如何在滚动时创建Elm Lang事件？

import Html exposing (text)
import Html.Events exposing (on)
import Window

type Msg
    = Scroll

main =
    Html.program
        { init = init
        , update = update
        , view = view
        , subscriptions = subscriptions
        }

init =
    ( (), Cmd.none )

update msg model =
    case msg of
        Scroll ->
            -- 在这里处理滚动事件
            ( model, Cmd.none )

view model =
    text "Scroll the page to trigger the event"

subscriptions model =
    Window.scroll Scroll