RE: highlight failed part of isearch input

[Drew Adams]

> >>       (when (string-match " +$" m)
> >>          (propertize (substring m (match-beginning 0)) 'face
> >>             'trailing-whitespace))
> >>
> >> This is a no-op.  But maybe it is good to remove this code because the
> >> failed trailing whitespace is highlighted in the new face
> >> isearch-failed. We could change its background to more strong color,
> >> e.g. to something like is used in Firefox failed search, so failed
> >> space will be more visible.
> >
> > Good catch. We need to change the face of the pertinent part of
> > `m' itself, not just a copy. Thx. The face to use for that is
> > `trailing-whitespace', no?
>
> Why use `trailing-whitespace' when `isearch-fail' face makes failed
> trailing whitespace visible as well?

I thought RMS decided he wanted two different faces. That's the only reason
I'm aware of.