bug#1580: zap-to-char too raw, or document

["Stephen J. Turnbull" <turnbull@sk.tsukuba.ac.jp>]

Lars Magne Ingebrigtsen writes:

 > Should there be an interactive spec that allows reading one character,
 > but allows input methods?  Or does that make no sense?

Yes, there should be such a spec.  Personally, I would expect "c" to
be that spec.  This does make sense both conceptually and
implementation-wise because input methods conceptually operate as a
"preedit" stage.  And of course if your input method is implemented in
the OS rather than Emacs you already can input non-ASCII characters to
the "c" interactive spec.

However, many input methods can return non-trivial strings (in
Japanese it's quite common to compose whole sentences in the input
method before the input method returns any characters), and IIRC the
XIM spec explicitly says a string is returned.  In cases of phonetic
input methods for Asian languages, it is often convenient to convert a
whole word then delete unneeded characters to get a specific
character.  My recommendation would be for "c" to read either a
character or a string, characters being used directly, and otherwise
extracting the first character from the string read.  An empty string
would be an error.