ludic/examples/lang/scenes.ludic

# scenes — one active scene at a time, each grouping handlers into layers behind
# an implicit active-scene register (see LANGUAGE.md §"Scenes & layers").
#
# Running it (feed a few keystrokes so the loop ticks) prints:
#   1000 1 101 102 2 3 900 201 900 202 900
#     1000     Boot (a global handler) runs once at Start
#     1        Title is `start`; its `on enter` fires at boot
#     101      frame 1 Update: only Title.Main.Tick runs (Play is not active)
#     102      frame 2 Update: Tick reaches 2 -> `become Play`…
#     2 3      …which runs Title's `on exit` then Play's `on enter`
#     900      Play renders the same frame it is entered (Hud.Draw)
#     201 900  frame 3: Play.World.Step, then Hud.Draw
#     202 900  frame 4: Step reaches 2 -> quit(); Hud.Draw paints the last frame
#
#   bin/x game-build bin/ludicc examples/lang/scenes.ludic /tmp/scenes
#   printf 'aaaa' | /tmp/scenes
program SceneDemo {
  var counter: int = 0

  handler Boot phase Start { counter = 0;  print(1000) }

  scene Title start {
    on enter { print(1) }
    on exit  { print(2) }
    layer Main {
      handler Tick phase Update {
        counter = counter + 1
        print(100 + counter)
        if counter >= 2 { become Play }
      }
    }
  }

  scene Play {
    on enter { print(3);  counter = 0 }
    on exit  { print(4) }
    layer World {
      handler Step phase Update {
        counter = counter + 1
        print(200 + counter)
        if counter >= 2 { quit() }
      }
    }
    layer Hud {
      handler Draw phase Render { print(900) }
    }
  }
}