bug#51821: 29.0.50; Suggest add variable or frame parameter: line-height

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: tumashu@163.com,  51821@debbugs.gnu.org
> Date: Tue, 16 Nov 2021 08:34:23 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> It has to work across different fonts -- I think that's the real use
> >> case here, that if you're missing different fonts (which you commonly
> >> are when writing with different scripts), then the Emacs display gets
> >> pretty messy (uneven line heights all over the place).
> >
> > You mean, because of "tofu"?  But tofu doesn't change the line height,
> > AFAIK.  So I think I'm missing something.
> 
> No, because they're using a mix of different fonts with different heights.

That shouldn't happen, normally.  Emacs selects fonts of the same size
for a face.  Maybe people force different sizes, via fontsets or some
similar customizations, because of the issue with pixel-width of
double-width characters, but then this is not a general problem with
mixing fonts in the same face.