[subset] support option --layout-features

src/hb-subset-input.cc

@@ -48,12 +48,14 @@ hb_subset_input_create_or_fail ()
   hb_set_add_range (input->name_ids, 0, 6);
   input->name_languages = hb_set_create ();
   hb_set_add (input->name_languages, 0x0409);
+  input->layout_features = hb_set_create ();
   input->drop_tables = hb_set_create ();
   input->drop_hints = false;
   input->desubroutinize = false;
   input->retain_gids = false;
   input->name_legacy = false;
   input->overlaps_flag = false;
+  input->retain_all_layout_features = false;
 
   hb_tag_t default_drop_tables[] = {
     // Layout disabled by default
@@ -82,6 +84,94 @@ hb_subset_input_create_or_fail ()
 
   input->drop_tables->add_array (default_drop_tables, ARRAY_LENGTH (default_drop_tables));
 
+  //copied from _layout_features_groups in fonttools
+  hb_tag_t default_layout_features[] = {
+    // default shaper
+    // common
+    HB_TAG ('r', 'v', 'r', 'n'),
+    HB_TAG ('c', 'c', 'm', 'p'),
+    HB_TAG ('l', 'i', 'g', 'a'),
+    HB_TAG ('l', 'o', 'c', 'l'),
+    HB_TAG ('m', 'a', 'r', 'k'),
+    HB_TAG ('m', 'k', 'm', 'k'),
+    HB_TAG ('r', 'l', 'i', 'g'),
+
+    //fractions
+    HB_TAG ('f', 'r', 'a', 'c'),
+    HB_TAG ('n', 'u', 'm', 'r'),
+    HB_TAG ('d', 'n', 'o', 'm'),
+
+    //horizontal
+    HB_TAG ('c', 'a', 'l', 't'),
+    HB_TAG ('c', 'l', 'i', 'g'),
+    HB_TAG ('c', 'u', 'r', 's'),
+    HB_TAG ('k', 'e', 'r', 'n'),
+    HB_TAG ('r', 'c', 'l', 't'),
+
+    //vertical
+    HB_TAG ('v', 'a', 'l', 't'),
+    HB_TAG ('v', 'e', 'r', 't'),
+    HB_TAG ('v', 'k', 'r', 'n'),
+    HB_TAG ('v', 'p', 'a', 'l'),
+    HB_TAG ('v', 'r', 't', '2'),
+
+    //ltr
+    HB_TAG ('l', 't', 'r', 'a'),
+    HB_TAG ('l', 't', 'r', 'm'),
+
+    //rtl
+    HB_TAG ('r', 't', 'l', 'a'),
+    HB_TAG ('r', 't', 'l', 'm'),
+
+    //Complex shapers
+    //arabic
+    HB_TAG ('i', 'n', 'i', 't'),
+    HB_TAG ('m', 'e', 'd', 'i'),
+    HB_TAG ('f', 'i', 'n', 'a'),
+    HB_TAG ('i', 's', 'o', 'l'),
+    HB_TAG ('m', 'e', 'd', '2'),
+    HB_TAG ('f', 'i', 'n', '2'),
+    HB_TAG ('f', 'i', 'n', '3'),
+    HB_TAG ('c', 's', 'w', 'h'),
+    HB_TAG ('m', 's', 'e', 't'),
+    HB_TAG ('s', 't', 'c', 'h'),
+
+    //hangul
+    HB_TAG ('l', 'j', 'm', 'o'),
+    HB_TAG ('v', 'j', 'm', 'o'),
+    HB_TAG ('t', 'j', 'm', 'o'),
+
+    //tibetan
+    HB_TAG ('a', 'b', 'v', 's'),
+    HB_TAG ('b', 'l', 'w', 's'),
+    HB_TAG ('a', 'b', 'v', 'm'),
+    HB_TAG ('b', 'l', 'w', 'm'),
+
+    //indic
+    HB_TAG ('n', 'u', 'k', 't'),
+    HB_TAG ('a', 'k', 'h', 'n'),
+    HB_TAG ('r', 'p', 'h', 'f'),
+    HB_TAG ('r', 'k', 'r', 'f'),
+    HB_TAG ('p', 'r', 'e', 'f'),
+    HB_TAG ('b', 'l', 'w', 'f'),
+    HB_TAG ('h', 'a', 'l', 'f'),
+    HB_TAG ('a', 'b', 'v', 'f'),
+    HB_TAG ('p', 's', 't', 'f'),
+    HB_TAG ('c', 'f', 'a', 'r'),
+    HB_TAG ('v', 'a', 't', 'u'),
+    HB_TAG ('c', 'j', 'c', 't'),
+    HB_TAG ('i', 'n', 'i', 't'),
+    HB_TAG ('p', 'r', 'e', 's'),
+    HB_TAG ('a', 'b', 'v', 's'),
+    HB_TAG ('b', 'l', 'w', 's'),
+    HB_TAG ('p', 's', 't', 's'),
+    HB_TAG ('h', 'a', 'l', 'n'),
+    HB_TAG ('d', 'i', 's', 't'),
+    HB_TAG ('a', 'b', 'v', 'm'),
+    HB_TAG ('b', 'l', 'w', 'm'),
+  };
+
+  input->layout_features->add_array (default_layout_features, ARRAY_LENGTH (default_layout_features));
   return input;
 }
 
