variations_t& vars: glyph_variations)
+    {
+      for (tuple_delta_t& var : vars.tuple_vars)
+      {
+        if (!var.compile_peak_coords (axes_index_map, axes_old_index_tag_map))
+          return false;
+        unsigned* count;
+        if (coords_count_map.has (&(var.compiled_peak_coords), &count))
+          coords_count_map.set (&(var.compiled_peak_coords), *count + 1);
+        else
+          coords_count_map.set (&(var.compiled_peak_coords), 1);
+      }
+    }
+
+    if (!coords_count_map || coords_count_map.in_error ())
+      return false;
+
+    /* add only those coords that are used more than once into the vector and sort */
+    hb_vector_t<const hb_vector_t<char>*> shared_coords;
+    if (unlikely (!shared_coords.alloc (coords_count_map.get_population ())))
+      return false;
+
+    for (const auto _ : coords_count_map.iter ())
+    {
+      if (_.second == 1) continue;
+      shared_coords.push (_.first);
+    }
+
+    /* no shared tuples: no coords are used more than once */
+    if (!shared_coords) return true;
+    /* sorting based on the coords frequency first (high to low), then compare
+     * the coords bytes */
+    hb_qsort (shared_coords.arrayZ, shared_coords.length, sizeof (hb_vector_t<char>*), _cmp_coords, (void *) (&coords_count_map));
+
+    /* build shared_coords->idx map and shared tuples byte array */
+
+    shared_tuples_count = hb_min (0xFFFu + 1, shared_coords.length);
+    unsigned len = shared_tuples_count * (shared_coords[0]->length);
+    if (unlikely (!compiled_shared_tuples.alloc (len)))
+      return false;
+
+    for (unsigned i = 0; i < shared_tuples_count; i++)
+    {
+      shared_tuples_idx_map.set (shared_coords[i], i);
+      /* add a concat() in hb_vector_t? */
+      for (char c : shared_coords[i]->iter ())
+        compiled_shared_tuples.push (c);
+    }
+
+    return true;
+  }
+
+  static int _cmp_coords (const void *pa, const void *pb, void *arg)
+  {
+    const hb_hashmap_t<const hb_vector_t<char>*, unsigned>* coords_count_map =
+        reinterpret_cast<const hb_hashmap_t<const hb_vector_t<char>*, unsigned>*> (arg);
+
+    /* shared_coords is hb_vector_t<const hb_vector_t<char>*> so casting pa/pb
+     * to be a pointer to a pointer */
+    const hb_vector_t<char>** a = reinterpret_cast<const hb_vector_t<char>**> (const_cast<void*>(pa));
+    const hb_vector_t<char>** b = reinterpret_cast<const hb_vector_t<char>**> (const_cast<void*>(pb));
+
+    bool has_a = coords_count_map->has (*a);
+    bool has_b = coords_count_map->has (*b);
+
+    if (has_a && has_b)
+    {
+      unsigned a_num = coords_count_map->get (*a);
+      unsigned b_num = coords_count_map->get (*b);
+
+      if (a_num != b_num)
+        return b_num - a_num;
+
+      return (*b)->as_array().cmp ((*a)->as_array ());
+    }
+    else if (has_a) return -1;
+    else if (has_b) return 1;
+    else return 0;
+  }
+};
+
 struct gvar
 {
   static constexpr hb_tag_t tableTag = HB_OT_TAG_gvar;