draw_paths.elm

import Window
import Mouse

main = render <~ Window.dimensions ~ allMoves

mousePos =
  let nomalize = \(w,h) (x,y) -> (toFloat x - toFloat w / 2, toFloat h / 2 - toFloat y)
  in nomalize <~ Window.dimensions ~ Mouse.position

mouseDownAndPos = lift2 (,) Mouse.isDown mousePos

allMoves = foldp inFirstList [[]] mouseDownAndPos


inFirstList (down, (x,y)) (l::ls) = 
  if down 
  then ((x, y)::l)::ls
  else (if l == [] 
        then l::ls
        else ([]::l::ls))

toPath moves = path moves |> traced (solid red)

render (w,h) moves =
  collage w h (map toPath moves)