viewport of browser from cross-site iframe

I need to find out the browser viewport s开发者_JAVA技巧ize from within a cross-domain iframe. The normal method doesn't work because it only gets the viewport of the iframe. If I use top.innerHeight, etc. in a cross-domain situation, I run into security issues. Is there a different property/method I can use? Cross-browser would be ideal, but even getting this on a single browser would be helpful.

(I'm trying to find out if my iframe is in view or not.)