toOutlines method

Iterable<List<LatLng>> toOutlines([ int overlap = 0 ])

Generate the list of rectangle segments formed from the locus of this line

Use the optional overlap argument to set the behaviour of the joints between segments:

• -1: joined by closest corners (largest gap)
• 0 (default): joined by centers
• 1 (as downloaded): joined by further corners (largest overlap)

Implementation

Iterable<List<LatLng>> toOutlines([int overlap = 0]) sync* {
  if (overlap < -1 || overlap > 1) {
    throw ArgumentError('`overlap` must be between -1 and 1 inclusive');
  }

  if (line.isEmpty) return;

  const dist = Distance();
  final rad = radius * math.pi / 4;

  for (int i = 0; i < line.length - 1; i++) {
    final cp = line[i];
    final np = line[i + 1];

    final bearing = dist.bearing(cp, np);
    final clockwiseRotation =
        (90 + bearing) > 360 ? 360 - (90 + bearing) : (90 + bearing);
    final anticlockwiseRotation =
        (bearing - 90) < 0 ? 360 + (bearing - 90) : (bearing - 90);

    final tr = dist.offset(cp, rad, clockwiseRotation); // Top right
    final br = dist.offset(np, rad, clockwiseRotation); // Bottom right
    final bl = dist.offset(np, rad, anticlockwiseRotation); // Bottom left
    final tl = dist.offset(cp, rad, anticlockwiseRotation); // Top left

    if (overlap == 0) yield [tr, br, bl, tl];

    final r = overlap == -1;
    final os = i == 0;
    final oe = i == line.length - 2;

    yield [
      if (os) tr else dist.offset(tr, r ? rad : -rad, bearing),
      if (oe) br else dist.offset(br, r ? -rad : rad, bearing),
      if (oe) bl else dist.offset(bl, r ? -rad : rad, bearing),
      if (os) tl else dist.offset(tl, r ? rad : -rad, bearing),
    ];
  }
}