Is there a way to subscribe to page scroll events?

[Rupert Smith]

I could use Dom.Scroll to get the y-offset of the body (http://package.elm-lang.org/packages/elm-lang/dom/1.1.1/Dom-Scroll), using its 'x' and 'y' tasks. The trouble is I don't know when the body may have been scrolled since this is a task and not a subscription.

Is a subscription for this available somewhere? Or just write my own port it...

[Rupert Smith]

On Friday, February 10, 2017 at 12:58:21 PM UTC, Rupert Smith wrote:

I could use Dom.Scroll to get the y-offset of the body (http://package.elm-lang.org/packages/elm-lang/dom/1.1.1/Dom-Scroll), using its 'x' and 'y' tasks. The trouble is I don't know when the body may have been scrolled since this is a task and not a subscription.

Is a subscription for this available somewhere? Or just write my own port it...

"elm-scroll" looks like it will do it:

http://package.elm-lang.org/packages/abrykajlo/elm-scroll/2.0.1 

[Scott Mueller]

Here's code for an onScroll function that can be used just like an Html.Events.onClick. Basically, you can always use a Decoder with Html.Events.on to listen to HTML events this way:

type alias ScrollEvent =

  { scrollHeight : Int

  , scrollPos : Int

  , visibleHeight : Int

  }

onScroll : (ScrollEvent -> msg) -> Html.Attribute msg

onScroll tagger =

  Html.Events.on "scroll" (Decode.map tagger onScrollJsonParser)

onScrollJsonParser : Decode.Decoder ScrollEvent

onScrollJsonParser =

  Decode.map3 ScrollEvent

    (Decode.at ["target", "scrollHeight"] Decode.int)

    (Decode.at ["target", "scrollTop"] Decode.int)

    (Decode.at ["target", "clientHeight"] Decode.int)