When the functions height and width are generated, since line 1325, source release. this[0] is compared against 'window' and 'document', that detection leaves out any other window and document that might be evaluated. These might come from an iframe, a popup, etc.

My suggestion is to use object detection instead. It'll certainly look less clear, but will cover these cases.

I came up with an option for detection which is:

windows: if( elem.scrollBy )....

documents: if( elem.nodeName == '#document' )......

Of course this also requires that if a window is detected, elem.document is used and not that document.

If a document is detected, elem.body and elem.documentElement are used instead.

This checks are just an example, maybe someone can come up with more reliable ones.