Re: Suggest installing more fonts?

[Eli Zaretskii]

> Date: Sat, 17 Oct 2020 17:37:30 +0000
> From: Gregory Heytings <ghe@sdf.org>
> cc: larsi@gnus.org, monnier@iro.umontreal.ca, emacs-devel@gnu.org
> 
> >> Apparently it's not clear, so I'll say one last time that the feature I 
> >> propose does _not_ require to install Unifont system-wide.  It is to 
> >> include Unifont in Emacs (say in etc/unifont), and to offer it as an 
> >> additional option for glyphless-char-display, along with hex-code, 
> >> empty-box, thin-space, and zero-width.  The bitmap data would be used 
> >> to draw the glyph in produce_glyphless_glyph() .
> >
> > I don't understand this proposal.  Are you saying Emacs can already use 
> > a font that is not installed?  If so, can you tell how to do that?
> 
> I don't (yet) know, but I'd be surprised if this could not be done. 
> Emacs already creates glyphs dynamically for tofus

No, Emacs doesn't create any glyphs dynamically for tofus, it simply
uses a smaller font in a box it itself draws.  See
xterm.c:x_draw_glyphless_glyph_string_foreground for how this is done
on X (w32 and ns do it very similarly).

> > The way Emacs uses fonts is by using various system libraries, such as 
> > Fontconfig, to find fonts that match certain criteria (script, encoding, 
> > character codepoint, size, slant, etc.).  How do you propose to do that 
> > if, for example, Fontconfig knows nothing about a font?
> 
> The proposal is not to change anything to the way Emacs uses fonts, but to 
> change something to the way Emacs behaves when it does not find an 
> appropriate font to display a character.  In that case Emacs would display 
> a "degraded" glyph (from Unifont), and would issue a warning that the user 
> should install another font.

I don't see how this can be done without serious changes in the code
that finds and uses fonts.  We _need_ the Fontconfig functionality.

> > Anyway, did you check the coverage of Hebrew by DejaVu Sans? does it 
> > cover Hebrew?
> 
> Yes, DejaVu Sans covers Hebrew (100% coverage).

And this is in "emacs -Q" and with DejaVu Sans the default font?