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

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

Lennart Borgman wrote:

> 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 too 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*")):

I wrote too early once again. I was adding the old bw-keymap to 
emulation-mode-map-alist, not the new one. When I changed this the above 
procedures work nicely.

Sorry for the unnecessary noise.