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

From: Caio Henrique <[email-masked]>
Date: Mon, 14 Sep 2020 18:44:03 -0300

Gnus has a function called gnus-tool-bar-update. I tried using it but
got the same result, i.e. the icon is only displayed when I click with
the mouse on the buffer. 

1. emacs -Q
2. eval this:
(progn
  (defvar tool-bar-mode)

  (defun gnus-tool-bar-update (&rest ignore)
    "Update the tool bar."
    (when (and (boundp 'tool-bar-mode)
	       tool-bar-mode)
      (let* ((args nil)
	     (func (cond ((fboundp 'tool-bar-update)
			  'tool-bar-update)
			 ((fboundp 'force-window-update)
			  'force-window-update)
			 ((fboundp 'redraw-frame)
			  (setq args (list (selected-frame)))
			  'redraw-frame)
			 (t 'ignore))))
	(apply func args))))

  (tool-bar-add-item-from-menu 'undo-redo
			       "redo" nil :vert-only t)

  (gnus-tool-bar-update))