method applyCurve

Source

@override
double applyCurve(double scrollOffset, double scrollDelta) {
  double newScrollOffset = scrollOffset + scrollDelta;
  // If we're overscrolling, we want move the scroll offset 2x
  // slower than we would otherwise. Therefore, we "rewind" the
  // newScrollOffset by half the amount that we moved it above.
  // Notice that we clamp the "old" value to 0.0 so that we only
  // reduce the portion of scrollDelta that's applied beyond 0.0. We
  // do similar things for overscroll in the other direction.
  if (newScrollOffset < minScrollOffset) {
    newScrollOffset -= (newScrollOffset - math.min(minScrollOffset, scrollOffset)) / 2.0;
  } else if (newScrollOffset > maxScrollOffset) {
    newScrollOffset -= (newScrollOffset - math.max(maxScrollOffset, scrollOffset)) / 2.0;
  }
  return newScrollOffset;
}