third_party/txt/src/minikin/HbFontCache.cpp

/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define LOG_TAG "Minikin"

#include "HbFontCache.h"

#include <log/log.h>
#include <utils/LruCache.h>

#include <hb-ot.h>
#include <hb.h>

#include <minikin/MinikinFont.h>
#include "MinikinInternal.h"

namespace minikin {

class HbFontCache : private android::OnEntryRemoved<int32_t, hb_font_t*> {
 public:
  HbFontCache() : mCache(kMaxEntries) {
    mCache.setOnEntryRemovedListener(this);
  }

  // callback for OnEntryRemoved
  void operator()(int32_t& /* key */, hb_font_t*& value) {
    hb_font_destroy(value);
  }

  hb_font_t* get(int32_t fontId) { return mCache.get(fontId); }

  void put(int32_t fontId, hb_font_t* font) { mCache.put(fontId, font); }

  void clear() { mCache.clear(); }

  void remove(int32_t fontId) { mCache.remove(fontId); }

 private:
  static const size_t kMaxEntries = 100;

  android::LruCache<int32_t, hb_font_t*> mCache;
};

HbFontCache* getFontCacheLocked() {
  assertMinikinLocked();
  static HbFontCache* cache = nullptr;
  if (cache == nullptr) {
    cache = new HbFontCache();
  }
  return cache;
}

void purgeHbFontCacheLocked() {
  assertMinikinLocked();
  getFontCacheLocked()->clear();
}

void purgeHbFontLocked(const MinikinFont* minikinFont) {
  assertMinikinLocked();
  const int32_t fontId = minikinFont->GetUniqueId();
  getFontCacheLocked()->remove(fontId);
}

// Returns a new reference to a hb_font_t object, caller is
// responsible for calling hb_font_destroy() on it.
hb_font_t* getHbFontLocked(const MinikinFont* minikinFont) {
  assertMinikinLocked();
  // TODO: get rid of nullFaceFont
  static hb_font_t* nullFaceFont = nullptr;
  if (minikinFont == nullptr) {
    if (nullFaceFont == nullptr) {
      nullFaceFont = hb_font_create(nullptr);
    }
    return hb_font_reference(nullFaceFont);
  }

  HbFontCache* fontCache = getFontCacheLocked();
  const int32_t fontId = minikinFont->GetUniqueId();
  hb_font_t* font = fontCache->get(fontId);
  if (font != nullptr) {
    return hb_font_reference(font);
  }

  hb_face_t* face = minikinFont->CreateHarfBuzzFace();

  hb_font_t* parent_font = hb_font_create(face);
  hb_ot_font_set_funcs(parent_font);

  unsigned int upem = hb_face_get_upem(face);
  hb_font_set_scale(parent_font, upem, upem);

  font = hb_font_create_sub_font(parent_font);
  std::vector<hb_variation_t> variations;
  for (const FontVariation& variation : minikinFont->GetAxes()) {
    variations.push_back({variation.axisTag, variation.value});
  }
  hb_font_set_variations(font, variations.data(), variations.size());
  hb_font_destroy(parent_font);
  hb_face_destroy(face);
  fontCache->put(fontId, font);
  return hb_font_reference(font);
}

}  // namespace minikin