bug#69993: Wrap window buffers while cycling

[martin rudalics via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

 > There is one problem with this line:
 >
 >    (add-to-list 'window-persistent-parameters '(tab-line-buffers . writable))
 >
 > This line is needed to be able to use 'window-swap-states'
 > because window-state-get/window-state-put should move the window
 > parameter 'tab-line-buffers' to the swapped window.

Why does it have to be "writable"?  'window-swap-states' doesn't care
about "writability".  If you really want something writable too, add a
second parameter, say 'tab-line-buffer-names', with the names in it.

 > A third solution would be to support a lambda in
 > 'window-persistent-parameters' that will process
 > the parameter before saving.  For example:
 >
 >    (add-to-list 'window-persistent-parameters
 >                 '(tab-line-buffers . (lambda (p) (mapcar #'buffer-name p))))
 >
 > Maybe this is the best thing to do?

You would call that function in window.el here

		    (when (and pers (or (not writable) (eq pers 'writable)))
		      (setq list (cons (cons (car par) (cdr par)) list)))))

iff WRITABLE is non-nil and you would not call it here in window.c

		    /* If the window has a value for the parameter,
		       save it.  */
		    p->window_parameters = Fcons (Fcons (XCAR (par), XCDR (par)),
					   p->window_parameters);

I suppose.

martin