Intent to Replace: Font Loading API's ready method with a ready attribute returning a promise

Kenji Baheux

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Dec 19, 2014, 2:03:16 AM12/19/14

to blink-dev, Kunihiko Sakamoto

Primary eng (and PM) emails

@chromium.org preferred over @google.com

Link to “Intent to Deprecate” thread

https://groups.google.com/a/chromium.org/d/msg/blink-dev/XqKrqbMEsZA/TUFfpd18QdwJ

Summary

In M40, we've been showing deprecation warnings on calls to document.fonts.ready(). In M41, we would like to make the switch from ready() as a method returning a promise to an attribute returning the same promise.

Motivation

For consistency with the pattern of having ready as an attribute (promise). This pattern started to get traction after we shipped our implementation of CSS font loading.

Usage information from UseCounter

Virtually unused as far as we can see from the UseCounter:

https://www.chromestatus.com/metrics/feature/timeline/popularity/464

Compatibility Risk

Theoretically there is a risk that we break websites relying on ready being a function. However, in practice the use counter for this particular feature of the CSS font loading API indicates that it's still rarely used (if ever).

https://www.chromestatus.com/metrics/feature/timeline/popularity/464

Firefox has recently finished their implementation of the CSS font loading API and I was able to confirm that it follows the latest spec when it comes to ready: https://bugzilla.mozilla.org/show_bug.cgi?id=1028497

Internet Explorer / Safari: N/A

Alternative implementation suggestion for web developers

Since the name didn't change, we can't have a deprecation period where both versions co-exist.

One solution would be to use the following approach:

var fontsReady = document.fonts.ready;
if (typeof(fontsReady) == "function")
fontsReady = document.fonts.ready();
fontsReady.then(...);

Entry on chromestatus.com, crbug.com, or MDN

Deprecation: https://code.google.com/p/chromium/issues/detail?id=425447

Impl: https://code.google.com/p/chromium/issues/detail?id=392077