Michael Heerdegen <michael_heerdegen@web.de> writes:

> Thierry Volpiatto <thievol@posteo.net> writes:
>
>> Why do you need another argument as long as you use `this-command`?
>> You can use e.g. (pcase this-command ('foo #'foo-p) etc...)
>
> I doubt all potential uses will use `this-command'.
>
> It's cleaner if the command that knows what it wants passes the
> information via argument than to make the other function derive it
> indirectly from the context (functional style).

It is what I did initially after realizing it is simpler to use
this-command from register-read-with-preview.

> Maybe in the future we might need to pass other predicates as well.
> What when a user wants to add another register command?

You can with the current register-preview.el add a new command and
control filtering of this command.

-- 
Thierry