2062388 - When dragging accessible caret end-of-selection marker, to select content inside of a button, the marker intermittently oscillates to the start-of-document (or something like that)

Status: RESOLVED WORKSFORME

(Core :: Layout: Form Controls, defect)

Description

[Daniel Holbert [:dholbert]]

STR:

1. View a chat conversation on X/Twitter in Firefox for Android, as described in bug 1990445 comment 0. Or, view youtube comments as described in bug 2011231 comment 0.
2. Long-press a word in a chat-message (or youtube comment) to select that word. (Note, this can only be done in builds after bug 1998331 landed.)
3. Click-and-drag the end-of-selection accessible-caret to try to broaden the selection to include some later word/words.

ACTUAL RESULTS:
As you drag the caret, the selection oscillates between...

• the "correct" selection (from the start to the point-where-you've dragged it)
• a sort of inverse selection (not quite the inverse), from the start of the document up to the "start" selection marker.

It seems like the caret that you're dragging gets intermittently snapped to the start of the document, creating a giant selection that causes the whole page to get highlighted and flicker. And if you drop the caret at the "wrong time", then this is literally the selection that you end up with.

EXPECTED RESULTS:
No such weird oscillation/jumping.

This means bug 1990445 and bug 2011231 are still not-quite-fixed -- it's at least possible to select text now, but the selection behavior is pretty weird and might not get the region that you're intending.

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: screencast of bug on X/Twitter

Comment 2

[Daniel Holbert [:dholbert]]

Attachment: screencast of bug on YouTube comments

Comment 3

[Daniel Holbert [:dholbert]]

I'm using Nightly 155 2026-08-10 on a Pixel 10 Pro XL with Android 17.

Comment 4

[Daniel Holbert [:dholbert]]

Retesting this today, I'm unable to reproduce on either of the mentioned sites here (x.com, youtube.com).

Maybe my phone or Firefox instance had just gotten itself into a weird state when I triggered this? Or maybe we had a selection bug in one or two Nightlies that was later fixed?

Anyway, in the absence of an ability to further investigate...
--> WORKSFORME, but we can reopen if we manage to find a way to repro.