On Mon, Oct 28, 2013 at 01:32:30PM +1100, Tim Starling wrote:
Yes, we should prefer to use free software. We should also strive to ensure that our support for users on non-free platforms is optimal, as long as that doesn't negatively impact on users of free platforms. So I don't think it is a problem to specify non-free fonts in font lists.
It's a bit more complicated than that. Linux distros ship with fontconfig (which is used by Cairo, which in turn is used by at least Firefox). Fontconfig aliases fonts via a set of rules and the default rules map popular non-free fonts to their free metric equivalents, or generics. e.g.
$ fc-match Helvetica n019003l.pfb: "Nimbus Sans L" "Regular"
$ fc-match Arial LiberationSans-Regular.ttf: "Liberation Sans" "Regular"
$ fc-match "Courier New" LiberationMono-Regular.ttf: "Liberation Mono" "Regular"
$ fc-match INVALID DejaVuSans.ttf: "DejaVu Sans" "Book"
This effectively means that, for Linux, having the free fonts at the end of the CSS font selection is probably[1] a no-op: the browser will never fallback via the CSS, but match the first font on the list to an equivalent found on the system via fontconfig's fallback mechanisms. It will be an educated guess and possibly do the right thing but it won't be what the web designer intended.
This basically strengthens your point: free fonts should be first in the list.
Regards, Faidon
[1]: I say "probably", because I vaguely remember the interactions between Firefox & fontconfig to be complicated. Maybe they're being smarter -- someone should test :)