> Is 'keep-windows' doable for 'window-state-put' as well?

I attach a patch that adds a fourth argument to 'window-state-put'.  It
and a new 'set-window-configuration' now use a new function I called
'marker-last-position' that returns the last position of a marker even
after its buffer was killed.

The patch also fixes a bug in 'window--state-put-2' that can be
reproduced with the following simple scenario

(let ((buffer (get-buffer-create "*foo*"))
       state)
   (pop-to-buffer buffer)
   (setq state (window-state-get))
   (kill-buffer buffer)
   (window-state-put state))

Did you never see it?

 > So maybe the same option 'keep-windows' could call the same hook
 > 'post-set-window-configuration-functions' from 'window-state-put' too?

I added a new hook called 'window-state-put-keep-window-functions' with
the same arguments as 'post-set-window-configuration-functions'.  Maybe
people wanted to keep them apart.  If you think the hook should be also
run when there are no "kept" windows, we can do that as well.

I tested it here with

(defun foo (frame windows)
   (while windows
     (let* ((quad (car windows))
	   (window (car quad))
	   (buffer (find-file-noselect
		    (buffer-file-name (nth 1 quad)))))
       (when buffer
	(set-window-buffer window buffer)
	(set-window-point window (nth 3 quad))
	(set-window-start window (nth 2 quad) t)))
     (setq windows (cdr windows))))

(add-hook 'window-state-put-keep-window-functions 'foo)

(let ((window (selected-window))
       (buffer (pop-to-buffer
	       (find-file-noselect "...")))
       (window-1 (split-window))
       (window-2 (split-window nil nil t))
       state)
   (set-window-point window-1 5000)
   (set-window-point window-2 10000)
   (setq state (window-state-get))
   (y-or-n-p "State saved ...")
   (delete-other-windows window)
   (kill-buffer buffer)
   (y-or-n-p "State reset ...")
   (window-state-put state nil nil t)
   (message "State restored"))

martin