1715546 - Support for @font-face src: descriptor's "tech(...)" syntax

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, enhancement)

Description

[Dominik Röttsches (drott)]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.39 Safari/537.36

Steps to reproduce:

FF drops @font-face src: lines which contain "supports ..." stances in their src: line. The CSS Fonts spec lists parsing rules for the src: line:
https://drafts.csswg.org/css-fonts/#font-face-src-parsing
which explain that the expected behaviour is to parse and analyse entries of the src: line according to the following grammar (excerpt)

<url> [ format(<font-format> [supports <font-technology>#]?)]? | local(<font-face-name>)
<font-format> = [<string> | woff | truetype | opentype | woff2 | embedded-opentype | collection | svg]
<font-technology> = [features | variations | color(<color-font-technology>) | palettes]

and then dropping entries which specify an unsupported format or technology but are considered syntactically correct.

Related issue for parsing issues for format() keywords instead of strings is issue 650372.

Actual results:

FF drops the complete src: line.

Expected results:

FF should understand the supports keyword and the listed technologies including color(...) and drop entries which reference a font with unsupported technologies.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::CSS Parsing and Computation' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Comment 5

[Jonathan Kew [:jfkthame]]

Updating the bug title to reflect the current spec: CSS Fonts 4 has evolved such that instead of supports <font-technology> within the format() function, there's now a separate tech() function that takes keywords such as variations, color-COLRv1, etc.

Comment 6

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1715546 - Add support for the @font-face src descriptor's tech() function. r=#firefox-style-system-reviewers

WPT tests to be added in a following patch.

Comment 7

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1715546 - Add WPT tests for parsing of the @font-face src descriptor's tech() function. r=#firefox-style-system-reviewers

Depends on D154399

Comment 8

[Jonathan Kew [:jfkthame]]

Dominik, I notice that tech() doesn't yet seem to be implemented in Chrome Canary (or is there a flag I need to set?) -- I wondered if you can say anything about plans here, as it'll be of somewhat limited use until it is more widely supported.

Comment 9

[Dominik Röttsches (drott)]

Planning to ship this, compare: https://bugs.chromium.org/p/chromium/issues/detail?id=1255685 - and hoping to get to it this quarter.

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f97705333d4c
Add support for the @font-face src descriptor's tech() function. r=emilio
https://hg.mozilla.org/integration/autoland/rev/e9dbc71b2f18
Add WPT tests for parsing of the @font-face src descriptor's tech() function. r=emilio

Comment 11

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/35459 for changes under testing/web-platform/tests

Comment 12

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/f97705333d4c
https://hg.mozilla.org/mozilla-central/rev/e9dbc71b2f18

Comment 13

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot

Comment 15

[Hamish Willee]

FYI Docs work for this can be tracked in https://github.com/mdn/content/issues/19833

Following this going behind a pref in 1786804 all I've done is added to the experimental features and also the browser compatibility data. We follow your lead and add documentation for tech() once the API stabilizes.