Continue shader refactor

src/GLHelp.hs

@@ -14,9 +14,9 @@ mglCreate f = do
 mglDelete :: (GLsizei -> Ptr GLuint -> IO ()) -> GLuint -> IO ()
 mglDelete f i = with i $ \ptr -> f 1 ptr
 
-checkGLError :: IO ()
-checkGLError = do
+checkGLError :: String -> IO ()
+checkGLError s = do
     err <- glGetError
     case err of
         0 -> return ()
-        i -> error $ "OpenGL error: " ++ show i
+        i -> error $ "OpenGL error: " ++ show i ++ " - " ++ s