1138549 - Odd scrolling behavior on Mac OS X

Status: RESOLVED WORKSFORME

(Core :: Widget: Cocoa, defect)

Description

[Mario Grgic]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:36.0) Gecko/20100101 Firefox/36.0
Build ID: 20150222232811

Steps to reproduce:

On some web sites Firefox has intermittent scrolling problem where it seems to "eat" scroll events altogether and fails to scroll the view up/down at all. In some instances scrolling is noticeably delayed. This is usually easier to reproduce on dynamically generated sites with complex layouts and with some images on the page, but it also happens on pure text simple sites as well (not as often though). 

Note that scrolling also uses significantly more CPU on Mac OS X (scrolling up/down repeatedly usually pegs one CPU core to 100%). 

This is a regression introduced in Firefox 36. Earlier versions didn't exhibit these problems.

Comment 1

[Ciprian Muresan [:cmuresan], Formerly of Ecosystem QA - please needinfo @mcoman for things regarding the team]

Hi,

I've tried to reproduce this issue on the latest Firefox release (44.0.2) and the latest Nightly (47.0a1) but I've not been able to see any instances in which the scroll events are not fired. However scrolling up and down a dynamically generated site (twitter for instance) does use significant CPU (80-110%) but the same behavior can be experienced on Chrome and Safari, this seems to be the way Mac OS treats web scrolling in general. Are you still having issues with the scroll events?
Could you please try to reproduce this on the latest Firefox release and the latest Nightly? When doing this please use a new profile. (https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems)

Thanks,
Cipri

Comment 2

[Mario Grgic]

I don't see this behaviour in Firefox 44.0.2 either.