@@ -117,6 +207,7 @@ hb_subset_input_destroy (hb_subset_input_t *subset_input)
   hb_set_destroy (subset_input->name_ids);
   hb_set_destroy (subset_input->name_languages);
   hb_set_destroy (subset_input->drop_tables);
+  hb_set_destroy (subset_input->layout_features);
 
   free (subset_input);
 }

src/hb-subset-input.hh

@@ -43,12 +43,14 @@ struct hb_subset_input_t
   hb_set_t *name_ids;
   hb_set_t *name_languages;
   hb_set_t *drop_tables;
+  hb_set_t *layout_features;
 
   bool drop_hints;
   bool desubroutinize;
   bool retain_gids;
   bool name_legacy;
   bool overlaps_flag;
+  bool retain_all_layout_features;
   /* TODO
    *
    * features

src/hb-subset-plan.cc

@@ -85,88 +85,96 @@ _remap_indexes (const hb_set_t *indexes,
 }
 
 #ifndef HB_NO_SUBSET_LAYOUT
-static inline void
-_gsub_closure_glyphs_lookups_features (hb_face_t *face,
-				       hb_set_t *gids_to_retain,
-				       hb_map_t *gsub_lookups,
-				       hb_map_t *gsub_features,
-				       script_langsys_map *gsub_langsys)
+typedef void (*layout_collect_func_t) (hb_face_t *face, hb_tag_t table_tag, const hb_tag_t *scripts, const hb_tag_t *languages, const hb_tag_t *features, hb_set_t *lookup_indexes /* OUT */);
+
+static void _collect_subset_layout (hb_face_t            *face,
+				    hb_tag_t              table_tag,
+				    const hb_set_t       *layout_features_to_retain,
+				    bool                  retain_all_features,
+				    layout_collect_func_t layout_collect_func,
+				    hb_set_t             *lookup_indices /* OUT */)
 {
-  hb_set_t lookup_indices;
-  hb_ot_layout_collect_lookups (face,
-				HB_OT_TAG_GSUB,
-				nullptr,
-				nullptr,
-				nullptr,
-				&lookup_indices);
-  hb_ot_layout_lookups_substitute_closure (face,
-					   &lookup_indices,
-					   gids_to_retain);
-  hb_blob_ptr_t<OT::GSUB> gsub = hb_sanitize_context_t ().reference_table<OT::GSUB> (face);
-  gsub->closure_lookups (face,
-			 gids_to_retain,
-			 &lookup_indices);
-  _remap_indexes (&lookup_indices, gsub_lookups);
-
-  // Collect and prune features
-  hb_set_t feature_indices;
-  hb_ot_layout_collect_features (face,
-                                 HB_OT_TAG_GSUB,
-                                 nullptr,
-                                 nullptr,
-                                 nullptr,
-                                 &feature_indices);
-
-  gsub->prune_features (gsub_lookups, &feature_indices);
-  hb_map_t duplicate_feature_map;
-  gsub->find_duplicate_features (gsub_lookups, &feature_indices, &duplicate_feature_map);
-
-  feature_indices.clear ();
-  gsub->prune_langsys (&duplicate_feature_map, gsub_langsys, &feature_indices);
-  _remap_indexes (&feature_indices, gsub_features);
+  if (retain_all_features)
+  {
+    layout_collect_func (face,
+			 table_tag,
+			 nullptr,
+			 nullptr,
+			 nullptr,
+			 lookup_indices);
+    return;
+  }
 
