'Using VisibilityDetector is there a good way to determine when a widget is some % distance from the bottom of the screen?

Im playing with VisibilityDetector and it looks quite powerful it what it can do. But I'm wondering if there is a reliable way to detect when a given widget is some % from the bottom of the screen, or better yet when the bottom margin of a given widget is some % from the bottom of the screen?



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