Rollup merge of #72092 - workingjubilee:patch-2, r=GuillaumeGomez

Unblock font loading in rustdoc.css

rustdoc's font loading defaults to "auto", so browsers may block render.
But rustdoc's case prefers a faster TTI for scrolling, this means the
strictest font-display in use should be "swap". rustdoc's fonts do provide
notable legibility improvements but first-time users will have little trouble
reading without. This means "optional" is preferred.

The one exception is Source Serif Pro: it's a big difference for body text, so
"fallback" is preferred over "optional" to cause a (tiny) block.

This follows up on (but does not resolve) #20962, taking PageSpeed Insight's rec fairly directly. Supporting reading material: https://drafts.csswg.org/css-fonts-4/#font-display-desc
This commit is contained in:
Dylan DPC 2020-05-24 00:00:45 +02:00 committed by GitHub
commit 238a0ce716
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@ -3,12 +3,14 @@
font-family: 'Fira Sans';
font-style: normal;
font-weight: 400;
font-display: optional;
src: local('Fira Sans'), url("FiraSans-Regular.woff") format('woff');
}
@font-face {
font-family: 'Fira Sans';
font-style: normal;
font-weight: 500;
font-display: optional;
src: local('Fira Sans Medium'), url("FiraSans-Medium.woff") format('woff');
}
@ -17,18 +19,23 @@
font-family: 'Source Serif Pro';
font-style: normal;
font-weight: 400;
/* The difference for body text without this font is greater than other fonts,
* so the 0~100ms block of fallback is preferred over optional, for legibility. */
font-display: fallback;
src: local('Source Serif Pro'), url("SourceSerifPro-Regular.ttf.woff") format('woff');
}
@font-face {
font-family: 'Source Serif Pro';
font-style: italic;
font-weight: 400;
font-display: optional;
src: local('Source Serif Pro Italic'), url("SourceSerifPro-It.ttf.woff") format('woff');
}
@font-face {
font-family: 'Source Serif Pro';
font-style: normal;
font-weight: 700;
font-display: optional;
src: local('Source Serif Pro Bold'), url("SourceSerifPro-Bold.ttf.woff") format('woff');
}
@ -37,6 +44,7 @@
font-family: 'Source Code Pro';
font-style: normal;
font-weight: 400;
font-display: optional;
/* Avoid using locally installed font because bad versions are in circulation:
* see https://github.com/rust-lang/rust/issues/24355 */
src: url("SourceCodePro-Regular.woff") format('woff');
@ -45,6 +53,7 @@
font-family: 'Source Code Pro';
font-style: normal;
font-weight: 600;
font-display: optional;
src: url("SourceCodePro-Semibold.woff") format('woff');
}