I am trying to implement a re-sizable widget with handles at the corners. The corner handles will be overflow the Stack
by half of its width/height.
This is the desired behavior. If widgets could catch pointer events outside of their boundaries; it would be easy to fall into a situation where it's impossible to determine which widget is targeted.
In short, don't use overflow. Refactor your layout to make sure it's well contained inside the bounds of its parent.