-  gsub.destroy ();
+  if (hb_set_is_empty (layout_features_to_retain)) return;
+  unsigned num = layout_features_to_retain->get_population () + 1;
+  hb_tag_t *features = (hb_tag_t *) malloc (num * sizeof (hb_tag_t));
+  if (!features) return;
+
+  unsigned i = 0;
+  for (hb_tag_t f : layout_features_to_retain->iter ())
+    features[i++] = f;
+
+  features[i] = 0;
+  
+  layout_collect_func (face,
+		       table_tag,
+		       nullptr,
+		       nullptr,
+		       features,
+		       lookup_indices);
+
+  free (features);
 }
 
+template <typename T>
 static inline void
-_gpos_closure_lookups_features (hb_face_t      *face,
-				const hb_set_t *gids_to_retain,
-				hb_map_t       *gpos_lookups,
-				hb_map_t       *gpos_features,
-				script_langsys_map *gpos_langsys)
+_closure_glyphs_lookups_features (hb_face_t          *face,
+				  hb_set_t           *gids_to_retain,
+				  const hb_set_t     *layout_features_to_retain,
+				  bool                retain_all_features,
+				  hb_map_t           *lookups,
+				  hb_map_t           *features,
+				  script_langsys_map *langsys_map)
 {
+  hb_blob_ptr_t<T> table = hb_sanitize_context_t ().reference_table<T> (face);
+  hb_tag_t table_tag = table->tableTag;
   hb_set_t lookup_indices;
-  hb_ot_layout_collect_lookups (face,
-				HB_OT_TAG_GPOS,
-				nullptr,
-				nullptr,
-				nullptr,
-				&lookup_indices);
-  hb_blob_ptr_t<OT::GPOS> gpos = hb_sanitize_context_t ().reference_table<OT::GPOS> (face);
-  gpos->closure_lookups (face,
-			 gids_to_retain,
+  _collect_subset_layout (face,
+			  table_tag,
+			  layout_features_to_retain,
+			  retain_all_features,
+			  hb_ot_layout_collect_lookups,
+			  &lookup_indices);
+
+  if (table_tag == HB_OT_TAG_GSUB)
+    hb_ot_layout_lookups_substitute_closure (face,
+					    &lookup_indices,
+					     gids_to_retain);
+  table->closure_lookups (face,
+			  gids_to_retain,
 			 &lookup_indices);
-  _remap_indexes (&lookup_indices, gpos_lookups);
+  _remap_indexes (&lookup_indices, lookups);
 
