1752138 - MouseEvent movementX and movementY wrong after requestPointerLock() when display scale is different from 100%

Status: UNCONFIRMED

(Core :: Widget: Win32, defect, P2)

Description

[gaps]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:96.0) Gecko/20100101 Firefox/96.0

Steps to reproduce:

OS: Windows 10 Education, Build 19042.1466
Browser: Firefox 96.0.2 (64-bit)
Display: 3840x2160, scale set to 150%

1 - Set the Windows display scale to 150% in Settings > Display > Scale and layout.
2 - Go to https://mdn.github.io/dom-examples/pointer-lock/
3 - Click on the black canvas area

It depends on the browser's window current size, resizing it sometimes makes the issue appear/disappear, so it is not 100% reproducible, but it happens fairly often.

Actual results:

The red ball starts to slowly move down without moving the mouse.
This is caused because the MouseEvent movementY is returning 1.

Expected results:

The red ball should not move if the mouse is not moving.
The MouseEvent movementY should return 0.

Comment 1

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

The Bugbug bot thinks this bug should belong to the 'Core::Layout' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.