Multiple runs of menu-bar-update-hook

[Marshall, Simon]

I noticed this when debugging something else that I found when trying to
debug a reason for poor Emacs responsiveness.  What comes around comes
around - I think I have found a problem that could cause poor
responsiveness.

This is with CVS as of 2006-07-24 with/without Martin's chars_modiff patch.

emacs -Q and evaluate in *scratch*:

(setq bar 0)
(defun foo ()
  (message "foo: %s %d" (buffer-name) (setq bar (1+ bar))))
(add-hook 'menu-bar-update-hook 'foo)

Now do a double mouse-1 on the word "message" in *scratch* to select the
word.  You can see from the messages in the minibuffer that
menu-bar-update-hook is run twice.  I am assuming that menu-bar-update-hook
need not be called to support region-sensitive menu entries, since they can
use an :enable property to achieve that.  Should menu-bar-update-hook be
called in this context?  Should it be called twice?

Now open multiple frames so there is more than 1 frame showing *scratch*,
and repeat the selection of a word in *scratch*.  You can see from the
messages in the minibuffer that menu-bar-update-hook is run twice for each
frame (both *scratch* and non-*scratch* frames).  Should it be run multiple
times for each frame?

Now do a single mouse-1 at EOB.  Again, menu-bar-update-hook is run twice
for each frame.  This happens regardless of the number of frames.

Now do a single mouse-1 anywhere in *scratch*.  When there is more than 1
frame showing *scratch*, menu-bar-update-hook is run twice for each frame.

Now do a down mouse-1 anywhere in *scratch* and slowly drag to extend the
region.  When there is more than 1 frame and there is more than 1 frame
showing *scratch*, menu-bar-update-hook is run once for each frame for each
character that the region is extended by.

I use msb.el and imenu.el, both of which put their functions on
menu-bar-update-hook, and I frequently use 5+ frames.  I know they attempt
to limit the amount of work they do, but I'm sure calling lisp in this way
is going to have an impact.

In GNU Emacs 22.0.50.10 (sparc-sun-solaris2.8, Motif Version 2.1.0)
 of 2006-07-26 on perth
X server distributor `Hummingbird Ltd.', version 11.0.100015
configured using `configure
'--prefix=/rvcarma/marshals/software/slash/usr/local'
'--with-x-toolkit=motif' 'CFLAGS=-g''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: en_GB.ISO8859-1
  value of $LC_CTYPE: en_GB.ISO8859-1
  value of $LC_MESSAGES: C
  value of $LC_MONETARY: en_GB.ISO8859-1
  value of $LC_NUMERIC: en_GB.ISO8859-1
  value of $LC_TIME: en_GB.ISO8859-1
  value of $LANG: en_GB.ISO8859-1
  locale-coding-system: iso-8859-1
  default-enable-multibyte-characters: t