*> 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-anchor-position?label=master&label=experimental&aligned&q=position-visibility <https://wpt.fyi/results/css/css-anchor-position?label=master&label=experimental&aligned&q=position-visibility>* The only of these tests I saw covering anchor-valid is this one: https://wpt.fyi/results/css/css-anchor-position/position-visibility-anchor-valid.tentative.html <http://Is%20this%20feature%20fully%20tested%20by%20web-platform-tests? Yes https://wpt.fyi/results/css/css-anchor-position?label=master&label=experimental&aligned&q=position-visibility> . Maybe not too many tests are needed, but does this fully cover the behavior called out in the summary? "[The new version is] better defined to be clear that only the default anchor matters , resolving a lot of ambiguity"? E.g. the test shows that this is hidden: <div id="target2" class="target" style="top: anchor(--does-not-exist bottom);">target2</div> But it'd be nice to include a case where position-anchor is unset but anchor() refers to an anchor name that actually does exist: <div id="target3" class="target" style="top: anchor(--a1 bottom);">target2</div> And maybe a similar set of checks with anchor-size(). Another case that seems important to have is an element that has a valid default anchor, but another anchor it depends on doesn't resolve. If I'm understanding correctly that would have resulted in the element being hidden in the original proposal <https://github.com/w3c/csswg-drafts/issues/7758#issuecomment-1965540529>, but in the current proposal the element would be shown, since only the default anchor matters. Thanks, Dan On Friday, September 25, 2026 at 2:53:52 PM UTC-7 Chris Harrelson wrote: > Thanks! LGTM1 > > On Fri, Sep 25, 2026 at 1:24 PM Mason Freed <[email protected]> wrote: > >> >> On Fri, Sep 25, 2026 at 9:36 AM Chris Harrelson <[email protected]> >> wrote: >> >>> My thought is that, because Firefox doesn't ship anchor-valid yet, it >>> seems helpful to just file the positions request to encourage interop on >>> this subfeature. Especially since this feature came a bit later than the >>> others due to additional spec discussion to align on its semantics, so >>> perhaps it fell through the cracks a bit (like it did in Chromium until >>> just now). >>> >> >> Fair point. Done: >> https://github.com/mozilla/standards-positions/issues/1457 >> >> Thanks, >> Mason >> >> >> >>> On Fri, Sep 25, 2026 at 9:30 AM Mason Freed <[email protected]> wrote: >>> >>>> >>>> On Thu, Sep 24, 2026 at 5:07 PM Chris Harrelson <[email protected]> >>>> wrote: >>>> >>>>> Could you file a Mozilla standards request? >>>>> >>>> >>>> So there's already a (positive) standards position for anchor >>>> positioning as a whole: >>>> https://github.com/mozilla/standards-positions/issues/794. Do you >>>> think `anchor-valid` by itself deserves its own standards position? I >>>> think >>>> perhaps we should think about #794 as a position on the entire feature, >>>> including all sub-features. If you disagree, of course I'm happy to file a >>>> new one. >>>> >>>> Thanks, >>>> Mason >>>> >>>> >>>> >>>>> On Wed, Sep 23, 2026 at 3:56 PM Mason Freed <[email protected]> >>>>> wrote: >>>>> >>>>>> *Contact emails* >>>>>> [email protected] >>>>>> >>>>>> *Explainer* >>>>>> *No information provided* >>>>>> >>>>>> *Specification* >>>>>> https://drafts.csswg.org/css-anchor-position-1/#position-visibility >>>>>> >>>>>> *Summary* >>>>>> The `anchors-valid` value was implemented as part of >>>>>> https://crbug.com/329703412 but subsequently reverted, due to spec >>>>>> questions about the exact definition of the value. Since that time, the >>>>>> value has been renamed to `anchor-valid` (see >>>>>> https://chromestatus.com/feature/5136123851571200) and also better >>>>>> defined to be clear that only the default anchor matters, resolving a >>>>>> lot >>>>>> of ambiguity, and making this value shippable. >>>>>> >>>>>> *Blink component* >>>>>> Blink>CSS >>>>>> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ECSS%22> >>>>>> >>>>>> *Web