1 files changed, 116 insertions, 4 deletions

diff --git a/thirdparty/harfbuzz/src/hb-subset.cc b/thirdparty/harfbuzz/src/hb-subset.cc
index 31ddb4f894..10c572c2f7 100644
--- a/thirdparty/harfbuzz/src/hb-subset.cc
+++ b/thirdparty/harfbuzz/src/hb-subset.cc
@@ -56,6 +56,7 @@
 #include "hb-repacker.hh"
 
 using OT::Layout::GSUB::GSUB;
+using OT::Layout::GPOS;
 
 /**
  * SECTION:hb-subset
@@ -78,6 +79,108 @@ using OT::Layout::GSUB::GSUB;
  * retain glyph ids option and configure the subset to pass through the layout tables untouched.
  */
 
+/*
+ * The list of tables in the open type spec. Used to check for tables that may need handling
+ * if we are unable to list the tables in a face.
+ */
+static hb_tag_t known_tables[] {
+  HB_TAG ('a', 'v', 'a', 'r'),
+  HB_OT_TAG_BASE,
+  HB_OT_TAG_CBDT,
+  HB_OT_TAG_CBLC,
+  HB_OT_TAG_cff1,
+  HB_OT_TAG_cff2,
+  HB_OT_TAG_cmap,
+  HB_OT_TAG_COLR,
+  HB_OT_TAG_CPAL,
+  HB_TAG ('c', 'v', 'a', 'r'),
+  HB_TAG ('c', 'v', 't', ' '),
+  HB_TAG ('D', 'S', 'I', 'G'),
+  HB_TAG ('E', 'B', 'D', 'T'),
+  HB_TAG ('E', 'B', 'L', 'C'),
+  HB_TAG ('E', 'B', 'S', 'C'),
+  HB_TAG ('f', 'p', 'g', 'm'),
+  HB_TAG ('f', 'v', 'a', 'r'),
+  HB_TAG ('g', 'a', 's', 'p'),
+  HB_OT_TAG_GDEF,
+  HB_OT_TAG_glyf,
+  HB_OT_TAG_GPOS,
+  HB_OT_TAG_GSUB,
+  HB_OT_TAG_gvar,
+  HB_OT_TAG_hdmx,
+  HB_OT_TAG_head,
+  HB_OT_TAG_hhea,
+  HB_OT_TAG_hmtx,
+  HB_OT_TAG_HVAR,
+  HB_OT_TAG_JSTF,
+  HB_TAG ('k', 'e', 'r', 'n'),
+  HB_OT_TAG_loca,
+  HB_TAG ('L', 'T', 'S', 'H'),
+  HB_OT_TAG_MATH,
+  HB_OT_TAG_maxp,
+  HB_TAG ('M', 'E', 'R', 'G'),
+  HB_TAG ('m', 'e', 't', 'a'),
+  HB_TAG ('M', 'V', 'A', 'R'),
+  HB_TAG ('P', 'C', 'L', 'T'),
+  HB_OT_TAG_post,
+  HB_TAG ('p', 'r', 'e', 'p'),
+  HB_OT_TAG_sbix,
+  HB_TAG ('S', 'T', 'A', 'T'),
+  HB_TAG ('S', 'V', 'G', ' '),
+  HB_TAG ('V', 'D', 'M', 'X'),
+  HB_OT_TAG_vhea,
+  HB_OT_TAG_vmtx,
+  HB_OT_TAG_VORG,
+  HB_OT_TAG_VVAR,
+  HB_OT_TAG_name,
+  HB_OT_TAG_OS2
+};
+
+static bool _table_is_empty (const hb_face_t *face, hb_tag_t tag)
+{
+  hb_blob_t* blob = hb_face_reference_table (face, tag);
+  bool result = (blob == hb_blob_get_empty ());
+  hb_blob_destroy (blob);
+  return result;
+}
+
+static unsigned int
+_get_table_tags (const hb_subset_plan_t* plan,
+                 unsigned int  start_offset,
+                 unsigned int *table_count, /* IN/OUT */
+                 hb_tag_t     *table_tags /* OUT */)
+{
+  unsigned num_tables = hb_face_get_table_tags (plan->source, 0, nullptr, nullptr);
+  if (num_tables)
+    return hb_face_get_table_tags (plan->source, start_offset, table_count, table_tags);
+
+  // If face has 0 tables associated with it, assume that it was built from
+  // hb_face_create_tables and thus is unable to list its tables. Fallback to
+  // checking each table type we can handle for existence instead.
