Call CMD w/ keybinding VS execute-extended-command: redisplay behaviour

[Tino Calancha <tino.calancha@gmail.com>]

Dear Emacs,

I have defined a command (see below snippet code) which updates
the header line in a buffer inheriting from tabulated-list.
The effect on the header line is visible inmediately, i.e.,
the screen is automatically redisplayed, but...

* If I bind this command to 'r', then there is no automatic
  redisplay anymore; I need to push some keys until a
  window redisplay is fired.

* If I call the command and rigth after run `repeat', i.e. `C-x z'
  then the header line is not automatically updated either.

Is there a reason why it is preferable this distintion between
calling a command with a keybinding VS calling
it via `execute-extended-command'?

I wish the keybinding 'r' update the screen as well.
How can I do that?

Note: I don't want to revert the buffer, just redisplay the header line.

To reproduce, create a file foo.el with following content:

--8<-----------------------------cut here---------------start------------->8---
(defvar foo-format
  [("Category" 12 t)
   ("Knight (best friend: hadoken)" 30 t)
   ("Energy" 50 t)]
  "Table format.")

(defvar foo-mode nil "Save status of the `foo-mode'.")

(defun foo-tabulated-list-entries ()
  (setq tabulated-list-entries
        '((1 ["bronze" "Seiya" "98"]) (2 ["bronze" "Shiryu" "95"])))
  (tabulated-list-init-header))

(defun foo ()
  (interactive)
  (let ((foo-buffer (generate-new-buffer "*foo*")))
    (switch-to-buffer foo-buffer)
    (or foo-mode (foo-mode))
    (setq tabulated-list-use-header-line t)
    (foo-tabulated-list-entries)
    (tabulated-list-print)))


(defun foo--new-knight()
  (let ((knights '("Ikki" "Shun" "Hyoga")))
    (nth (random (length knights)) knights)))

(defun foo-update-friend()
  "Update header line with new friend."
  (interactive)
  (let ((regexp "Knight (best friend: \\([^)]+\\))")
        (knight-new (foo--new-knight)))
    (when (string-match regexp header-line-format)
      (let ((knight (match-string 1 header-line-format)))
        (while (string= knight knight-new) (setq knight-new (foo--new-knight)))
        (setq header-line-format
              (replace-match
               knight-new nil nil header-line-format 1))
        (message "Updated knight to: '%s'" knight-new)
        ;; Don't regenerate all rows because it might be expensive;
        ;; just redisplay the header line.
        (redisplay)))))

;;; Foo Mode map
(defvar foo-mode-map
  (let ((map (make-keymap)))
    (define-key map (kbd "r") 'foo-update-friend)
    map))

;;; Define mode
(define-derived-mode foo-mode tabulated-list-mode "Foo"
  (setq tabulated-list-format foo-format))
--8<-----------------------------cut here---------------end--------------->8---

emacs -Q -l foo.el:

M-x foo RET
;; Note the difference between the following:

M-x foo-update-friend RET
;; Updates the knight's friend in the header line, i.e., the name
;; showed in the minibuffer matches the friend name in the header line.

r
;; It doesn't update the knight's friend; you can see that name in the
;; minibuffer doesn't match the one in the header line.  If you input
;; something for example if you use the down arrow, then the header
;; line is updated.