_onMouseMoveWithZoomMode({ e }) {
    const canvas = this.getCanvas();
    const pointer = canvas.getPointer(e);
    const { x, y } = pointer;
    const { zoomArea, _startPoint } = this;
    const deltaX = Math.abs(x - _startPoint.x);
    const deltaY = Math.abs(y - _startPoint.y);

    if (deltaX + deltaY > MOUSE_MOVE_THRESHOLD) {
      canvas.remove(zoomArea);
      zoomArea.set(this._calcRectDimensionFromPoint(x, y));
      canvas.add(zoomArea);
    }
  }
onMousemove handler in fabric canvas
@param {{e: MouseEvent}} fEvent - Fabric event
@private