I do not understand input-decode-map

I do not understand input-decode-map

[Lennart Borgman (gmail)]

This works, ie typing "." gives ":" (even in for example Viper)

  (define-key input-decode-map [?\.] [?\:])

Why does not the next work?

  (setq input-decode-map (make-sparse-keymap))
  (defvar my-second-map (make-sparse-keymap))
  (define-key my-second-map [?\:] [?\.])
  (define-key input-decode-map [?\,] my-second-map)

Typing "," does what it use to do. Not too bad, but not what I expected ...

Re: I do not understand input-decode-map

[Stefan Monnier]

> This works, ie typing "." gives ":" (even in for example Viper)
>   (define-key input-decode-map [?\.] [?\:])

> Why does not the next work?

>   (setq input-decode-map (make-sparse-keymap))
>   (defvar my-second-map (make-sparse-keymap))
>   (define-key my-second-map [?\:] [?\.])
>   (define-key input-decode-map [?\,] my-second-map)

> Typing "," does what it use to do. Not too bad, but not what I expected ...

The detailed behavior is fairly tricky.  Basically, it's difficult to
know when to stop waiting for more keys.  IIRC the code basically stops
if the current input (rewritten/remapped as necessary) is a valid key
sequence bound to a command.


        Stefan

Re: I do not understand input-decode-map

[Lennart Borgman (gmail)]

Stefan Monnier wrote:
>> This works, ie typing "." gives ":" (even in for example Viper)
>>   (define-key input-decode-map [?\.] [?\:])
> 
>> Why does not the next work?
> 
>>   (setq input-decode-map (make-sparse-keymap))
>>   (defvar my-second-map (make-sparse-keymap))
>>   (define-key my-second-map [?\:] [?\.])
>>   (define-key input-decode-map [?\,] my-second-map)
> 
>> Typing "," does what it use to do. Not too bad, but not what I expected ...
> 
> The detailed behavior is fairly tricky.  Basically, it's difficult to
> know when to stop waiting for more keys.  IIRC the code basically stops
> if the current input (rewritten/remapped as necessary) is a valid key
> sequence bound to a command.


I am not sure I understand. It is a bit unexpected that it stops before
there is a matching valid key sequence in input-decode-map. Why is that
useful?