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

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

[hugo]

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Dear all,

The attached patch adds commands for adding and removing entries in
`keyboard-translate-table' interactively:
- add an interactive spec to `key-translate'
- add a new command `key-translate-remove', which does the opposite of
   `key-translate'.
- add an option for users to customise how the latter function prompts
   for which from/to pair is removed. The default just lists them with
   `completing-read'.

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 "=").

The patch doesn't contain a NEWS entry yet -- I wanted to get the
greenlight on the code first.

Best,

Hugo

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From b5b0d6e4c53fcedea92df03e86c57af856c9fbb7 Mon Sep 17 00:00:00 2001
From: Hugo Heagren <hugo@heagren.com>
Date: Sun, 4 Aug 2024 12:54:27 +0100
Subject: [PATCH] Add commands to interactively set/unset keyboard translations

* lisp/keymap.el (key-translate): Add an interactive form, prompting for
keys to translate, and update docstring to reflect this.
(key-translate-selection-function): New custom option.
(key-select-translation): New function, default value of above option.
(key-translate-remove): New command, for removing entries from
`keyboard-translate-table'.
---
 lisp/keymap.el | 57 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 56 insertions(+), 1 deletion(-)

diff --git a/lisp/keymap.el b/lisp/keymap.el
index 861d6724c9e..d5bf51fd849 100644
--- a/lisp/keymap.el
+++ b/lisp/keymap.el
@@ -392,9 +392,13 @@ key-translate
 and then modifies one entry in it.
 
 Both FROM and TO should be specified by strings that satisfy `key-valid-p'.
-If TO is nil, remove any existing translation for FROM."
+If TO is nil, remove any existing translation for FROM.
+
+Interactively, prompt for FROM and TO with `read-char'."
   (declare (compiler-macro
             (lambda (form) (keymap--compile-check from to) form)))
+  (interactive `(,(key-description `[,(read-char "From: ")])
+                 ,(key-description `[,(read-char "To: ")])))
   (keymap--check from)
   (when to
     (keymap--check to))
@@ -417,6 +421,57 @@ key-translate
           (aref from-key 0)
           (and to (aref to-key 0)))))
 
+(defcustom key-translate-selection-function #'key-select-translation
+  "Function to select one current key translation pair.
+
+`key-translate-remove' uses this function to prompt for the translation
+to remove.  It must take no arguments, prompt the user for a translation
+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])"
+  :type 'function
+  :group 'keyboard)
+
+(defun key-select-translation ()
+  "Prompt for a current keyboard translation pair with `'completing-read'.
+
+Each pair is formatted as \"FROM -> TO\"."
+  (let* ((minibuffer-allow-text-properties t)
+         (collection)
+         ;; Alignment helpers
+         (pad 0)
+         (_ (map-char-table
+             (lambda (k _)
+               (when (> (length (key-description `[,k])) pad)
+                 (setq pad (length (key-description `[,k])))))
+             keyboard-translate-table
+             ))
+         (format-func
+          (lambda (k v)
+            (setq collection
+                  (cons
+                   (propertize
+                    (format
+                     "%s -> %s"
+                     (string-pad (key-description `[,k]) pad)
+                     (key-description `[,v]))
+                    'key-translate-from `[,k])
+                   collection)))))
+    ;; Populate collection
+    (map-char-table format-func keyboard-translate-table)
+    (get-text-property 0 'key-translate-from
+                       (completing-read "Key Translation: " collection))))
+
+(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))
+
 (defun keymap-lookup (keymap key &optional accept-default no-remap position)
   "Return the binding for command KEY in KEYMAP.
 KEY is a string that satisfies `key-valid-p'.
-- 
2.20.1

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

[Eli Zaretskii]

> Date: Sun, 04 Aug 2024 13:16:29 +0100
> From: hugo@heagren.com
> 
> The attached patch adds commands for adding and removing entries in
> `keyboard-translate-table' interactively:
> - add an interactive spec to `key-translate'
> - add a new command `key-translate-remove', which does the opposite of
>    `key-translate'.
> - add an option for users to customise how the latter function prompts
>    for which from/to pair is removed. The default just lists them with
>    `completing-read'.
> 
> 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 "=").
> 
> The patch doesn't contain a NEWS entry yet -- I wanted to get the
> greenlight on the code first.

Thanks.

Stefan, any comments?

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]

> 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

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

[Eli Zaretskii]

Ping! Hugo, can you please respond to Stefan's review comments, so we
could make progress here?

