started referencing ui widgets by id via hashmap, WIP, does not compile

src/UI/UIOperations.hs

@@ -0,0 +1,26 @@
+module UI.UIOperations where
+
+import Data.HashMap.Strict
+
+import UI.UIBaseData
+import UI.UIClasses
+
+defaultUIState :: UIButtonState
+defaultUIState = UIButtonState False False False False False False
+
+--TODO
+-- |The function 'isInside' tests whether a point is inside the widget or any child.
+--  A screen position may be inside the bounding box of a widget but not considered part of the component.
+--  The function returns all hit widgets that have no hit children or 'Nothing' if the point neither hits any
+--  component nor the parent widget itself.
+isInside :: ScreenUnit -- ^screen x coordinate
+         -> ScreenUnit -- ^screen y coordinate
+         -> UIId       -- ^the parent widget
+         -> [UIId]
+isInside x' y' wg =
+    case isInsideSelf x' y' wg of -- test inside parent's bounding box
+        False -> []
+        True -> case concat $ map (isInside x' y') (getChildren wg) of
+            [] -> [toGUIAny wg]
+            l  -> l
+--TODO: Priority queue?