1355106 - stylo: Consider adding support for UTF-8-encoded string parameters in WebIDL, for CSSOM

Status: RESOLVED WORKSFORME

(Core :: CSS Parsing and Computation, enhancement, P4)

Description

[Simon Sapin (:SimonSapin)]

Continuing from https://bugzilla.mozilla.org/show_bug.cgi?id=1354566#c3

SpiderMonkey strings can be stored as Latin-1, and currently the WebIDL bindings layer converts them to UTF-16. Then Stylo’s CSSOM implementation converts UTF-16 to UTF-8.

If we add support in WebIDL for UTF-8 strings, Latin-1 strings could be converted directly to UTF-8 by the WebIDL bindings, thus avoiding the time spent doing two conversions.

This is tricky as long as we support two style systems, unless we’re willing to pay the cost for an opposite conversion for non-Stylo.

Comment 1

[Henri Sivonen (:hsivonen) (not reading bugmail until 2025-02-06)]

I think we should do this.

(Aside: Then TextEncoder should do its conversion step entirely on the binding layer.)

Comment 2

[Bobby Holley (:bholley)]

Performance optimization - defaulting to P4, but feel free to promote it if we're actively pursuing it to solve any of the P1 performance targets.

Comment 3

[Simon Sapin (:SimonSapin)]

In terms of WebIDL syntax, this could be a non-standard extended attribute:

    interface Foo {
       void bar([MozUTF8] USVString baz);
    };

(Well-formed UTF-8 excludes surrogates, which matches the USVString type. Something similar for DOMString that would preserve all possible value would need to use WTF-8. Whether we want to use WTF-8 at all is bug 1355101.)

Comment 4

[Simon Sapin (:SimonSapin)]

This should be the default for the newly-added CSSOMString type: https://github.com/w3c/csswg-drafts/pull/1266

Comment 5

[Henri Sivonen (:hsivonen) (not reading bugmail until 2025-02-06)]

As part of bug 1402247, I'm developing some functions that could help with this.

Comment 6

[Chris Peterson [:cpeterson]]

status-firefox57=wontfix unless someone thinks this bug should block 57

Comment 7

[Xidorn Quan [:xidorn] UTC+10]

Now that the old style system has gone, we should try to fix this.

Comment 8

[Henri Sivonen (:hsivonen) (not reading bugmail until 2025-02-06)]

Do we want to make bug 1449861 duplicate of this one and move this to the binding component or make this one about making Stylo use the new binding feature (i.e. dependent on bug 1449861)?

Comment 9

[Xidorn Quan [:xidorn] UTC+10]

I think either way works, as far as CSSOM is the only usecase at the moment.

Comment 10

[Emilio Cobos Álvarez (:emilio)]

We have this now.