Intent to Implement and Ship: 'font-display: optional' without relayout

[Xiaocheng Hu]

Contact emails xiaoc...@chromium.org Explainer https://bit.ly/2FELF7e Design docs/spec Specification: https://drafts.csswg.org/css-fonts-4/#valdef-font-face-font-display-optional https://bit.ly/36E8UKB TAG review Not needed, as this is a minor change to an already launched feature. Summary Slightly tweak web font loading, so that: - Web fonts with 'font-display: optional' never cause relayout - Web font preloading is allowed to slightly block rendering (for all font-display values), so that if the font loads fast enough, we don't need to render with fallback Therefore, when 'font-display: optional' and preloading are used together, we'll never see layout shifting due to font swapping, and still have a good chance to use the font if it loads fast enough (e.g., from disk cache). Motivation Relayout after font loading is an issue, as it leads to unstable layout, and increases the latency for the font to show up. Now that CSSWG has reached a resolution to avoid that, our implementation should catch up. Risks

Interoperability and Compatibility Not expected, as this is a minor change to an already launched feature. Firefox: No public signals (https://github.com/w3c/csswg-drafts/issues/4108#issuecomment-578222439) No objection at the CSSWG meeting. Edge: No public signals (https://github.com/w3c/csswg-drafts/issues/4108#issuecomment-578222439) No objection at the CSSWG meeting. Safari: No public signals (https://github.com/w3c/csswg-drafts/issues/4108#issuecomment-578222439) No objection at the CSSWG meeting. Web developers: No signals Ergonomics It is expected to be used together with <link rel="preload"> or the imperiative Font Loading API to achieve good performance.

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)? Yes Is this feature fully tested by web-platform-tests? Yes https://wpt.fyi/results/css/css-fonts/font-display Tracking bug https://crbug.com/1040632 Link to entry on the Chrome Platform Status https://chromestatus.com/feature/6386634616471552

This intent message was generated by Chrome Platform Status.

[Xiaocheng Hu]

Additional clarification: for fonts which are *not* font-display: optional, there is also a greater chance that the first render will use the web font, if it loads quickly enough.

[sligh...@chromium.org]

LGTM1

[Daniel Bratell]

LGTM2

/Daniel

[Yoav Weiss]

LGTM3

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