document.caretPositionFromPoint API in shadow DOM scenario #949
Labels
Focus: Accessibility (pending)
Focus: API design (pending)
Topic: DOM
About or relating to the Document Object Model
Milestone
こんにちは TAG-さん!
I'm requesting a TAG review of document.caretPositionFromPoint API in shadow DOM scenario.
The document.caretPositionFromPoint returns a CaretPosition which represents the caret position indicating current text insertion point. However, the current spec is vague about the behavior in shadow DOM scenario. The proposal attempts to specify the behavior in shadow DOM.
shadowRoots
parameter tocaretPositionFromPoint
API. w3c/csswg-drafts#10200Further details:
[1] document.caretPositionFromPoint in shadow DOM scenario explainer:
Use case/developer need
It's necessary for web developers to have a method to determine the caret position within shadow roots. This allows for indentifying node
and offset within the shadow root so that range/selection creation is possible in shadow root at specific point.
With the proposal, web developer can get caret position inside shadow root like:
Background
The document.caretPositionFromPoint API returns a
CaretPosition which represents the caret position indicating current
text insertion point. However, the current spec doesn't
specifically define if and how shadow DOM scenarios should be supported. We want to update the API and spec to support shadow DOM cases
in a well defined way.
Proposal
Similar to Selection.getComposedRanges API, We should
introduce another argument
shadowRoots
which is the list of shadow roots that the API can pierce into. The API will look like:the returned caret position will only be in the shadow root if it's provided in
shadowRoots
argument. Otherwise, the caret position willbe in the shadow host's parent at the offset of the shadow host.
The proposed change to the API maintains the boundary of closed shadow tree unless the shadow root is provided to the API.
Alternative considered
DocumentOrShadowRoot
.The con to this approach is that the usage might be cumbersome to get a position inside nested shadow roots (need to call the API on each
level of shadow root).
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