[subset] layout closure_features and store them in subset-plan

docs/harfbuzz-sections.txt

@@ -552,6 +552,7 @@ HB_OT_TAG_GSUB
 HB_OT_TAG_JSTF
 hb_ot_layout_baseline_tag_t
 hb_ot_layout_closure_lookups
+hb_ot_layout_closure_features
 hb_ot_layout_collect_lookups
 hb_ot_layout_collect_features
 hb_ot_layout_feature_get_characters

src/hb-ot-layout-common.hh

@@ -289,6 +289,9 @@ DECLARE_NULL_NAMESPACE_BYTES (OT, RangeRecord);
 
 struct IndexArray : ArrayOf<Index>
 {
+  bool intersects (const hb_map_t *indexes) const
+  { return hb_any (*this, indexes); }
+
   unsigned int get_indexes (unsigned int start_offset,
 			    unsigned int *_count /* IN/OUT */,
 			    unsigned int *_indexes /* OUT */) const
@@ -682,6 +685,9 @@ struct Feature
   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, RecordList_subset_context_t *r) const
   {
     TRACE_SUBSET (this);
@@ -2304,6 +2310,14 @@ struct FeatureTableSubstitutionRecord
     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);
+  }
+
   bool sanitize (hb_sanitize_context_t *c, const void *base) const
   {
     TRACE_SANITIZE (this);
@@ -2343,6 +2357,13 @@ struct FeatureTableSubstitution
     ;
   }
 
+  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 sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
@@ -2370,6 +2391,13 @@ struct FeatureVariationRecord
     return (base+substitutions).collect_lookups (feature_indexes, 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 sanitize (hb_sanitize_context_t *c, const void *base) const
   {
     TRACE_SANITIZE (this);
@@ -2427,6 +2455,13 @@ struct FeatureVariations
       r.collect_lookups (this, feature_indexes, lookup_indexes);
   }
 
+  void closure_features (const hb_map_t *lookup_indexes,
+			 hb_set_t       *feature_indexes /* OUT */) const
+  {
+    for (const FeatureVariationRecord& record : varRecords)
+      record.closure_features (this, lookup_indexes, feature_indexes);
+  }
+
   bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);

src/hb-ot-layout-gsubgpos.hh

@@ -3083,6 +3083,20 @@ struct GSUBGPOS
     return_trace (true);
   }
 
+  void closure_features (const hb_map_t *lookup_indexes, /* IN */
+			 hb_set_t       *feature_indexes /* OUT */) const
+  {
+    for (unsigned i = 0; i < get_feature_count (); i++)
+    {
+      if (get_feature (i).intersects_lookup_indexes (lookup_indexes))
+        feature_indexes->add (i);
+    }
+#ifndef HB_NO_VAR
+    if (version.to_int () >= 0x00010001u)
+      (this+featureVars).closure_features (lookup_indexes, feature_indexes);
+#endif
+  }
+
   unsigned int get_size () const
   {
     return min_size +

src/hb-ot-layout.cc

@@ -1238,6 +1238,27 @@ hb_ot_layout_closure_lookups (hb_face_t      *face,
   hb_set_subtract (lookup_indexes, &inactive_lookups);
 }
 
+/**
+ * hb_ot_layout_closure_features:
+ * @face: #hb_face_t to work upon
+ * @table_tag: HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
+ * @lookup_indexes: (in): collected active lookup_indices
+ * @feature_indexes: (out): all active feature indexes collected
+ *
+ * Returns all active feature indexes
+ *
+ * Since: REPLACEME
+ **/
+void
+hb_ot_layout_closure_features (hb_face_t      *face,
+			       hb_tag_t        table_tag,
+			       const hb_map_t *lookup_indexes, /* IN */
+			       hb_set_t       *feature_indexes /* OUT */)
+{
+  const OT::GSUBGPOS &g = get_gsubgpos_table (face, table_tag);
+  g.closure_features (lookup_indexes, feature_indexes);
+}
+
 
 #ifndef HB_NO_LAYOUT_COLLECT_GLYPHS
 /**

src/hb-ot-layout.h

@@ -269,6 +269,12 @@ hb_ot_layout_closure_lookups (hb_face_t      *face,
 			      const hb_set_t *glyphs,
 			      hb_set_t       *lookup_indexes /* IN/OUT */);
 
+HB_EXTERN void
+hb_ot_layout_closure_features (hb_face_t      *face,
+			       hb_tag_t        table_tag,
+			       const hb_map_t *lookup_indexes, /* IN */
+			       hb_set_t       *feature_indexes /* OUT */);
+
 HB_EXTERN void
 hb_ot_layout_lookup_collect_glyphs (hb_face_t    *face,
 				    hb_tag_t      table_tag,

src/hb-subset-plan.cc

@@ -51,20 +51,21 @@ _add_cff_seac_components (const OT::cff1::accelerator_t &cff,
 
