852845 - FF 19 Javascript Engine stalls when the mouse is moved over Mac OSX Dock

Status: UNCONFIRMED

(Core :: DOM: Core & HTML, defect, P5)

Description

[Steve]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:19.0) Gecko/20100101 Firefox/19.0
Build ID: 20130307023931

Steps to reproduce:

Viewing some page with Javascript actively calculating #s and updating the view.
Viewing with FF 19.0.2 on OSX 10.6.8 (Snow Leopard).  Moved mouse out of browser onto the OSX Dock.


Actual results:

Javascript on the page slows down to a crawl.  When the mouse is moved off of the taskbar, back to the browser or the menubar (anything but the Dock and the program icons in the Dock) the javascript engine resumes at it's normal pace.


Expected results:

Javascript execution speed shouldn't change when the mouse is moved to the Dock.

Comment 1

[Steve]

Correction it seems that moving the mouse onto the desktop anywhere outside of the browser causes the JS engine to drop it's execution speed.

Comment 2

[Matthias Versen [:Matti]]

Can you provide a small testcase ?
This could be an expected result of bug 633421

Comment 3

[Steve]

Matthias,

When I go to this jsfiddle, then move the mouse outside of the current FF window as described the JS engine slows down noticeably.

http://jsfiddle.net/tXSp9/23/


Again this is 10.6.8 Snow Leopard on FF 19.0.2

Thanks

Comment 4

[Matthias Versen [:Matti]]

setTimeout is used by that example and this would be indeed a result of bug 633421
See also http://stackoverflow.com/questions/6585112/javascript-performance-when-running-in-an-unfocused-tab

I don't know the OSX focus behavior but should just moving the mouse out of the window enough to trigger the slowdown ?

Moving to DOM to confirm this

Comment 5

[Boris Zbarsky [:bzbarsky]]

The testcase in comment 3 doesn't show the described behavior for me on Mac.  No matter where I move the mouse it updates at about the same speed, as expected.

Steve, do you have extensions that are setting tabs inactive in some cases?  Do you see the problem in safe mode?

Comment 6

[Steve]

Hi Boris,

FF had been running for several hours through several machine sleeps, quitting and exiting firefox then reopening did not resolve the problem.  It didn't seem like an OS issue because chrome and safari had no problem with their js engine speed.  I tested a second mac of mine (same OS) and there was no problem.  Rebooting the original machine seems to have corrected the issue, and I haven't been able to duplicate it yet.

Comment 7

[Boris Zbarsky [:bzbarsky]]

Hmm.  It sounds like something is being confused about our minimized state or some such....

Comment 8

[Steve]

I don't usually shutdown this laptop on the trip to and from work, just close the lid, so I'll see if I can reduplicate, but seems like there might be some kind of issue.

If I find anything further on this I will reopen this bug.

Comment 9

[Firefox Bug Husbandry Bot]

https://bugzilla.mozilla.org/show_bug.cgi?id=1472046

Move all DOM bugs that haven't been updated in more than 3 years and has no one currently assigned to P5.

If you have questions, please contact :mdaly.