1977004 - Remove about:config prefs for :has and :has-slotted that we've been shipping on-by-default for a while

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, task)

Description

[Daniel Holbert [:dholbert]]

We've been shipping with layout.css.has-slotted-selector.enabled set to true since 136 (bug 1940691). Let's remove that pref, and a few others that are similarly removable.

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: Bug 1977004: Remove about:config pref layout.css.has-slotted-selector.enabled which has been default-enabled for many releases. r?#layout,#style

Notes:

• The selector_parser.rs change here will make 'HasSlotted' fall down
  to a general case that returns true (matching what we currently do when the
  pref is enabled) unless the PSEUDO_CLASS_ENABLED_IN_UA_SHEETS_AND_CHROME flag
  is present. And that flag is not present for this pseudo-class, so we're good.

• There are a surprising number of failures annotated in
  parse-has-slotted.tentative.html.ini, but we fail all the same subtests as
  Chrome there (and nearly the same subtests as Safari) so I don't think we need
  to worry about those. (Not sure whether that test is invalid vs. testing some
  hypothetical not-shipped-anywhere changes to the feature, but in any case it
  doesn't look like our failures are problematic.)

Comment 2

[Daniel Holbert [:dholbert]]

Attachment: Bug 1977004: Remove about:config pref layout.css.has-selector.enabled which has been default-enabled for many releases. r?#layout,#style

We shipped this default-enabled in Firefox 121, so it's probably not useful for it to be preffable at this point.

Comment 3

[Daniel Holbert [:dholbert]]

A few more that I intend to remove here or in a followup (going AFK in a few minutes so I'll add them later):

• layout.css.intrinsic-size-first-letter.enabled -- added as an escape-hatch in case of regressions (per bug 385615 comment 80), not needed anymore at this point.
• layout.css.motion-path-url.enabled -- default-enabled for ~2 years.
• layout.css.hyphenate-limit-chars.enabled -- default-enabled since 137 (5 releases now) in bug 1947183

Comment 4

[Daniel Holbert [:dholbert]]

(For now I'll land these patches as-is and file a followup on comment 3.)

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/8667d50d4bad
https://hg.mozilla.org/integration/autoland/rev/43b53698b2b1
Remove about:config pref layout.css.has-slotted-selector.enabled which has been default-enabled for many releases. r=layout-reviewers,firefox-style-system-reviewers,TYLin,emilio
https://github.com/mozilla-firefox/firefox/commit/3b477c9e3c57
https://hg.mozilla.org/integration/autoland/rev/3d130958f3f2
Remove about:config pref layout.css.has-selector.enabled which has been default-enabled for many releases. r=TYLin

Comment 6

[amarc]

https://hg.mozilla.org/mozilla-central/rev/43b53698b2b1
https://hg.mozilla.org/mozilla-central/rev/3d130958f3f2