bug#29078: 25.2; font issue with FreeType 2.8; should not use the rounded ascender and descender

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 18 Nov 2019 19:20:49 +0100
> From: Vincent Lefevre <vincent@vinc17.net>
> Cc: larsi@gnus.org, 29078@debbugs.gnu.org
> 
> > Could it be that the same happens on your system?  If you press and
> > hold the right arrow key on the first line with the boxes (the 3rd
> > line of the file, starting from top), do you see the block cursor
> > sometimes becoming slightly larger?
> 
> No, the block cursor still seems to have the same size.
> 
> > If so, the characters where it becomes larger come from a different
> > font, which is slightly taller than the default font; delete those
> > taller characters, and the gaps should disappear. They did here.
> 
> Even if I take just
> 
> ╔══╦══╗
> ║┌─╨─┐║
> 
> I still see the gap.

OK, so the next step is for someone to step through the code in
xdisp.c that computes the line metrics, and see what are the metrics
of these characters.  We can then compare with a build that doesn't
use FreeType, and take it from there.

Or maybe some FreeType expert could look at our code and suggest what
to do, because I don't have a clue.