scrivito.editors._file_dropzone = (fields, callback) -> fields.each(-> setup $(this), callback)
setup = (el, callback) ->
  field = el.closest('[data-scrivito-field-name]')
  el.on 'dragenter', -> field.addClass('image-editor-dragover') and off
  el.on 'dragleave', -> field.removeClass('image-editor-dragover') and off
  el.on 'drop', (e) ->
    field.removeClass 'image-editor-dragover'
    if (files = e.originalEvent.dataTransfer?.files)?.length is 1
      callback field, files[0]
    off