[VisibleOnScreenNotifier2D] represents a rectangular region of 2D space. When any part of this region becomes visible on screen or in a viewport, it will emit a [signal screen_entered] signal, and likewise it will emit a [signal screen_exited] signal when no part of it remains visible.
If you want a node to be enabled automatically when this region is visible on screen, use [VisibleOnScreenEnabler2D].
[b]Note:[/b] [VisibleOnScreenNotifier2D] uses the render culling code to determine whether it's visible on screen, so it won't function unless [member CanvasItem.visible] is set to [code]true[/code].
[b]Note:[/b] It takes one frame for the [VisibleOnScreenNotifier2D]'s visibility to be determined once added to the scene tree, so this method will always return [code]false[/code] right after it is instantiated, before the draw pass.