Factor out the <textPath> positioning mapping code into a helper class

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"
 
 namespace blink {
 
+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();
 }
 
-Path LayoutSVGTextPath::layoutPath() const
+PassOwnPtr<PathPositionMapper> LayoutSVGTextPath::layoutPath() const
 {
-    SVGTextPathElement* textPathElement = toSVGTextPathElement(node());
-    Element* targetElement = SVGURIReference::targetElementFromIRIString(textPathElement->href()->currentValue()->value(), textPathElement->treeScope());
+    const SVGTextPathElement& textPathElement = toSVGTextPathElement(*node());
+    Element* targetElement = SVGURIReference::targetElementFromIRIString(
+        textPathElement.hrefString(), textPathElement.treeScope());
     if (!isSVGPathElement(targetElement))
-        return Path();
+        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 pathData;
+
+    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