Intent to Ship: meta name="text-scale"

[Chromestatus]

Contact emails

dgr...@chromium.org, p...@chromium.org

Explainer

https://github.com/w3c/csswg-drafts/blob/main/css-env-1/explainers/meta-text-scale.md

Specification

https://drafts.csswg.org/css-fonts-5/#text-scale-meta

Summary

Makes the root element's default font size scale in proportion to both the operating system's and browser's text scale setting. This allows pages that follow best practices around font-relative units (i.e. use rem and em for font sizes and page elements that should change with the user's text size preferences) to respect the user's OS-level text scale setting. This also causes the browser to disable existing browser-based mechanisms (i.e. full-page zoom on windows) and heuristics (i.e. text autosizing on mobile). Now web developers can signal to the browser that the page is constructed in a way (i.e. with rem and em) that will scale well across various user-selected font size preferences. Similar to env(preferred-text-scale), which provides authors with a way to access the text scale; this API extends that by enabling scaling via the root element's default font size and opting-out of automatic text scaling.

Blink component

Blink>Accessibility

Web Feature ID

Missing feature

Motivation

Authors currently don't have an easy way to respect the OS-level text scale setting on all devices. It is practically impossible to detect and respect this on desktop. On mobile, there is env(preferred-text-scale), but authors would need to use it in calc() functions to set the root font-size and some media queries. They would need a lot of guidance to ensure it gets used correctly and there would be little variation in how they would use it. Therefore, it would be much easier for authors if they could continue to use font-relative units as they do now and the UA initial font-size was redefined to incorporate the OS-level text scale setting.

Initial public proposal

https://github.com/w3c/csswg-drafts/issues/12380

TAG review

https://github.com/w3ctag/design-reviews/issues/1172

TAG review status

Issues addressed

Risks

Interoperability and Compatibility

Compat – no issues as it's a new feature Interop – none really – even if other browsers don't implement it's a progressive enhancement

Gecko: No signal (https://github.com/mozilla/standards-positions/issues/1326)

WebKit: No signal (https://github.com/WebKit/standards-positions/issues/587)

Web developers: Positive (https://github.com/w3c/csswg-drafts/issues/12380) Positive emoji votes on the initial proposal

Other signals:

Activation

We intend to do some outreach after the feature has baked on Stable. Some ideas are discussed at the end of this TAG review comment: https://github.com/w3ctag/design-reviews/issues/1172#issuecomment-3667481287

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?

No higher risk. This opt-in feature has WebView-specific behaviors. The goal of the WebView-specific parts is to allow authors to ensure their pages render identically on Chrome and WebView. Today renderings may not be identical due to some WebView font-sizing quirks. See commit message at https://chromium-review.googlesource.com/c/chromium/src/+/7280046 for more info.

Debuggability

No information provided

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

Yes

Is this feature fully tested by web-platform-tests?

No
Not tested in WPT because there is no API to simulate changing user font size preferences. The wpt_internal tests are at https://source.chromium.org/search?q=file:meta&sq=&ss=chromium%2Fchromium%2Fsrc:third_party%2Fblink%2Fweb_tests%2Fwpt_internal%2Fcss%2Fcss-fonts%2F There are other automated WebView java tests and C++ Unit tests.

Flag name on about://flags

No information provided

Finch feature name

TextScaleMetaTag

Rollout plan

Will ship enabled for all users

Requires code in //chrome?

False

Tracking bug

https://crbug.com/430566925

Measurement

Added WebDX UseCounter in https://chromium-review.googlesource.com/c/chromium/src/+/7267330

Estimated milestones

Shipping on desktop	146
Shipping on Android	146
Shipping on WebView	146

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).

No information provided

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5112244702674944?gate=5080483318857728

Links to previous Intent discussions

Intent to Prototype: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAOZbSt0S4JY2pHY23SVKTFR63Q3ak5Z8RXmqqNhHkXigb2feKw%40mail.gmail.com

This intent message was generated by Chrome Platform Status.