add Scene class

src/Classes/Scene.hs

@@ -0,0 +1,26 @@
+{-# LANGUAGE ExistentialQuantification #-}
+module Scenes.Scene where
+
+import Affection
+
+import qualified SDL
+
+class Scene a where
+
+  -- | Perform initialization and output a (possibly empty) data container.
+  initScene :: IO a
+
+  -- | Load actual data into the initialized container.
+  loadScene :: a -> Affection ()
+
+  -- | Query whether loading data is finished.
+  isSceneLoaded :: a -> Affection Bool
+
+  -- | Run updates on the data given the time elapsed since last frame
+  update :: a -> Float -> Affection ()
+
+  -- | Handle input events
+  onEvents :: a -> [SDL.EventPayload] -> Affection ()
+
+  -- | perform the drawing
+  render :: a -> Affection ()