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SMILKeySpline.h (3146B)

      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 <cstdint>
     11 
     12 namespace mozilla {
     13 
     14 /**
     15 * Utility class to provide scaling defined in a keySplines element.
     16 */
     17 class SMILKeySpline {
     18 public:
     19  constexpr SMILKeySpline() : mX1(0), mY1(0), mX2(0), mY2(0) {
     20    /* caller must call Init later */\
     21  }
     22 
     23    /**
     24     * Creates a new key spline control point description.
     25     *
     26     * aX1, etc. are the x1, y1, x2, y2 cubic Bezier control points as defined
     27     * by SMILANIM 3.2.3. They must each be in the range 0.0 <= x <= 1.0
     28     */
     29    SMILKeySpline(double aX1, double aY1, double aX2, double aY2)
     30        : mX1(0), mY1(0), mX2(0), mY2(0) {
     31      Init(aX1, aY1, aX2, aY2);
     32    }
     33 
     34    double X1() const { return mX1; }
     35    double Y1() const { return mY1; }
     36    double X2() const { return mX2; }
     37    double Y2() const { return mY2; }
     38 
     39    void Init(double aX1, double aY1, double aX2, double aY2);
     40 
     41    /**
     42     * Gets the output (y) value for an input (x).
     43     *
     44     * @param aX  The input x value. A floating-point number between 0 and
     45     *            1 (inclusive).
     46     */
     47    double GetSplineValue(double aX) const;
     48 
     49    void GetSplineDerivativeValues(double aX, double& aDX, double& aDY) const;
     50 
     51    bool operator==(const SMILKeySpline& aOther) const {
     52      return mX1 == aOther.mX1 && mY1 == aOther.mY1 && mX2 == aOther.mX2 &&
     53             mY2 == aOther.mY2;
     54    }
     55    bool operator!=(const SMILKeySpline& aOther) const {
     56      return !(*this == aOther);
     57    }
     58    int32_t Compare(const SMILKeySpline& aRhs) const {
     59      if (mX1 != aRhs.mX1) return mX1 < aRhs.mX1 ? -1 : 1;
     60      if (mY1 != aRhs.mY1) return mY1 < aRhs.mY1 ? -1 : 1;
     61      if (mX2 != aRhs.mX2) return mX2 < aRhs.mX2 ? -1 : 1;
     62      if (mY2 != aRhs.mY2) return mY2 < aRhs.mY2 ? -1 : 1;
     63      return 0;
     64    }
     65 
     66   private:
     67    void CalcSampleValues();
     68 
     69    /**
     70     * Returns x(t) given t, x1, and x2, or y(t) given t, y1, and y2.
     71     */
     72    static double CalcBezier(double aT, double aA1, double aA2);
     73 
     74    /**
     75     * Returns dx/dt given t, x1, and x2, or dy/dt given t, y1, and y2.
     76     */
     77    static double GetSlope(double aT, double aA1, double aA2);
     78 
     79    double GetTForX(double aX) const;
     80 
     81    double NewtonRaphsonIterate(double aX, double aGuessT) const;
     82 
     83    double BinarySubdivide(double aX, double aA, double aB) const;
     84 
     85    static double A(double aA1, double aA2) {
     86      return 1.0 - 3.0 * aA2 + 3.0 * aA1;
     87    }
     88 
     89    static double B(double aA1, double aA2) { return 3.0 * aA2 - 6.0 * aA1; }
     90 
     91    static double C(double aA1) { return 3.0 * aA1; }
     92 
     93    double mX1;
     94    double mY1;
     95    double mX2;
     96    double mY2;
     97 
     98    enum { kSplineTableSize = 11 };
     99    double mSampleValues[kSplineTableSize] = {};
    100 
    101    static const double kSampleStepSize;
    102 };
    103 
    104 }  // namespace mozilla
    105 
    106 #endif  // DOM_SMIL_SMILKEYSPLINE_H_