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

[martin rudalics <rudalics@gmx.at>]

 > It seems to me it should be frame parameter rather than a variable:
 > Does that seem sensible?

We have to document this option so people can find it easily and I'm
not sure where and how.  Basically, it should go to the Emacs manual
and we can provide a reference to section 21.11 Frame Parameters to
that effect.  So something like mentioning

(add-to-list 'default-frame-alist '(gtk-menubar-no-auto-resize  . t))

should do, but where?  In appendix D.5.3 we say how to set the menu
and menu bar style in GTK+ and people might start searching there but
I doubt it.

In the Tooltips section we say

    If Emacs is built with GTK+ support, it displays tooltips via GTK+,
using the default appearance of GTK+ tooltips.  To disable this, change
the variable `x-gtk-use-system-tooltips' to `nil'.  If you do this, or
if Emacs is built without GTK+ support, most attributes of the tooltip
text are specified by the `tooltip' face, and by X resources (*note X
Resources::).

Maybe we could use that as boilerplate for section 21.15 Menu Bars:

    If Emacs is built with GTK+ support, the latter tries to keep all
items on the menu bar visible sometimes resizing the menu bar's frame
for that purpose.  If you want to keep the frame size constant when
Emacs adds an item to the menu bar, customize the frame parameter
'x-gtk-menubar-no-auto-resize' to a non-nil value like

(add-to-list 'default-frame-alist '(x-gtk-menubar-no-auto-resize  . t))

see section 21.11 ...

martin