bug#50178: 28.0.50; Size of echo area does not account for line-spacing

[Eli Zaretskii]

> From: Óscar Fuentes <ofv@wanadoo.es>
> Cc: 50178@debbugs.gnu.org
> Date: Tue, 24 Aug 2021 21:36:58 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Or it could calculate max-mini-window-height more accurately.
> 
> It must know and handle every setting that affects line height, current
> and future. It would be handy if Emacs provided a function that does
> that.

We already have it: window-text-pixel-size.