bug#12054: 24.1; regression? font-lock no-break-space with nil nobreak-char-display

[Chong Yidong]

"Drew Adams" <drew.adams@oracle.com> writes:

> (defface foo '((t (:background "Yellow"))) "" :group 'faces)
> (setq nobreak-char-display nil)
> (font-lock-add-keywords nil '(("[\240]+" (0 'foo t))) 'APPEND)
>  
> Insert a no-break space:
> C-x 8 RET no-break-space (or C-q 240 RET)
>  
> Turn font-lock-mode off, then back on.
>  
> With point before the no-break-space, C-u C-x =.  That shows that the
> character is indeed a no-break-space, and there is no face on it.

"[\240]+" doesn't do what you want.  Octal 240 is a unibyte character,
so that string constant specifies a unibyte string.  When this unibyte
string is converted to multibyte, the raw byte becomes codepoint
#x3ffa0.

You should use either of these instead:

(font-lock-add-keywords nil '(("[\u00a0]+" (0 'foo t))) 'APPEND)
(font-lock-add-keywords nil '(("[ ]+" (0 'foo t))) 'APPEND)