[instance] Add struct definition for cvar table

Also add functions to add cvt tables with cvar deltas applied

src/Makefile.sources

@@ -225,6 +225,7 @@ HB_BASE_sources = \
 	hb-ot-tag.cc \
 	hb-ot-var-avar-table.hh \
 	hb-ot-var-common.hh \
+	hb-ot-var-cvar-table.hh \
 	hb-ot-var-fvar-table.hh \
 	hb-ot-var-gvar-table.hh \
 	hb-ot-var-hvar-table.hh \

src/hb-ot-var-common.hh

@@ -346,6 +346,25 @@ struct TupleVariationHeader
 
 struct TupleVariationData
 {
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    // here check on min_size only, TupleVariationHeader and var data will be
+    // checked while accessing through iterator.
+    return_trace (c->check_struct (this));
+  }
+
+  unsigned get_size (unsigned axis_count) const
+  {
+    unsigned total_size = min_size;
+    unsigned count = tupleVarCount;
+    const TupleVariationHeader& tuple_var_header = get_tuple_var_header();
+    for (unsigned i = 0; i < count; i++)
+      total_size += tuple_var_header.get_size (axis_count) + tuple_var_header.get_data_size ();
+
+    return total_size;
+  }
+
   const TupleVariationHeader &get_tuple_var_header (void) const
   { return StructAfter<TupleVariationHeader> (data); }
 

src/hb-ot-var-cvar-table.hh

@@ -0,0 +1,151 @@
+/*
+ * Copyright © 2023  Google, Inc.
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ */
+
+#ifndef HB_OT_VAR_CVAR_TABLE_HH
+#define HB_OT_VAR_CVAR_TABLE_HH
+
+#include "hb-ot-var-common.hh"
+
+
+namespace OT {
+/*
+ * cvar -- control value table (CVT) Variations
+ * https://docs.microsoft.com/en-us/typography/opentype/spec/cvar
+ */
+#define HB_OT_TAG_cvar HB_TAG('c','v','a','r')
+
+struct cvar
+{
+  static constexpr hb_tag_t tableTag = HB_OT_TAG_cvar;
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (c->check_struct (this) &&
+		  version.sanitize (c) && likely (version.major == 1) &&
+		  tupleVariationData.sanitize (c));
+  }
+
+  bool calculate_cvt_deltas (unsigned axis_count,
+                             hb_array_t<int> coords,
+                             unsigned num_cvt_item,
+                             hb_vector_t<float>& cvt_deltas /* OUT */) const
+  {
+    if (!coords) return true;
+    hb_vector_t<unsigned> shared_indices;
+    TupleVariationData::tuple_iterator_t iterator;
+    unsigned var_data_length = tupleVariationData.get_size (axis_count);
+    hb_bytes_t var_data_bytes = hb_bytes_t (reinterpret_cast<const char*> (&tupleVariationData), var_data_length);
+    if (!TupleVariationData::get_tuple_iterator (var_data_bytes, axis_count,
+                                                 this,
+                                                 shared_indices, &iterator))
+      return true; /* isn't applied at all */
+
+    hb_array_t<const F2DOT14> shared_tuples = hb_array<F2DOT14> ();
+    hb_vector_t<unsigned> private_indices;
+    hb_vector_t<int> unpacked_deltas;
+
+    do
+    {
+      float scalar = iterator.current_tuple->calculate_scalar (coords, axis_count, shared_tuples);
+      if (scalar == 0.f) continue;
+      const HBUINT8 *p = iterator.get_serialized_data ();
+      unsigned int length = iterator.current_tuple->get_data_size ();
+      if (unlikely (!iterator.var_data_bytes.check_range (p, length)))
+        return false;
+
+      const HBUINT8 *end = p + length;
+
+      bool has_private_points = iterator.current_tuple->has_private_points ();
+      if (has_private_points &&
+          !TupleVariationData::unpack_points (p, private_indices, end))
+        return false;
+      const hb_vector_t<unsigned int> &indices = has_private_points ? private_indices : shared_indices;
+
+      bool apply_to_all = (indices.length == 0);
+      unsigned num_deltas = apply_to_all ? num_cvt_item : indices.length;
+      if (unlikely (!unpacked_deltas.resize (num_deltas, false))) return false;
+      if (unlikely (!TupleVariationData::unpack_deltas (p, unpacked_deltas, end))) return false;
+
+      for (unsigned int i = 0; i < num_deltas; i++)
+      {
+        unsigned int idx = apply_to_all ? i : indices[i];
+        if (unlikely (idx >= num_cvt_item)) continue;
+        if (scalar != 1.0f) cvt_deltas[idx] += unpacked_deltas[i] * scalar ;
+        else cvt_deltas[idx] += unpacked_deltas[i];
+      }
+    } while (iterator.move_to_next ());
+
+    return true;
+  }
+
+  bool add_cvt_and_apply_deltas (hb_subset_plan_t *plan) const
+  {
+    const hb_tag_t cvt = HB_TAG('c','v','t',' ');
+    hb_blob_t *cvt_blob = hb_face_reference_table (plan->source, cvt);
+    hb_blob_t *cvt_prime_blob = hb_blob_copy_writable_or_fail (cvt_blob);
+    hb_blob_destroy (cvt_blob);
+  
+    if (unlikely (!cvt_prime_blob))
+      return false;
+ 
+    unsigned cvt_blob_length = hb_blob_get_length (cvt_prime_blob);
+    unsigned num_cvt_item = cvt_blob_length / FWORD::static_size;
+
+    hb_vector_t<float> cvt_deltas;
+    if (unlikely (!cvt_deltas.resize (num_cvt_item)))
+    {
+      hb_blob_destroy (cvt_prime_blob);
+      return false;
+    }
+    hb_memset (cvt_deltas.arrayZ, 0, cvt_deltas.get_size ());
+
+    if (!calculate_cvt_deltas (plan->normalized_coords.length, plan->normalized_coords.as_array (), num_cvt_item, cvt_deltas))
+    {
+      hb_blob_destroy (cvt_prime_blob);
+      return false;
+    }
+
+    FWORD *cvt_prime = (FWORD *) hb_blob_get_data_writable (cvt_prime_blob, nullptr);
+    for (unsigned i = 0; i < num_cvt_item; i++)
+      cvt_prime[i] += roundf (cvt_deltas[i]);
+    
+    bool success = plan->add_table (cvt, cvt_prime_blob);
+    hb_blob_destroy (cvt_prime_blob);
+    return success;
+  }
+
+  protected:
+  FixedVersion<>version;		/* Version of the CVT variation table
+					 * initially set to 0x00010000u */
+  TupleVariationData tupleVariationData; /* TupleVariationDate for cvar table */
+  public:
+  DEFINE_SIZE_MIN (8);
+};
+
+} /* namespace OT */
+
+
+#endif /* HB_OT_VAR_CVAR_TABLE_HH */

src/meson.build

@@ -226,6 +226,7 @@ hb_base_sources = files(
   'hb-ot-tag.cc',
   'hb-ot-var-avar-table.hh',
   'hb-ot-var-common.hh',
+  'hb-ot-var-cvar-table.hh',
   'hb-ot-var-fvar-table.hh',
   'hb-ot-var-gvar-table.hh',
   'hb-ot-var-hvar-table.hh',