Intent to Re-implement and Ship: CSS Font Loading API - FontFaceSet: check() method
ChangSeok Oh
Summary
The FontFaceSet's check() function verifies whether it's possible to display text using the specified fonts without attempting to utilize fonts in the FontFaceSet that have not completed loading. This allows users to safely employ the font without later triggering a font replacement (i.e., font swap).
While having a review [1] to fix issue 1416842 [2], I heard that an "Intent to ship" email is required since the fix changes Blink's behavior. The font loading API was updated, so we need to update our implementation in conformance with the spec.
Risks
Interoperability and Compatibility
The current behavior of Blink does neither follow the updated spec nor match other engines' behavior. This proposal aims at fixing it. https://github.com/w3c/csswg-drafts/issues/5744
Gecko: Shipped/Shipping (https://bugzilla.mozilla.org/show_bug.cgi?id=1252821)
WebKit: Shipped/Shipping (https://bugs.webkit.org/show_bug.cgi?id=156035)
Web developers: No signals
Other signals:
WebView application risks
Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?
None
Debuggability
None
Is this feature fully tested by web-platform-tests?Yes
The following WPT tests cover this feature. * css/css-fonts/fallback-remote-to-data-url.html * css/css-fonts/fallback-url-to-local.html
Estimated milestones
Shipping on desktop
120
Shipping on Android
120
Shipping on WebView
120
Shipping on WebView
120
Anticipated spec changes
Open questions about a feature may be a source of future web compat or interop issues. Please list open issues (e.g. links to known github issues in the project for the feature specification) whose resolution may introduce web compat/interop risk (e.g., changing to naming or structure of the API in a non-backward-compatible way).
None
Alex Russell
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Mike Taylor
LGTM2
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Yoav Weiss
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ChangSeok Oh
Yes, Safari and Firefox support the check method [1], and I confirmed it. The test failures are due to other factors (e.g., pixel mismatches), not FontFaceSet::check(). Sub-tests on the check() method have passed.
[1] https://caniuse.com/mdn-api_fontfaceset_check
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ChangSeok