Firefox font fallback

Question

Perhaps I'm just misunderstanding something, but it seems like Firefox doesn't handle font fallback the way that I would consider to be correct.
Instead of respecting the font-family list defined in CSS, it appears to just take the first font from that list and use whatever fontconfig returns as the best match. In most cases, this is fine, but sometimes the first font listed in the CSS is one that I don't have, and in that case fontconfig returns something bogus, completely unlike the requested font. I understand why it does this, but in the specific case of rendering web pages, it would be preferable for the browser to just try the next font in the CSS list instead of blindly going with fontconfig's "best match".
Chromium seems to do the "right thing" in this case, so I know that it must be possible for Firefox as well. But it seems that no matter what I try, Firefox simply refuses to use anything other than the first font listed in the font-family list. This kind of defeats the whole purpose of having that list, doesn't it? Web designers shouldn't have to worry about specifying obscure fonts in CSS as long as they provide sane fallbacks.
I know about adding alias rules in fontconfig's config files so that fonts that I don't have will render using some other, similar font. But my /etc/fonts/local.conf is getting very large with all of my special case rules, and yet I still run into webpages, on nearly a daily basis, where the fonts are clearly wrong. If Firefox would just respect the way that CSS is supposed to work in this case, this wouldn't be necessary.
Am I the only one that sees this problem? Is there some configuration setting that I'm just stupidly overlooking here? Or am I stuck forever adding zillions of special rules to fontconfig for all the obscure fonts that web designers decide to use?
Last edited by tmhedberg (2011-07-31 07:08:59)

Answer 1

brebs wrote:Please provide some examples of bad web pages, and the fontconfig tweaks you're using.
Actually, I think I explained the problem poorly, and I omitted some relevant information from the original post.
To illustrate:
$ fc-match 'DejaVu Sans'
DejaVuSans.ttf: "DejaVu Sans" "Book"
$ fc-match Century
DejaVuSans.ttf: "DejaVu Sans" "Book"
I don't have a font called "Century" installed, so fontconfig just falls back to its default, which happens to be DejaVu Sans. That's fine in the general case.
Here's a webpage with `font-family: Century, serif` in its CSS: http://goertzel.org/dynapsyc/yamaguchi.htm. So if Century is not available, Firefox should fall back to the default "serif" font set in the Firefox preferenes, which in my case is Times New Roman.
Instead, I get this ugliness: http://tmh.cc/img/ff_ugly.png
If I use Firebug to change the first font in the CSS font-family list to "DejaVu Sans", it looks good: http://tmh.cc/img/ff_dejavu.png. Or, if I just remove Century from the list entirely, so that it just says "serif", the I get Times New Roman, as expected: http://tmh.cc/img/ff_times.png.
So it seems that Firefox is consulting fontconfig for the first font in the CSS list, as I said before. But when fontconfig just returns its default font (or more likely, if the fontconfig value is too far off from what Firefox wants), then it's not using fontconfig's font, nor is it falling back to the second font in the CSS list. It just uses something completely different, and quite ugly.
My custom rules in /etc/fonts/local.conf are just a bunch of these:
<!-- Replace Times with Times New Roman -->
<match target="pattern" name="family">
<test name="family" qual="any">
<string>Times</string>
</test>
<edit name="family" mode="assign">
<string>Times New Roman</string>
</edit>
</match>
Each of which maps a font name that fontconfig doesn't match properly to a font that I actually have. But having to add so many of these rules specifically for Firefox when other applications, even other web browsers, seem to have no problem is very irritating and seems unneccesary. I suspect that I'm missing something obvious, hence this thread.