Ray Satiro Reporter
	Description • 9 years ago

User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:43.0) Gecko/20100101 Firefox/43.0
Build ID: 20150908030203

Steps to reproduce:

When I use the scroll wheel to scroll up or down the page I'm seeing the background color before the newly shown portion of the page appears. This is the first time I've seen something like this. My Nightly profile has all add-ons and extensions disabled and is otherwise normal except for:

layers.acceleration.disabled = true
layers.offmainthreadcomposition.enabled = false

I tried to reproduce with those settings but was unable.

This currently happens in all e10s tabs. Non-e10s tabs are unaffected.


Actual results:

I've attached a video that shows what is happening. The page has a black background so it's easier to see the difference. On a page like bugzilla with a gray background it's harder to see.


Expected results:

Shouldn't happen

	Ray Satiro Reporter
	Comment 1 • 9 years ago

This is the URL I used in the video: https://forum.linode.com/viewtopic.php?f=20&t=12130

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 2 • 9 years ago

(In reply to Ray Satiro from comment #0)
> I tried to reproduce with those settings but was unable.

I assume you meant to say "... without those settings ...".

> layers.offmainthreadcomposition.enabled = false

Any particular reason you are running with OMTC disabled? The APZ feature (which is enabled by default on nightly only) requires OMTC in order to work properly. If you are disabling OMTC then you should disable APZ as well, by setting the layers.async-pan-zoom.enabled pref to false. We do not intend (and cannot) support APZ without OMTC.

Closing as INVALID for now, but feel free to reopen if you disagree with this or have an argument against what I said. Thanks!

	Ray Satiro Reporter
	Comment 3 • 9 years ago

(In reply to Kartikaya Gupta (email:kats@mozilla.com) from comment #2)
> (In reply to Ray Satiro from comment #0)
> > I tried to reproduce with those settings but was unable.
> 
> I assume you meant to say "... without those settings ...".

I did not. I tried to reproduce in a profile with the settings in my current profile.

> > layers.offmainthreadcomposition.enabled = false
> 
> Any particular reason you are running with OMTC disabled?

I had several bugs where disabling omtc was suggested and though it doesn't seem to have made a difference in any of them I left it disabled. It's been a while so I will enable it and see what happens.

> The APZ feature
> (which is enabled by default on nightly only) requires OMTC in order to work
> properly. If you are disabling OMTC then you should disable APZ as well, by
> setting the layers.async-pan-zoom.enabled pref to false. We do not intend
> (and cannot) support APZ without OMTC.

I think that is something you guys should address because I'm not the only one with omtc disabled. I had no idea until not mentioned it.

> Closing as INVALID for now, but feel free to reopen if you disagree with
> this or have an argument against what I said. Thanks!

I'll reopen if I encounter it again with OMTC and APZ enabled or with OMTC and APZ disabled.

	Ray Satiro Reporter
	Comment 4 • 9 years ago

It's happening again.

Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:43.0) Gecko/20100101 Firefox/43.0
Version 	43.0a1
Build ID 	20150921030204

layers.offmainthreadcomposition.enabled = true
layers.async-pan-zoom.enabled = true

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 5 • 9 years ago

Just to confirm - you're seeing it in e10s tabs with the OMTC and APZ prefs set to true, on a recent windows nightly? Can you reproduce it on a clean profile (which should also have e10s/OMTC/APZ enabled)? I just want to make sure you don't have any other prefs/settings which are causing this. Thanks.

	Ray Satiro Reporter
	Comment 6 • 9 years ago

Yes that's correct. All the information is in the post above. No, I cannot reproduce it in a clean profile. I still have Nightly open from yesterday, when it showed the problem in all e10s tabs, but when I resumed this computer moments ago the problem was gone again.

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 7 • 9 years ago

Sounds similar to an issue Botond saw the other day where it looked like the displayport suppression got stuck on and so there was effectively no displayport.

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 8 • 9 years ago

If you manage to find steps to consistently reproduce please let us know.

	Ray Satiro Reporter
	Comment 9 • 9 years ago

Considering the last time I saw it before this was two weeks ago I think that's unlikely. If there's any diagnostic I can do on my end the next time I encounter it please let me know. I'll report here if I see it again.

	Brad Lassey [:blassey] (use needinfo?)
	Comment 10 • 9 years ago

kats, this sounds like apz, how are you tracking those?

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 11 • 9 years ago

Everything apz-related should be directly or indirectly blocking bug 1013364.

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 12 • 9 years ago

Closing WFM based on comment 9, but please reopen if you are still seeing this.