Update head table with loca format selected by glyf+loca subsetting.

src/hb-subset-glyf.cc

@@ -103,10 +103,8 @@ _hb_subset_glyf_and_loca (const OT::glyf::accelerator_t  &glyf,
 {
   // TODO(grieger): Sanity check writes to make sure they are in-bounds.
   // TODO(grieger): Sanity check allocation size for the new table.
-  // TODO(grieger): Subset loca simultaneously.
   // TODO(grieger): Don't fail on bad offsets, just dump them.
   // TODO(grieger): Support short loca output.
-  // TODO(grieger): Add a extra loca entry at the end.
 
   unsigned int glyf_prime_size;
   unsigned int loca_prime_size;
@@ -150,7 +148,8 @@ _hb_subset_glyf_and_loca (const OT::glyf::accelerator_t  &glyf,
 bool
 hb_subset_glyf_and_loca (hb_subset_plan_t *plan,
                          hb_face_t        *face,
-                         hb_blob_t       **glyf_prime /* OUT */,
+                         bool             *use_short_loca, /* OUT */
+                         hb_blob_t       **glyf_prime, /* OUT */
                          hb_blob_t       **loca_prime /* OUT */)
 {
   hb_blob_t *glyf_blob = OT::Sanitizer<OT::glyf>().sanitize (face->reference_table (HB_OT_TAG_glyf));
@@ -161,7 +160,7 @@ hb_subset_glyf_and_loca (hb_subset_plan_t *plan,
   bool result = _hb_subset_glyf_and_loca (glyf, glyf_data, plan->gids_to_retain, glyf_prime, loca_prime);
   glyf.fini();
 
-  // TODO(grieger): Subset loca
+  *use_short_loca = false;
 
   return result;
 }

src/hb-subset-glyf.hh

@@ -34,6 +34,7 @@
 bool
 hb_subset_glyf_and_loca (hb_subset_plan_t *plan,
                          hb_face_t        *face,
+                         bool             *use_short_loca, /* OUT */
                          hb_blob_t       **glyf_prime /* OUT */,
                          hb_blob_t       **loca_prime /* OUT */);
 

src/hb-subset.cc

@@ -253,6 +253,32 @@ hb_subset_face_add_table (hb_face_t *face, hb_tag_t tag, hb_blob_t *blob)
   return true;
 }
 
+bool
+_add_head_and_set_loca_version (hb_face_t *source, bool use_short_loca, hb_face_t *dest)
+{
+  hb_blob_t *head_blob = OT::Sanitizer<OT::head>().sanitize (hb_face_reference_table (source, HB_OT_TAG_head));
+  const OT::head *head = OT::Sanitizer<OT::head>::lock_instance (head_blob);
+
+  if (head) {
+    OT::head *head_prime = (OT::head *) calloc (OT::head::static_size, 1);
+    memcpy (head_prime, head, OT::head::static_size);
+    head_prime->indexToLocFormat.set (use_short_loca ? 0 : 1);
+
+    hb_blob_t *head_prime_blob = hb_blob_create ((const char*) head_prime,
+                                                 OT::head::static_size,
+                                                 HB_MEMORY_MODE_WRITABLE,
+                                                 head_prime,
+                                                 free);
+    hb_subset_face_add_table (dest, HB_OT_TAG_head, head_prime_blob);
+
+    hb_blob_destroy (head_prime_blob);
+  }
+
+  hb_blob_destroy (head_blob);
+
+  return !head;
+}
+
 bool
 _subset_glyf (hb_subset_plan_t *plan, hb_face_t *source, hb_face_t *dest)
 {
@@ -260,16 +286,20 @@ _subset_glyf (hb_subset_plan_t *plan, hb_face_t *source, hb_face_t *dest)
   hb_blob_t *loca_prime = nullptr;
 
   bool success = true;
+  bool use_short_loca = false;
   // TODO(grieger): Migrate to subset function on the table like cmap.
-  if (hb_subset_glyf_and_loca (plan, source, &glyf_prime, &loca_prime)) {
+  if (hb_subset_glyf_and_loca (plan, source, &use_short_loca, &glyf_prime, &loca_prime)) {
     hb_subset_face_add_table (dest, HB_OT_TAG_glyf, glyf_prime);
     hb_subset_face_add_table (dest, HB_OT_TAG_loca, loca_prime);
+    success = success && _add_head_and_set_loca_version (source, use_short_loca, dest);
   } else {
     success = false;
   }
   hb_blob_destroy (loca_prime);
   hb_blob_destroy (glyf_prime);
 
+  _add_head_and_set_loca_version (source, use_short_loca, dest);
+
   return success;
 }
 
@@ -284,8 +314,11 @@ _subset_table (hb_subset_plan_t *plan,
   switch (tag) {
     case HB_OT_TAG_glyf:
       return _subset_glyf (plan, source, dest);
+    case HB_OT_TAG_head:
+      // SKIP head, it's handled by glyf
+      return true;
     case HB_OT_TAG_loca:
-      // SKIP loca, it's handle by the glyf subsetter.
+      // SKIP loca, it's handle by glyf
       return true;
     case HB_OT_TAG_cmap:
       // TODO(rsheeter): remove hb_subset_face_add_table