pixelXToTileX method
Converts a pixel X coordinate to the corresponding tile X number.
pixelX The pixel X coordinate to convert
Returns the tile X coordinate containing this pixel
Implementation
int pixelXToTileX(double pixelX) {
assert(pixelX >= 0);
assert(pixelX <= _mapSize);
return max(min(pixelX / tileSize, scalefactor.scalefactor - 1), 0).floor();
}