move the rendered picture around on key presses

src/Main.hs

@@ -114,10 +114,14 @@ main = do
 
   -- -- MATRICES
 
-  let proj = ortho 0 800 0 600 (-1) 1 :: M44 GL.GLfloat
+  let mproj = ortho 0 800 0 600 (-1) 1 :: M44 GL.GLfloat
-      view = mkTransformationMat (identity :: M33 GL.GLfloat) (V3 (-100) 0 0)
+      mview = mkTransformationMat (identity :: M33 GL.GLfloat) (V3 (-100) 0 0)
-      model = mkTransformationMat (identity :: M33 GL.GLfloat) (V3 200 200 0)
+      mmodel = mkTransformationMat (identity :: M33 GL.GLfloat) (V3 200 200 0)
-      mvp = proj !*! view !*! model
+
+  -- store the mtrices for later adjustments
+  proj <- newMVar mproj
+  view <- newMVar mview
+  model <- newMVar mmodel
 
   -- -- TEXTURE
   
@@ -142,7 +146,7 @@ main = do
   -- -- tell the shader where to find the texture
   bind sp
   setUniform sp "u_texture" (texSlot tex)
-  setUniform sp "u_mvp" mvp
+  setUniform sp "u_mvp" (mproj !*! mview !*! mmodel)
 
   -- -- UNIFORMS
 
@@ -188,8 +192,63 @@ main = do
       redValue <- takeMVar red
       let newRed = redValue + incrementValue
 
-      -- write data to the uniform
+      -- retrieve matrices from MVars
-      -- setUniform sp "u_color" (GL.Color4 newRed 0.5 0 1 :: GL.Color4 GL.GLfloat)
+      modifyMVar_ proj (\mproj -> do
+        modifyMVar_ view (\mview -> do
+          modifyMVar_ model (\mmodel -> do
+            plusModel <- foldl (\acc ev -> case SDL.eventPayload ev of
+                  (SDL.KeyboardEvent
+                    ( SDL.KeyboardEventData
+                      _
+                      SDL.Pressed
+                      _
+                      (SDL.Keysym _ code mod)
+                    ))
+                    ->
+                      let trans =
+                            mkTransformationMat
+                              (identity :: M33 GL.GLfloat)
+                              ( ( if not (SDL.keyModifierLeftShift mod)
+                                  then (-1)
+                                  else 1
+                                  )
+                                *
+                                ( case code of
+                                  SDL.KeycodeX ->
+                                    V3 1 0 0
+                                  SDL.KeycodeY ->
+                                    V3 0 1 0
+                                  _ ->
+                                    V3 0 0 0
+                                  )
+                                )
+                            !-!
+                              (identity :: M44 GL.GLfloat)
+                      in acc !+! trans
+                  _ -> acc !+!
+                    (V4
+                      (V4 0 0 0 0)
+                      (V4 0 0 0 0)
+                      (V4 0 0 0 0)
+                      (V4 0 0 0 0)
+                      )
+                  )
+                  (V4
+                    (V4 0 0 0 0)
+                    (V4 0 0 0 0)
+                    (V4 0 0 0 0)
+                    (V4 0 0 0 0)
+                    )
+                  <$> readMVar evs
+            let nmodel = mmodel !+! plusModel
+            setUniform sp "u_mvp" (mproj !*! mview !*! nmodel)
+            return nmodel
+            )
+          return mview
+          )
+        return mproj
+        )
+
 
       -- the actual drawing happens here
       draw vao ibo sp