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

/*
 * Copyright © 2017  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.
 *
 * Google Author(s): Behdad Esfahbod
 */

#ifndef HB_OT_VAR_MVAR_TABLE_HH
#define HB_OT_VAR_MVAR_TABLE_HH

#include "hb-ot-layout-common.hh"


namespace OT {


struct VariationValueRecord
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  public:
  Tag		valueTag;	/* Four-byte tag identifying a font-wide measure. */
  HBUINT32		varIdx;		/* Outer/inner index into VariationStore item. */

  public:
  DEFINE_SIZE_STATIC (8);
};


/*
 * MVAR -- Metrics Variations
 * https://docs.microsoft.com/en-us/typography/opentype/spec/mvar
 */
#define HB_OT_TAG_MVAR HB_TAG('M','V','A','R')

struct MVAR
{
  static constexpr hb_tag_t tableTag = HB_OT_TAG_MVAR;

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (version.sanitize (c) &&
		  likely (version.major == 1) &&
		  c->check_struct (this) &&
		  valueRecordSize >= VariationValueRecord::static_size &&
		  varStore.sanitize (c, this) &&
		  c->check_range (valuesZ.arrayZ,
				  valueRecordCount,
				  valueRecordSize));
  }

  float get_var (hb_tag_t tag,
		 const int *coords, unsigned int coord_count) const
  {
    const VariationValueRecord *record;
    record = (VariationValueRecord *) bsearch (&tag, valuesZ.arrayZ,
					       valueRecordCount, valueRecordSize,
					       tag_compare);
    if (!record)
      return 0.;

    return (this+varStore).get_delta (record->varIdx, coords, coord_count);
  }

protected:
  static int tag_compare (const void *pa, const void *pb)
  {
    const hb_tag_t *a = (const hb_tag_t *) pa;
    const Tag *b = (const Tag *) pb;
    return b->cmp (*a);
  }

  protected:
  FixedVersion<>version;	/* Version of the metrics variation table
				 * initially set to 0x00010000u */
  HBUINT16	reserved;	/* Not used; set to 0. */
  HBUINT16	valueRecordSize;/* The size in bytes of each value record —
				 * must be greater than zero. */
  HBUINT16	valueRecordCount;/* The number of value records — may be zero. */
  OffsetTo<VariationStore>
		varStore;	/* Offset to item variation store table. */
  UnsizedArrayOf<HBUINT8>
		valuesZ;	/* Array of value records. The records must be
				 * in binary order of their valueTag field. */

  public:
  DEFINE_SIZE_ARRAY (12, valuesZ);
};

} /* namespace OT */


#endif /* HB_OT_VAR_MVAR_TABLE_HH */