1741051 - Cannot select content across top-level elements inside a shadow DOM within a custom element

Status: NEW

(Core :: DOM: Core & HTML, defect)

Description

[Xidorn Quan [:xidorn] UTC+11]

Attachment: testcase

Steps to reproduce:

1. open the attached testcase
2. try to select from the first paragraph to the second paragraph

Expected behavior:
You can select them.

Actual behavior:
You can't.

In this test case, both paragraphs are under the same shadow root, so it's not crossing a shadow boundary like bug 1455893. Also this only happens with custom element + shadow DOM. Simply adding the elements to a custom element or adding the elements to a shadow root of a normal element doesn't have this issue.

Comment 1

[Hsin-Yi Tsai (she/her) [:hsinyi]]

Mirko, do you have thoughts about this?

Comment 2

[Mirko Brodesser (:mbrodesser-Igalia), offline until April 25h]

Attachment: non-failing-testcase-without-custom-element.html

Thanks for filing the issue, Xidorn.

Indeed, this works with non-custom elements. Attached a testcase.

Moreover, it's not a a very recent issue, occurs on Firefox 94 as well as Nightly.

I don't see anything very obvious.

Comment 3

[Mirko Brodesser (:mbrodesser-Igalia), offline until April 25h]

For the provided STR, the selection should contain exactly one range, therefore the bug might not be directly in Selection code. Maybe around nsFrameSelection.

Comment 4

[BugBot [:suhaib / :marco/ :calixte]]

Change the status for beta to have the same as nightly and release.
For more information, please visit auto_nag documentation.

Comment 5

[Xidorn Quan [:xidorn] UTC+11]

FWIW, I did some regression check, and it seems to me that this happens from the very beginning when Firefox started supporting shadow dom and custom element on Firefox 63.