Re: Function for deleting a key binding in a sparse keymap

[Lennart Borgman]

Stefan Monnier wrote:

> > I set the "help keys" to nil so that the help is still available during
> > resizing. Those are the keys I want to remove afterwards. The default value
> > in the sparse keymap bw-keymap is:
> >    
>
>  
>
> >       (define-key bw-keymap [t]  'bw-exit-resize-mode)
> >    
>
> I see.  Coming from a functional programming background, I'd use anoter
> approach based on the idea of reusing the original value rather than using
> side-effects to try and coerce it back to the same shape it had originally:
>
>       (defvar bw-keymap
>           (let ((map (make-sparse-keymap)))
>             (define-key map [t]  'bw-exit-resize-mode)
>             map))
>
> then when adding help-event-list bindings:
>
>       (setq bw-keymap (let ((map (make-sparse-keymap)))
>                         (set-keymap-parent map bw-keymap)
>                         map))
>       ;; dolist is more efficient than mapc.
>       (dolist (key help-event-list)
>         (define-key bw-keymap (vector key) nil))
>
> and when you want to remove those keys, just do
>
>       (setq bw-keymap (keymap-parent bw-keymap))
>
> Of course, you can use variants of it, e.g. introduce a "bw-basic-map"
> variable to keep the original map, rather than rely on (keymap-parent
> bw-keymap) holding that original map.
>  
I wrote to early. For some reason this does not work. It seems like the 
help keys just runs the default function (ie 'bw-exit-resize-mode). Here 
is the output from (describe-variable 'bw-keymap (get-buffer-create 
"*Help*")):

bw-keymap is a variable defined in `c:/emacs-lisp/test/bwcvs.el'.
Its value is shown below.

Documentation:
Keymap used by `bw-window-resize-mode'.

Value:
(keymap
(f1)
(help)
keymap
(right . bw-mode-resize-right)
(left . bw-mode-resize-left)
(down . bw-mode-resize-down)
(up . bw-mode-resize-up)
(102 . bw-shrink-windows-horizontally)
(46 . bw-balance-siblings)
(43 . bw-balance)
(t . bw-exit-resize-mode)
(menu-bar keymap
          (bw "&Resize" keymap
              (balance "Balance Windows" . bw-balance)
              (siblings "Balance Window Siblings" . bw-balance-siblings)
              (shrink "Shrink to Buffers" . bw-shrink-windows-horizontally)
              "second"))
"Window Resizing")

[back]