Re: Increase default `line-spacing' to 0.05, 0.10 or 0.15 [proposal]

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 06 May 2021 20:53:31 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: emacs-devel@gnu.org
> 
> > From: Daniele Nicolodi <daniele@grinta.net>
> > Date: Thu, 6 May 2021 18:57:46 +0200
> > 
> > I didn't look at the code, but I don't think this is true: on my Emacs,
> > lines containing only "." or containing only "l" have exactly the same
> > height, as I would expect.
> 
> You assume that the metrics of these two glyphs are different in
> monospaced fonts?
> 
> > Also, lines containing only a new line character (thus no printable
> > characters) still have the same height as lines with content, as
> > expected.
> 
> Newline leaves no glyphs on display, so their metrics cannot be
> calculated from the font.
> 
> > Are you sure Emacs does not consider the maximum ascent and descent of
> > each _font_ contained in a line and not of each _glyph_?
> 
> Why do you think there's a difference?

And in any case, line-spacing of nil adds nothing to the metrics, no
matter where they come from.  IOW, Emacs doesn't determine this; the
font does.