Re: master 3b41141708: Expose the name of an event's input device to Lisp

[Stefan Monnier <monnier@iro.umontreal.ca>]

> `register-device-function-key' takes a device or device class, and a
> recommended function key.  If no function key was previously registered
> for that device, it associates the function key with the device.
> Otherwise, it returns the function key that was previously registered.

That means all users of `register-device-function-key` need to write
their code under the assumption that the actual "function key" (I'd
call it a "prefix event" rather than a "function key") is not the one
they asked for but the one returned, which ends up being the same as
dynamically-generated "function keys".

It makes it rather inconvenient to use for the end user who wants to

    (define-key map [foot-pedal ?b] 'foo)

and has to do

    (define-key map (vector (register-device-function-key <blabla>) ?b) 'foo)

instead.

I hope we will settle over time on some naming convention so that
conflicting names almost never happen and `register-device-function-key`
can presume the caller knows what it does, so instead of returning the
previously chosen name, it doesn't return anything and overrides the old
name instead.


        Stefan