Re: Start keybinding combination

[Ergus <spacibba@aol.com>]

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