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> I will try on GNU/Linux as soon as I have that machine running again.

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I tried your functions on GNU/Linux now.  The GTK build seems to handle

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t

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h

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pected.  The other builds (Motif, Lucid and no-toolkit) have
the frame lose its title bar after executing the

  (progn (set-frame-parameter (display-until-get-frame-by-name "My-Frame") 'visibility t)
         (display-frame-until "My-Frame"))

form.