Simple example of drawing a point and then make that point "moveable"

move-point.elm

import Mouse
import Window

main : Signal Element
main = lift2 scene Window.dimensions lastClickLocation

input : Signal (Int, Int)
input = sampleOn Mouse.clicks Mouse.position

lastClickLocation = lift (take 1) clickLocations

clickLocations : Signal [(Int,Int)]
clickLocations = foldp (::) [] input



scene : (Int,Int) -> [(Int,Int)] -> Element
scene (w,h) locs =
  let drawCircle (x,y) =
          circle 5  |> filled (rgba 0 76 255 1)
                    |> move (toFloat x - toFloat w / 2, toFloat h / 2 - toFloat y)

  in  layers [ collage w h (map drawCircle locs)
             , plainText "Click to stamp a circle."
             ]