src/hb-ot-map-private.hh

/*
 * Copyright (C) 2009,2010  Red Hat, Inc.
 * Copyright (C) 2010  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.
 *
 * Red Hat Author(s): Behdad Esfahbod
 * Google Author(s): Behdad Esfahbod
 */

#ifndef HB_OT_MAP_PRIVATE_HH
#define HB_OT_MAP_PRIVATE_HH

#include "hb-ot-shape-private.hh"

#include "hb-ot-layout.h"

HB_BEGIN_DECLS


#define MAX_FEATURES 100 /* FIXME */
#define MAX_LOOKUPS 1000 /* FIXME */

static const hb_tag_t table_tags[2] = {HB_OT_TAG_GSUB, HB_OT_TAG_GPOS};

struct hb_mask_allocator_t {

  struct feature_info_t {
    hb_tag_t tag;
    unsigned int value;
    unsigned int seq;
    bool global;

    static int
    cmp (const void *p1, const void *p2)
    {
      const feature_info_t *a = reinterpret_cast<const feature_info_t *>(p1);
      const feature_info_t *b = reinterpret_cast<const feature_info_t *>(p2);

      if (a->tag != b->tag)
        return a->tag < b->tag ? -1 : 1;

      return a->seq < b->seq ? -1 : 1;
    }
  };

  struct feature_map_t {
    hb_tag_t tag; /* should be first for our bsearch to work */
    unsigned int index[2]; /* GSUB, GPOS */
    unsigned int shift;
    hb_mask_t mask;

    static int
    cmp (const void *p1, const void *p2)
    {
      const feature_map_t *a = reinterpret_cast<const feature_map_t *>(p1);
      const feature_map_t *b = reinterpret_cast<const feature_map_t *>(p2);

      return a->tag < b->tag ? -1 : a->tag > b->tag ? 1 : 0;
    }
  };

  struct lookup_map_t {
    unsigned int index;
    hb_mask_t mask;

    static int
    cmp (const void *p1, const void *p2)
    {
      const lookup_map_t *a = reinterpret_cast<const lookup_map_t *>(p1);
      const lookup_map_t *b = reinterpret_cast<const lookup_map_t *>(p2);

      return a->index < b->index ? -1 : a->index > b->index ? 1 : 0;
    }
  };


  void
  add_lookups (hb_ot_shape_context_t *c,
	       unsigned int  table_index,
	       unsigned int  feature_index,
	       hb_mask_t     mask)
  {
    unsigned int i = MAX_LOOKUPS - lookup_count[table_index];
    lookup_map_t *lookups = lookup_maps[table_index] + lookup_count[table_index];

    unsigned int *lookup_indices = (unsigned int *) lookups;

    hb_ot_layout_feature_get_lookup_indexes (c->face,
					     table_tags[table_index],
					     feature_index,
					     0, &i,
					     lookup_indices);

    lookup_count[table_index] += i;

    while (i--) {
      lookups[i].mask = mask;
      lookups[i].index = lookup_indices[i];
    }
  }




  hb_mask_allocator_t (void) : feature_count (0) {}

  void add_feature (hb_tag_t tag,
		    unsigned int value,
		    bool global)
  {
    feature_info_t *info = &feature_infos[feature_count++];
    info->tag = tag;
    info->value = value;
    info->seq = feature_count;
    info->global = global;
  }

  void compile (hb_ot_shape_context_t *c)
  {
   global_mask = 0;
   lookup_count[0] = lookup_count[1] = 0;

    if (!feature_count)
      return;


    /* Fetch script/language indices for GSUB/GPOS.  We need these later to skip
     * features not available in either table and not waste precious bits for them. */

    const hb_tag_t *script_tags;
    hb_tag_t language_tag;

    script_tags = hb_ot_tags_from_script (c->buffer->props.script);
    language_tag = hb_ot_tag_from_language (c->buffer->props.language);

    unsigned int script_index[2], language_index[2];
    for (unsigned int table_index = 0; table_index < 2; table_index++) {
      hb_tag_t table_tag = table_tags[table_index];
      hb_ot_layout_table_choose_script (c->face, table_tag, script_tags, &script_index[table_index]);
      hb_ot_layout_script_find_language (c->face, table_tag, script_index[table_index], language_tag, &language_index[table_index]);
    }


    /* Sort the features so we can bsearch later */
    qsort (feature_infos, feature_count, sizeof (feature_infos[0]), feature_info_t::cmp);

