503705 - Clicking checkbox/dropdown causes page recompile

Status: RESOLVED INCOMPLETE

(Firefox :: General, defect)

Description

[ngrier+bugz]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1) Gecko/20090624 Firefox/3.5
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1) Gecko/20090624 Firefox/3.5

Clicking a checkbox or dropdown (which are part of a passive form), results in a whole 'recompile' of the page. For large, complex pages, this causes the app to become non-responsive while it churns away at 100% cpu. Once this processing is complete, everything returns to normal.

This occurs with passive form elements (i.e. ones without 'onclick' properties or similar) where there is no dynamic page content.


Reproducible: Always

Steps to Reproduce:
1. Go to a complex page with checkbox and/or dropdown elements.
2. Change the status of an element (check a box or change the drop-down selection)
3. Attempt to scroll, interact with other elements or wait a couple hundred ms
4. Continue attempting to interact with the page; after one or more changes the page will hang as it recompiles
Actual Results:  
Firefox hangs while recompiling the page after interacting with passive form elements.

Expected Results:  
Since it is a passive form, no recompile/rendering of the page should be necessary.

This appears to be a new bug as this was not occurring on previous versions as far back as I can remember. I assume it has to do with the new rendering engine as the scrolling is very smooth for these complex pages once it finishes the render, but to have it freeze for a minute when the check box should only matter with the form submission is crazy.

Note that this is on an Athlon XP+ at 1.7GHz with 1.5GB of RAM. Viewing process details it is clearly processor-bound not RAM bound. 

The recompile of the page seems to take longer than the initial time to load.

Comment 1

[Remko de Keijzer]

I've just testd it with the page provided by you and I don't have this problem.
Can you reproduce this using Safe mode?

Comment 2

[ngrier+bugz]

Attachment: Sample webpage exhibiting problem

I hadn't realized that the website requires you to log in to get to the problem page. Here is a copy of a particularly long, and thus problematic, page.

Comment 3

[ngrier+bugz]

I have tested in safe mode and in safe mode with all extensions disabled and still experience the bug. It appears as if there may be a timer involved in that sometimes it starts the intensive processing immediately, but other times you can continue to interact with the page for up to one second or so. But it will invariably hang. Simply scrolling does not cause a problem. When it hangs, it freezes the entire UI and nothing responds.

Comment 4

[Remko de Keijzer]

With the sample page you provided I experience the same problem.

Comment 5

[Tyler Downer [He/Him]]

Reporter, are you still seeing this issue with Firefox 3.6.12 or later in safe mode? If not, please close. These links can help you in your testing.
http://support.mozilla.com/kb/Safe+Mode
http://support.mozilla.com/kb/Managing+profiles
Also, please consider using the most recent Firefox 4 beta build, your bug may be resolved there.

Comment 6

[Tyler Downer [He/Him]]

No reply, INCOMPLETE. Please retest with Firefox 3.6.13 or later and a new profile (http://support.mozilla.com/kb/Managing+profiles). If you continue to see this issue with the newest firefox and a new profile, then please comment on this bug.