It renders an arbitrary SystemWindow in a ffenestri-window (on mac at least) in the simplest way I could think of at least. (not efficient (3MB or so per window), nor exactly pretty), but it makes for a nice demo imo, even though the window is unresponsible to input. 

Render update on resizing works, with a faux render loop instead of real window resize event response :) 

In theory you can do openInWorld on the same window, and manipulate that,  but I wouldn't recommend it, as the faux loop in the workspace is in no way synchronized with World Drawing and you will get DNU's after awhile.

Install the changesets from ftp.smalltalkconsulting.com/experimental/Ffenestri/ first, then the changeset in the attached zip.

Doit'ing the workspace in the .rtf should then open a Hierarchy Browser on HierarchyBrowser, read comments there for more details :) 

Should work on any SystemWindow instance, though actually getting to an instance before it's opened can be surprisingly hard...

Cheers,

Henry