disabledTT(stage) {
    const move = (e, elem) => {
      const fieldOffset = elem.field.getBoundingClientRect()
      const x = e.clientX - fieldOffset.left - 21
      const y = e.clientY - fieldOffset.top - elem.tt.offsetHeight - 12
      elem.tt.style.transform = `translate(${x}px, ${y}px)`
    }

    const disabledFields = stage.querySelectorAll('.disabled-field')
    forEach(disabledFields, index => {
      const field = disabledFields[index]
      const title = mi18n.get('fieldNonEditable')

      if (title) {
        const tt = m('p', title, { className: 'frmb-tt' })
        field.appendChild(tt)
        field.addEventListener('mousemove', e => move(e, { tt, field }))
      }
    })
  }
Display a custom tooltip for disabled fields.

@param  {Object} stage