1641723 - offsetX and offsetY for mouseMove event shift in the -x -y direction when mouse has moved less than 1px

Status: UNCONFIRMED

(Core :: DOM: Events, defect)

Description

[conartist6]

Attachment: Spiny line

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36

Steps to reproduce:

Registered a mousemove handler and drew resulting offsetX and offsetY coordinates while moving the mouse very slowly.

I'm including a repro in react app form: https://github.com/plangrid/drawing-in-space/tree/firefox-bug-report

Actual results:

The line drawn has exciting spines pointing up and to the left an amount that is semi-consistent. If I reload the page the size of the spines will differ (and sometimes even within one page load). It seems a few directions are possible, but the direction is usually consistent.

Expected results:

The line is smooth, following only where the mouse cursor has been.

Comment 1

[conartist6]

I also checked to make sure it wasn't a defect in my line renderer -- the aberrations can be seen in the data coming directly from the event listener.

Comment 2

[conartist6]

100% repro rate across three devices. Input devices in included mouse and touchpad. Issue not seen in Safari or Chrome.

Comment 3

[Simona Badau, Desktop QA]

I could not reproduce this issue, tried on Mac OS X 10.15 using the latest Nightly 79.0a1. I'm going to set the component Dom: Events, so that someone with more experience in the area could take a look.

Comment 4

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

I don't see any odd behavior in the mouse event test suite on Win10.

smaug, any ideas?

Comment 5

[Olli Pettay [:smaug][[e-mail]]]

I don't have.

Comment 6

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

Maybe Edgar has ideas?

Comment 7

[Edgar Chen [:edgar]]

I tried with https://github.com/plangrid/drawing-in-space/tree/firefox-bug-report on macOS, but I could not reproduce the issue.