circleTiles function

List<Coords<num>> circleTiles(Map<String, dynamic> input)

Implementation

List<Coords<num>> circleTiles(Map<String, dynamic> input) {
  // This took some time and is fairly complicated, so this is the overall explanation:
  // 1. Given a `LatLng` for every x degrees on a circle's circumference, convert it into a tile number
  // 2. Using a `Map` per zoom level, record all the X values in it without duplicates
  // 3. Under the previous record, add all the Y values within the circle (ie. to opposite the X value)
  // 4. Loop over these XY values and add them to the list
  // Theoretically, this could have been done using the same method as `lineTiles`, but `lineTiles` was built after this algorithm and this makes more sense for a circle

  final List<LatLng> circleOutline = input['circleOutline'];
  final int minZoom = input['minZoom'];
  final int maxZoom = input['maxZoom'];
  final Crs crs = input['crs'];
  final CustomPoint<num> tileSize = input['tileSize'];

  // Format: Map<z, Map<x, List<y>>>
  final Map<int, Map<int, List<int>>> outlineTileNums = {};

  final List<Coords<num>> coords = [];

  for (int zoomLvl = minZoom; zoomLvl <= maxZoom; zoomLvl++) {
    outlineTileNums[zoomLvl] = <int, List<int>>{};

    for (final LatLng node in circleOutline) {
      final CustomPoint<num> tile = crs
          .latLngToPoint(node, zoomLvl.toDouble())
          .unscaleBy(tileSize)
          .floor();

      outlineTileNums[zoomLvl]![tile.x.toInt()] ??= [
        1000000000000,
        -1000000000000
      ];

      outlineTileNums[zoomLvl]![tile.x.toInt()] = [
        tile.y < outlineTileNums[zoomLvl]![tile.x.toInt()]![0]
            ? tile.y.toInt()
            : outlineTileNums[zoomLvl]![tile.x.toInt()]![0],
        tile.y > outlineTileNums[zoomLvl]![tile.x.toInt()]![1]
            ? tile.y.toInt()
            : outlineTileNums[zoomLvl]![tile.x.toInt()]![1],
      ];
    }

    for (final int x in outlineTileNums[zoomLvl]!.keys) {
      for (int y = outlineTileNums[zoomLvl]![x]![0];
          y <= outlineTileNums[zoomLvl]![x]![1];
          y++) {
        coords.add(
          Coords(x.toDouble(), y.toDouble())..z = zoomLvl.toDouble(),
        );
      }
    }
  }

  return coords;
}