elisp programming questions

[Evan Driscoll]

I have a question: I'm working on a (major) mode, and when I make
changes to the keymap, they don't "stick" until I restart emacs. It'd
be nice to know how to fix this, but as I was typing it, I realized
there may be a better way to solve this problem anyway; see below.

To demo my problem:

1. Save the code below to a file, open in emacs
2. M-x eval-buffer
3. M-x say-hi-mode
4. Press [left]; note how the minibuffer says hi
   Press [right]; note how the cursor moves
5. M-x revert-buffer
6. Uncomment the second define-key on line 8
7. M-x eval-buffer
8. Repeat steps 3 and 4. Note how [right] still
   moves the cursor instead of saying hi

Can someone tell me if there's a way to make the changes take effect?

-----

ALTERNATELY: is there some hook or something I can use which will get
called whenever (after) the point is moved by any means? I will be
overriding the cursor controls, but really what I want is just to
display some stuff related to the point's new location, and ideally it'd
work whether the user uses arrow keys, C-p/C-n/etc., the mouse, or
anything else.

Thanks,
Evan

-----

The code:

(defun say-hi ()
  (interactive)
  (message "Hello!"))

(defvar say-hi-mode-map
  (let ((map (make-keymap)))
    (define-key map [left] 'say-hi)
    ;;(define-key map [right] 'say-hi)
    map
    ))

(define-derived-mode say-hi-mode
  special-mode "Trace"
  "Major mode for viewing IO traces"
  (use-local-map say-hi-mode-map))