the scene structure like that:
the Node2d can't receive any event , _input(event) never called.
but when I put Node2d outside Viewport the event work well.
what am i missing? Any one who can give me a hint .
Does the viewport has gui_disable_input unchecked?
Sorry! so late to update the question,
My question have been resolved, I use viewport.input(event) to forward the event in it's parent.