apply method

@override void apply(ForceSimulation simulation)

Applies the force to the simulation.

Implementation

@override
void apply(ForceSimulation simulation) {
  final nodes = simulation.nodes;
  final n = nodes.length;
  if (n == 0) return;

  // Calculate center of mass
  double sx = 0, sy = 0;
  for (final node in nodes) {
    sx += node.x;
    sy += node.y;
  }
  sx = (sx / n - x) * strength;
  sy = (sy / n - y) * strength;

  // Move nodes toward center
  for (final node in nodes) {
    node.x -= sx;
    node.y -= sy;
  }
}