Example use of Elm 0.17 - taking advantage of subscriptions, and tasks.

newVersion.elm

import Html.App as Html
import Html exposing ( Html, div, text )
import Html.Attributes exposing ( .. )
import Html.Events exposing ( onClick )
import Window
import Task


main = Html.program
  { init = ( ( initSize, initSize ), triggerGetSize )
  , view = view
  , update = update
  , subscriptions = subscriptions
  }

initSize = { width = 10, height = 10 }

triggerGetSize = Task.perform ( \_ -> None ) ( \x -> SetSize2 x ) Window.size

type Msg = SetSize1 Window.Size | SetSize2 Window.Size | GetSize | None
type alias Model = ( Window.Size, Window.Size )

view: Model -> Html Msg
view model = 
  let viewStyle = 
        style
          [ ( "padding", "20px" )
          , ( "background", "lightgrey" )
          , ( "display", "block" )
          ]
      ( size1, size2 ) = model
  in
    div 
      [ onClick GetSize ] 
      [ div [ viewStyle ] [ text ( toString size1 ) ]
      , div [ viewStyle ] [ text ( toString size2 ) ] ]

update: Msg -> Model -> ( Model, Cmd Msg )
update msg model = 
  let ( size1, size2 ) = model
  in 
    case msg of
      SetSize1 size -> ( ( size, size2 ), Cmd.none )
      SetSize2 size -> ( ( size1, size ), Cmd.none )
      GetSize -> ( model, triggerGetSize )
      None -> ( model, Cmd.none )
    
subscriptions model = 
  Sub.batch [ Window.resizes ( \size -> SetSize1 size ) ]