read-face-name

read-face-name is a compiled Lisp function in `faces.el'.

(read-face-name PROMPT &optional DEFAULT MULTIPLE)

Read one or more face names, prompting with PROMPT.
PROMPT should not end in a space or a colon.

Return DEFAULT if the user enters the empty string.
If DEFAULT is non-nil, it should be a single face or a list of face names
(symbols or strings). In the latter case, return the `car' of DEFAULT
(if MULTIPLE is nil, see below), or DEFAULT (if MULTIPLE is non-nil).

If MULTIPLE is non-nil, this function uses `completing-read-multiple'
to read multiple faces with "[ \t]*,[ \t]*" as the separator regexp
and it returns a list of face names. Otherwise, it reads and returns
a single face name.