624171 - multitouch scrolling of Minefield is very choppy, esp. with flash embedded

Status: RESOLVED DUPLICATE of bug 675866

(Firefox :: General, defect)

Description

[Michael]

User-Agent:       Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0b9pre) Gecko/20110105 Firefox/4.0b9pre
Build Identifier: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0b9pre) Gecko/20110105 Firefox/4.0b9pre

When scrolling a page in Minefield using a multitouch trackpad, such as a Magic Trackpad or the trackpads in unibody Mac laptops, the scrolling is very smooth once the page has been completely rendered.  However, if you try to scroll while some object on the page is rendering, scrolling becomes very choppy - it stutters and jumps.  This is most noticeable on pages containing flash.  However, I can also replicate it on pages that do not contain flash, but that are rendering some component of the page while I scroll.  I've seen this on many pages in the past few days, including ones such as news.google.com where part of the page is being loaded by javascript.  Once the page has been fully rendered, the problem goes away.  The problem is less noticeable on pages that have had much of their content cached.


Reproducible: Always

Steps to Reproduce:
1.  Go to a website you haven't been to recently.  Best if it contains embedded flash, but this is even observable on news.google.com.  Engadget.com is a particularly good choice.
2.  Using a multitouch trackpad, scroll down while the page loads and renders
3.  Scrolling is very choppy while the page loads.
4.  If the page contains no flash, scrolling will be smooth once the page has rendered.  However, if it contains flash, scrolling will be VERY choppy while the flash video is viewable within the window.  The video does not need to be playing.  For example, if you go to http://www.engadget.com/2011/01/08/skullcandy-fix-versus-yurbuds-ironman-battle-of-the-in-ear-h/ you will see a video with a single frame and a play button displayed (as a thumbnail).  Scrolling will be choppy while the embedded flash is in view.
Actual Results:  
Scrolling is very choppy when page is rendering and especially when flash content is visible in the window.  Scrolling is smooth when no new rendering is taking place and there is no embedded flash.

Expected Results:  
Scrolling is always smooth

Comment 1

[Tyler Downer [He/Him]]

This bug was reported using a pre-release version of Firefox 4. Now that Firefox 4.0.1 final has been released, can you please update and retest your bug? A fresh profile would be a good starting place to test, 
http://support.mozilla.com/kb/Managing+profiles. If you continue to see the issue, can you please update this bug with your results?

Filter: firefox4prebugsunco