flutter_flutter/sky/engine/platform/fonts/FontDescription.cpp

/*
 * Copyright (C) 2007 Nicholas Shanks <contact@nickshanks.com>
 * Copyright (C) 2008 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS 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 APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "flutter/sky/engine/platform/fonts/FontDescription.h"

#include "flutter/sky/engine/wtf/text/AtomicStringHash.h"
#include "flutter/sky/engine/wtf/text/StringHash.h"

namespace blink {

struct SameSizeAsFontDescription {
  FontFamily familyList;
  RefPtr<FontFeatureSettings> m_featureSettings;
  String locale;
  float sizes[4];
  // FXIME: Make them fit into one word.
  uint32_t bitfields;
  uint32_t bitfields2 : 7;
};

COMPILE_ASSERT(sizeof(FontDescription) == sizeof(SameSizeAsFontDescription),
               FontDescription_should_stay_small);

TypesettingFeatures FontDescription::s_defaultTypesettingFeatures = 0;

bool FontDescription::s_useSubpixelTextPositioning = false;

FontWeight FontDescription::lighterWeight(FontWeight weight) {
  switch (weight) {
    case FontWeight100:
    case FontWeight200:
    case FontWeight300:
    case FontWeight400:
    case FontWeight500:
      return FontWeight100;

    case FontWeight600:
    case FontWeight700:
      return FontWeight400;

    case FontWeight800:
    case FontWeight900:
      return FontWeight700;
  }
  ASSERT_NOT_REACHED();
  return FontWeightNormal;
}

FontWeight FontDescription::bolderWeight(FontWeight weight) {
  switch (weight) {
    case FontWeight100:
    case FontWeight200:
    case FontWeight300:
      return FontWeight400;

    case FontWeight400:
    case FontWeight500:
      return FontWeight700;

    case FontWeight600:
    case FontWeight700:
    case FontWeight800:
    case FontWeight900:
      return FontWeight900;
  }
  ASSERT_NOT_REACHED();
  return FontWeightNormal;
}

FontTraits FontDescription::traits() const {
  return FontTraits(style(), variant(), weight(), stretch());
}

FontDescription::VariantLigatures FontDescription::variantLigatures() const {
  VariantLigatures ligatures;

  ligatures.common = commonLigaturesState();
  ligatures.discretionary = discretionaryLigaturesState();
  ligatures.historical = historicalLigaturesState();
  ligatures.contextual = contextualLigaturesState();

  return ligatures;
}

void FontDescription::setTraits(FontTraits traits) {
  setStyle(traits.style());
  setVariant(traits.variant());
  setWeight(traits.weight());
  setStretch(traits.stretch());
}

void FontDescription::setVariantLigatures(const VariantLigatures& ligatures) {
  m_commonLigaturesState = ligatures.common;
  m_discretionaryLigaturesState = ligatures.discretionary;
  m_historicalLigaturesState = ligatures.historical;
  m_contextualLigaturesState = ligatures.contextual;

  updateTypesettingFeatures();
}

float FontDescription::effectiveFontSize() const {
  float size = computedSize();

  // Ensure that the effective precision matches the font-cache precision.
  // This guarantees that the same precision is used regardless of cache status.
  return floorf(size * FontCacheKey::precisionMultiplier()) /
         FontCacheKey::precisionMultiplier();
}

FontCacheKey FontDescription::cacheKey(
    const FontFaceCreationParams& creationParams,
    FontTraits desiredTraits) const {
  FontTraits fontTraits = desiredTraits.bitfield() ? desiredTraits : traits();

  unsigned options = static_cast<unsigned>(m_syntheticItalic) << 7 |  // bit 8
                     static_cast<unsigned>(m_syntheticBold) << 6 |    // bit 7
                     static_cast<unsigned>(m_fontSmoothing) << 4 |   // bits 5-6
                     static_cast<unsigned>(m_textRendering) << 2 |   // bits 3-4
                     static_cast<unsigned>(m_orientation) << 1 |     // bit 2
                     static_cast<unsigned>(m_subpixelTextPosition);  // bit 1

  return FontCacheKey(creationParams, effectiveFontSize(),
                      options | fontTraits.bitfield() << 8);
}

void FontDescription::setDefaultTypesettingFeatures(
    TypesettingFeatures typesettingFeatures) {
  s_defaultTypesettingFeatures = typesettingFeatures;
}

TypesettingFeatures FontDescription::defaultTypesettingFeatures() {
  return s_defaultTypesettingFeatures;
}

void FontDescription::updateTypesettingFeatures() const {
  m_typesettingFeatures = s_defaultTypesettingFeatures;

  switch (textRendering()) {
    case AutoTextRendering:
      break;
    case OptimizeSpeed:
      m_typesettingFeatures &= ~(blink::Kerning | Ligatures);
      break;
    case GeometricPrecision:
    case OptimizeLegibility:
      m_typesettingFeatures |= blink::Kerning | Ligatures;
      break;
  }

  switch (kerning()) {
    case FontDescription::NoneKerning:
      m_typesettingFeatures &= ~blink::Kerning;
      break;
    case FontDescription::NormalKerning:
      m_typesettingFeatures |= blink::Kerning;
      break;
    case FontDescription::AutoKerning:
      break;
  }

  // As per CSS (http://dev.w3.org/csswg/css-text-3/#letter-spacing-property),
  // When the effective letter-spacing between two characters is not zero (due
  // to either justification or non-zero computed letter-spacing), user agents
  // should not apply optional ligatures.
  if (m_letterSpacing == 0) {
    switch (commonLigaturesState()) {
      case FontDescription::DisabledLigaturesState:
        m_typesettingFeatures &= ~Ligatures;
        break;
      case FontDescription::EnabledLigaturesState:
        m_typesettingFeatures |= Ligatures;
        break;
      case FontDescription::NormalLigaturesState:
        break;
    }

    if (discretionaryLigaturesState() ==
            FontDescription::EnabledLigaturesState ||
        historicalLigaturesState() == FontDescription::EnabledLigaturesState ||
        contextualLigaturesState() == FontDescription::EnabledLigaturesState) {
      m_typesettingFeatures |= blink::Ligatures;
    }
  }
}

}  // namespace blink