UI GFX Geometry: Make UnitBezier a wrapper for gfx::CubicBezier

third_party/WebKit/Source/platform/animation/UnitBezier.h

-/*
- * 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.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 INC. OR
- * 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.
- */
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
 
 #ifndef UnitBezier_h
 #define UnitBezier_h
 
-#include "platform/PlatformExport.h"
+#include "ui/gfx/geometry/cubic_bezier.h"
 #include "wtf/Allocator.h"
-#include "wtf/Assertions.h"
-
-#include <algorithm>
-#include <cmath>
 
 namespace blink {
 
-struct PLATFORM_EXPORT UnitBezier {
+// TODO(loyso): Erase blink::UnitBezier and use gfx::CubicBezier directly.
+struct UnitBezier {
     USING_FAST_MALLOC(UnitBezier);
 public:
-    UnitBezier(double p1x, double p1y, double p2x, double p2y);
-
-    static const double kBezierEpsilon;
+    UnitBezier(double p1x, double p1y, double p2x, double p2y)
+        : m_cubicBezier(p1x, p1y, p2x, p2y)
+    {
+    }
 
     double sampleCurveX(double t) const
     {
-        // `ax t^3 + bx t^2 + cx t' expanded using Horner's rule.
-        return ((ax * t + bx) * t + cx) * t;
+        return m_cubicBezier.SampleCurveX(t);
     }
 
     double sampleCurveY(double t) const
     {
-        return ((ay * t + by) * t + cy) * t;
-    }
-
-    double sampleCurveDerivativeX(double t) const
-    {
-        return (3.0 * ax * t + 2.0 * bx) * t + cx;
-    }
-
-    double sampleCurveDerivativeY(double t) const
-    {
-        return (3.0 * ay * t + 2.0 * by) * t + cy;
-    }
-
-    // Given an x value, find a parametric value it came from.
-    double solveCurveX(double x, double epsilon) const
-    {
-        ASSERT(x >= 0.0);
-        ASSERT(x <= 1.0);
-
-        double t0;
-        double t1;
-        double t2;
-        double x2;
-        double d2;
-        int i;
-
-        // First try a few iterations of Newton's method -- normally very fast.
-        for (t2 = x, i = 0; i < 8; i++) {
-            x2 = sampleCurveX(t2) - x;
-            if (fabs (x2) < epsilon)
-                return t2;
-            d2 = sampleCurveDerivativeX(t2);
-            if (fabs(d2) < 1e-6)
-                break;
-            t2 = t2 - x2 / d2;
-        }
-
-        // Fall back to the bisection method for reliability.
-        t0 = 0.0;
-        t1 = 1.0;
-        t2 = x;
-
-        while (t0 < t1) {
-            x2 = sampleCurveX(t2);
-            if (fabs(x2 - x) < epsilon)
-                return t2;
-            if (x > x2)
-                t0 = t2;
-            else
-                t1 = t2;
-            t2 = (t1 - t0) * .5 + t0;
-        }
-
-        // Failure.
-        return t2;
+        return m_cubicBezier.SampleCurveY(t);
     }
 
     // Evaluates y at the given x.
     double solve(double x) const
     {
-        return solveWithEpsilon(x, kBezierEpsilon);
+        return m_cubicBezier.Solve(x);
     }
 
     // Evaluates y at the given x. The epsilon parameter provides a hint as to the required
     // accuracy and is not guaranteed.
     double solveWithEpsilon(double x, double epsilon) const
     {
-        if (x < 0.0)
-            return 0.0 + m_startGradient * x;
-        if (x > 1.0)
-            return 1.0 + m_endGradient * (x - 1.0);
-        return sampleCurveY(solveCurveX(x, epsilon));
-    }
-
-    // Returns an approximation of dy/dx at the given x.
-    double slope(double x) const
-    {
-        return slopeWithEpsilon(x, kBezierEpsilon);
-    }
-
-    double slopeWithEpsilon(double x, double epsilon) const
-    {
-        double t = solveCurveX(x, epsilon);
-        double dx = sampleCurveDerivativeX(t);
-        double dy = sampleCurveDerivativeY(t);
-        return dy / dx;
-    }
-
-    // Sets |min| and |max| to the bezier's minimum and maximium y values in the
-    // interval [0, 1].
-    void range(double* min, double* max) const
-    {
-        *min = m_rangeMin;
-        *max = m_rangeMax;
+        return m_cubicBezier.SolveWithEpsilon(x, epsilon);
     }
 
 private:
-    void initCoefficients(double p1x, double p1y, double p2x, double p2y);
-    void initGradients(double p1x, double p1y, double p2x, double p2y);
-    void initRange(double p1y, double p2y);
-
-    double ax;
-    double bx;
-    double cx;
-
-    double ay;
-    double by;
-    double cy;
-
-    double m_startGradient;
-    double m_endGradient;
-
-    double m_rangeMin;
-    double m_rangeMax;
+    gfx::CubicBezier m_cubicBezier;
 };
 
 } // namespace blink
 
 #endif // UnitBezier_h