Should use comma-separated font-family
Librsvg only parses the first item in a font-family list, and uses that single family name for the Pango font description.
It should be able to do fallbacks like font-family: "Times New Roman", serif;
.
Pango::FontDescription::set_family
can indeed handle comma-separated names; I'm not sure how it deals with font families with spaces or other characters, or it it accepts quote characters.