RE: how to display a character with a specific glyph and face ?

[Drew Adams]

> > Instead of modifying the standard-display-table, I should modify
> > the escape-glyph face, isn't it ?
> 
> Either the escape-glyph face, or, if you are only interested in the
> no-break space character, the nobreak-space face.

If you want to highlight only hard (i.e., no-break) spaces, and
not also hard hyphens, or if you want font-lock to control the
highlighting, then you can use library `highlight-chars.el'.
http://www.emacswiki.org/emacs/ShowWhiteSpace#HighlightChars
http://www.emacswiki.org/emacs-en/download/highlight-chars.el

You can turn on/off such highlighting:
 * in the current buffer only (i.e., locally),
 * globally whenever FontLockMode is turned on, or
 * automatically whenever a buffer is in a given major mode