Intent to Implement: Alternative Text in CSS Generated Content

[Meredith Lane]

Contact emails mere...@chromium.org,abox...@chromium.org Explainer https://gist.github.com/alice/756caca028b2dae610e4ed5184c2f93e Design docs/spec Specification: https://drafts.csswg.org/css-content/#alt In progress TAG review https://drafts.csswg.org/css-content/#alt Summary This change allows for alternative text to be supplied for the content supplied using the CSS content property, to be used for non-visual mediums. Motivation The content property can be used to provide semantically important information to the user. Alternative text is used by assistive technologies to communicate the contents/caption of DOM content. This change would allow alternative text to be provided through CSS purely, making it available on pseudo elements like ::before and ::after, which are otherwise ignored for accessibility. It also allows for purely decorative elements to be explicitly labelled as such (by providing an empty string after the slash), and therefore still ignored for accessibility. Risks

Interoperability and Compatibility Syntax is not backwards compatible with the content property. See discussion: https://lists.w3.org/Archives/Public/www-style/2016May/0109.html Firefox: No public signals P3 bug filed for implementation, see: https://bugzilla.mozilla.org/show_bug.cgi?id=1281158 Edge: No public signals Safari: Public support (https://bugs.webkit.org/show_bug.cgi?id=120188) Implementation of vendor prefixed version, uses an alt property rather than the optional slash syntax, but support exists for the concept. Web developers: Positive (https://twitter.com/rob_dodson/status/1090060058224803840)

Debuggability Can use DevTools Style and Accessibility Panels, chrome://accessibility > Show accessibility tree 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? No Can’t be tested in WPT yet because WPT tests lack a mechanism to assert things about the accessibility tree, for now. Link to entry on the Chrome Platform Status https://www.chromestatus.com/features/4550056227110912

[Rune Lillesveen]

On Tue, Mar 12, 2019 at 7:41 PM 'Meredith Lane' via blink-dev <blin...@chromium.org> wrote:

Risks

Interoperability and Compatibility Syntax is not backwards compatible with the content property. See discussion: https://lists.w3.org/Archives/Public/www-style/2016May/0109.html

I don't see this as a big issue. Existing content not accidentally using the extended syntax will work. An author can do:

  content: "text";

  content: "text" / "alt-text";

to support UAs with and without support for the extended syntax.