`graphic-char-p' t for non-ASCII non-printable Unicode code-points esp. #\UFFFF #\UFFFE

[mon_key]

The doc for `graphic-char-p' is kinda misleading (esp. in current UTF-8 era):

,----
| "The argument must be a character object. GRAPHIC-CHAR-P returns T if the
| argument is a printing character (space through ~ in ASCII), otherwise returns
| NIL."
`----

Might this be otherwise better stated as:

,----
| "The argument must be a character object. GRAPHIC-CHAR-P returns T if the
| argument is an ASCII printable character with char-code _not_ in the integer
| range 0-31 nor 128-159 inclusive, (e.g all but Space through ~ in ASCII).
| Whether characters outside these bounds are printable is encoding system/
| locale dependent and the return value should not be relied upon in Portable Code. "
`----

Likewise, my current SBCL "1.0.42.25" returns true with `graphic-char-p' with
UTF-8 `code-char's from the so called UCS "non-characters" at the top of each
plane (e.g. the *FFFE and *FFFF codes).

In particular, some care should be taken with the two at the top of the
so-called "Private Use Area" (PUA) e.g. :

 (code-char 65534) and (code-char 65535)

(let ((gthr (loop for a downfrom 160 to 0 collecting a)))
  (loop for b in (nreverse (append '(65534 65535) gthr))
     collecting (list :char b
        :is-graphic (graphic-char-p (code-char b))
        :w-code-char (code-char b))))

--
/s_P\