_2v(index) {
    return (pt) => {
      const x = pt.x, y = pt.y;
      const [ x2p, y2p ] = this._2p(index);
      const p2vX = this.gridCanvas.p2vX, p2vY = this.gridCanvas.p2vY;
      return [ p2vX(x2p(x)), p2vY(y2p(y)) ];
    }
  }
Glyph transformation to view coordinates
@param { number } index 
@returns { {({ x: number, y: number, on: boolean }) => [number, number]} }