open Graphics2D

let portal = {view=Some(vec2 0. 0., vec2 0. 0.); scene=Tiger.scene}

let target = ref (bound_of portal.scene)

let dt = dt()

let paint() =
  match portal.view, !target with
  | Some (ol, ou), Some (nl, nu) ->
      let p = 0.1 ** dt() in
      portal.view <-
	Some (p *| ol +| (1. -. p) *| nl, p *| ou +| (1. -. p) *| nu)
  | None, target ->
      portal.view <- target
  | _ -> ()

let click = function
  | Some(i::_) ->
      (* If an object is clicked on then zoom to it. *)
      target := bound_of(get [i] portal.scene)
  | _ ->
      (* If the background is clicked on then zoom out to see the whole
	 scene. *)
      target := bound_of portal.scene

let () =
  let on_paint = Event.create() in
  Event.add paint on_paint;
  let on_click = Event.create() in
  Event.add click on_click;
  GUI.spawn ~on_paint ~on_click portal