@type t() ::
  (((((((((((((((:on_click | :after_timeout) | :mouse_in) | :mouse_out)
              | :on_hover)
             | :mouse_down)
            | :mouse_up)
           | :on_press)
          | :none)
         | :drag)
        | :on_key_down)
       | :on_voice)
      | :on_media_hit)
     | :on_media_end)
    | :mouse_enter)
   | :mouse_leave)
  | integer()