Re: momentary-string-display

[Kevin Rodgers <kevin.d.rodgers@gmail.com>]

Richard Stallman wrote:
> It would be clean to make momentary-string-display use overlays
> and not change the buffer text at all.  Would you like to try
> writing that?  But let's not delay the release for it.

I'd like to try.  Note that I removed all the code that tries to
compensate for the text being inserted in such a way that its end or
start is not displayed in the selected window (under the assumption that
the display engine will DTRT with the overlay); but it should be
possible to restore that code, replacing the reference to message-end
with (+ pos (length string)).

I also added a small feature: a new face, used to display the text.


*** subr.el~	Thu Dec 11 09:37:00 2006
--- subr.el	Thu Dec 28 21:26:33 2006
***************
*** 1884,1889 ****
--- 1884,1894 ----
     (if all (save-excursion (set-buffer (other-buffer))))
     (set-buffer-modified-p (buffer-modified-p)))

+ (defface momentary
+   '((t (:inherit mode-line)))
+   "Face for momentarily displaying text in the current buffer."
+   :group 'display)
+
   (defun momentary-string-display (string pos &optional exit-char message)
     "Momentarily display STRING in the buffer at POS.
   Display remains until next event is input.
***************
*** 1894,1923 ****
   Display MESSAGE (optional fourth arg) in the echo area.
   If MESSAGE is nil, instructions to type EXIT-CHAR are displayed there."
     (or exit-char (setq exit-char ?\s))
!   (let ((inhibit-read-only t)
! 	;; Don't modify the undo list at all.
! 	(buffer-undo-list t)
! 	(modified (buffer-modified-p))
! 	(name buffer-file-name)
! 	insert-end)
       (unwind-protect
   	(progn
! 	  (save-excursion
! 	    (goto-char pos)
! 	    ;; defeat file locking... don't try this at home, kids!
! 	    (setq buffer-file-name nil)
! 	    (insert-before-markers string)
! 	    (setq insert-end (point))
! 	    ;; If the message end is off screen, recenter now.
! 	    (if (< (window-end nil t) insert-end)
! 		(recenter (/ (window-height) 2)))
! 	    ;; If that pushed message start off the screen,
! 	    ;; scroll to start it at the top of the screen.
! 	    (move-to-window-line 0)
! 	    (if (> (point) pos)
! 		(progn
! 		  (goto-char pos)
! 		  (recenter 0))))
   	  (message (or message "Type %s to continue editing.")
   		   (single-key-description exit-char))
   	  (let (char)
--- 1899,1909 ----
   Display MESSAGE (optional fourth arg) in the echo area.
   If MESSAGE is nil, instructions to type EXIT-CHAR are displayed there."
     (or exit-char (setq exit-char ?\s))
!   (let ((momentary-overlay (make-overlay pos pos nil t)))
       (unwind-protect
   	(progn
! 	  (overlay-put momentary-overlay 'before-string
! 		       (propertize string 'face 'momentary))
   	  (message (or message "Type %s to continue editing.")
   		   (single-key-description exit-char))
   	  (let (char)
***************
*** 1937,1947 ****
   	      (or (eq char exit-char)
   		  (eq char (event-convert-list exit-char))
   		  (setq unread-command-events (list char))))))
!       (if insert-end
! 	  (save-excursion
! 	    (delete-region pos insert-end)))
!       (setq buffer-file-name name)
!       (set-buffer-modified-p modified))))

   \f
   ;;;; Overlay operations
--- 1923,1930 ----
   	      (or (eq char exit-char)
   		  (eq char (event-convert-list exit-char))
   		  (setq unread-command-events (list char))))))
!       (when (overlay-get momentary-overlay 'before-string)
! 	(delete-overlay momentary-overlay)))))

   \f
   ;;;; Overlay operations


-- 
Kevin Rodgers
Denver, Colorado, USA