bug#43397: 28.0.50; Adding tool bar items: update tool bar

[Lars Ingebrigtsen <larsi@gnus.org>]

Eli Zaretskii <eliz@gnu.org> writes:

> Then evaluate the forms and press F5.  The tool bar won't change.

This was a year ago, but I can still reproduce this on the current
trunk.  Here's an even easier variation of the recipe:

(progn
  (blink-cursor-mode -1)
  (global-eldoc-mode -1)

  (defun myfun ()
    (interactive)
    (tool-bar-add-item "redo" 'undo-redo 'undo-redo))

  (global-set-key [f5] 'myfun))

And then M-: (garbage-collect) makes the tool bar update.

However!  The garbage-collect in itself isn't sufficient to trigger it.
With this variation:

(progn
  (blink-cursor-mode -1)
  (global-eldoc-mode -1)
  (tool-bar-add-item "redo" 'undo-redo 'undo-redo)
  (global-set-key [f5] (lambda () (interactive) (garbage-collect))))

pressing <f5> does not make the icon appear.

> Now do some random clicks, watching the echo area: you will see that
> the tool bar is updated with the "redo" icon precisely when the
> "Garbage collecting..." message appears in the echo area.

Very mysterious.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no