> Cc: 72460@debbugs.gnu.org
> Date: Mon, 19 Aug 2024 10:42:43 -0400
> From:  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
> 
> 
> 
> 
> 

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]

>> > +(defcustom key-translate-selection-function #'key-select-translation
>> Do we need this?
> Short answer: yes.
>
> I wanted a way for users to customise how the current translation
> pairs are presented when they choose one to remove. The initial
> motivation was that some users might want to customise the formatting
> of the pairs; "X -> Y" vs "X → Y" vs "X Y" etc. (I'm the sort of user
> who cares about this sort of thing a lot).

Rewriting a whole new `key-translate-selection-function` function for
that is not significantly easier than rewriting a whole new
`key-translate-remove`, so I think this is firmly in the overengineering
side of the camp.

> I also envisage that many users will want to use/expect
> completing-read (as in the default) and will want the from/to elements
> vertically aligned (again, I am this user).

AFAICT, you're the first user to propose this functionality in Emacs's
40 years life, so I wouldn't bet on "many users".

BTW, I just noticed:

> +    ;; Populate collection
> +    (map-char-table format-func keyboard-translate-table)
> +    (get-text-property 0 'key-translate-from
> +                       (completing-read "Key Translation: " collection))))

You can't trust `get-text-property` here (especially since you don't
even force `completing-read` to `require-match`).
Instead you should do something like `key-parse`.

> I think here I was just copying the current calling convention for the
> existing (non-interactive) `key-translate'. Its docstring reads:
>
>> Both FROM and TO should be specified by strings that satisfy
>> `key-valid-p'.
>
> I sort of assumed someone cleverer than me had a good reason.

I suspect this is because we expect this function to be called from
a `~/.emacs` with a literal constant as argument, and we've tried to
unify on using the "KBD" syntax for those cases, since it's a friendlier
syntax than the "vector of events" where you need to distinguish between
symbols and chars with/without modifiers.

Since the arg of `key-translate` can be only a valid char (rather than
any arbitrary key potentially with modifiers), the argument is much less
strong, but my guess is that it was uniformity.

In the case of `key-translate-remove` I don't expect the arg to be
a literal constant in the code, so "nice/uniform syntax to write the
argument value" shouldn't be a concern.  🙂


        Stefan

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

[Eli Zaretskii]

Hugo,

Any followups to Stefan's comments?

> Cc: 72460@debbugs.gnu.org
> Date: Sat, 31 Aug 2024 09:56:58 -0400
> From:  Stefan Monnier via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> >> > +(defcustom key-translate-selection-function #'key-select-translation
> >> Do we need this?
> > Short answer: yes.
> >
> > I wanted a way for users to customise how the current translation
> > pairs are presented when they choose one to remove. The initial
> > motivation was that some users might want to customise the formatting
> > of the pairs; "X -> Y" vs "X → Y" vs "X Y" etc. (I'm the sort of user
> > who cares about this sort of thing a lot).
> 
> Rewriting a whole new `key-translate-selection-function` function for
> that is not significantly easier than rewriting a whole new
> `key-translate-remove`, so I think this is firmly in the overengineering
> side of the camp.
> 
> > I also envisage that many users will want to use/expect
> > completing-read (as in the default) and will want the from/to elements
> > vertically aligned (again, I am this user).
> 
> AFAICT, you're the first user to propose this functionality in Emacs's
> 40 years life, so I wouldn't bet on "many users".
> 
> BTW, I just noticed:
> 
> > +    ;; Populate collection
> > +    (map-char-table format-func keyboard-translate-table)
> > +    (get-text-property 0 'key-translate-from
> > +                       (completing-read "Key Translation: " collection))))
> 
> You can't trust `get-text-property` here (especially since you don't
> even force `completing-read` to `require-match`).
> Instead you should do something like `key-parse`.
> 
> > I think here I was just copying the current calling convention for the
> > existing (non-interactive) `key-translate'. Its docstring reads:
> >
> >> Both FROM and TO should be specified by strings that satisfy
> >> `key-valid-p'.
> >
> > I sort of assumed someone cleverer than me had a good reason.
> 
> I suspect this is because we expect this function to be called from
> a `~/.emacs` with a literal constant as argument, and we've tried to
> unify on using the "KBD" syntax for those cases, since it's a friendlier
> syntax than the "vector of events" where you need to distinguish between
> symbols and chars with/without modifiers.
> 
> Since the arg of `key-translate` can be only a valid char (rather than
> any arbitrary key potentially with modifiers), the argument is much less
> strong, but my guess is that it was uniformity.
> 
> In the case of `key-translate-remove` I don't expect the arg to be
> a literal constant in the code, so "nice/uniform syntax to write the
> argument value" shouldn't be a concern.  🙂
> 
> 
>         Stefan
> 
> 
> 
> 
>