From 94b3cafc3a042aea69ee7040227557fe98a21d87 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 11 Oct 2017 17:22:44 +0200
Subject: [PATCH] Add hb_face_get_table_tags()

New API:
hb_face_get_table_tags()

Fixes https://github.com/behdad/harfbuzz/issues/560
---
 src/hb-face.cc              | 29 +++++++++++++++++++++++++++++
 src/hb-face.h               |  5 +++++
 src/hb-open-file-private.hh | 18 ++++++++++++++++++
 3 files changed, 52 insertions(+)

diff --git a/src/hb-face.cc b/src/hb-face.cc
index 0f90b59f3..e96c8acd3 100644
--- a/src/hb-face.cc
+++ b/src/hb-face.cc
@@ -474,4 +474,33 @@ hb_face_t::load_num_glyphs (void) const
   hb_blob_destroy (maxp_blob);
 }
 
+/**
+ * hb_face_get_table_tags:
+ * @face: a face.
+ *
+ * Retrieves table tags for a face, if possible.
+ *
+ * Return value: total number of tables, or 0 if not possible to list.
+ *
+ * Since: 1.6.0
+ **/
+unsigned int
+hb_face_get_table_tags (hb_face_t    *face,
+			unsigned int  start_offset,
+			unsigned int *table_count, /* IN/OUT */
+			hb_tag_t     *table_tags /* OUT */)
+{
+  if (face->destroy != _hb_face_for_data_closure_destroy)
+  {
+    if (table_count)
+      *table_count = 0;
+    return 0;
+  }
 
+  hb_face_for_data_closure_t *data = (hb_face_for_data_closure_t *) face->user_data;
+
+  const OT::OpenTypeFontFile &ot_file = *OT::Sanitizer<OT::OpenTypeFontFile>::lock_instance (data->blob);
+  const OT::OpenTypeFontFace &ot_face = ot_file.get_face (data->index);
+
+  return ot_face.get_table_tags (start_offset, table_count, table_tags);
+}
diff --git a/src/hb-face.h b/src/hb-face.h
index 91237b708..9842d52b6 100644
--- a/src/hb-face.h
+++ b/src/hb-face.h
@@ -111,6 +111,11 @@ hb_face_set_glyph_count (hb_face_t    *face,
 HB_EXTERN unsigned int
 hb_face_get_glyph_count (hb_face_t *face);
 
+HB_EXTERN unsigned int
+hb_face_get_table_tags (hb_face_t    *face,
+			unsigned int  start_offset,
+			unsigned int *table_count, /* IN/OUT */
+			hb_tag_t     *table_tags /* OUT */);
 
 HB_END_DECLS
 
diff --git a/src/hb-open-file-private.hh b/src/hb-open-file-private.hh
index f208419aa..dcfdfd6ca 100644
--- a/src/hb-open-file-private.hh
+++ b/src/hb-open-file-private.hh
@@ -79,6 +79,24 @@ typedef struct OffsetTable
     if (unlikely (i >= numTables)) return Null(TableRecord);
     return tables[i];
   }
+  inline unsigned int get_table_tags (unsigned int start_offset,
+				      unsigned int *table_count, /* IN/OUT */
+				      hb_tag_t     *table_tags /* OUT */) const
+  {
+    if (table_count)
+    {
+      if (start_offset >= numTables)
+        *table_count = 0;
+      else
+        *table_count = MIN (*table_count, numTables - start_offset);
+
+      const TableRecord *sub_tables = tables + start_offset;
+      unsigned int count = *table_count;
+      for (unsigned int i = 0; i < count; i++)
+	table_tags[i] = sub_tables[i].tag;
+    }
+    return numTables;
+  }
   inline bool find_table_index (hb_tag_t tag, unsigned int *table_index) const
   {
     Tag t;