 #ifndef HB_NO_SUBSET_LAYOUT
 static void
-_remap_lookups (const hb_set_t *lookup_indices,
+_remap_indexes (const hb_set_t *indexes,
-		hb_map_t       *lookups /* OUT */)
+		hb_map_t       *mapping /* OUT */)
 {
-  unsigned count = lookup_indices->get_population ();
+  unsigned count = indexes->get_population ();
 
-  for (auto _ : + hb_zip (lookup_indices->iter (), hb_range (count)))
+  for (auto _ : + hb_zip (indexes->iter (), hb_range (count)))
-    lookups->set (_.first, _.second);
+    mapping->set (_.first, _.second);
 
 }
 
 static inline void
-_gsub_closure_glyphs_and_lookups (hb_face_t *face,
+_gsub_closure_glyphs_lookups_features (hb_face_t *face,
 				       hb_set_t *gids_to_retain,
-				  hb_map_t *gsub_lookups)
+				       hb_map_t *gsub_lookups,
+				       hb_map_t *gsub_features)
 {
   hb_set_t lookup_indices;
   hb_ot_layout_collect_lookups (face,
@@ -80,13 +81,22 @@ _gsub_closure_glyphs_and_lookups (hb_face_t *face,
 				HB_OT_TAG_GSUB,
 				gids_to_retain,
 				&lookup_indices);
-  _remap_lookups (&lookup_indices, gsub_lookups);
+  _remap_indexes (&lookup_indices, gsub_lookups);
+
+  //closure features
+  hb_set_t feature_indices;
+  hb_ot_layout_closure_features (face,
+				 HB_OT_TAG_GSUB,
+				 gsub_lookups,
+				 &feature_indices);
+  _remap_indexes (&feature_indices, gsub_features);
 }
 
 static inline void
-_gpos_closure_lookups (hb_face_t      *face,
+_gpos_closure_lookups_features (hb_face_t      *face,
 				const hb_set_t *gids_to_retain,
-		       hb_map_t       *gpos_lookups)
+				hb_map_t       *gpos_lookups,
+				hb_map_t       *gpos_features)
 {
   hb_set_t lookup_indices;
   hb_ot_layout_collect_lookups (face,
@@ -99,7 +109,15 @@ _gpos_closure_lookups (hb_face_t      *face,
 				HB_OT_TAG_GPOS,
 				gids_to_retain,
 				&lookup_indices);
-  _remap_lookups (&lookup_indices, gpos_lookups);
+  _remap_indexes (&lookup_indices, gpos_lookups);
+
+  //closure features
+  hb_set_t feature_indices;
+  hb_ot_layout_closure_features (face,
+				 HB_OT_TAG_GPOS,
+				 gpos_lookups,
+				 &feature_indices);
+  _remap_indexes (&feature_indices, gpos_features);
 }
 #endif
 
@@ -165,11 +183,11 @@ _populate_gids_to_retain (hb_subset_plan_t* plan,
 
 #ifndef HB_NO_SUBSET_LAYOUT
   if (close_over_gsub)
-    // closure all glyphs/lookups needed for GSUB substitutions.
+    // closure all glyphs/lookups/features needed for GSUB substitutions.
-    _gsub_closure_glyphs_and_lookups (plan->source, plan->_glyphset_gsub, plan->gsub_lookups);
+    _gsub_closure_glyphs_lookups_features (plan->source, plan->_glyphset_gsub, plan->gsub_lookups, plan->gsub_features);
 
   if (close_over_gpos)
-    _gpos_closure_lookups (plan->source, plan->_glyphset_gsub, plan->gpos_lookups);
+    _gpos_closure_lookups_features (plan->source, plan->_glyphset_gsub, plan->gpos_lookups, plan->gpos_features);
 #endif
   _remove_invalid_gids (plan->_glyphset_gsub, plan->source->get_num_glyphs ());
 
@@ -274,6 +292,8 @@ hb_subset_plan_create (hb_face_t         *face,
   plan->reverse_glyph_map = hb_map_create ();
   plan->gsub_lookups = hb_map_create ();
   plan->gpos_lookups = hb_map_create ();
+  plan->gsub_features = hb_map_create ();
+  plan->gpos_features = hb_map_create ();
 
   _populate_gids_to_retain (plan,
 			    input->unicodes,
@@ -313,6 +333,9 @@ hb_subset_plan_destroy (hb_subset_plan_t *plan)
   hb_set_destroy (plan->_glyphset_gsub);
   hb_map_destroy (plan->gsub_lookups);
   hb_map_destroy (plan->gpos_lookups);
+  hb_map_destroy (plan->gsub_features);
+  hb_map_destroy (plan->gpos_features);
+
 
   free (plan);
 }

src/hb-subset-plan.hh

@@ -71,6 +71,10 @@ struct hb_subset_plan_t
   hb_map_t *gsub_lookups;
   hb_map_t *gpos_lookups;
 
+  //active features we'd like to retain
+  hb_map_t *gsub_features;
+  hb_map_t *gpos_features;
+
  public:
 
   /*