paragraph_builder_skia.cc

/*
 * Copyright 2019 Google Inc.
 *
 * 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.
 */

#include "paragraph_builder_skia.h"
#include "paragraph_skia.h"

#include "third_party/skia/modules/skparagraph/include/ParagraphStyle.h"
#include "third_party/skia/modules/skparagraph/include/TextStyle.h"
#include "txt/paragraph_style.h"

namespace skt = skia::textlayout;

namespace txt {

namespace {

// Convert txt::FontWeight values (ranging from 0-8) to SkFontStyle::Weight
// values (ranging from 100-900).
SkFontStyle::Weight GetSkFontStyleWeight(txt::FontWeight font_weight) {
  return static_cast<SkFontStyle::Weight>(static_cast<int>(font_weight) * 100 +
                                          100);
}

SkFontStyle MakeSkFontStyle(txt::FontWeight font_weight,
                            txt::FontStyle font_style) {
  return SkFontStyle(
      GetSkFontStyleWeight(font_weight), SkFontStyle::Width::kNormal_Width,
      font_style == txt::FontStyle::normal ? SkFontStyle::Slant::kUpright_Slant
                                           : SkFontStyle::Slant::kItalic_Slant);
}

skt::ParagraphStyle TxtToSkia(const ParagraphStyle& txt) {
  skt::ParagraphStyle skia;
  skt::TextStyle text_style;

  text_style.setFontStyle(MakeSkFontStyle(txt.font_weight, txt.font_style));
  text_style.setFontSize(SkDoubleToScalar(txt.font_size));
  text_style.setHeight(SkDoubleToScalar(txt.height));
  text_style.setHeightOverride(txt.has_height_override);
  text_style.setFontFamilies({SkString(txt.font_family.c_str())});
  text_style.setLocale(SkString(txt.locale.c_str()));
  skia.setTextStyle(text_style);

  skt::StrutStyle strut_style;
  strut_style.setFontStyle(
      MakeSkFontStyle(txt.strut_font_weight, txt.strut_font_style));
  strut_style.setFontSize(SkDoubleToScalar(txt.strut_font_size));
  strut_style.setHeight(SkDoubleToScalar(txt.strut_height));
  strut_style.setHeightOverride(txt.strut_has_height_override);

  std::vector<SkString> strut_fonts;
  std::transform(txt.strut_font_families.begin(), txt.strut_font_families.end(),
                 std::back_inserter(strut_fonts),
                 [](const std::string& f) { return SkString(f.c_str()); });
  strut_style.setFontFamilies(strut_fonts);
  strut_style.setLeading(txt.strut_leading);
  strut_style.setForceStrutHeight(txt.force_strut_height);
  strut_style.setStrutEnabled(txt.strut_enabled);
  skia.setStrutStyle(strut_style);

  skia.setTextAlign(static_cast<skt::TextAlign>(txt.text_align));
  skia.setTextDirection(static_cast<skt::TextDirection>(txt.text_direction));
  skia.setMaxLines(txt.max_lines);
  skia.setEllipsis(txt.ellipsis);
  skia.setTextHeightBehavior(
      static_cast<skt::TextHeightBehavior>(txt.text_height_behavior));

  skia.turnHintingOff();

  return skia;
}

skt::TextStyle TxtToSkia(const TextStyle& txt) {
  skt::TextStyle skia;

  skia.setColor(txt.color);
  skia.setDecoration(static_cast<skt::TextDecoration>(txt.decoration));
  skia.setDecorationColor(txt.decoration_color);
  skia.setDecorationStyle(
      static_cast<skt::TextDecorationStyle>(txt.decoration_style));
  skia.setDecorationThicknessMultiplier(
      SkDoubleToScalar(txt.decoration_thickness_multiplier));
  skia.setFontStyle(MakeSkFontStyle(txt.font_weight, txt.font_style));
  skia.setTextBaseline(static_cast<skt::TextBaseline>(txt.text_baseline));

  std::vector<SkString> skia_fonts;
  std::transform(txt.font_families.begin(), txt.font_families.end(),
                 std::back_inserter(skia_fonts),
                 [](const std::string& f) { return SkString(f.c_str()); });
  skia.setFontFamilies(skia_fonts);

  skia.setFontSize(SkDoubleToScalar(txt.font_size));
  skia.setLetterSpacing(SkDoubleToScalar(txt.letter_spacing));
  skia.setWordSpacing(SkDoubleToScalar(txt.word_spacing));
  skia.setHeight(SkDoubleToScalar(txt.height));
  skia.setHeightOverride(txt.has_height_override);
  skia.setHalfLeading(txt.half_leading);

  skia.setLocale(SkString(txt.locale.c_str()));
  if (txt.has_background) {
    skia.setBackgroundColor(txt.background);
  }
  if (txt.has_foreground) {
    skia.setForegroundColor(txt.foreground);
  }

  skia.resetFontFeatures();
  for (const auto& ff : txt.font_features.GetFontFeatures()) {
    skia.addFontFeature(SkString(ff.first.c_str()), ff.second);
  }

  skia.resetShadows();
  for (const txt::TextShadow& txt_shadow : txt.text_shadows) {
    skt::TextShadow shadow;
    shadow.fOffset = txt_shadow.offset;
    shadow.fBlurSigma = txt_shadow.blur_radius;
    shadow.fColor = txt_shadow.color;
    skia.addShadow(shadow);
  }

  return skia;
}

}  // anonymous namespace

ParagraphBuilderSkia::ParagraphBuilderSkia(
    const ParagraphStyle& style,
    std::shared_ptr<FontCollection> font_collection)
    : builder_(skt::ParagraphBuilder::make(
          TxtToSkia(style),
          font_collection->CreateSktFontCollection())),
      base_style_(style.GetTextStyle()) {}

ParagraphBuilderSkia::~ParagraphBuilderSkia() = default;

void ParagraphBuilderSkia::PushStyle(const TextStyle& style) {
  builder_->pushStyle(TxtToSkia(style));
  txt_style_stack_.push(style);
}

void ParagraphBuilderSkia::Pop() {
  builder_->pop();
  txt_style_stack_.pop();
}

const TextStyle& ParagraphBuilderSkia::PeekStyle() {
  return txt_style_stack_.empty() ? base_style_ : txt_style_stack_.top();
}

void ParagraphBuilderSkia::AddText(const std::u16string& text) {
  builder_->addText(text);
}

void ParagraphBuilderSkia::AddPlaceholder(PlaceholderRun& span) {
  skt::PlaceholderStyle placeholder_style;
  placeholder_style.fHeight = span.height;
  placeholder_style.fWidth = span.width;
  placeholder_style.fBaseline = static_cast<skt::TextBaseline>(span.baseline);
  placeholder_style.fBaselineOffset = span.baseline_offset;
  placeholder_style.fAlignment =
      static_cast<skt::PlaceholderAlignment>(span.alignment);

  builder_->addPlaceholder(placeholder_style);
}

std::unique_ptr<Paragraph> ParagraphBuilderSkia::Build() {
  return std::unique_ptr<Paragraph>(new ParagraphSkia(builder_->Build()));
}

}  // namespace txt