dom/smil/SMILKeySpline.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef DOM_SMIL_SMILKEYSPLINE_H_
   8 #define DOM_SMIL_SMILKEYSPLINE_H_
   9
  10 #include "mozilla/ArrayUtils.h"
  11 #include "mozilla/PodOperations.h"
  12
  13 namespace mozilla {
  14
  15 /**
  16  * Utility class to provide scaling defined in a keySplines element.
  17  */
  18 class SMILKeySpline {
  19  public:
  20   constexpr SMILKeySpline() : mX1(0), mY1(0), mX2(0), mY2(0) {
  21     /* caller must call Init later */\
  22   }
  23
  24     /**
  25      * Creates a new key spline control point description.
  26      *
  27      * aX1, etc. are the x1, y1, x2, y2 cubic Bezier control points as defined
  28      * by SMILANIM 3.2.3. They must each be in the range 0.0 <= x <= 1.0
  29      */
  30     SMILKeySpline(double aX1, double aY1, double aX2, double aY2)
  31         : mX1(0), mY1(0), mX2(0), mY2(0) {
  32       Init(aX1, aY1, aX2, aY2);
  33     }
  34
  35     double X1() const { return mX1; }
  36     double Y1() const { return mY1; }
  37     double X2() const { return mX2; }
  38     double Y2() const { return mY2; }
  39
  40     void Init(double aX1, double aY1, double aX2, double aY2);
  41
  42     /**
  43      * Gets the output (y) value for an input (x).
  44      *
  45      * @param aX  The input x value. A floating-point number between 0 and
  46      *            1 (inclusive).
  47      */
  48     double GetSplineValue(double aX) const;
  49
  50     void GetSplineDerivativeValues(double aX, double& aDX, double& aDY) const;
  51
  52     bool operator==(const SMILKeySpline& aOther) const {
  53       return mX1 == aOther.mX1 && mY1 == aOther.mY1 && mX2 == aOther.mX2 &&
  54              mY2 == aOther.mY2;
  55     }
  56     bool operator!=(const SMILKeySpline& aOther) const {
  57       return !(*this == aOther);
  58     }
  59     int32_t Compare(const SMILKeySpline& aRhs) const {
  60       if (mX1 != aRhs.mX1) return mX1 < aRhs.mX1 ? -1 : 1;
  61       if (mY1 != aRhs.mY1) return mY1 < aRhs.mY1 ? -1 : 1;
  62       if (mX2 != aRhs.mX2) return mX2 < aRhs.mX2 ? -1 : 1;
  63       if (mY2 != aRhs.mY2) return mY2 < aRhs.mY2 ? -1 : 1;
  64       return 0;
  65     }
  66
  67    private:
  68     void CalcSampleValues();
  69
  70     /**
  71      * Returns x(t) given t, x1, and x2, or y(t) given t, y1, and y2.
  72      */
  73     static double CalcBezier(double aT, double aA1, double aA2);
  74
  75     /**
  76      * Returns dx/dt given t, x1, and x2, or dy/dt given t, y1, and y2.
  77      */
  78     static double GetSlope(double aT, double aA1, double aA2);
  79
  80     double GetTForX(double aX) const;
  81
  82     double NewtonRaphsonIterate(double aX, double aGuessT) const;
  83
  84     double BinarySubdivide(double aX, double aA, double aB) const;
  85
  86     static double A(double aA1, double aA2) {
  87       return 1.0 - 3.0 * aA2 + 3.0 * aA1;
  88     }
  89
  90     static double B(double aA1, double aA2) { return 3.0 * aA2 - 6.0 * aA1; }
  91
  92     static double C(double aA1) { return 3.0 * aA1; }
  93
  94     double mX1;
  95     double mY1;
  96     double mX2;
  97     double mY2;
  98
  99     enum { kSplineTableSize = 11 };
 100     double mSampleValues[kSplineTableSize] = {};
 101
 102     static const double kSampleStepSize;
 103 };
 104
 105 }  // namespace mozilla
 106
 107 #endif  // DOM_SMIL_SMILKEYSPLINE_H_