activeMenu = menu;
      activeMenuHdr = hdr;
      menu.style.display = 'block';
    }
    hdr.addEventListener('mousedown', showMenu);
    hdr.addEventListener('touchstart', showMenu);
  }

  // If there is an active menu and a down event outside, retract the menu.
  for (const t of ['mousedown', 'touchstart']) {
    document.addEventListener(t, (e) => {
      // Note: to avoid unnecessary flicker, if the down event is inside

  window.addEventListener('popstate', render);
  search.addEventListener('keydown', handleSearchKey);

  // Withdraw action menu when clicking outside, or when item selected.
  document.addEventListener('mousedown', (e) => {
    if (!actions.contains(e.target)) {
      hideActionMenu();
    }
  });
  actions.addEventListener('click', hideActionMenu);

  // Initialize menus and other general UI elements.

        svg.addEventListener('pointermove', drag);
        svg.addEventListener('pointerup', endDrag);
        svg.addEventListener('pointerleave', endDrag);
    } else {
        svg.addEventListener('mousedown', startDrag);
        svg.addEventListener('mousemove', drag);
        svg.addEventListener('mouseup', endDrag);
        svg.addEventListener('mouseleave', endDrag);
    }

    var point = svg.createSVGPoint();