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

[Lennart Borgman <lennart.borgman.073@student.lu.se>]

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")

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