on how not to do it

affection.cabal

@@ -122,6 +122,23 @@ executable example02
   else
     buildable:       False
 
+executable example02.1
+  hs-source-dirs:    examples
+  main-is:           example02.1.hs
+  ghc-options:       -threaded -Wall
+  default-language:  Haskell2010
+  default-extensions: OverloadedStrings
+  if flag(examples)
+    build-depends:     base
+                     , affection
+                     , sdl2
+                     , gegl
+                     , babl
+                     , containers
+                     , mtl
+  else
+    buildable:       False
+
 executable example03
   hs-source-dirs:    examples
   main-is:           example03.hs

examples/example02.1.hs

@@ -0,0 +1,169 @@
+{-# LANGUAGE RecordWildCards #-}
+
+import Affection
+import qualified SDL
+import qualified GEGL as G
+import qualified BABL as B
+import qualified Data.Map.Strict as M
+
+import Debug.Trace
+
+main :: IO ()
+main = do
+  conf <- return $ AffectionConfig
+    { initComponents = All
+    , windowTitle    = "Affection: example00"
+    , windowConfig   = SDL.defaultWindow
+    , preLoop        = return ()
+    , eventLoop      = handle
+    , updateLoop     = update
+    , drawLoop       = draw
+    , loadState      = load
+    , cleanUp        = clean
+    }
+  withAffection conf
+
+data UserData = UserData
+  -- { nodeGraph   :: M.Map String G.GeglNode
+  -- , foreground  :: G.GeglBuffer
+  -- , lastTick    :: Double
+  -- }
+  { coordinates :: (Double, Double)
+  , lastTick    :: Double
+  }
+
+load :: SDL.Surface -> IO UserData
+load _ = do
+  -- traceM "loading"
+  -- root <- G.gegl_node_new
+  -- traceM "new root node"
+  -- checkerboard <- G.gegl_node_new_child root $ G.checkerboardOperation $
+  --   props $ do
+  --       prop "color1" $ G.RGBA 0.4 0.4 0.4 1
+  --       prop "color2" $ G.RGBA 0.6 0.6 0.6 1
+  -- traceM "checkerboard"
+  -- over <- G.gegl_node_new_child root G.defaultOverOperation
+  -- traceM "over"
+  -- buffer <- G.gegl_buffer_new (Just $ G.GeglRectangle 0 0 800 600) =<<
+  --   B.babl_format (B.PixelFormat B.RGBA B.CFfloat)
+  -- sink <- G.gegl_node_new_child root $ G.Operation "gegl:copy-buffer" $
+  --   props $
+  --   prop "buffer" buffer
+  -- traceM "buffer-sink"
+  -- rect <- G.gegl_node_new_child root $ G.Operation "gegl:rectangle" $
+  --   props $ do
+  --       prop "x" (0::Double)
+  --       prop "y" (0::Double)
+  --       prop "width" (20::Double)
+  --       prop "height" (20::Double)
+  --       prop "color" $ G.RGBA 1 0 0 0.5
+  -- traceM "rect"
+  -- crop <- G.gegl_node_new_child root $ G.Operation "gegl:crop" $
+  --   props $ do
+  --       prop "width" (800::Double)
+  --       prop "height" (600::Double)
+  -- G.gegl_node_link_many [checkerboard, over, crop, sink]
+  -- _ <- G.gegl_node_connect_to rect "output" over "aux"
+  -- traceM "connections made"
+  -- myMap <- return $ M.fromList
+  --   [ ("root"        , root)
+  --   , ("over"        , over)
+  --   , ("background"  , checkerboard)
+  --   , ("sink"        , sink)
+  --   , ("rect"        , rect)
+  --   , ("crop"        , crop)
+  --   ]
+  -- traceM "loading complete"
+  -- return $ UserData
+  --   { nodeGraph = myMap
+  --   , foreground = buffer
+  --   , lastTick = 0
+  --   }
+  return $ UserData
+    { coordinates = (400, 300)
+    , lastTick = 0
+    }
+
+-- drawInit :: Affection UserData ()
+-- drawInit = do
+--   UserData{..} <- getAffection
+--   present (GeglRectangle 0 0 800 600) foreground True
+
+draw :: Affection UserData ()
+draw = do
+  UserData{..} <- getAffection
+  traceM "loading"
+  root <- liftIO $ G.gegl_node_new
+  traceM "new root node"
+  checkerboard <- liftIO $ G.gegl_node_new_child root $ G.checkerboardOperation $
+    props $ do
+        prop "color1" $ G.RGBA 0.4 0.4 0.4 1
+        prop "color2" $ G.RGBA 0.6 0.6 0.6 1
+  traceM "checkerboard"
+  over <- liftIO $ G.gegl_node_new_child root G.defaultOverOperation
+  traceM "over"
+  buffer <- liftIO $ G.gegl_buffer_new (Just $ G.GeglRectangle 0 0 800 600) =<<
+    B.babl_format (B.PixelFormat B.RGBA B.CFfloat)
+  sink <- liftIO $ G.gegl_node_new_child root $ G.Operation "gegl:copy-buffer" $
+    props $
+    prop "buffer" buffer
+  traceM "buffer-sink"
+  rect <- liftIO $ G.gegl_node_new_child root $ G.Operation "gegl:rectangle" $
+    props $ do
+        prop "x" $ fst coordinates
+        prop "y" $ snd coordinates
+        prop "width" (20::Double)
+        prop "height" (20::Double)
+        prop "color" $ G.RGBA 1 0 0 0.5
+  traceM "rect"
+  crop <- liftIO $ G.gegl_node_new_child root $ G.Operation "gegl:crop" $
+    props $ do
+        prop "width" (800::Double)
+        prop "height" (600::Double)
+  liftIO $ G.gegl_node_link_many [checkerboard, over, crop, sink]
+  _ <- liftIO $ G.gegl_node_connect_to rect "output" over "aux"
+  traceM "connections made"
+  myMap <- return $ M.fromList
+    [ ("root"        , root)
+    , ("over"        , over)
+    , ("background"  , checkerboard)
+    , ("sink"        , sink)
+    , ("rect"        , rect)
+    , ("crop"        , crop)
+    ]
+  traceM "loading complete"
+  process (myMap M.! "sink")
+  present (GeglRectangle 0 0 800 600) buffer True
+
+update :: Affection UserData ()
+update = do
+  traceM "updating"
+
+  tick <- getElapsedTime
+  ud <- getAffection
+  putAffection $ ud { lastTick = tick }
+
+  let dt = tick - lastTick ud
+  return ()
+  traceM $ (show $ 1 / dt) ++ " FPS"
+
+handle (SDL.MouseMotionEvent dat) = do
+  let (SDL.P (SDL.V2 x y)) = SDL.mouseMotionEventPos dat
+  ud <- getAffection
+  putAffection ud
+    { coordinates = (fromIntegral (x - 10), fromIntegral (y - 10))
+    }
+  -- liftIO $ G.gegl_node_set (nodeGraph ud M.! "rect") $ G.Operation "" $
+  --   props $ do
+  --       prop "x" (fromIntegral (x - 10) :: Double)
+  --       prop "y" $ (fromIntegral (y - 10) :: Double)
+
+handle (SDL.WindowClosedEvent _) = do
+  traceM "seeya!"
+  quit
+
+handle _ =
+  return ()
+
+clean :: UserData -> IO ()
+clean _ = return ()