bug#45780: 28.0.50; [PATCH] Face used for affixation function annotations

[Clemens]

> Do you want to use the completion-annotations face conditionally only
> for annotations, i.e. when only the suffix is provided by the client?
> Because when a prefix is provided as well, then it's not an annotation
> anymore, so the completion-annotations face is not applicable to prefixes.


I see, personally I think of all strings besides the completions 
themselves as annotations ;) Makes sense to do it only for the suffix then.

> Doing this is not something new, we already have the same logic
> in minibuffer-message:
>
>      (unless (or (null minibuffer-message-properties)
>                  ;; Don't overwrite the face properties the caller has set
>                  (text-properties-at 0 message))
>        (setq message (apply #'propertize message 
> minibuffer-message-properties)))
>
> Is this logic suitable for completion-annotations?

I guess this could also be used, the version I posted earlier only 
checks for the face property and then also check the whole string:

(if (text-property-not-all 0 (length str) 'face nil str)
        str
      (propertize str 'face face))


When only the face matters my proposed version might be better?