Use the safer Foreign.Concurrent.ForeignPtr with the GTK bindings in definitive-graphics

definitive-graphics/source/Graphics/Widget/Traits.hs

@@ -22,7 +22,8 @@ module Graphics.Widget.Traits(
 
 import Definitive
 import Foreign.Ptr
-import Foreign.ForeignPtr
+import Foreign.ForeignPtr hiding (newForeignPtr)
+import Foreign.Concurrent
 import IO.Time (Seconds)
 import Graphics.GDK.KeyCodes
 import IO.Dynamic
@@ -38,8 +39,7 @@ data WProps a = WProps {
   _wPropsValue :: a
   }
 nullWidgetPtr = thunk $^ do
-  cb <- callback_p_ (const unit)
-  newForeignPtr cb nullPtr
+  newForeignPtr nullPtr unit
 instance Functor WProps where map f (WProps h a) = WProps h (f a)
 instance Unit WProps where pure x = WProps nullWidgetPtr x
 instance SemiApplicative WProps where WProps h f <*> WProps h' x = WProps (max h h') (f x)