handleDownEvent(mapBrowserEvent) {
    if (this.targetPointers.length == 1) {
      const map = mapBrowserEvent.map;
      this.anchor_ = null;
      this.lastDistance_ = undefined;
      this.lastScaleDelta_ = 1;
      this.down_ = mapBrowserEvent.originalEvent;
      if (!this.handlingDownUpSequence_) {
        map.getView().beginInteraction();
      }
      return true;
    }
    return false;
  }
Handle pointer down events.
@param {import("../MapBrowserEvent.js").default<PointerEvent>} mapBrowserEvent Event.
@return {boolean} If the event was consumed.