third_party/WebKit/Source/core/layout/svg/LayoutSVGTextPath.cpp

/*
 * Copyright (C) 2007 Nikolas Zimmermann <zimmermann@kde.org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#include "core/layout/svg/LayoutSVGTextPath.h"

#include "core/layout/svg/SVGLayoutSupport.h"
#include "core/svg/SVGPathElement.h"
#include "core/svg/SVGTextPathElement.h"
#include "platform/graphics/Path.h"
#include <memory>

namespace blink {

TreeScope& treeScopeForIdResolution(const SVGElement& element) {
  if (SVGElement* correspondingElement = element.correspondingElement())
    return correspondingElement->treeScope();
  return element.treeScope();
}

PathPositionMapper::PathPositionMapper(const Path& path)
    : m_positionCalculator(path), m_pathLength(path.length()) {}

PathPositionMapper::PositionType PathPositionMapper::pointAndNormalAtLength(
    float length,
    FloatPoint& point,
    float& angle) {
  if (length < 0)
    return BeforePath;
  if (length > m_pathLength)
    return AfterPath;
  ASSERT(length >= 0 && length <= m_pathLength);
  m_positionCalculator.pointAndNormalAtLength(length, point, angle);
  return OnPath;
}

LayoutSVGTextPath::LayoutSVGTextPath(Element* element)
    : LayoutSVGInline(element) {}

bool LayoutSVGTextPath::isChildAllowed(LayoutObject* child,
                                       const ComputedStyle&) const {
  if (child->isText())
    return SVGLayoutSupport::isLayoutableTextNode(child);

  return child->isSVGInline() && !child->isSVGTextPath();
}

std::unique_ptr<PathPositionMapper> LayoutSVGTextPath::layoutPath() const {
  const SVGTextPathElement& textPathElement = toSVGTextPathElement(*node());
  Element* targetElement = SVGURIReference::targetElementFromIRIString(
      textPathElement.hrefString(), treeScopeForIdResolution(textPathElement));

  if (!isSVGPathElement(targetElement))
    return nullptr;

  SVGPathElement& pathElement = toSVGPathElement(*targetElement);
  Path pathData = pathElement.asPath();
  if (pathData.isEmpty())
    return nullptr;

  // Spec:  The transform attribute on the referenced 'path' element represents
  // a supplemental transformation relative to the current user coordinate
  // system for the current 'text' element, including any adjustments to the
  // current user coordinate system due to a possible transform attribute on the
  // current 'text' element. http://www.w3.org/TR/SVG/text.html#TextPathElement
  pathData.transform(pathElement.calculateAnimatedLocalTransform());

  return PathPositionMapper::create(pathData);
}

float LayoutSVGTextPath::calculateStartOffset(float pathLength) const {
  const SVGLength& startOffset =
      *toSVGTextPathElement(node())->startOffset()->currentValue();
  float textPathStartOffset = startOffset.valueAsPercentage();
  if (startOffset.typeWithCalcResolved() ==
      CSSPrimitiveValue::UnitType::Percentage)
    textPathStartOffset *= pathLength;

  return textPathStartOffset;
}

}  // namespace blink