Detects when the node is visible on screen. The VisibilityNotifier2D detects when it is visible on the screen. It also notifies when its bounding rectangle enters or exits the screen or a viewport. If [code]true[/code] the bounding rectangle is on the screen. The VisibilityNotifier2D's bounding rectangle. Emitted when the VisibilityNotifier2D enters the screen. Emitted when the VisibilityNotifier2D exits the screen. Emitted when the VisibilityNotifier2D enters a [Viewport]'s view. Emitted when the VisibilityNotifier2D exits a [Viewport]'s view.