method lerp

Source

static RRect lerp(RRect a, RRect b, double t) {
  if (a == null && b == null)
    return null;
  if (a == null) {
    return new RRect._fromList(<double>[
      b.left * t,
      b.top * t,
      b.right * t,
      b.bottom * t,
      b.tlRadiusX * t,
      b.tlRadiusY * t,
      b.trRadiusX * t,
      b.trRadiusY * t,
      b.brRadiusX * t,
      b.brRadiusY * t,
      b.blRadiusX * t,
      b.blRadiusY * t
    ]);
  }
  if (b == null) {
    double k = 1.0 - t;
    return new RRect._fromList(<double>[
      a.left * k,
      a.top * k,
      a.right * k,
      a.bottom * k,
      a.tlRadiusX * k,
      a.tlRadiusY * k,
      a.trRadiusX * k,
      a.trRadiusY * k,
      a.brRadiusX * k,
      a.brRadiusY * k,
      a.blRadiusX * k,
      a.blRadiusY * k
    ]);
  }
  return new RRect._fromList(<double>[
    lerpDouble(a.left, b.left, t),
    lerpDouble(a.top, b.top, t),
    lerpDouble(a.right, b.right, t),
    lerpDouble(a.bottom, b.bottom, t),
    lerpDouble(a.tlRadiusX, b.tlRadiusX, t),
    lerpDouble(a.tlRadiusY, b.tlRadiusY, t),
    lerpDouble(a.trRadiusX, b.trRadiusX, t),
    lerpDouble(a.trRadiusY, b.trRadiusY, t),
    lerpDouble(a.brRadiusX, b.brRadiusX, t),
    lerpDouble(a.brRadiusY, b.brRadiusY, t),
    lerpDouble(a.blRadiusX, b.blRadiusX, t),
    lerpDouble(a.blRadiusY, b.blRadiusY, t)
  ]);
}