flutter_flutter/sky/engine/platform/fonts/harfbuzz/HarfBuzzFace.cpp

/*
 * Copyright (c) 2012 Google Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
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 *
 *     * Redistributions of source code must retain the above copyright
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
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 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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#include "flutter/sky/engine/platform/fonts/harfbuzz/HarfBuzzFace.h"

#include "flutter/sky/engine/platform/fonts/FontPlatformData.h"
#include "hb-ot.h"
#include "hb.h"

namespace blink {

const hb_tag_t HarfBuzzFace::vertTag = HB_TAG('v', 'e', 'r', 't');
const hb_tag_t HarfBuzzFace::vrt2Tag = HB_TAG('v', 'r', 't', '2');

// Though we have FontCache class, which provides the cache mechanism for
// WebKit's font objects, we also need additional caching layer for HarfBuzz
// to reduce the memory consumption because hb_face_t should be associated with
// underling font data (e.g. CTFontRef, FTFace).

class FaceCacheEntry : public RefCounted<FaceCacheEntry> {
 public:
  static PassRefPtr<FaceCacheEntry> create(hb_face_t* face) {
    ASSERT(face);
    return adoptRef(new FaceCacheEntry(face));
  }
  ~FaceCacheEntry() { hb_face_destroy(m_face); }

  hb_face_t* face() { return m_face; }
  HashMap<uint32_t, uint16_t>* glyphCache() { return &m_glyphCache; }

 private:
  explicit FaceCacheEntry(hb_face_t* face) : m_face(face) {}

  hb_face_t* m_face;
  HashMap<uint32_t, uint16_t> m_glyphCache;
};

typedef HashMap<uint64_t,
                RefPtr<FaceCacheEntry>,
                WTF::IntHash<uint64_t>,
                WTF::UnsignedWithZeroKeyHashTraits<uint64_t>>
    HarfBuzzFaceCache;

static HarfBuzzFaceCache* harfBuzzFaceCache() {
  DEFINE_STATIC_LOCAL(HarfBuzzFaceCache, s_harfBuzzFaceCache, ());
  return &s_harfBuzzFaceCache;
}

HarfBuzzFace::HarfBuzzFace(FontPlatformData* platformData, uint64_t uniqueID)
    : m_platformData(platformData),
      m_uniqueID(uniqueID),
      m_scriptForVerticalText(HB_SCRIPT_INVALID) {
  HarfBuzzFaceCache::AddResult result =
      harfBuzzFaceCache()->add(m_uniqueID, nullptr);
  if (result.isNewEntry)
    result.storedValue->value = FaceCacheEntry::create(createFace());
  result.storedValue->value->ref();
  m_face = result.storedValue->value->face();
  m_glyphCacheForFaceCacheEntry = result.storedValue->value->glyphCache();
}

HarfBuzzFace::~HarfBuzzFace() {
  HarfBuzzFaceCache::iterator result = harfBuzzFaceCache()->find(m_uniqueID);
  ASSERT_WITH_SECURITY_IMPLICATION(result != harfBuzzFaceCache()->end());
  ASSERT(result.get()->value->refCount() > 1);
  result.get()->value->deref();
  if (result.get()->value->refCount() == 1)
    harfBuzzFaceCache()->remove(m_uniqueID);
}

static hb_script_t findScriptForVerticalGlyphSubstitution(hb_face_t* face) {
  static const unsigned maxCount = 32;

  unsigned scriptCount = maxCount;
  hb_tag_t scriptTags[maxCount];
  hb_ot_layout_table_get_script_tags(face, HB_OT_TAG_GSUB, 0, &scriptCount,
                                     scriptTags);
  for (unsigned scriptIndex = 0; scriptIndex < scriptCount; ++scriptIndex) {
    unsigned languageCount = maxCount;
    hb_tag_t languageTags[maxCount];
    hb_ot_layout_script_get_language_tags(face, HB_OT_TAG_GSUB, scriptIndex, 0,
                                          &languageCount, languageTags);
    for (unsigned languageIndex = 0; languageIndex < languageCount;
         ++languageIndex) {
      unsigned featureIndex;
      if (hb_ot_layout_language_find_feature(
              face, HB_OT_TAG_GSUB, scriptIndex, languageIndex,
              HarfBuzzFace::vertTag, &featureIndex) ||
          hb_ot_layout_language_find_feature(
              face, HB_OT_TAG_GSUB, scriptIndex, languageIndex,
              HarfBuzzFace::vrt2Tag, &featureIndex))
        return hb_ot_tag_to_script(scriptTags[scriptIndex]);
    }
  }
  return HB_SCRIPT_INVALID;
}

void HarfBuzzFace::setScriptForVerticalGlyphSubstitution(hb_buffer_t* buffer) {
  if (m_scriptForVerticalText == HB_SCRIPT_INVALID)
    m_scriptForVerticalText = findScriptForVerticalGlyphSubstitution(m_face);
  hb_buffer_set_script(buffer, m_scriptForVerticalText);
}

}  // namespace blink