itle)
  d3.select('#title').html(title)
}

function updateExpand () {
  d3.select('#expand').property('value', expand)
}

function updateChronology () {
  d3.select('#chronology').property('checked', chronology)
}

function clearPopup () {
  if (popup) {
    clearTimeout(hoverTimeout)
    hoverTimeout = null
    popup = null
    updatePopup()
  }
}

function updatePopupBounds () {
  if (popup) {
    const r = popup.srcElement.getBoundingClientRect()
    const shift = (r.bottom - r.top) * 0.5
    const width