Re: Delegating user-reserved key binding space definition to users

[Stefan Monnier]

>>> I suggest introducing a notion of "generalized" commands. Such commands
>>> will represent common actions executed by users (like move to
>>> next/previous element). Major and minor modes can then define specific
>>> implementation of the actions.
>>
>> I think it's a non-starter because it requires foresight: only those
>> commands defined with this mechanism will be extensible.  I agree that
>> an additional level of indirection is probably necessary, but I suspect
>> it needs to be placed elsewhere.
>
> Auto-remapping will need some kind of grouping for commands one way or
> another. There is no way we can do it auto-magically. Developer or users
> should decide.

Agreed.  But it should apply to all bindings.

> Currently, the commands in major mods are bound to specific key
> bindings. The bindings are chosen either arbitrarily, according to major
> mode author preferences, or according to semi-established default key
> binding scheme (like C-f/C-M-f/C-n/C-v/etc). Either way, trying to
> re-bind commands in multiple major modes is not easy.

Yup.  I fully agree that it's a real problem.

I'd welcome a solution to it.  Even an "unrealistic" one would be good.
Currently, I don't even know what a good solution could look like.

To me a solution should allow packages to declare that command FOO
should be bound to some key based on SOME-INFO, such that it will be
bound to one key in "normal Emacs mode", and to another in `evil-mode`
and to yet another in `god-mode`, etc...

Some SOME-INFO needs to provide not a specific key, but some information
from which we can compute the "natural key" that fits the keybinding
style that the user selected.

Then there are also the issues of overloading several operations on
a single key (like TAB).  So far we've solved this along the lines you
suggest (a "generalized command", such as `indent-for-tab-command`), and
maybe that's good enough for this, tho it prevents changing this
overloading according to the keybinding style.

[ BTW, another way to look at it is not "how can we compute which key to
  bind FOO to" but rather "how can we compute which command to run when
  KEY is hit".  IOW, we could make keymaps more dynamic such that when
  you hit KEY, Emacs passes that to a "procedural keymap" which will
  *compute* (rather than lookup) which command to run, according to the
  current keybinding style.
  Not sure it would be better: I just mention it as one of the many
  things that we may want to consider in order to find a good solution
  to the problem.  ]

>> [ FWIW, you can get similar results with the current setup using
>>   command remapping.  ]
> You are absolutely right: when a major mode command is related to
> built-in command in command map.

Just to be clear: I don't think command remapping solves the problem
at hand.  It can sometimes be used for that, but not in general.

> However, some major modes introduce new concepts.  For example, think
> about paredit-forward-slurp-sexp, which can be an equivalent of Org's
> heading promotion or moving word at point forward in sentences.  How
> could you remap to group these 3 very different yet similar (for some
> users) commands together?

Great example, indeed, thanks.

In this context, I'd like the package to be able to explain that this
command is about a "sexp"-granularity operation and about
"forward"-direction operation, so that the keybinding style may
automatically find a natural/consistent key (or set of keys) to use for
it depending on whether the current keybinding style uses f/b, or j/k,
or left/right, or ... for forward/backward operations.


        Stefan