653909 - Firefox hangs for approx. 2 seconds by tab switching after update to v4.0.1

Status: RESOLVED WORKSFORME

(Firefox :: Shell Integration, defect)

Description

[René Schwarz]

User-Agent:       Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0.1) Gecko/20100101 Firefox/4.0.1
Build Identifier: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0.1) Gecko/20100101 Firefox/4.0.1

After update to Firefox 4.0.1 Firefox hangs every time when I switch a tab or open a website in a new tab. FF hangs for approx. 2 seconds every time and is not useable.

Same when I open a new, empty tab or when I close an existing tab.

Reproducible: Always

Comment 1

[Thomas Ahlblom]

Does the issue still occur if you start Firefox in Safe Mode?
https://support.mozilla.com/en-US/kb/Safe+Mode

How about with a new, empty profile?
https://support.mozilla.com/en-US/kb/Basic%20Troubleshooting#w_8-make-a-new-profile

Comment 2

[René Schwarz]

The issue still occurs if I start Firefox in Safe Mode. But if I start Firefox with a new profile, the problem seems to be gone.

So what could be the reason for the problem?

Comment 3

[(mostly gone) XtC4UaLL [:xtc4uall]]

Maybe comparing modified Prefs of both Profiles through the Troubleshooting Info Page would help?

Comment 4

[Tyler Downer [He/Him]]

Or you may not have started safe mode properly and still had a Firefox window open. try comparing the prefs, or reinstalling your addons one by one in the new profile.

Comment 5

[René Schwarz]

Attachment: Contents of the Troubleshooting Info Page

Safe mode has been started properly; Firefox process was terminated completely before.

The attached file shows the comparison of preference changes out of the Troubleshooting Info Page.

Comment 6

[René Schwarz]

Supplement:

Even with manually deactivated add-ons in my profile Firefox behaves similar.

Comment 7

[René Schwarz]

Solution:

After some hours with different test methods, I discovered following line in my prefs.js as reason for the issue:

user_pref("browser.taskbar.previews.enable", true);

After removing that line everything is fine. No one of the described problems above originates.

Comment 8

[(mostly gone) XtC4UaLL [:xtc4uall]]

This really does not happen on 4.0 with that Pref enabled?
Looking at the Fixed Bugs for 4.0.1 nothing obvious landed what could have caused this ....

Comment 9

[René Schwarz]

No, in FF 4.0 everything was fine with enabled taskbar previews (I changed that setting a long time ago to true). Since I installed FF 4.0.1 yesterday, the problem arose.

Comment 10

[(mostly gone) XtC4UaLL [:xtc4uall]]

Hmm, maybe finding a Regression Range on the mozilla-2.0 Branch could help then?!

Comment 11

[[not reading bugmail]]

hmm, we do know that tab previews are default off (unchecked in tabs pane of options preferences)

Comment 12

[Matthias Versen [:Matti]]

Is this still an issue ?

Comment 13

[René Schwarz]

It seems not to be an issue with Firefox 15.0.1 anymore. However, I noticed that setting 

user_pref("browser.taskbar.previews.enable", true);

has no effect to Firefox (even after restarting Firefox). No tab previews will be displayed in the Windows task bar after enabling this option (still only one preview of the currently active tab is shown by hovering over the Firefox icon).

Comment 14

[Virtual_ManPL [:Virtual] 🇵🇱 - (please needinfo? me - so I will see your comment/message/reply/question/etc.)]

If it isn't reproducible with latest Firefox please mark this bug as WORKSFORME, thank you.

Also I can reproduce not working Taskbar preview. Bug reported here #794561