Experiment: make StateRef wrappers optional

Author: dpwiz

src/DearImGui.hs

@@ -570,21 +570,36 @@ arrowButton strId dir = liftIO do
   withCString strId \strIdPtr ->
     Raw.arrowButton strIdPtr dir
 
-
 -- | Wraps @ImGui::Checkbox()@.
 checkbox :: (HasSetter ref Bool, HasGetter ref Bool, MonadIO m) => String -> ref -> m Bool
-checkbox label ref = liftIO do
-  currentValue <- get ref
+checkbox label ref = stateful ref $ checkboxM label
+
+{-# INLINEABLE stateful #-}
+stateful
+  :: (HasGetter t a, MonadIO m, HasSetter t a)
+  => t -> (a -> m (Maybe a)) -> m Bool
+stateful ref action = get ref >>= action >>= maybeSet ref
+
+{-# INLINEABLE maybeSet #-}
+maybeSet :: (HasSetter t a, MonadIO f) => t -> Maybe a -> f Bool
+maybeSet ref = \case
+  Nothing ->
+    pure False
+  Just val -> do
+    ref $=! val
+    pure True
+
+-- | Wraps @ImGui::Checkbox()@.
+checkboxM :: (MonadIO m) => String -> Bool -> m (Maybe Bool)
+checkboxM label currentValue = liftIO do
   with (bool 0 1 currentValue) \boolPtr -> do
     changed <- withCString label \labelPtr ->
       Raw.checkbox labelPtr boolPtr
 
-    when changed do
-      newValue <- peek boolPtr
-      ref $=! (newValue == 1)
-
-    return changed
-
+    if changed then
+      (Just . (/=) 0) <$> peek boolPtr
+    else
+      pure Nothing
 
 progressBar :: MonadIO m => Float -> Maybe String -> m ()
 progressBar progress overlay = liftIO do