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

[Eli Zaretskii]

> From: Óscar Fuentes <ofv@wanadoo.es>
> Date: Wed, 25 Aug 2021 19:09:14 +0200
> Cc: 50178-done@debbugs.gnu.org
> 
> Gregory Heytings <gregory@heytings.org> writes:
> 
> > Try emacs -Q, C-h h to see why it is impossible to have "an API that
> > returns how many lines fit on a given window".
> 
> Any graphics environment worth its salt has methods for measuring
> whatever object without actually rendering it.

So does Emacs: that's what window-text-pixel-size does.

> If an integer, it specifies the maximum height in units of the
> mini-window frame’s default font’s height.
> "
> 
> Why that was implemented that way? (instead of using pixels, for
> instance.)

Because in most cases it's more useful: it approximates the actual
number of lines quite well.