Deiconifying GTK frames on GNOME shell

[martin rudalics]

When running a GTK3 build of Emacs on GNOME shell, the following
sequence of actions

(setq frame (make-frame))
(iconify-frame frame)
(make-frame-visible frame)

does not produce a visible frame here.  Rather, the frame stays
iconified although (frame-visible-p frame) for it returns t.
(raise-frame frame) and (select-frame-set-input-focus frame) do not work
either.  A similar problem happens when running Emacs under the
Enlightenment WM.

I invite users running Emacs under GNOME shell to tell us whether they
see the same behavior or whether the above sequence of operations works
as intended.

This affects all frame management routines calling candidate_frame and
people who customized `frame-auto-hide-function' to `iconify-frame'.  In
particular, if you show the minibuffer in a separate frame, you cannot
raise that frame from Emacs once you have iconified it.

If we decide that this is a bug _we_ want to fix then I can offer the
following changes which seem to make things work here:

(1) In xterm.c swap the calls to

      gtk_widget_show_all (FRAME_GTK_OUTER_WIDGET (f));
      gtk_window_deiconify (GTK_WINDOW (FRAME_GTK_OUTER_WIDGET (f)));

(2) When trying to deiconify an iconified frame make it invisible first
    and only then make it visible.

I have no idea whether and how these changes might affect other builds
so making these customizable might be a good idea.  But first I'd like
to know whether we really care about this issue.  Since I use GNOME
shell for testing purposes only, I do not care personally.

Thanks in advance, martin