Inject unicode-range into the original @font-face declaration when it's missing some of the glyphs that are used

[papandreou]

See the discussion here: Munter/netlify-plugin-subfont#55

It fixes the double download when I run subfont on the test case we use for the missing glyph warning.

Fixes Munter/netlify-plugin-subfont#55

Before

After

[coveralls]

Pull Request Test Coverage Report for Build 349

• 10 of 10 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.08%) to 89.486%

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Totals
Change from base Build 347:	0.08%
Covered Lines:	999
Relevant Lines:	1069

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💛 - Coveralls

[Munter]

Looks great. I can't quite remember the details here. Do we know if this behaves well for google fonts?

[papandreou]

Do we know if this behaves well for google fonts?

Yeah, it should work great. Because of the User-Agent we use, we get CSS without unicode-range:

@font-face {
  font-family: 'Roboto';
  font-style: normal;
  font-weight: 400;
  src: local('Roboto'), local('Roboto-Regular'), url(https://fonts.gstatic.com/s/roboto/v20/KFOmCnqEu92Fr1Mu4mxP.ttf) format('truetype');
}

... So it should make a very positive difference :)

[Munter]

It's just hat Google fonts fallbacks are still loaded from Google itself. But I guess that just means the addition adds a benefit to self-hosted fonts for now, and when we switch to self-hosted fallback fonts from Google fonts, they will get the benefit as well

[Munter]

Just did a manual test with Google hosted fonts. Obviously there is nowhere we can add the unicode-range because google controls the stylesheet. So I was worried that the updated error message was incorrect. But of course, google serves unicode-range to capable browsers, so the error message is still correct even when Google supplies the CSS for the fallback font :D

[papandreou]

Ah, right, yes 🤦

You’re right that the fallback CSS that gets async loaded from fonts.googleapis.com won’t benefit from this. We really should self-host that as well.

[daveredfern]

Thanks for your hard work fixing this @Munter @papandreou. It’s really appreciated.