Fonts dialogue in Firefox, what does that horizontal line indicate?

[Joe Smith]

Chris G wrote:
> ...
> Does anyone know what this horizontal line indicates?

It /appears/ to be "text" fonts on top, and "decorative" fonts on the 
bottom, but the segregation does not appear to be accurate on my system. 
At least all the dingbat or symbol fonts seem to be in the bottom list, 
although there are also (apparently) normal text fonts in there as well.

That would make sense to split those off to the bottom, but it's just a 
guess.

> ...
> Also, a final question, there are fonts one can select called
> 'monospace', 'serif' and 'sans-serif'.  Presumably if you use these
> then what you get is the system default which is defined somewhere in
> the build/distribution, there aren't actual font files with these
> names.  Have I got this right?                                   

Correct.

The mappings are in /etc/fonts/conf.d/*, although good luck trying to 
make any sense of it.

You can see the final result easily using fc-match:

$ for f in sans serif monospace; do fc-match "$f"; done
DejaVuLGCSans.ttf: "DejaVu LGC Sans" "Book"
DejaVuLGCSerif.ttf: "DejaVu LGC Serif" "Book"
DejaVuLGCSansMono.ttf: "DejaVu LGC Sans Mono" "Book"

<Joe