tick method

@override void tick(Duration duration)

Implementation

@override
void tick(Duration duration) {
  if (spriteSheet.image == null) {
    return;
  }
  fillInitialData();

  _hue -= 1;

  int frameCount = spriteSheet.length;
  const double maxD = 100.0;

  for (int i = 0; i < count; i++) {
    _Particle o = particles![i] as _Particle;
    double dx, dy, d;

    if (touchPoint != null &&
        (dy = touchPoint!.dy - o.y) < maxD &&
        (dx = touchPoint!.dx - o.x) < maxD &&
        (d = sqrt(dx * dx + dy * dy)) < maxD) {
      double a = atan2(dy, dx);
      double v = (maxD - d) / maxD * -1.0;
      o.vx += v * cos(a);
      o.vy += v * sin(a);
    }

    o.vy += 0.1;
    o.x += o.vx;

    o.vx *= 0.99;
    o.y += o.vy;

    if (o.y > height) {
      _activateParticle(i);
    }

    double r = 12.0 * o.scale;
    injectVertex(i, xy, o.x - r, o.y - r, o.x + r, o.y + r);
    if (o.animate) {
      spriteSheet.injectTexCoords(i, uv, (++o.frame % frameCount));
    }
  }

  super.tick(duration);
}