567472 - content.css performance issues

Status: RESOLVED FIXED

(Firefox for Android Graveyard :: General, defect)

Description

[Brian Crowder]

looking through content.css the other day with dbaron, he suggested that we may have some relatively serious performance issues in content.css.  For example:

<dbaron> "html e" selectors are much slower than "e"; did you really want namespaces instead of descendant combinators?

We may have other issues, this is definitely worth auditing.

Comment 1

[Vivien Nicolas (:vingtetun) (:21) - (NOT reading bugmails, needinfo? please)]

we don't really want "html e" selectors, I've start a patch (on bug 562031) to remove them a few ago but I need to update it.

Comment 2

[Vivien Nicolas (:vingtetun) (:21) - (NOT reading bugmails, needinfo? please)]

Attachment: Patch

Remove all the "html e" rules but prevent content.css to apply to the textbox inner input text.

Comment 3

[Mark Finkle (:mfinkle) (use needinfo?)]

Comment on attachment 447501 [details] [diff] [review]
Patch

Code works well on the few widget test site we have and on live web sites.

Looks like you are minimizing the use of the "html" namespace too.

We don't have a good to test pageload speed due to the changes, but it can't be slower than what it was.

Comment 4

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Comment on attachment 447501 [details] [diff] [review]
Patch

This seems like a big improvement, so r=dbaron.

However, it would simplify things a bit if you declared the html namespace as the default namespace:

@namespace url(...);

, dropped all the "html|", and then declared the xul namespace and used xul| for the scrollbar-related rules (which looks like the only place that really wants to style anything non-html).  I think that would also be slightly more correct since there are a few places where you're styling elements in any namespace, which is wrong (in so far as we care about Web content in somebody's-random-XML-dialect).  So I'd recommend that as well.

Comment 5

[Vivien Nicolas (:vingtetun) (:21) - (NOT reading bugmails, needinfo? please)]

http://hg.mozilla.org/mobile-browser/rev/09a4cf2bcaf1