http://purl.org/tcl/home/man/tcl8.4/TkCmd/toplevel.htm

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[DKF] notes that, "toplevels on UNIX/X are really a collection of several windows; the window you draw on (which is what [winfo id] will tell you), another window for a menubar (if you've installed one) and a third one to contain the other two.
If you do 'xwininfo -tree' you should be able to find out what's *really* going on."

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[Martin Lemburg]: How can I detect if a widget is a toplevel? If I ask a widget for its class, this will fail e.g. at the root widget, because it doesn't return "Toplevel", but "Wish83". And toplevels could be given a class differing from "Toplevel" during their creation. So ... how can I detect a toplevel?

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[IDG]
   [winfo toplevel .]

returns . 
whereas

   [winfo toplevel .someothertoplevel]

returns .someothertoplevel

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''[MGS]'' - In other words:

   proc istoplevel {W} {
     return [string equal [winfo toplevel $W] $W]
   }

''[MGS]'' [[2003/05/08]] - Actually, does a menu count as a toplevel? Probably not (in some cases). SO how about this? Toplevels can have a -menu option ...

   proc isToplevel {W} {
     return [expr {[string equal [winfo toplevel $W] $W] &&
                  ![catch {$W cget -menu}]}]
   }

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