addCtrlGripMethod = function (id) {
  let pointGrip = getElement('ctrlpointgrip_' + id)
  if (pointGrip) { return pointGrip }

  pointGrip = document.createElementNS(NS.SVG, 'circle')
  const atts = {
    id: 'ctrlpointgrip_' + id,
    display: 'none',
    r: 4,
    fill: '#0FF',
    stroke: '#55F',
    'stroke-width': 1,
    cursor: 'move',
    style: 'pointer-events:all'
  }
  const uiStrings = svgCanvas.getUIStrings()
  if ('pathCtrlPtTooltip' in uiStrings) { // May be empty if running path.js without svg-editor
    atts['xlink:title'] = uiStrings.pathCtrlPtTooltip
  }
  assignAttributes(pointGrip, atts)
  getGripContainerMethod().append(pointGrip)
  return pointGrip
}
Requires prior call to `setUiStrings` if `xlink:title`
   to be set on the grip.
@function module:path.addCtrlGrip
@param {string} id
@returns {SVGCircleElement}