How to detect if an element is visible within an iframe that is on a cross domain parent

Just as the question states, I have an iframe that is on a cross domain parent. I need to trigger an event if that content is scrolled into view or already in view on page load. Normal checks for distance from top/side of page and viewport height/width don't seem to work as they measure the page within the iframe itself. I cannot edit/add anything on the parent page to enable this functionality, e