transformInternal method Null safety

Implementation

@override
double transformInternal(double t) {
  // Linearly interpolate between the two closest samples generated when the
  // curve was created.
  if (_precomputedSamples.isEmpty) {
    // Compute the samples now if we were constructed lazily.
    _precomputedSamples.addAll(_computeSamples(controlPoints, tension));
  }
  int start = 0;
  int end = _precomputedSamples.length - 1;
  int mid;
  Offset value;
  Offset startValue = _precomputedSamples[start].value;
  Offset endValue = _precomputedSamples[end].value;
  // Use a binary search to find the index of the sample point that is just
  // before t.
  while (end - start > 1) {
    mid = (end + start) ~/ 2;
    value = _precomputedSamples[mid].value;
    if (t >= value.dx) {
      start = mid;
      startValue = value;
    } else {
      end = mid;
      endValue = value;
    }
  }

  // Now interpolate between the found sample and the next one.
  final double t2 = (t - startValue.dx) / (endValue.dx - startValue.dx);
  return lerpDouble(startValue.dy, endValue.dy, t2)!;
}