document.addEventListener('mousedown', (e) => {
    if (!actions.contains(e.target)) {
      hideActionMenu();
    }
  });
  actions.addEventListener('click', hideActionMenu);

  // Initialize menus and other general UI elements.
  viewer(new URL(window.location.href), nodes, {
    hiliter: (n, on) => { return hilite(n, on); },
    current: () => {
      let r = new Map();
      if (pivots.length == 1 && pivots[0] == 0) {