bug#72460: [patch] add commands for setting keyboard translations interactively

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

> I find this sort of thing useful for cases where I want to use
> something other than space as a word separator (e.g. when typing lots
> of function names), or when for a long period I want to use the symbol
> which is usually on the shift of a key (i.e. I know I want to type "+"
> a lot, but not "=").

Interesting.  I can see that `keyboard-translate-table` is indeed
a cheap way to implement it.

[ This said, it applies at a very low level (directly inside
  `read-event`) and only to "characters" (e.g. not to the `tab` or
  `return` keys), which can make it both maybe too powerful and yet not
  flexible enough.  ]

> +  (interactive `(,(key-description `[,(read-char "From: ")])
> +                 ,(key-description `[,(read-char "To: ")])))

[ Personally, I'd add a comment lamenting the fact that `keymap-*`
  functions force us to use `key-description` here only for that to be
  undone by `key-parse`.  ]

> +(defcustom key-translate-selection-function #'key-select-translation

Do we need this?

> +pair in `keyboard-translate-table', and return a vector containing only
> +the FROM key of the selected pair (e.g. if the selected pair translates
> +\"=\" to \"+\", the function should return the vector [61])"

Why not return just the char rather than a vector containing the char?

> +(defun key-translate-remove (from)
> +  "Remove translation of FROM from `keyboard-translate-table'.
> +
> +FROM must satisfy `key-valid-p'.  If FROM has no entry in
> +`keyboard-translate-table', this has no effect."
> +  (interactive (list (key-description
> +                      (funcall key-translate-selection-function))))
> +  (set-char-table-range
> +   keyboard-translate-table (aref (key-parse from) 0) nil))

If FROM maps to a sequence of length != 1, we'll either signal an ugly
error or silently ignore the rest.
Any reason why you didn't make FROM be a simple character?


        Stefan