[subset] don't let VariationStore subset() produce inner_maps

Make it a subset-planning object so VariationStore can subset to
specified inner_maps.

Also add a layout_variation_idx_delta_map in subset_plan

src/hb-ot-layout-common.hh

@@ -2562,7 +2562,7 @@ struct VariationStore
 
   bool serialize (hb_serialize_context_t *c,
 		  const VariationStore *src,
-		  const hb_array_t <hb_inc_bimap_t> &inner_maps)
+		  const hb_array_t <const hb_inc_bimap_t> &inner_maps)
   {
     TRACE_SERIALIZE (this);
 #ifdef HB_NO_VAR
@@ -2617,7 +2617,7 @@ struct VariationStore
     return_trace (true);
   }
 
-  bool subset (hb_subset_context_t *c) const
+  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
@@ -2627,22 +2627,7 @@ struct VariationStore
     VariationStore *varstore_prime = c->serializer->start_embed<VariationStore> ();
     if (unlikely (!varstore_prime)) return_trace (false);
 
-    const hb_set_t *variation_indices = c->plan->layout_variation_indices;
-    if (variation_indices->is_empty ()) return_trace (false);
-
-    hb_vector_t<hb_inc_bimap_t> inner_maps;
-    inner_maps.resize ((unsigned) dataSets.len);
-
-    for (unsigned idx : c->plan->layout_variation_indices->iter ())
-    {
-      uint16_t major = idx >> 16;
-      uint16_t minor = idx & 0xFFFF;
-
-      if (major >= inner_maps.length)
-	return_trace (false);
-      inner_maps[major].add (minor);
-    }
-    varstore_prime->serialize (c->serializer, this, inner_maps.as_array ());
+    varstore_prime->serialize (c->serializer, this, inner_maps);
 
     return_trace (
         !c->serializer->in_error()

src/hb-ot-layout-gdef-table.hh

@@ -586,7 +586,7 @@ struct GDEFVersion1_2
     bool subset_varstore = false;
     if (version.to_int () >= 0x00010003u)
     {
-      subset_varstore = out->varStore.serialize_subset (c, varStore, this);
+      subset_varstore = out->varStore.serialize_subset (c, varStore, this, c->plan->gdef_varstore_inner_maps.as_array ());
     }
 
     if (subset_varstore)

src/hb-subset-plan.cc

@@ -269,11 +269,26 @@ _closure_glyphs_lookups_features (hb_subset_plan_t   *plan,
 
 #ifndef HB_NO_VAR
 static inline void
-_collect_layout_variation_indices (hb_subset_plan_t* plan,
-				   const hb_set_t *glyphset,
-				   const hb_map_t *gpos_lookups,
-				   hb_set_t  *layout_variation_indices,
-				   hb_map_t  *layout_variation_idx_map)
+_generate_varstore_inner_maps (const hb_set_t& varidx_set,
+                               unsigned subtable_count,
+                               hb_vector_t<hb_inc_bimap_t> &inner_maps /* OUT */)
+{
+  if (varidx_set.is_empty () || subtable_count == 0) return;
+
+  inner_maps.resize (subtable_count);
+  for (unsigned idx : varidx_set)
+  {
+    uint16_t major = idx >> 16;
+    uint16_t minor = idx & 0xFFFF;
+
+    if (major >= subtable_count)
+      continue;
+    inner_maps[major].add (minor);
+  }
+}
+
+static inline void
+_collect_layout_variation_indices (hb_subset_plan_t* plan)
 {
   hb_blob_ptr_t<OT::GDEF> gdef = plan->source_table<OT::GDEF> ();
   hb_blob_ptr_t<GPOS> gpos = plan->source_table<GPOS> ();
@@ -284,13 +299,18 @@ _collect_layout_variation_indices (hb_subset_plan_t* plan,
     gpos.destroy ();
     return;
   }
-  OT::hb_collect_variation_indices_context_t c (layout_variation_indices, glyphset, gpos_lookups);
+
+  hb_set_t varidx_set;
+  OT::hb_collect_variation_indices_context_t c (&varidx_set, plan->_glyphset_gsub, plan->gpos_lookups);
   gdef->collect_variation_indices (&c);
 
   if (hb_ot_layout_has_positioning (plan->source))
     gpos->collect_variation_indices (&c);
 
