Re: Segfault in format-mode-line

[Richard Stallman]

    This leads me to think that the `face' arg is only put on chars which would
    otherwise have a face property of value nil.  I.e. it does not return
    something that will look the same as the mode-line (or header-line).

Isn't that what happens in the mode line?  It uses the same
code to do the work; isn't that what it does?