>Move the form to negative coordinates, just like we did in Fox. It will be formally visible, just off the viewport.
>
>I've seen this used for other purposes (one version of autogrow editbox did that), although it didn't move the form - the form was there already - it created ghost
versions of other controls at -10000, -10000.

This is no longer supported in browser because of security issue. Moving things out of the boundaring area will make it 1,1.