code: function (event) {
              // Check if left mouse button is pressed
              if (event.button === 0 && this.isClickable) {
                  this.updated = true;
                  this.released = false;
                  if (this.isHoldable) {
                      if (this.holdTimeout !== null) {
                          me.timer.clearTimeout(this.holdTimeout);
                      }
                      this.holdTimeout = me.timer.setTimeout(this.hold.bind(this), this.holdThreshold, false);
                      this.released = false;
                  }
                  return this.onClick.call(this, event);
              }
          }
docs: function callback for the pointerdown event
  @ignore