slicesEntered method

List<int> slicesEntered(double from, double to, double pointerAngle, { int limit = 100000, })

The slices that come under the pointer, in order, as the wheel turns from rotation from to rotation to. A slice is listed each time the pointer enters it, so a full turn lists every visible slice once.

Stops after limit entries.

Implementation

List<int> slicesEntered(double from, double to, double pointerAngle,
    {int limit = 100000}) {
  final List<int> entered = [];
  if (length == 0 || from == to || !from.isFinite || !to.isFinite) {
    return entered;
  }
  // Turning the wheel clockwise moves the pointer backwards over the
  // slices (towards lower indexes).
  final bool backwards = to > from;
  double remaining = (to - from).abs();
  int index = indexAt(from, pointerAngle);
  if (index < 0) return entered;
  double u = _positionUnderPointer(from, pointerAngle);
  // The position can sit a hair past its slice's end from rounding.
  u = u.clamp(offsets[index], offsets[index] + sweeps[index]);

  while (entered.length < limit) {
    final double toEdge =
        backwards ? u - offsets[index] : offsets[index] + sweeps[index] - u;
    if (remaining <= toEdge) break;
    remaining -= toEdge;
    index = _nextVisible(index, backwards ? -1 : 1);
    u = backwards ? offsets[index] + sweeps[index] : offsets[index];
    entered.add(index);
  }
  return entered;
}