643999 - Auto scrolling is jerky

Status: RESOLVED INCOMPLETE

(Core :: Layout, defect)

Description

[Marcin Wisnicki]

User-Agent:       Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0) Gecko/20100101 Firefox/4.0
Build Identifier: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0) Gecko/20100101 Firefox/4.0

When autoscrolling, every few seconds (sometimes faster, depends on speed) there is a small jump of content in reverse direction (about 20 pixels) for a split of a second, probably for a single frame.

Faster scrolling speed results in bigger jump.

Machine speed is more than sufficient (2.1ghz dual core, 4GB ram, GF8800).
Happens with and without Direct2D.

It's rather annoying so it probably didn't occur in FF3.6 or I would have noticed.

Reproducible: Always

Steps to Reproduce:
1. Enable auto scrolling
2. On any simple page (like this submission form) press middle button
3. Move mouse down to start scrolling
Actual Results:  
Choppy scrolling

Comment 1

[Ed Morley [:emorley]]

Could you see if the issue occurs if using Firefox in safe mode:
http://support.mozilla.com/kb/Safe+Mode

How about with a new, empty testing profile? (Don't install any addons into it)
http://support.mozilla.com/kb/Basic+Troubleshooting#w_8-make-a-new-profile

Comment 2

[Marcin Wisnicki]

Yes, fresh profile and safe mode still exhibits this behaviour.

Comment 3

[Marcin Wisnicki]

In case it's important, my software is as follows:
 - win7 with sp1
 - nvidia drivers 266.58

Comment 4

[Ed Morley [:emorley]]

Reporter, please can you confirm whether this issue still occurs using Firefox 4.0.1 (http://www.mozilla.com/firefox/new/) or higher, in Firefox safe mode (http://support.mozilla.com/kb/Safe+Mode) and/or with a clean profile (http://support.mozilla.com/kb/Basic+Troubleshooting#w_8-make-a-new-profile). Ideally, also check using the latest nightly: http://nightly.mozilla.org/

If this issue no longer occurs, please close as "Resolved Worksforme".

It it in fact still occurs, please provide as much extra information as possible, including what versions tried, whether safe mode/new profile tested etc. Thanks! :-)

(Template reply to inactive UNCO bugs)

Comment 5

[Marcin Wisnicki]

Yes it still happens, only now I have Radeon HD5670.
It's possible that there is no jump in reverse direction but just a freeze for a frame or two. Sometimes there are longer freezes. It's like garbage collection pauses in older Java but Firefox doesn't use GC in renderer, does it ?

Also I've noticed that if I disable Aero/DWM (or use another computer with Windows XP) then scrolling is not really as smooth so you need Aero enabled to observe that occasional jerkiness. I've tried recording with Fraps but unfortunately doing it at 60fps slows down things.

Comment 6

[(mostly gone) XtC4UaLL [:xtc4uall]]

Marcin, is this still an Issue for you in Nightlys?
There have been made Improvements in the Past regarding CC/GC/Scrolling.

Comment 7

[Marcin Wisnicki]

It's no longer an issue for me as I got used to it ;-)

But it seems there are still some small jumps/freezes compared to 3.6.28 (vs whatever is latest, smooth scrolling disabled).

Some way of accurately measuring rendering times would be useful.