Attempt to modify read-only value

Attempt to modify read-only value

[Juanma Barranquero]

After this:

2002-04-23  Miles Bader  <miles@gnu.org>

        * menu-bar.el (menu-bar-update-buffers): Add `Select Named Buffer'.
        Add separator line before commands
        Remove old crufty code that tried to line things up by adding
        spaces to entries (it doesn't work).
        Move `Frames' submenu after the normal buffers, and add a
        separator line before it.
        (menu-bar-buffers-menu-list-buffers-entry): Variable removed.

I'm getting "attempt to modify read-only value" while bootstraping.


                                                           /L/e/k/t/u

Re: Attempt to modify read-only value

[Kenichi Handa]

Juanma Barranquero <lektu@terra.es> writes:
> After this:
> 2002-04-23  Miles Bader  <miles@gnu.org>

>         * menu-bar.el (menu-bar-update-buffers): Add `Select Named Buffer'.
>         Add separator line before commands
>         Remove old crufty code that tried to line things up by adding
>         spaces to entries (it doesn't work).
>         Move `Frames' submenu after the normal buffers, and add a
>         separator line before it.
>         (menu-bar-buffers-menu-list-buffers-entry): Variable removed.

> I'm getting "attempt to modify read-only value" while bootstraping.

Me too.  This is because, in keyboard.c, we do this:
  if (NILP (cachelist))
    {
      /* We have to create a cachelist.  */
      CHECK_IMPURE (start);   <-- this causes the error
      XSETCDR (start, Fcons (Fcons (Qnil, Qnil), XCDR (start)));

Changing this part (line 1363 of menu-bar.el):
		      '((command-separator "--")
			(select-named-buffer
			 menu-item
			 "Select Named Buffer..."
			 switch-to-buffer
			 :help "Prompt for a buffer name, and select that buffer in the current window")
			(list-all-buffers
			 menu-item
			 "List All Buffers"
			 list-buffers
			 :help "Pop up a window listing all emacs buffers"))))

to something like:
		      `((command-separator "--")
			,(list 'select-named-buffer
			       'menu-item
			       "Select Named Buffer..."
			       'switch-to-buffer
			       ...)
			,(list 'list-all-buffers
			       'menu-item
			       "List All Buffers"
			       'list-buffers
			       ...))

fixes this problem.  But, this workaround is very weird.
There should be a better solution.

---
Ken'ichi HANDA
handa@etl.go.jp

Re: Attempt to modify read-only value

[Miles Bader]

Juanma Barranquero <lektu@terra.es> writes:
> I'm getting "attempt to modify read-only value" while bootstraping.

I've fixed it in CVS:


2002-04-23  Miles Bader  <miles@gnu.org>

	* menu-bar.el (menu-bar-update-buffers): Don't use constant lists
	for command menu entries, since the low-level menu code modifies
	them.  Cache the resulting list.
	(menu-bar-buffers-menu-command-entries): New variable.

Index: menu-bar.el
===================================================================
RCS file: /cvs/emacs/lisp/menu-bar.el,v
retrieving revision 1.207
retrieving revision 1.208
diff -u -p -r1.207 -r1.208
--- menu-bar.el	23 Apr 2002 05:01:50 -0000	1.207
+++ menu-bar.el	23 Apr 2002 08:34:57 -0000	1.208
@@ -1282,6 +1282,9 @@ key (or menu-item)"))
 	   file))
 	(car elt)))
 
+;; Used to cache the menu entries for commands in the Buffers menu
+(defvar menu-bar-buffers-menu-command-entries nil)
+
 (defun menu-bar-update-buffers (&optional force)
   ;; If user discards the Buffers item, play along.
   (and (lookup-key (current-global-map) [menu-bar buffer])
@@ -1357,20 +1360,27 @@ key (or menu-item)"))
 			  `((frames-separator "--")
 			    (frames menu-item "Frames" ,frames-menu))))))
 
-	 ;; Add in some normal commands at the end of the menu
+	 ;; Add in some normal commands at the end of the menu.  We use
+	 ;; the copy cached in `menu-bar-buffers-menu-command-entries'
+	 ;; if it's been set already.  Note that we can't use constant
+	 ;; lists for the menu-entries, because the low-level menu-code
+	 ;; modifies them.
+	 (unless menu-bar-buffers-menu-command-entries
+	   (setq menu-bar-buffers-menu-command-entries
+		 (list '(command-separator "--")
+		       (list 'select-named-buffer
+			     'menu-item
+			     "Select Named Buffer..."
+			     'switch-to-buffer
+			     :help "Prompt for a buffer name, and select that buffer in the current window")
+		       (list 'list-all-buffers
+			     'menu-item
+			     "List All Buffers"
+			     'list-buffers
+			     :help "Pop up a window listing all emacs buffers"
+			     ))))
 	 (setq buffers-menu
-	       (nconc buffers-menu
-		      '((command-separator "--")
-			(select-named-buffer
-			 menu-item
-			 "Select Named Buffer..."
-			 switch-to-buffer
-			 :help "Prompt for a buffer name, and select that buffer in the current window")
-			(list-all-buffers
-			 menu-item
-			 "List All Buffers"
-			 list-buffers
-			 :help "Pop up a window listing all emacs buffers"))))
+	       (nconc buffers-menu menu-bar-buffers-menu-command-entries))
 
 	 (setq buffers-menu (cons 'keymap (cons "Select Buffer" buffers-menu)))
 	 (define-key (current-global-map) [menu-bar buffer]


-Miles
-- 
80% of success is just showing up.  --Woody Allen

Re: Attempt to modify read-only value

[Miles Bader]

Kenichi Handa <handa@etl.go.jp> writes:
> fixes this problem.  But, this workaround is very weird.
> There should be a better solution.

I suspect the prettiest thing would be to not construct raw menu
entries, but rather use official functions like `define-key' to make
them.

However, this throws away the cached key lookups that the low-level menu
code adds (this is why it's modifying the menu entry), which might be
bad because the Buffers menu can get rebuilt pretty often.

-Miles
-- 
Run away!  Run away!

Re: Attempt to modify read-only value

[Kenichi Handa]

Miles Bader <miles@lsi.nec.co.jp> writes:
> Kenichi Handa <handa@etl.go.jp> writes:
>>  fixes this problem.  But, this workaround is very weird.
>>  There should be a better solution.

> I suspect the prettiest thing would be to not construct raw menu
> entries, but rather use official functions like `define-key' to make
> them.

> However, this throws away the cached key lookups that the low-level menu
> code adds (this is why it's modifying the menu entry), which might be
> bad because the Buffers menu can get rebuilt pretty often.

Thank you for the explanation.  I understand.

---
Ken'ichi HANDA
handa@etl.go.jp