bug#20628: 25.0.50; Incorrect line height for some fonts

[Eli Zaretskii <eliz@gnu.org>]

> From: Oleh Krehel <ohwoeowho@gmail.com>
> Cc: clement.pitclaudel@live.com,  20628@debbugs.gnu.org
> Date: Fri, 22 May 2015 18:33:43 +0200
> 
> > Math fonts are notorious for requesting huge ascent and descent
> > values.  I always disable them using fontsets.
> 
> Can you explain what are fontsets

Type "i fontset RET" in the ELisp manual and "i fontsets RET" in the
Emacs User manual, and you will be able to read about that.  The
latter includes (in the section next to the one where the above
command lands you) several examples of how to set up your fontset to
display certain ranges of characters with specific fonts.

> and how to use the to disable ascent/descent in math?

You cannot disable that.  What you can do is find a font that covers
the same range of characters, but does not specify such huge ascend
and descent values.

> Is it possible for Emacs to do so by default?

You mean, have the default fontset set up to avoid the problem?  The
difficulty with that is that the fonts we'd need to put into the
default fontset are not free, and there's an understandable reluctance
to advertise them.

> maybe Emacs could fix the problem specifically for this file / font
> family. That's what gedit does, I guess.

It would be nice if someone could look at gedit sources and describe
what it does to avoid the problem.  Finding such a solution is what
this discussion is all about, no?