-  gdef->remap_layout_variation_indices (layout_variation_indices, layout_variation_idx_map);
+  gdef->remap_layout_variation_indices (&varidx_set, plan->layout_variation_idx_delta_map);
+
+  unsigned subtable_count = gdef->has_var_store () ? gdef->get_var_store ().get_sub_table_count () : 0;
+  _generate_varstore_inner_maps (varidx_set, subtable_count, plan->gdef_varstore_inner_maps);
 
   gdef.destroy ();
   gpos.destroy ();
@@ -506,11 +526,7 @@ _populate_gids_to_retain (hb_subset_plan_t* plan,
 
 #ifndef HB_NO_VAR
   if (close_over_gdef)
-    _collect_layout_variation_indices (plan,
-				       plan->_glyphset_gsub,
-				       plan->gpos_lookups,
-				       plan->layout_variation_indices,
-				       plan->layout_variation_idx_map);
+    _collect_layout_variation_indices (plan);
 #endif
 }
 
@@ -682,8 +698,8 @@ hb_subset_plan_create_or_fail (hb_face_t	 *face,
   plan->gpos_features = hb_map_create ();
   plan->colrv1_layers = hb_map_create ();
   plan->colr_palettes = hb_map_create ();
-  plan->layout_variation_indices = hb_set_create ();
-  plan->layout_variation_idx_map = hb_map_create ();
+  plan->check_success (plan->layout_variation_idx_delta_map = hb_hashmap_create<unsigned, hb_pair_t<unsigned, int>> ());
+  plan->gdef_varstore_inner_maps.init ();
 
   plan->check_success (plan->sanitized_table_cache = hb_hashmap_create<hb_tag_t, hb::unique_ptr<hb_blob_t>> ());
   plan->check_success (plan->axes_location = hb_hashmap_create<hb_tag_t, int> ());

src/hb-subset-plan.hh

@@ -33,6 +33,7 @@
 #include "hb-subset-input.hh"
 
 #include "hb-map.hh"
+#include "hb-bimap.hh"
 #include "hb-set.hh"
 
 struct hb_subset_plan_t
@@ -66,8 +67,6 @@ struct hb_subset_plan_t
     hb_map_destroy (gpos_features);
     hb_map_destroy (colrv1_layers);
     hb_map_destroy (colr_palettes);
-    hb_set_destroy (layout_variation_indices);
-    hb_map_destroy (layout_variation_idx_map);
 
     hb_hashmap_destroy (gsub_langsys);
     hb_hashmap_destroy (gpos_langsys);
@@ -75,6 +74,7 @@ struct hb_subset_plan_t
     hb_hashmap_destroy (sanitized_table_cache);
     hb_hashmap_destroy (hmtx_map);
     hb_hashmap_destroy (vmtx_map);
+    hb_hashmap_destroy (layout_variation_idx_delta_map);
 
     if (user_axes_location)
     {
@@ -147,10 +147,11 @@ struct hb_subset_plan_t
   hb_map_t *colrv1_layers;
   hb_map_t *colr_palettes;
 
-  //The set of layout item variation store delta set indices to be retained
-  hb_set_t *layout_variation_indices;
-  //Old -> New layout item variation store delta set index mapping
-  hb_map_t *layout_variation_idx_map;
+  //Old layout item variation index -> (New varidx, delta) mapping
+  hb_hashmap_t<unsigned, hb_pair_t<unsigned, int>> *layout_variation_idx_delta_map;
+
+  //gdef varstore retained varidx mapping
+  hb_vector_t<hb_inc_bimap_t> gdef_varstore_inner_maps;
 
   hb_hashmap_t<hb_tag_t, hb::unique_ptr<hb_blob_t>>* sanitized_table_cache;
   //normalized axes location map