Ready for Developer Testing: Mirroring of RTL MathML operators

[Chromestatus]

Contact emails

e...@igalia.com, fw...@igalia.com

Specification

https://w3c.github.io/mathml-core/#layout-of-operators

Summary

Support for character-level and glyph-level mirroring when rendering MathML operators in right-to-left mode. When using RTL mode some operators can be mirrored by changing them to another code point (e.g. a right parentheses becomes a left parentheses). This is character-level mirroring, with equivalences defined by Unicode's `Bidi_Mirrored` property. There are operators that have no appropriate mirroring character. Glyph-level mirroring applies in this case, with the `rtlm` font feature, where another glyph can replace it in a mirrored context. Some existing implementations mirror the original glyph directly, but this may change the meaning for asymmetrical characters, such as the clockwise contour integral.

Blink component

Blink>MathML

Web Feature ID

mathml

TAG review

None

TAG review status

Not applicable

Risks

Interoperability and Compatibility

None

Gecko: Shipped/Shipping (https://bugzilla.mozilla.org/show_bug.cgi?id=945183) Working implementation shipping under the `mathml.rtl_operator_mirroring.enabled` feature. Planning to send an intent to ship.

WebKit: In development Already has character-level mirroring. rtlm support is being worked on for the harfbuzz ports.

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

Goals for experimentation

Ongoing technical constraints

None

Debuggability

None

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?

Yes
New tests: - Character-level mirroring: checks that when switching text direction the codepoints of the characters change to the corresponding BidiMirrored equivalent (e.g. right to left parentheses) - Glyph-level mirroring: checks that the rtlm font feature is supported and that a specific glyph is used for certain characters when switching text direction.

Flag name on about://flags

None

Finch feature name

MathMLOperatorRTLMirroring

Requires code in //chrome?

False

Tracking bug

https://issues.chromium.org/issues/40120782

Estimated milestones

DevTrial on desktop	140
DevTrial on Android	140

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/6317308531965952

Links to previous Intent discussions

Intent to Prototype: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/686d2758.170a0220.a35ba.00d7.GAE%40google.com

This intent message was generated by Chrome Platform Status.