Re: Customizing key bindings

[Richard Stallman <rms@gnu.org>]

    Another question is `if there the implementation uses two keymaps
    (either for nesting at lookup time, or just for bookkeeping purposes),
    where is the second one stored?'  I really dislike your idea of having
    two separate lisp variable to store them.

In my two-keymap proposal, the second one is found only as the parent
of the first.  The first is marked somehow as a customization keymap
so that define-key knows to keep moving and define in its parent.

My two-keymap proposal is #1 below.

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Here's what I think the :set for a keymap should do.
Actually, I have two alternative ideas:

1. Create a new keymap, as above, but make its parent be
the keymap that was the value of SYM before.  Put the
symbol `custom' in the keymap to mark it as made here.

If Custom had already run and done this, strip off the
keymap it made before, and make a new one.

Change define-key so that it skips that keymap and makes the change in
the parent.

Now all changes made outside Custom will be permanent.  However, the
bindings specified with Custom will shadow those changes.  In some
cases the user might not like that, but I don't see that any
alternative is clearly better.

[In fact, it seems to me that this is more correct than any other
alternative.]

2. Instead of making a new keymap, just install the changes in the
original keymap, saving the original definitions.

More precisely, here's what :set would do:

* Reinstall all the saved original bindings

* For each key that has a Custom key binding,
save is current binding.

* Install the Custom key bindings.

This way, changes made outside Custom all take effect immediately.
If the key has no Custom binding, the change is permanent.
If the key does have a Custom binding, the change is lost when
Custom runs again, but maybe that is reasonable in this case.