On Wed, Nov 1, 2023 at 11:11 AM Stephen Chenney <schen...@chromium.org> wrote:
> Answers inline. Regarding Ander's comment on the current base_feature > setting: I'll fix that. > > Cheers, > Stephen. > > On Wed, Nov 1, 2023 at 4:17 AM Yoav Weiss <yoavwe...@chromium.org> wrote: > >> >> >> On Tue, Oct 31, 2023 at 1:45 PM Stephen Chenney <schen...@chromium.org> >> wrote: >> >>> Contact emailsschen...@chromium.org >>> >>> Specificationhttps://drafts.csswg.org/css-pseudo-4/#highlight-cascade >>> >>> Summary >>> >>> With CSS Highlight Inheritance, the CSS Highlight pseudo classes, such >>> as ::selection and ::highlight, inherit their properties through the pseudo >>> highlight chain, rather than the element chain. The result is a more >>> intuitive model for inheritance of properties in highlights. Specifically, >>> "When any supported property is not given a value by the cascade ... its >>> specified value is determined by inheritance from the corresponding >>> highlight pseudo-element of its originating element’s parent element." ( >>> https://drafts.csswg.org/css-pseudo-4/#highlight-cascade) >>> >>> >>> Blink componentBlink>CSS >>> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3ECSS> >>> >>> TAG reviewNone >>> >> >> Features are exempt from a TAG review only when another vendor has >> already shipped them. That doesn't seem to be the case here. >> > > The feature is in the CSS pseudos spec and has been for quite a while. The > CSS Working Group has been discussing issues too and Safari, at least, is > implementing according to the spec. I think the ship has sailed for any > major revision to the behavior. (For context, there was no feature defined > for this change until recently because it was originally viewed as a "make > the code implement the spec" change.) > > >> >>> >>> TAG review statusNot applicable >>> >>> Risks >>> >>> >>> Interoperability and Compatibility >>> >>> The feature is still under implementation in other browser engines, but >>> the standards are well developed and there is general agreement on the >>> spec. I think compat risk is very limited at this time. >>> >> >> Does this feature change the behavior of existing uses of ::highlight and >> ::selection? Is there risk from breakage there? >> > > The change aligns the behavior of ::selection with Firefox. ::highlight is > already implemented with this behavior. There was breakage of ::selection > due to custom property handling, which was resolved at the spec level and > fixed in chromium before sending this intent. No other bugs have come in > over the extended period that this has been on for experimental web > platform features (since M111). > My above comment is wrong: The spec defining this feature does change the behavior of ::selection (not ::highlight) for all browsers. But evidence suggests that the mitigations that sites used to work around the old behavior still work with the new behavior, so breakage is very limited. There was a single source of significant breakage when the feature was first turned on and the spec and code have been changed to maintain the former behavior (related to custom properties on root applying to ::selection). We have had zero other reported bugs from enabling the feature experimentally. Some history ... The spec was changed in response to an issue where Firefox wanted to un-prefix -moz-selection but was not obeying the old spec. As I understand it, the selection style was checking for ::selection on the selected element, using it if found, otherwise using the root selection styling. All browsers were doing this. Sites were designed to work around this through the judicious use of ::selection on various elements. That is, put ::selection on anything you wanted a specified selection on, and if the inheritance was wrong, add a more specific ::selection selector. Hence the heavy use of custom properties to keep all these ::selection declarations in sync. You can see this, for example, on GitHub where they define ::selection for an element, element > span, and element > span > span, and again for light and dark mode. Sass even has an operator with a comment on it saying they would remove it if the spec is fixed. This intent to ship does not break sites that have taken this approach. Specific selectors for ::selection will resolve to the same properties as they do now. The improvement is that "element > span::selection" and "element > span > span::selection" can now be removed in favor of just "element::selection". > > >>> *Gecko*: Neutral ( >>> https://github.com/mozilla/standards-positions/issues/548) emilio@ is >>> active in standards discussions on the issues, but I am not aware of >>> implementation. https://bugzilla.mozilla.org/show_bug.cgi?id=1703963 >>> https://bugzilla.mozilla.org/show_bug.cgi?id=1703961 >>> >>> *WebKit*: In development ( >>> https://github.com/WebKit/standards-positions/issues/95) I have a >>> private email from the Apple engineer tasked with implementing. I don't >>> want to reveal PI. >>> >>> *Web developers*: Developer ergonomics is the primary concern >>> motivating highlight inheritance. See >>> https://github.com/w3c/csswg-drafts/issues/2474 for the initial spec >>> discussion related to the behavior of ::selection. See >>> https://bugs.chromium.org/p/chromium/issues/detail?id=1490471 for an >>> example of a user seeing unexpected behavior without this feature. >>> >>> *Other signals*: >>> >>> Ergonomics >>> >>> None. >>> >>> >>> Activation >>> >>> No. This reflects the already active behavior for ::selection in Firefox >>> and the already used behavior for ::highlight, ::spelling and ::grammar. >>> >>> >>> Security >>> >>> There are no security risks. >>> >>> >>> WebView application risks >>> >>> None >>> >>> >>> Debuggability >>> >>> Devtools supports highlight pseudos and correctly shows the inheritance >>> chain. >>> >>> >>> Will this feature be supported on all six Blink platforms (Windows, Mac, >>> Linux, Chrome OS, Android, and Android WebView)?Yes >>> >>> There are no cross-platform issues with implementation and no reason to >>> discriminate on platform. >>> >>> >>> Is this feature fully tested by web-platform-tests >>> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> >>> ?Yes >>> >>> >>> https://wpt.fyi/results/css/css-pseudo?label=experimental&label=master&aligned >>> highlight-cascade-* covers this functionality. There are additional WPT >>> that make use of the feature in >>> https://wpt.fyi/results/css/css-highlight-api?label=experimental&label=master&aligned >>> >>> >>> Flag name on chrome://flagsexperimental-web-platform-features >>> >>> Finch feature nameHighlightInheritance >>> >>> Non-finch justification >>> >>> The feature was enabled as experimental way back in M111 and stayed that >>> way until M116 when it was switched back to test, and it is back on >>> experimental for M118. Developers have significant experience with the >>> feature enabled via experimental web platform features. There is no value >>> to running a finch trial given the large amount of existing experience with >>> the feature. >>> >>> >>> Requires code in //chrome?False >>> >>> Estimated milestones >>> Shipping on desktop 120 >>> DevTrial on desktop 118 >>> Shipping on Android 120 >>> DevTrial on Android 118 >>> Shipping on WebView 120 >>> >>> Anticipated spec changesNone >>> >>> Link to entry on the Chrome Platform Status >>> https://chromestatus.com/feature/5090853643354112 >>> >>> Links to previous Intent discussionsReady for Trial: >>> https://groups.google.com/a/chromium.org/g/blink-dev/c/BbvI5VAguvk >>> >>> >>> This intent message was generated by Chrome Platform Status >>> <https://chromestatus.com/>. >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "blink-dev" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to blink-dev+unsubscr...@chromium.org. >>> To view this discussion on the web visit >>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAGsbWzQfdRQU81Cdm2phXD9f4wktm4f%2BReeYJaYVZKLrt_T4rg%40mail.gmail.com >>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAGsbWzQfdRQU81Cdm2phXD9f4wktm4f%2BReeYJaYVZKLrt_T4rg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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