Compositing in Cocoa tk

Hello,
I was trying to obtain some compostiting effects with the new Cocoa tk  
but I could not get it to work.

Is compositing currently supported?

A long time ago I had a look at the MacOSX specifics of tk and I  
noticed that a big effort was necessary to emulate subwindow  
functionality.

With tk Cocoa, is a tk widget now basically a Cocoa view within the  
view hierarchy?

If not, is that the direction tk Cocoa will evolve?

kind regards,
Uwe

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