constructor(parent) {
    super(parent)

    this.grabber = null
    this.grabbedAmount = 0
    this.gripSpaceTransform = null

    this._lastGripPose = null

    this.addEventListener('xrsqueezestart', this._onSqueezeStart.bind(this))
    this.addEventListener('beforerender', this._onBeforeRender.bind(this))
    this._onSqueezeEnd = this._onSqueezeEnd.bind(this)
  }
Experimental: Wrapper facade that syncs its world matrix to match that of a
tracked-pointer XRInputSource when the user presses its "squeeze" button.