acquire method

InstanceHandle acquire({ Matrix4? transform, LinearColor color = LinearColor.white, Vector4? data, })

Takes a slot for something that comes and goes, and returns the handle that keeps finding it: a shot, a spark, an invader.

For a batch whose members leave in any order. Written by index, a batch whose middle member left had a hole to fill, and filling it moved another member to a slot its owner did not know about. release fills the hole with the last slot and tells the last slot's handle where it went, so an owner holding a handle is never pointed at someone else's.

Grows the buffer when it is full, the way ensureCapacity does: a batch of things that come and go has no size to name in advance.

Implementation

InstanceHandle acquire({
  Matrix4? transform,
  LinearColor color = LinearColor.white,
  Vector4? data,
}) {
  ensureCapacity(_count + 1);
  final index = _count;
  final handle = InstanceHandle._(this, index);
  while (_holders.length <= index) {
    _holders.add(null);
  }
  _holders[index] = handle;
  count = index + 1;
  setTransform(index, transform ?? Matrix4.identity());
  setColor(index, color);
  // A slot a released member left holds its numbers; the new one starts
  // from nought, as a fresh batch does.
  setInstanceData(index, data ?? Vector4.zero());
  final weights = _weights;
  if (weights != null) {
    weights.fillRange(
      index * maxMorphTargets,
      (index + 1) * maxMorphTargets,
      0.0,
    );
    _weightsVersion++;
  }
  return handle;
}