806099 - Floating button causes full page invalidation

Status: VERIFIED FIXED

(Core :: Layout, defect)

Description

[Mayank Bansal]

Attachment: about support.txt

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:19.0) Gecko/19.0 Firefox/19.0
Build ID: 20121027030611

Steps to reproduce:

1. enable debug paint flashing.
2. Disable HWA
3. go to : http://grssam.com/
4. Scroll down/up
5. See the psychedelic world!


Actual results:

Constant repaints. 

 If possible, check CPU usage during scrolling. Hits 80% usage on my system. For a simple page, CPU usage shouldnt be this high.


Expected results:

minimal repainting.
With HWA on, the repainting is minimal.

Also made a note of this on Taras' blog here : https://blog.mozilla.org/tglek/2012/10/26/snappy-42/#comments

Comment 1

[Mayank Bansal]

with further testing, this is reproducible only when both

1. HWA off  AND
2. layers.acceleration.disabled = false.

Comment 2

[Mayank Bansal]

This also causes 100% CPU usage. 
Profiler link :  http://people.mozilla.com/~bgirard/cleopatra/?report=da6f29d78630bd41b1f3a67cbf3eeffb0d74167a

BoxBlurVertical and BoxBlurHorizontal are present a lot in the profile.

Comment 3

[Mayank Bansal]

HWA ON :    http://people.mozilla.com/~bgirard/cleopatra/#report=ccd2502f490fb9acf05ab07566ac8a8cb53916e4&mergeUnbranched=true&invertCallback=true&selection=%255B%2522(total)%2522%252C%2522NtUserPeekMessage%2522%255D


HWA OFF : http://people.mozilla.com/~bgirard/cleopatra/#report=dbbae9a4418c37323cdd0e7ad573d820955f877f&mergeUnbranched=true&invertCallback=true


With HWA OFF, 
1. Full page invalidation while scrolling
2.AlphaBoxBlur increases to 10% of profile. In HWA on, its hardly 2%.

Comment 4

[Mayank Bansal]

So after more testing, i found that a specific element on the page causes the invalidation. 
The element is the floating "back to top" button that appears on the page when you scroll a little.  If you use Adblockplus to hide this element, there will be no invalidation.

Better STR :
1. Disable HWA
2. Go to http://grssam.com/
3. Scroll down a bit. Stop scrolling.
4. A floating button labeled "back to top" will appear on the bottom of the screen.
5. Now start scrolling again. 

6. There will be full page invalidation.

Comment 5

[Mayank Bansal]

Also happens here  :

http://www.asstr.org/files/Collections/nifty/gay/encounters/backpack-to-europe
(NSFW)

Comment 6

[Nick Cameron [:nrc]]

We do get a whole page invalidation on scrolling with layers disabled on the original URL, which is weird because I didn't think we changed invalidation or layerisation depedning on the layers backend.

Comment 7

[Matt Woodrow (:mattwoodrow)]

Attachment: Use the best active scrolled root, even if it isn't a parent of everything

I can't see any reason why this wouldn't work, fixes this page.

It also stops us from choosing a new active scrolled root when we recurse into ProcessDisplayItems for a clip.

Comment 8

[Matt Woodrow (:mattwoodrow)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/1cc90ffcd6b6

Comment 9

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/1cc90ffcd6b6

Comment 11

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Comment on attachment 690698 [details] [diff] [review]
Use the best active scrolled root, even if it isn't a parent of everything

[Approval Request Comment]
Bug caused by (feature/regressing bug #): 810302
User impact if declined: Loss of cleartype in some cases (bug 828206)
Testing completed (on m-c, etc.): more than 6 weeks on central
Risk to taking this patch (and alternatives if risky): pretty low risk given the exposure already
String or UUID changes made by this patch: none

Comment 12

[bhavana bajaj [:bajaj]]

Comment on attachment 690698 [details] [diff] [review]
Use the best active scrolled root, even if it isn't a parent of everything

We have heard a lot of users reporting this in 18.0 & approving the low risk fix for beta to get this fixed in Fx 19 timeframe

Comment 13

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-beta/rev/aeac7e173136

Comment 14

[Mihai Morar, (:MihaiMorar)]

I confirm this fix is verified on FF 19b3 on Windows 7 x64.

Mozilla/5.0 (Windows NT 6.1; WOW64; rv:19.0) Gecko/20100101 Firefox/19.0(20130123083802)

Comment 15

[Mihai Morar, (:MihaiMorar)]

I confirm the fix is verified on FF 20.b1 too following STR from Comment 0:

Mozilla/5.0 (Windows NT 6.1; rv:20.0) Gecko/20100101 Firefox/20.0