   // Collect and prune features
   hb_set_t feature_indices;
-  hb_ot_layout_collect_features (face,
-                                 HB_OT_TAG_GPOS,
-                                 nullptr,
-                                 nullptr,
-                                 nullptr,
-                                 &feature_indices);
-
-  gpos->prune_features (gpos_lookups, &feature_indices);
+  _collect_subset_layout (face,
+			  table_tag,
+			  layout_features_to_retain,
+			  retain_all_features,
+			  hb_ot_layout_collect_features,
+			  &feature_indices);
+
+  table->prune_features (lookups, &feature_indices);
   hb_map_t duplicate_feature_map;
-  gpos->find_duplicate_features (gpos_lookups, &feature_indices, &duplicate_feature_map);
+  table->find_duplicate_features (lookups, &feature_indices, &duplicate_feature_map);
 
   feature_indices.clear ();
-  gpos->prune_langsys (&duplicate_feature_map, gpos_langsys, &feature_indices);
-  _remap_indexes (&feature_indices, gpos_features);
+  table->prune_langsys (&duplicate_feature_map, langsys_map, &feature_indices);
+  _remap_indexes (&feature_indices, features);
 
-  gpos.destroy ();
+  table.destroy ();
 }
+
 #endif
 
 #ifndef HB_NO_VAR
@@ -265,10 +273,10 @@ _populate_gids_to_retain (hb_subset_plan_t* plan,
 #ifndef HB_NO_SUBSET_LAYOUT
   if (close_over_gsub)
     // closure all glyphs/lookups/features needed for GSUB substitutions.
-    _gsub_closure_glyphs_lookups_features (plan->source, plan->_glyphset_gsub, plan->gsub_lookups, plan->gsub_features, plan->gsub_langsys);
+    _closure_glyphs_lookups_features<OT::GSUB> (plan->source, plan->_glyphset_gsub, plan->layout_features, plan->retain_all_layout_features, plan->gsub_lookups, plan->gsub_features, plan->gsub_langsys);
 
   if (close_over_gpos)
-    _gpos_closure_lookups_features (plan->source, plan->_glyphset_gsub, plan->gpos_lookups, plan->gpos_features, plan->gpos_langsys);
+    _closure_glyphs_lookups_features<OT::GPOS> (plan->source, plan->_glyphset_gsub, plan->layout_features, plan->retain_all_layout_features, plan->gpos_lookups, plan->gpos_features, plan->gpos_langsys);
 #endif
   _remove_invalid_gids (plan->_glyphset_gsub, plan->source->get_num_glyphs ());
 
@@ -393,10 +401,12 @@ hb_subset_plan_create (hb_face_t         *face,
   plan->retain_gids = input->retain_gids;
   plan->name_legacy = input->name_legacy;
   plan->overlaps_flag = input->overlaps_flag;
+  plan->retain_all_layout_features = input->retain_all_layout_features;
   plan->unicodes = hb_set_create ();
   plan->name_ids = hb_set_reference (input->name_ids);
   _nameid_closure (face, plan->name_ids);
   plan->name_languages = hb_set_reference (input->name_languages);
+  plan->layout_features = hb_set_reference (input->layout_features);
   plan->glyphs_requested = hb_set_reference (input->glyphs);
   plan->drop_tables = hb_set_reference (input->drop_tables);
   plan->source = hb_face_reference (face);
@@ -456,6 +466,7 @@ hb_subset_plan_destroy (hb_subset_plan_t *plan)
   hb_set_destroy (plan->unicodes);
   hb_set_destroy (plan->name_ids);
   hb_set_destroy (plan->name_languages);
+  hb_set_destroy (plan->layout_features);
   hb_set_destroy (plan->glyphs_requested);
   hb_set_destroy (plan->drop_tables);
   hb_face_destroy (plan->source);

src/hb-subset-plan.hh

@@ -45,6 +45,7 @@ struct hb_subset_plan_t
   bool retain_gids : 1;
   bool name_legacy : 1;
   bool overlaps_flag : 1;
+  bool retain_all_layout_features : 1;
 
   // For each cp that we'd like to retain maps to the corresponding gid.
   hb_set_t *unicodes;
@@ -55,6 +56,9 @@ struct hb_subset_plan_t
   // name_languages we would like to retain
   hb_set_t *name_languages;
 
+  //layout features which will be preserved
+  hb_set_t *layout_features;
+
   //glyph ids requested to retain
   hb_set_t *glyphs_requested;