Stop mutating inputs to decomposeArcToCubic

Source/core/svg/SVGPathParser.cpp

 /*
  * Copyright (C) 2002, 2003 The Karbon Developers
  * Copyright (C) 2006 Alexander Kellett <lypanov@kde.org>
  * Copyright (C) 2006, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * 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
@@ skipping 378 matching lines @@
 
         m_consumer->incrementPathSegmentCount();
     }
 
     return false;
 }
 
 // This works by converting the SVG arc to "simple" beziers.
 // Partly adapted from Niko's code in kdelibs/kdecore/svgicons.
 // See also SVG implementation notes: http://www.w3.org/TR/SVG/implnote.html#ArcConversionEndpointToCenter
-bool SVGPathParser::decomposeArcToCubic(float angle, float rx, float ry, FloatPoint& point1, FloatPoint& point2, bool largeArcFlag, bool sweepFlag)
+bool SVGPathParser::decomposeArcToCubic(float angle, float rx, float ry, const FloatPoint& start, const FloatPoint& end, bool largeArcFlag, bool sweepFlag)
 {
-    FloatSize midPointDistance = point1 - point2;
+    FloatSize midPointDistance = start - end;
     midPointDistance.scale(0.5f);
 
     AffineTransform pointTransform;
     pointTransform.rotate(-angle);
 
     FloatPoint transformedMidPoint = pointTransform.mapPoint(FloatPoint(midPointDistance.width(), midPointDistance.height()));
     float squareRx = rx * rx;
     float squareRy = ry * ry;
     float squareX = transformedMidPoint.x() * transformedMidPoint.x();
     float squareY = transformedMidPoint.y() * transformedMidPoint.y();
 
     // Check if the radii are big enough to draw the arc, scale radii if not.
     // http://www.w3.org/TR/SVG/implnote.html#ArcCorrectionOutOfRangeRadii
     float radiiScale = squareX / squareRx + squareY / squareRy;
     if (radiiScale > 1) {
         rx *= sqrtf(radiiScale);
         ry *= sqrtf(radiiScale);
     }
 
     pointTransform.makeIdentity();
     pointTransform.scale(1 / rx, 1 / ry);
     pointTransform.rotate(-angle);
 
-    point1 = pointTransform.mapPoint(point1);
-    point2 = pointTransform.mapPoint(point2);
+    FloatPoint point1 = pointTransform.mapPoint(start);
+    FloatPoint point2 = pointTransform.mapPoint(end);
     FloatSize delta = point2 - point1;
 
     float d = delta.width() * delta.width() + delta.height() * delta.height();
     float scaleFactorSquared = std::max(1 / d - 0.25f, 0.f);
 
     float scaleFactor = sqrtf(scaleFactorSquared);
     if (sweepFlag == largeArcFlag)
         scaleFactor = -scaleFactor;
 
     delta.scale(scaleFactor);
@@ skipping 36 matching lines @@
         point2 = targetPoint;
         point2.move(t * sinEndTheta, -t * cosEndTheta);
 
         m_consumer->curveToCubic(pointTransform.mapPoint(point1), pointTransform.mapPoint(point2),
                                  pointTransform.mapPoint(targetPoint), AbsoluteCoordinates);
     }
     return true;
 }
 
 }