Re: Start keybinding combination

[Ergus]

On Mon, Jan 31, 2022 at 02:23:34PM +0200, Eli Zaretskii wrote:
> > Date: Sun, 30 Jan 2022 21:54:47 +0100
> > From: Ergus <spacibba@aol.com>
> > Cc: help-gnu-emacs@gnu.org
> >
> > >What would such a hook do to produce the effect that you want?  The
> > >mode-line color change will not be visible unless you force redisplay
> > >of the mode line.
> > >
> > Hi Eli:
> >
> > My question comes from the fact that I see the prefix in the echo area
> > and it looks inconspicuous. So, some redisplay is actually done
> > right?
>
> A very limited variant of redisplay, which only updates the echo-area.
Oh, I see.

> > Something like:
> >
> > (add-hook the-new-hook (lambda ()
> >            (face-remap-add-relative 'mode-line :background some-color)))
> >
> > And then call `face-remap-remove-relative` in the opposed|symmetric exit
> > hook... similar to what minibuffer-setup-hook/minibuffer-exit-hook do.
> >
> > But I could be wrong.
> >
> > Does it makes sense?
>
> It would make the prompt much slower, because updating the mode line
> requires a very thorough redisplay, the way it is implemented.  And if
> you on top of that change the mode-line face, Emacs will need to
> recompute all the faces (twice) as well.  I wonder if it's worth it.
I understand. I don't think that in practice that slowness may be even
noticeable in our days, but considering I am always concerned about
performance, then probably you are right.

Very thanks,
Ergus