RE: bind commands that change buffer contents to `undefined' when read-only?

["Drew Adams" <drew.adams@oracle.com>]

> > 2. It doesn't really help users see that such keys are, in effect,
> > available for binding in such read-only contexts. That was a main
> > motivation behind my proposal.
>
> Exactly how much help does an semi-knowledgeable user (who knows enough to
> want to bind a key) need beyond the error?
> ...
> I don't see the reaction to C-h c proceeding like that, but rather
> "Aha.  Good to know, but I can obviously use it here, since it doesn't
> work anyway."

It's not about the reaction to `C-h c' or to the read-only error message.
It's about a user looking for available keys to bind in a particular
context.

Are you assuming that a user looking for available keys to bind starts with
that error message, that is, by trying a key and seeing if it produces an
error?

A user is more likely to try `C-h b' to see which keys are available.
Especially if s?he wants to find multiple available bindings for a set of
related commands. Have you never done that: check to see which keys are not
bound in the current mode?

So, yes, such an isolated error message might (though a bit indirectly) help
a user to see that that particular key is, in effect, available. But:

a. It is an indirect indication. It requires understanding that since that
key cannot be used here because the buffer is read-only, it is, in effect,
available for some other use. It is far clearer to simply tell the user that
the key is `undefined'.

b. The information is after the fact (after trying that particular key).

c. It provides information for only that one key - it does not help you see
that _all_ "such keys" are also available, and it doesn't tell you what
those keys are.

d. It helps only if you start by trying that key, not if you try to look up
the current bindings (`C-h b') to see all that might be available.


Please see also the rest of the referenced email - in particular, point #1
and this part of #2:

> I don't think you have given any reason _why_ you "don't like much this
> idea"; you've just stated a preference. What are the disadvantages you see
> to this idea? Deciding on a good way to handle this should
> involve weighing the pros & cons.