    /* Remove dups, let later-occurring features override earlier ones. */
    unsigned int j = 0;
    for (unsigned int i = 1; i < feature_count; i++)
      if (feature_infos[i].tag != feature_infos[j].tag)
	feature_infos[++j] = feature_infos[i];
      else {
	if (feature_infos[i].global)
	  feature_infos[j] = feature_infos[i];
	else {
	  feature_infos[j].global = feature_infos[j].global && (feature_infos[j].value == feature_infos[i].value);
	  feature_infos[j].value = MAX (feature_infos[j].value, feature_infos[i].value);
	}
      }
    feature_count = j + 1;


    /* Allocate bits now */
    unsigned int next_bit = 1;
    j = 0;
    for (unsigned int i = 0; i < feature_count; i++) {
      const feature_info_t *info = &feature_infos[i];

      unsigned int bits_needed;

      if (info->global && info->value == 1)
        /* Uses the global bit */
        bits_needed = 0;
      else
        bits_needed = _hb_bit_storage (info->value);

      if (!info->value || next_bit + bits_needed > 8 * sizeof (hb_mask_t))
        continue; /* Feature disabled, or not enough bits. */


      bool found = false;
      unsigned int feature_index[2];
      for (unsigned int table_index = 0; table_index < 2; table_index++)
        found |= hb_ot_layout_language_find_feature (c->face,
						     table_tags[table_index],
						     script_index[table_index],
						     language_index[table_index],
						     info->tag,
						     &feature_index[table_index]);
      if (!found)
        continue;


      feature_map_t *map = &feature_maps[j++];

      map->tag = info->tag;
      map->index[0] = feature_index[0];
      map->index[1] = feature_index[1];
      if (info->global && info->value == 1) {
        /* Uses the global bit */
        map->shift = 0;
	map->mask = 1;
      } else {
	map->shift = next_bit;
	map->mask = (1 << (next_bit + bits_needed)) - (1 << next_bit);
	next_bit += bits_needed;
	if (info->global)
	  global_mask |= map->mask;
      }

    }
    feature_count = j;


    for (unsigned int table_index = 0; table_index < 2; table_index++) {
      hb_tag_t table_tag = table_tags[table_index];

      /* Collect lookup indices for features */

      unsigned int required_feature_index;
      if (hb_ot_layout_language_get_required_feature_index (c->face,
							    table_tag,
							    script_index[table_index],
							    language_index[table_index],
							    &required_feature_index))
	add_lookups (c, table_index, required_feature_index, 1);

      for (unsigned i = 0; i < feature_count; i++)
	add_lookups (c, table_index, feature_maps[i].index[table_index], feature_maps[i].mask);

      /* Sort lookups and merge duplicates */

      qsort (lookup_maps[table_index], lookup_count[table_index], sizeof (lookup_maps[table_index][0]), lookup_map_t::cmp);

      if (lookup_count[table_index])
      {
	unsigned int j = 0;
	for (unsigned int i = 1; i < lookup_count[table_index]; i++)
	  if (lookup_maps[table_index][i].index != lookup_maps[table_index][j].index)
	    lookup_maps[table_index][++j] = lookup_maps[table_index][i];
	  else
	    lookup_maps[table_index][j].mask |= lookup_maps[table_index][i].mask;
	j++;
	lookup_count[table_index] = j;
      }
    }
  }

  hb_mask_t get_global_mask (void) { return global_mask; }

  hb_mask_t get_mask (hb_tag_t tag, unsigned int *shift) const {
    const feature_map_t *map = (const feature_map_t *) bsearch (&tag, feature_maps, feature_count, sizeof (feature_maps[0]), feature_map_t::cmp);
    if (likely (map)) {
      if (shift) *shift = map->shift;
      return map->mask;
    } else {
      if (shift) *shift = 0;
      return 0;
    }
  }

  void substitute (hb_ot_shape_context_t *c) const {
    for (unsigned int i = 0; i < lookup_count[0]; i++)
      hb_ot_layout_substitute_lookup (c->face, c->buffer, lookup_maps[0][i].index, lookup_maps[0][i].mask);
  }

  void position (hb_ot_shape_context_t *c) const {
    for (unsigned int i = 0; i < lookup_count[1]; i++)
      hb_ot_layout_position_lookup (c->font, c->face, c->buffer, lookup_maps[1][i].index, lookup_maps[1][i].mask);
  }

  private:

  hb_mask_t global_mask;

  unsigned int feature_count;
  feature_info_t feature_infos[MAX_FEATURES]; /* used before compile() only */
  feature_map_t feature_maps[MAX_FEATURES];

  lookup_map_t lookup_maps[2][MAX_LOOKUPS]; /* GSUB/GPOS */
  unsigned int lookup_count[2];
};



HB_END_DECLS

#endif /* HB_OT_MAP_PRIVATE_HH */