+  auto it =
+      hb_concat (
+          + hb_array (known_tables)
+          | hb_filter ([&] (hb_tag_t tag) {
+            return !_table_is_empty (plan->source, tag) && !plan->no_subset_tables->has (tag);
+          })
+          | hb_map ([] (hb_tag_t tag) -> hb_tag_t { return tag; }),
+
+          plan->no_subset_tables->iter ()
+          | hb_filter([&] (hb_tag_t tag) {
+            return !_table_is_empty (plan->source, tag);
+          }));
+
+  it += start_offset;
+
+  unsigned num_written = 0;
+  while (bool (it) && num_written < *table_count)
+    table_tags[num_written++] = *it++;
+
+  *table_count = num_written;
+  return num_written;
+}
+
+
 static unsigned
 _plan_estimate_subset_table_size (hb_subset_plan_t *plan,
 				  unsigned table_len,
@@ -224,9 +327,17 @@ _subset (hb_subset_plan_t *plan, hb_vector_t<char> &buf)
 static bool
 _is_table_present (hb_face_t *source, hb_tag_t tag)
 {
+
+  if (!hb_face_get_table_tags (source, 0, nullptr, nullptr)) {
+    // If face has 0 tables associated with it, assume that it was built from
+    // hb_face_create_tables and thus is unable to list its tables. Fallback to
+    // checking if the blob associated with tag is empty.
+    return !_table_is_empty (source, tag);
+  }
+
   hb_tag_t table_tags[32];
   unsigned offset = 0, num_tables = ARRAY_LENGTH (table_tags);
-  while ((hb_face_get_table_tags (source, offset, &num_tables, table_tags), num_tables))
+  while (((void) hb_face_get_table_tags (source, offset, &num_tables, table_tags), num_tables))
   {
     for (unsigned i = 0; i < num_tables; ++i)
       if (table_tags[i] == tag)
@@ -322,7 +433,7 @@ _subset_table (hb_subset_plan_t *plan,
 #ifndef HB_NO_SUBSET_LAYOUT
   case HB_OT_TAG_GDEF: return _subset<const OT::GDEF> (plan, buf);
   case HB_OT_TAG_GSUB: return _subset<const GSUB> (plan, buf);
-  case HB_OT_TAG_GPOS: return _subset<const OT::GPOS> (plan, buf);
+  case HB_OT_TAG_GPOS: return _subset<const GPOS> (plan, buf);
   case HB_OT_TAG_gvar: return _subset<const OT::gvar> (plan, buf);
   case HB_OT_TAG_HVAR: return _subset<const OT::HVAR> (plan, buf);
   case HB_OT_TAG_VVAR: return _subset<const OT::VVAR> (plan, buf);
@@ -388,7 +499,8 @@ hb_subset_plan_execute_or_fail (hb_subset_plan_t *plan)
   unsigned offset = 0, num_tables = ARRAY_LENGTH (table_tags);
   hb_vector_t<char> buf;
   buf.alloc (4096 - 16);
-  while ((hb_face_get_table_tags (plan->source, offset, &num_tables, table_tags), num_tables))
+
+  while (((void) _get_table_tags (plan, offset, &num_tables, table_tags), num_tables))
   {
     for (unsigned i = 0; i < num_tables; ++i)
     {
@@ -400,7 +512,7 @@ hb_subset_plan_execute_or_fail (hb_subset_plan_t *plan)
     }
     offset += num_tables;
   }
-end:
 
+end:
   return success ? hb_face_reference (plan->dest) : nullptr;
 }