`::selection`, `::target-text`, `::highlight`, `::spelling-error`, `::grammar-error` style should propagate across shadow boundaries

[mantou132]

Custom elements within the page should inherit the document's ::selection, ::target-text, ::highlight, ::spelling-error, ::grammar-error style by default, otherwise each custom element needs to be inherited manually.

example: https://codepen.io/mantou132/pen/mdvQMwz?editors=0110

Chrome current inherit: https://issues.chromium.org/issues/381335069 , but something strange:

Firefox not inherit: https://bugzilla.mozilla.org/show_bug.cgi?id=1868009

[schenney-chromium]

Chrome works because Chrome has implemented the Highlight Inheritance model, whereas Firefox has not. The Highlight Inheritance spec does not say anything specific about shadow roots or flat tree but maybe it should?

[mantou132]

Hi, would you like to ask if the working group has discussed this issue? Currently, neither Safari nor Firefox inherits the highlight style in Shadow DOM.