[subset] add option to have the subsetter set the mac overlaps flag on each glyph.

src/hb-ot-glyf-table.hh

@@ -281,6 +281,11 @@ struct glyf
     hb_codepoint_t get_glyph_index ()       const { return glyphIndex; }
 
     void drop_instructions_flag ()  { flags = (uint16_t) flags & ~WE_HAVE_INSTRUCTIONS; }
+    void set_overlaps_flag ()
+    {
+      flags = (uint16_t) flags | OVERLAP_COMPOUND;
+    }
+
     bool has_instructions ()  const { return   flags & WE_HAVE_INSTRUCTIONS; }
 
     bool has_more ()          const { return   flags & MORE_COMPONENTS; }
@@ -433,7 +438,7 @@ struct glyf
       FLAG_REPEAT         = 0x08,
       FLAG_X_SAME         = 0x10,
       FLAG_Y_SAME         = 0x20,
-      FLAG_RESERVED1 = 0x40,
+      FLAG_OVERLAP_SIMPLE = 0x40,
       FLAG_RESERVED2      = 0x80
     };
 
@@ -553,6 +558,17 @@ struct glyf
 	dest_end = bytes.sub_array (glyph_length, bytes.length - glyph_length);
       }
 
+      void set_overlaps_flag ()
+      {
+        if (unlikely (!header.numberOfContours)) return;
+
+        unsigned flags_offset = length (instructions_length ());
+        if (unlikely (length (flags_offset + 1) > bytes.length)) return;
+
+	HBUINT8 &first_flag = (HBUINT8 &) StructAtOffset<HBUINT16> (&bytes, flags_offset);
+        first_flag = (uint8_t) first_flag | FLAG_OVERLAP_SIMPLE;
+      }
+
       static bool read_points (const HBUINT8 *&p /* IN/OUT */,
 			       contour_point_vector_t &points_ /* IN/OUT */,
 			       const hb_bytes_t &bytes,
@@ -666,6 +682,12 @@ struct glyf
       /* Chop instructions off the end */
       void drop_hints_bytes (hb_bytes_t &dest_start) const
       { dest_start = bytes.sub_array (0, bytes.length - instructions_length (bytes)); }
+
+      void set_overlaps_flag ()
+      {
+        const_cast<CompositeGlyphChain &> (StructAfter<CompositeGlyphChain, GlyphHeader> (header))
+                .set_overlaps_flag ();
+      }
     };
 
     enum glyph_type_t { EMPTY, SIMPLE, COMPOSITE };
@@ -695,6 +717,15 @@ struct glyf
       }
     }
 
+    void set_overlaps_flag ()
+    {
+      switch (type) {
+      case COMPOSITE: CompositeGlyph (*header, bytes).set_overlaps_flag (); return;
+      case SIMPLE:    SimpleGlyph (*header, bytes).set_overlaps_flag (); return;
+      default:        return;
+      }
+    }
+
     void drop_hints_bytes (hb_bytes_t &dest_start, hb_bytes_t &dest_end) const
     {
       switch (type) {
@@ -1232,6 +1263,9 @@ struct glyf
 
       if (plan->drop_hints) Glyph (dest_glyph).drop_hints ();
 
+      if (plan->overlaps_flag)
+        Glyph (dest_glyph).set_overlaps_flag ();
+
       return_trace (true);
     }
 

src/hb-subset-input.cc

@@ -53,6 +53,7 @@ hb_subset_input_create_or_fail ()
   input->desubroutinize = false;
   input->retain_gids = false;
   input->name_legacy = false;
+  input->overlaps_flag = false;
 
   hb_tag_t default_drop_tables[] = {
     // Layout disabled by default
@@ -224,3 +225,16 @@ hb_subset_input_get_name_legacy (hb_subset_input_t *subset_input)
 {
   return subset_input->name_legacy;
 }
+
+HB_EXTERN void
+hb_subset_input_set_overlaps_flag (hb_subset_input_t *subset_input,
+                                   hb_bool_t overlaps_flag)
+{
+  subset_input->overlaps_flag = overlaps_flag;
+}
+
+HB_EXTERN hb_bool_t
+hb_subset_input_get_overlaps_flag (hb_subset_input_t *subset_input)
+{
+  return subset_input->overlaps_flag;
+}

src/hb-subset-input.hh

@@ -48,6 +48,7 @@ struct hb_subset_input_t
   bool desubroutinize;
   bool retain_gids;
   bool name_legacy;
+  bool overlaps_flag;
   /* TODO
    *
    * features

src/hb-subset-plan.cc

@@ -392,6 +392,7 @@ hb_subset_plan_create (hb_face_t         *face,
   plan->desubroutinize = input->desubroutinize;
   plan->retain_gids = input->retain_gids;
   plan->name_legacy = input->name_legacy;
+  plan->overlaps_flag = input->overlaps_flag;
   plan->unicodes = hb_set_create ();
   plan->name_ids = hb_set_reference (input->name_ids);
   _nameid_closure (face, plan->name_ids);

src/hb-subset-plan.hh

@@ -44,6 +44,7 @@ struct hb_subset_plan_t
   bool desubroutinize : 1;
   bool retain_gids : 1;
   bool name_legacy : 1;
+  bool overlaps_flag : 1;
 
   // For each cp that we'd like to retain maps to the corresponding gid.
   hb_set_t *unicodes;

src/hb-subset.h

@@ -87,6 +87,13 @@ hb_subset_input_set_name_legacy (hb_subset_input_t *subset_input,
 HB_EXTERN hb_bool_t
 hb_subset_input_get_name_legacy (hb_subset_input_t *subset_input);
 
+HB_EXTERN void
+hb_subset_input_set_overlaps_flag (hb_subset_input_t *subset_input,
+                                   hb_bool_t overlaps_flag);
+
+HB_EXTERN hb_bool_t
+hb_subset_input_get_overlaps_flag (hb_subset_input_t *subset_input);
+
 /* hb_subset () */
 HB_EXTERN hb_face_t *
 hb_subset (hb_face_t *source, hb_subset_input_t *input);

util/options-subset.cc

@@ -255,7 +255,8 @@ subset_options_t::add_options (option_parser_t *parser)
     {"num-iterations", 'n', 0, G_OPTION_ARG_INT,
      &this->num_iterations,
      "Run subsetter N times (default: 1)", "N"},
-
+    {"set-overlaps-flag", 0, 0, G_OPTION_ARG_NONE,  &this->input->overlaps_flag,
+     "Set the overlaps flag on each glyph.",   nullptr},
     {nullptr}
   };
   parser->add_group (entries,