bug#22000: Patch addressing the menu-bar frame-resize interaction

[Vivek Dasmohapatra]

> suppose we used a non-scrolled container window to put the menu bar
> in, get its size before updating the menu bar, update the menu bar and
> make a gtk_widget_set_size request for that container window to
> restore its previous size.  Would that fail and why?

Depends on the behaviour of the container. The menu bar gets poked
to emit its size from time to time by an internal gtk callback
so if the container respects its wishes it will pop back to the larger
size semi-predictably (this behaviour can occasionally be seen in
the currently released emacs as that's how the hbox behaves).

So we'd need a container that didn't grant such space requests.
gtk fixed is close, but from its documentation has other
limitations we don't want (no RTL support).

You can turn scrollbars off in a scrolled window but unfortunately
this results in the scrolled window responding to size allocation
requests from its child.