1670534 - Dragging outside of canvas scrolls page up

Status: NEW

(Core :: DOM: UI Events & Focus Handling, defect, P2)

Description

[wjmacfarland]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:81.0) Gecko/20100101 Firefox/81.0

Steps to reproduce:

Click within game window on https://unexploredterritories.com/ and drag (to move character.) Release mouse outside of the canvas.

Actual results:

The page scrolls up removing the game window from view.

Expected results:

The page shouldn't scroll at all in this case. Tested in Microsoft Edge and Opera and the correct behavior occurs.

Comment 1

[Alice0775 White]

Attachment: reproducible html

Comment 2

[Alice0775 White]

Regression window:
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=28ca0dfe8d723df5c41a5d79114a5e42609e3a3c&tochange=15748795cb4b4450cbb198b030af29b7f273d46e

Comment 3

[Neil Deakin]

This is some issue related how PresShell::ScrollContentIntoView determines the right scroll position when focusing an element. If the starting document scroll position and/or the height values in the testcase are adjusted, the testcase can be made to not scroll using the same steps.

The focus behaviour seems correct here, but the scrolling behaviour could be modified to not adjust the position under some circumstances that would fix the case here. Not sure what that would be, perhaps don't scroll if the element is already visible but larger that the display?

It doesn't reproduce in other browsers only because the root element doesn't seem to be focusable there.

Comment 4

[Henri Sivonen (:hsivonen) (away from Bugzilla until 2026-09-24)]

Neil, do you think you could take this bug?

Comment 5

[wjmacfarland]

Do any JS ninjas know a workaround to this issue for the time being? Hoping to update my web-game to avoid the issue for Firefox users.