On Wed, Feb 4, 2026 at 1:14 PM PhistucK <[email protected]> wrote:
> My button has disappeared (well, turned black) :O
> The apply class exists in both of the trees, is it expected to be
> disregarded now?
>
The "apply" class is not in the <use> shadow tree because it's not part of
the cloned tree, which is why it doesn't match. It used to match because we
incorrectly matched the rules against the wrong tree.
> <!DOCTYPE html>
> <html><head><style>
> body
> {
> background: black;
> }
> .apply [stroke="black"]
> {
> fill: #ffffff;
> stroke: #ffffff;
> }
> </style>
> </head><body>
> <div>
> <svg width="90vw" height="90vh" viewBox="0 0 50 50" class="apply">
> <symbol id="svg-pause" viewBox="0 0 50 50">
> <rect x="5" y="5" width="15" height="40" stroke="black"></rect>
> <rect x="30" y="5" width="15" height="40" stroke="black"></rect>
> </symbol>
> <a href="#">
> <use href="#svg-pause" x="20" y="37" width="10" height="11"></use>
> </a>
> </svg>
> </div>
> </body></html>
>
>
>
>
> ☆*PhistucK*
>
>
> On Wed, Nov 12, 2025 at 5:11 PM Daniel Bratell <[email protected]>
> wrote:
>
>> LGTM3 - Risk seems manageable even though it's unfortunately hard to
>> measure. That it has worked for such a long time in Gecko without major
>> push towards something else is a good sign. Good luck. We're all counting
>> on you.
>>
>> /Daniel
>>
>> On 2025-11-12 10:32, Mike Taylor wrote:
>>
>> On 11/10/25 7:22 p.m., Rune Lillesveen wrote:
>>
>> On Sat, Nov 8, 2025 at 12:59 AM Rick Byers <[email protected]> wrote:
>>
>>> This has some risk of being a breaking change, right? How would
>>> you characterize that risk? Firefox having this is obviously a good sign,
>>> but any other data or arguments on the risk? I imagine SVG use is fairly
>>> rare, and any selector mismatch would most likely be a minor formatting
>>> issue, right?
>>>
>> That, or some display:none rule that didn't work before, starts working
>> now, which could be a major or minor issue.
>>
>>
>> An instantiated subtree will no longer be able to do selector matching
>> against the surrounding elements from where it was instantiated from.
>>
>> In the following case, the use instance of the rect would no longer be
>> red:
>>
>> <!DOCTYPE html>
>> <style>
>> .original rect { fill: red; }
>> rect { fill: green; }
>> </style>
>> <svg>
>> <defs class="original">
>> <rect id="r" x="0" y="0" width="100" height="100" />
>> </defs>
>> <use href="#r"></use>
>> </svg>
>>
>> I think this is unlikely to break real sites.
>>
>> I spent some time poking through the Firefox bug and its various
>> associated bugs. I think it's a pretty good sign that this landed 8 years
>> ago and the reported regressions were due to implementation bugs that were
>> quickly fixed.
>>
>> The absence of bugs in Bugzilla isn't a perfect compat signal, but it's
>> at least promising.
>>
>> In order to use-count this, we would have to run both ways of cascading
>> (or at least selector matching) to detect such cases.
>>
>> This sounds like a lot of complexity (but feel free to respond telling me
>> it's trivial to implement). So, LGTM2 and hopefully I'm not wrong about the
>> risk here.
>>
>>
>> The main benefit from this change, I think, is that it fixes
>> https://crbug.com/40663285 which is about :hover and other state
>> selector matching which is currently broken in <use> instances.
>>
>> On Fri, Nov 7, 2025 at 1:51 AM Philip Jägenstedt <[email protected]>
>>> wrote:
>>>
>>>> LGTM1
>>>>
>>>> The WebKit standards position was only filed yesterday, but this seems
>>>> straightforward and aligns with spec+Firefox, so I don't think we should
>>>> wait on it. In the unlikely event there is feedback, please ping this
>>>> thread.
>>>>
>>>> On Fri, Nov 7, 2025 at 9:44 AM Rune Lillesveen <[email protected]>
>>>> wrote:
>>>>
>>>>> *Contact emails*
>>>>> [email protected]
>>>>>
>>>>> *Specification*
>>>>> https://www.w3.org/TR/SVG2/struct.html#UseElement
>>>>>
>>>>> *Summary*
>>>>> Align the Blink implementation with the SVG2 specification for
>>>>> matching CSS rules in <use> element trees.
