loadNavigationElements() {
    this.cleanNavigation();

    this.navigationDOM = {};
    const navigationDivs = [
      "up",
      "down",
      "left",
      "right",
      "zoomIn",
      "zoomOut",
      "zoomExtends",
    ];
    const navigationDivActions = [
      "_moveUp",
      "_moveDown",
      "_moveLeft",
      "_moveRight",
      "_zoomIn",
      "_zoomOut",
      "_fit",
    ];

    this.navigationDOM["wrapper"] = document.createElement("div");
    this.navigationDOM["wrapper"].className = "vis-navigation";
    this.canvas.frame.appendChild(this.navigationDOM["wrapper"]);

    for (let i = 0; i < navigationDivs.length; i++) {
      this.navigationDOM[navigationDivs[i]] = document.createElement("div");
      this.navigationDOM[navigationDivs[i]].className =
        "vis-button vis-" + navigationDivs[i];
      this.navigationDOM["wrapper"].appendChild(
        this.navigationDOM[navigationDivs[i]]
      );

      const hammer = new Hammer(this.navigationDOM[navigationDivs[i]]);
      if (navigationDivActions[i] === "_fit") {
        onTouch(hammer, this._fit.bind(this));
      } else {
        onTouch(hammer, this.bindToRedraw.bind(this, navigationDivActions[i]));
      }

      this.navigationHammers.push(hammer);
    }

    // use a hammer for the release so we do not require the one used in the rest of the network
    // the one the rest uses can be overloaded by the manipulation system.
    const hammerFrame = new Hammer(this.canvas.frame);
    onRelease(hammerFrame, () => {
      this._stopMovement();
    });
    this.navigationHammers.push(hammerFrame);

    this.iconsCreated = true;
  }
Creation of the navigation controls nodes. They are drawn over the rest of the nodes and are not affected by scale and translation
they have a triggerFunction which is called on click. If the position of the navigation controls is dependent
on this.frame.canvas.clientWidth or this.frame.canvas.clientHeight, we flag horizontalAlignLeft and verticalAlignTop false.
This means that the location will be corrected by the _relocateNavigation function on a size change of the canvas.
@private