500214 - tabbrowser.xml and browser-tabPreviews.js use mutation event listeners

Status: VERIFIED FIXED

(Firefox :: Tabbed Browser, defect)

Description

[Olli Pettay [:smaug][[e-mail]]]

Using mutation event listeners slows down all the dom mutations in the document they are used. We should try to avoid them in chrome.

Comment 1

[Dão Gottwald [:dao]]

The event listeners are only added when the ctrl-tab panel opens and removed when it closes. Is that really a problem?

Comment 2

[Olli Pettay [:smaug][[e-mail]]]

Currently just adding a mutation listener sets a flag to the window object, which
triggers checks for the particular mutation event.
Removing listener doesn't remove the flag.
We could fix that by using a counter and not a flag, but not sure if it is
really worth it.
Would it be possible to change tabPreviews to not to use mutation events?

Comment 3

[Dão Gottwald [:dao]]

It's certainly possible, but it seems like a non-trivial task, and it would duplicate the existing infrastructure that updates the tab attributes.

Comment 4

[Olli Pettay [:smaug][[e-mail]]]

(In reply to comment #2)
> We could fix that by using a counter and not a flag, but not sure if it is
> really worth it.
And this is certainly not trivial way to fix this bug.

Comment 5

[Dão Gottwald [:dao]]

Note that the legacy all tabs popup also uses mutation events, and did so for ages.

Comment 6

[Olli Pettay [:smaug][[e-mail]]]

Ah, perhaps this shouldn't then block 3.6. But should be fixed anyway.

Comment 7

[Mike Beltzner [:beltzner, not reading bugmail]]

As per comment 6

Comment 8

[Dão Gottwald [:dao]]

Attachment: patch

Comment 9

[Dão Gottwald [:dao]]

http://hg.mozilla.org/mozilla-central/rev/d2d26dfc4d50

Comment 10

[Henrik Skupin [:whimboo][⌚️UTC+2]]

Ctrl-Tab and All-Tabs panel work fine. Verified fixed with Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.3a1pre) Gecko/20091221 Minefield/3.7a1pre ID:20091221034526

Comment 11

[Dão Gottwald [:dao]]

need to document the TabAttrModified event

Comment 12

[Eric Shepherd [:sheppy]]

Documented:

https://developer.mozilla.org/en/Code_snippets/Tabbed_browser#Notification_when_a_tab%27s_attributes_change

And added to the Fx4 for developers page.