Tearoffs not showing for deep cascades

Consider the following example:

menu .main
menu .main.submain
menu .main.submain.subsub
. configure -menu .main
.main add cascade -label submain -menu .main.submain
.main.submain add cascade -label subsub -menu .main.submain.subsub
.main.submain.subsub add command -label subsubcmd -command {puts "subsubcmd executed"}

Now open "subsub" cascade and tear it off - nothing happens. Well, not exactly, but it looks so - the torn-off menu is invisible.

Try something different - first tear the "submain" off, and then tear the "subsub" off from it (not from the main window). This works as expected.

It was the latest change in tearoff.tcl that causes it (2010-01-03 Pat Thoyts <patthoyts@users.sourceforge.net> - "tearoff menus should be transient and use the toolwindow style on Windows").

The attached patch contains a proposed fix for this.