> If I don't do (1), BTW, I can do (2) twice, and that also makes the frame visible.
 >
 > Meaning
 >
 >    (make-frame-invisible frame)
 >    (make-frame-visible frame)
 >    (make-frame-invisible frame)
 >    (make-frame-visible frame)

I attach a patch based on this recipe but it causes (occasionally
terrible) flickers on other desktops so I would have to special-case it
on mutter anyway.  I still have no good idea what's really going on
here.

martin