Feature ID* >>>>>> anchor-positioning >>>>>> <https://webstatus.dev/features/anchor-positioning> >>>>>> >>>>>> *Motivation* >>>>>> *No information provided* >>>>>> >>>>>> *Initial public proposal* >>>>>> *No information provided* >>>>>> >>>>>> *Search tags* >>>>>> position-visibility >>>>>> <https://chromestatus.com/features#tags:position-visibility>, >>>>>> anchor-valid <https://chromestatus.com/features#tags:anchor-valid>, >>>>>> anchors-valid <https://chromestatus.com/features#tags:anchors-valid> >>>>>> >>>>>> *TAG review* >>>>>> *No information provided* >>>>>> >>>>>> *TAG review status* >>>>>> Not applicable >>>>>> >>>>>> *Goals for experimentation* >>>>>> None >>>>>> >>>>>> *Risks* >>>>>> >>>>>> >>>>>> *Interoperability and Compatibility* >>>>>> This is new support for a value for `position-visibility` so it >>>>>> should not create compat risks. Shipping this value will improve interop >>>>>> - >>>>>> WebKit already ships it. >>>>>> >>>>>> *Gecko*: No signal >>>>>> >>>>>> *WebKit*: Shipped/Shipping >>>>>> >>>>>> *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? >>>>>> *No information provided* >>>>>> >>>>>> >>>>>> *Debuggability* >>>>>> *No information provided* >>>>>> >>>>>> *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 >>>>>> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?* >>>>>> Yes >>>>>> >>>>>> https://wpt.fyi/results/css/css-anchor-position?label=master&label=experimental&aligned&q=position-visibility >>>>>> >>>>>> *Flag name on about://flags* >>>>>> *No information provided* >>>>>> >>>>>> *Finch feature name* >>>>>> CSSPositionVisibilityAnchorValid >>>>>> >>>>>> *Rollout plan* >>>>>> Will ship enabled for all users >>>>>> >>>>>> *Requires code in //chrome?* >>>>>> False >>>>>> >>>>>> *Tracking bug* >>>>>> https://crbug.com/333421963 >>>>>> >>>>>> *Estimated milestones* >>>>>> Shipping on desktop 157 >>>>>> DevTrial on desktop 157 >>>>>> Shipping on Android 157 >>>>>> DevTrial on Android 157 >>>>>> Shipping on WebView 123 >>>>>> >>>>>> *Anticipated spec changes* >>>>>> >>>>>> Open questions about a feature may be a source of future web compat >>>>>> or interop issues. Please list open issues (e.g. links to known github >>>>>> issues in the project for the feature specification) whose resolution >>>>>> may >>>>>> introduce web compat/interop risk (e.g., changing to naming or structure >>>>>> of >>>>>> the API in a non-backward-compatible way). >>>>>> *No information provided* >>>>>> >>>>>> *Link to entry on the Chrome Platform Status* >>>>>> >>>>>> https://chromestatus.com/feature/5136856479039488?gate=5692419038380032 >>>>>> >>>>>> 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 [email protected]. >>>>>> To view this discussion visit >>>>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM%3DNeDgQ_W7-2FxYgaXc4-r7-vuaq1rexfHn4w4YEEW-Cz0%2BSA%40mail.gmail.com >>>>>> >>>>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM%3DNeDgQ_W7-2FxYgaXc4-r7-vuaq1rexfHn4w4YEEW-Cz0%2BSA%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>>>> . >>>>>> >>>>> -- >>>> 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 [email protected]. >>>> To view this discussion visit >>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM%3DNeDjXTYLG_kz2nEhK19VGFOvQQZcds38-6jzoDk7ZeNBUQg%40mail.gmail.com >>>> >>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM%3DNeDjXTYLG_kz2nEhK19VGFOvQQZcds38-6jzoDk7ZeNBUQg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- >> 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 [email protected]. >> > To view this discussion visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM%3DNeDgCzuuVhhsikDnHq_iZu2XkXuK1cJ6dT23134Qg4WKV0w%40mail.gmail.com >> >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM%3DNeDgCzuuVhhsikDnHq_iZu2XkXuK1cJ6dT23134Qg4WKV0w%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- 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 [email protected]. To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/45a32b62-0829-4764-b2a2-d35c6987f556n%40chromium.org.
