Intent to Ship: document.caretPositionFromPoint API

[Siye Liu]

Contact emails

si...@microsoft.com, sa...@microsoft.com

Explainer

None

Specification

https://drafts.csswg.org/cssom-view/#dom-document-caretpositionfrompoint

Summary

This new API allows users to get current caret position from a given screen point.

The API returns a CaretPosition object which represents the caret position indicating current text insertion point including the containing DOM node, caret's character offset, and the client rectangle of caret range. The API also supports get CaretPosition inside Shadow DOM. To get CaretPosition inside Shadow DOM, caller needs to provide reference to all the shadow roots that this API can pierce into.

Blink component

Blink>CSS

TAG review

document.caretPositionFromPoint API in shadow DOM scenario · Issue #949 · w3ctag/design-reviews (github.com)

TAG review status

Issues open

Risks

Interoperability and Compatibility

Gecko already implemented the API without the argument that contains shadow roots that this API can pierce into. Webkit/Blink didn't implement it. The Gecko implementation in shadow DOM scenario is not spec-compliant either (Spec changed recently to cover shadow DOM scenario). Gecko 's position is positive on this API. We expect that Gecko's behavior will be changed to be spec-compliant in the future. There is also a future compat risk too if we decided to deprecate the non-standard API `document.caretRangeFromPoint`: https://crbug.com/690599

Gecko: Positive (https://github.com/mozilla/standards-positions/issues/1012)

WebKit: Support (https://github.com/WebKit/standards-positions/issues/301)

Web developers: Positive (https://bugs.chromium.org/p/chromium/issues/detail?id=388976#c34) Web developers are asking to have document.caretPositionFromPoint API implemented in Blink: https://bugs.chromium.org/p/chromium/issues/detail?id=388976#c28 https://bugs.chromium.org/p/chromium/issues/detail?id=388976#c34

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?

None

Debuggability

None

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?

Yes

https://github.com/web-platform-tests/wpt/blob/master/css/cssom/caretPositionFromPoint.html https://github.com/web-platform-tests/wpt/blob/master/shadow-dom/Document-caretPositionFromPoint.tentative.html

Flag name on chrome://flags

None

Finch feature name

CaretPositionFromPoint

Requires code in //chrome?

False

Tracking bug

https://crbug.com/388976

Estimated milestones

Shipping on desktop	127
DevTrial on desktop	127

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).

None

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5201014343073792

Links to previous Intent discussions

Intent to prototype: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/2618db7c-56d2-4ff2-89c5-df65e1dfe6c7n%40chromium.org Ready for Trial: https://groups.google.com/a/chromium.org/g/blink-dev/c/v4MLESmFR1c/m/UhstKjucAAAJ

This intent message was generated by Chrome Platform Status.

[Brian Birtles]

Hi,

Does this return the offset inside text input elements like Gecko's implementation?

Best regards,

Brian

2024年6月6日木曜日 3:20:24 UTC+9 si...@microsoft.com:

[Siye Liu]

Yes, the API returns offset inside text input and textarea elements.

Thanks,

Siye

[Chris Harrelson]

Hi, please fill out these reviews on your chromestatus entry:

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[Siye Liu]

Reviews requested.

Thanks,

Siye

[Yoav Weiss (@Shopify)]

Looking at https://wpt.fyi/results/css/cssom/caretPositionFromPoint.html?label=experimental&label=master&aligned and https://wpt.fyi/results/shadow-dom/Document-caretPositionFromPoint.tentative.html?label=experimental&label=master&aligned, I see that Chromium is failing all of them, due to the "test" status of the relevant flag.

Are we passing the tests with the flag enabled? Do the few Mozilla failures represent their deviation from the spec? Or something else?

To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/866260c4-6f0e-420e-a8a8-f1e46a162d8dn%40chromium.org.

[Siye Liu]

Yes, these tests will all pass if we enable the runtime flag `CaretPositionFromPoint`. 

The few Mozilla failures do represent their non-spec compliant behavior.

Thanks,

Siye

[Chris Harrelson]

LGTM1

To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/145ad7ba-3c87-466b-b55f-2ebe263da186n%40chromium.org.

[Yoav Weiss (@Shopify)]

LGTM2

[Daniel Bratell]

LGTM3

/Daniel

To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAOmohSJzCry6w0mj-kVPNs7_ZCb5b0hifUB2H7rdTWUc%2BOkTwA%40mail.gmail.com.

[Yoav Weiss (@Shopify)]

Note that the TAG just came back with some feedback regarding the API shape. Please address it before shipping.

[Siye Liu]

TAG suggested we put the shadow roots in a dictionary with a `shadowRoots` option (The API shape changed in spec after the TAG review was filed). That's what Chromium implemented: document.idl - Chromium Code Search. I think we are good here.

[Yoav Weiss (@Shopify)]

On Mon, Jun 17, 2024 at 6:16 PM 'Siye Liu' via blink-dev <blin...@chromium.org> wrote:

TAG suggested we put the shadow roots in a dictionary with a `shadowRoots` option (The API shape changed in spec after the TAG review was filed). That's what Chromium implemented: document.idl - Chromium Code Search. I think we are good here.

Awesome, thanks!

 

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