>>>>>
>>>>> Match selectors against the <use> instantiation elements instead of
>>>>> the originating element subtree. This means selectors will no longer match
>>>>> ancestor and sibling elements outside the cloned subtree. More
>>>>> importantly,
>>>>> state selectors like :hover will now start matching in <use> instances.
>>>>>
>>>>> *Blink component*
>>>>> Blink>SVG
>>>>> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ESVG%22>
>>>>>
>>>>> *Web Feature ID*
>>>>> Missing feature
>>>>>
>>>>> *Motivation*
>>>>> CSS selectors match against the wrong tree for <use> instantiations,
>>>>> which means selectors do not match correctly for structural relationships
>>>>> and user interaction state (see :hover issue that will be fixed shipping
>>>>> this feature: https://crbug.com/40663285)
>>>>>
>>>>> *Initial public proposal*
>>>>> *No information provided*
>>>>>
>>>>> *TAG review*
>>>>> *No information provided*
>>>>>
>>>>> *TAG review status*
>>>>> Not applicable
>>>>>
>>>>> *Risks*
>>>>>
>>>>>
>>>>> *Interoperability and Compatibility*
>>>>> Firefox has shipped the SVG2 behavior for years. Bug for WebKit:
>>>>> https://bugs.webkit.org/show_bug.cgi?id=249080
>>>>>
>>>>> *Gecko*: Shipped/Shipping (
>>>>> https://bugzilla.mozilla.org/show_bug.cgi?id=265894#c190) Shipped in
>>>>> Firefox 56
>>>>>
>>>>> *WebKit*: No signal (
>>>>> https://github.com/WebKit/standards-positions/issues/571)
>>>>>
>>>>> *Web developers*: Positive 44 votes on the crbug issue, and
>>>>> additional 5 votes on the :hover bug https://crbug.com/40663285
>>>>>
>>>>> *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/svg/linking/reftests/use-descendant-combinator-003.html
>>>>> https://wpt.fyi/svg/struct/reftests/use-inheritance-001.svg
>>>>> https://wpt.fyi/svg/struct/reftests/use-inheritance-nth-child-of.svg
>>>>>
>>>>> https://wpt.fyi/svg/struct/reftests/use-inheritance-nth-last-child-of.svg
>>>>>
>>>>> https://wpt.fyi/svg/styling/use-element-attr-selector-transition.tentative.html
>>>>>
>>>>> https://wpt.fyi/svg/styling/use-element-id-selector-transition.tentative.html
>>>>>
>>>>> *Flag name on about://flags*
>>>>> #enable-experimental-web-platform-features
>>>>>
>>>>> *Finch feature name*
>>>>> Svg2Cascade
>>>>>
>>>>> *Rollout plan*
>>>>> Will ship enabled for all users
>>>>>
>>>>> *Requires code in //chrome?*
>>>>> False
>>>>>
>>>>> *Tracking bug*
>>>>> https://crbug.com/40550039
>>>>>
>>>>> *Estimated milestones*
>>>>> Shipping on desktop 144
>>>>> Shipping on Android 144
>>>>> Shipping on WebView 144
>>>>>
>>>>> *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/5134266027606016?gate=6607474169872384
>>>>>
>>>>> This intent message was generated by Chrome Platform Status
>>>>> <https://chromestatus.com/>.
>>>>>
>>>>> --
>>>>> Rune Lillesveen
>>>>>
>>>>> --
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>>>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CACuPfeQQp_NW%3DnoTwk2jpcjGzMb6wFyqj4KGm%3DqpMVyAM767tg%40mail.gmail.com?utm_medium=email&utm_source=footer>
>>>>> .
>>>>>
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>>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAARdPYcTTt4PNoX7oxUT_bTN2QGhbELKgFK7M_ojnne1NZgTfQ%40mail.gmail.com?utm_medium=email&utm_source=footer>
>>>> .
>>>>
>>>
>>
>> --
>> Rune Lillesveen
>>
>> --
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>
--
Rune Lillesveen
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