608030 - Disable MozAfterPaint for content by default

Status: VERIFIED FIXED

(Core :: Layout, defect, P3)

Description

[Collin Jackson]

In bug 557579 comment 6, I pointed out that doing anything conditionally on the visitedness of a link has the potential to leak private history state. Currently the behavior of MozAfterPaint is influenced by the visitedness of links, so this event can be used to detect sites the user has or hasn't been to before.

In bug 557579 comment 9, dbaron suggests disabling MozAfterPaint for content by default, but have a pref that allows people who want to do performance testing with it to enable it.

See also: bug 600025, bug 147777

Comment 1

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

I should do this after bug 612190 lands, to avoid merge conflicts.

Comment 2

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

The relevant part of bug 612190 is now landed (see bug 612190 comment 26).

Comment 3

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

Attachment: patch

Comment 4

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

Attachment: pre-patch: clean up reftest pref handling

As part of fixing tests for the main patch, I realized I needed to add setting of a new pref to reftest and mochitest.  But before I did that, I decided to clean up the reftest prefs code a bit, so that:
 * it doesn't risk changing the profile, even if interrupted
 * prefs that are needed for reftests to work are in the harness, not the optional runreftest.py

Comment 5

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

Attachment: patch

With some additional test changes so that we pass tests.

It seemed easier to just flip the pref by default for our tests than to make the individual tests flip it.

Comment 6

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

http://hg.mozilla.org/mozilla-central/rev/ffebdc3ddb62
http://hg.mozilla.org/mozilla-central/rev/3248feddc867

Comment 7

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

Backed out:
http://hg.mozilla.org/mozilla-central/rev/f5cf80c6dae4
http://hg.mozilla.org/mozilla-central/rev/80266029824b

Comment 8

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

Attachment: honor the force_srgb pref even when it's a default pref

This fixes some highly unusual use of the pref API.  I simplified the reftest pref-setting code by making it set the prefs as default prefs (which avoids having to unset them), but the code reading the force_srgb pref was explicitly checking that the pref was a user-set and not a default pref.  It shouldn't do that.

The pref API exposes "unset" by throwing from GetBoolPref (etc.), so the NS_SUCCEEEDED(rv) check on the result of GetBoolPref is sufficient here.

This code originated in http://hg.mozilla.org/mozilla-central/rev/4b2977a03aba

Comment 9

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

http://hg.mozilla.org/mozilla-central/rev/dfc9b86cea80
http://hg.mozilla.org/mozilla-central/rev/9c1bea8d506b
http://hg.mozilla.org/mozilla-central/rev/742bc2628690

Comment 10

[Eric Shepherd [:sheppy]]

Documented:

https://developer.mozilla.org/en/Gecko-Specific_DOM_Events#MozAfterPaint
https://developer.mozilla.org/en/Preferences/Mozilla_preferences_for_uber-geeks

Also noted on Fx4 for developers.

Comment 11

[Colby Russell :crussell (no longer Mozilla-ing)]

From what I gather, this bug is about not sending MozAfterPaint for (to) content, but the docs just say it's not sent (at all, as I take it).

Does MozAfterPaint still work for trusted listeners, or no?

Comment 12

[Eric Shepherd [:sheppy]]

(In reply to comment #11)
> From what I gather, this bug is about not sending MozAfterPaint for (to)
> content, but the docs just say it's not sent (at all, as I take it).
> 
> Does MozAfterPaint still work for trusted listeners, or no?

You're right; I've clarified that. Nice catch, thank you.

Comment 13

[Aleksei Perepelkin [:chaos]]

Verified with Mozilla/5.0 (X11; Linux i686; rv:2.0b12pre) Gecko/20110204 Firefox/4.0b12pre